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'[EE:] homemade CNC pick and place'
2001\12\29@063559 by Roman Black

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Hi everyone, has anyone built a home made
CNC pick and place machine to do SMD work?

I'm thinking of doing one with a couple of
old matrix printer chassis, they have sliders,
belts and stepper motors ready and will do good
speeds with 0.1mm repeatability easily.

I have an idea for a new product that will
require lots of 0805 SMD parts and I like the
thought of using a machine to do glue spots,
then pick and place, then once parts are glued
I can just hold them into a solder cauldron
(with bamboo tongs!) to solder them in one go.

The whole operation would be almost totally
automated. Maybe it could be automated later
by attaching the solder cualdron to the process?
Any thoughts??
:o)
-Roman

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2001\12\29@162717 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi, Roman


> Hi everyone, has anyone built a home made
> CNC pick and place machine to do SMD work?


   I have the first one built from printer parts and it works but I am
going for the second one with real guides. The linear guides are cheap
enough and will give better results. The one I have built is too big, too
ugly and too slow :-(

   Take a look at http://www.igus.com and you will find nice linear guides.
Subscribing to the http://groups.yahoo.com/group/CAD_CAM_EDM_DRO  will also
give great insight about CNC machines in general. The design I will be using
as the base for my new machine can be seen at
http://groups.yahoo.com/group/Homebrew_PCBs/files/Dscn0329.jpg . It is the
best thought machine that I have seem for the purpose we want. It is not
worth it, in my opnion and by some experience trying, to use old printe
parts for it. It is cheap enough to make one with the proper mechanical
parts. You can use simple plastic nuts to drive the screws. The only
problems is that you will need access to a mill and a lathe to make the
screws with the proper advance characteristics. You need a screw with big
advance to make the table move fast. The stepper can be stolen from any old
printer. If you decide to go to belts instead of screws for driving the
table take a look at http://www.smallparts.com . They have nice parts.

> I have an idea for a new product that will
> require lots of 0805 SMD parts and I like the
> thought of using a machine to do glue spots,
> then pick and place, then once parts are glued
> I can just hold them into a solder cauldron
> (with bamboo tongs!) to solder them in one go.

   I prefer using the machine to put solder paste and then the components
and use the toaster oven method. You do not need any glue !! Even if you use
components on both sides of the board you do not need glue at all. The
solder cauldron will probably not work, the glue could melt and the
components will not like all that heat on them. I can assure you that the
toster oven works great. I have more than 3000 boards on the streets done
that way with no returns caused by bad soldering !

> Any thoughts??

   The problems I have not adequately solved yet are how to control the Z
axis of the machine cheaply and how to take the components out of the rolls.
The Z can be controlled by a hobby servo motor and the components might be
taken from the rolls by using the Z axis vacumm pen pulling the roll and
getting the component afterwards. I have not tried that yet. Please tell me
if you have a better idea on this areas.

   I have been looking at this problem for a while and if you need more
information I might have it...

Best regards,
Alexandre Guimaraes

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2001\12\29@165703 by Dal Wheeler

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----- Original Message -----
From: Alexandre Guimarces <spam_OUTalexgTakeThisOuTspamIIS.COM.BR>
>     I have the first one built from printer parts and it works but I am
> going for the second one with real guides. The linear guides are cheap
> enough and will give better results. The one I have built is too big, too
> ugly and too slow :-(

Sorry to horg in on the conversation, but how cheap can you get linear
guides  --Production cheap?  Hobby cheap?  Tightwad cheap?  I've toyed with
this idea as well, but obviously not gotten very far with it (other than
cluttering up the basement with misc. tractor type drives gleaned off of
other equipment.)

-Dal

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2001\12\29@190307 by Aaron Blohowiak

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toaster oven? solder PASTE? wha?!?!?

woefully unaware,

Aaron
----- Original Message -----
From: "Alexandre Guimarces" <.....alexgKILLspamspam@spam@IIS.COM.BR>
To: <PICLISTspamKILLspamMITVMA.MIT.EDU>
Sent: Saturday, December 29, 2001 4:24 PM
Subject: Re: [EE:] homemade CNC pick and place


{Quote hidden}

also
> give great insight about CNC machines in general. The design I will be
using
> as the base for my new machine can be seen at
> http://groups.yahoo.com/group/Homebrew_PCBs/files/Dscn0329.jpg . It is the
> best thought machine that I have seem for the purpose we want. It is not
> worth it, in my opnion and by some experience trying, to use old printe
> parts for it. It is cheap enough to make one with the proper mechanical
> parts. You can use simple plastic nuts to drive the screws. The only
> problems is that you will need access to a mill and a lathe to make the
> screws with the proper advance characteristics. You need a screw with big
> advance to make the table move fast. The stepper can be stolen from any
old
{Quote hidden}

use
> components on both sides of the board you do not need glue at all. The
> solder cauldron will probably not work, the glue could melt and the
> components will not like all that heat on them. I can assure you that the
> toster oven works great. I have more than 3000 boards on the streets done
> that way with no returns caused by bad soldering !
>
> > Any thoughts??
>
>     The problems I have not adequately solved yet are how to control the Z
> axis of the machine cheaply and how to take the components out of the
rolls.
> The Z can be controlled by a hobby servo motor and the components might be
> taken from the rolls by using the Z axis vacumm pen pulling the roll and
> getting the component afterwards. I have not tried that yet. Please tell
me
{Quote hidden}

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2001\12\29@203713 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi,

> Sorry to horg in on the conversation, but how cheap can you get linear
> guides

   This is our list... The messages belong to all of us... We are here to
help each other.

>--Production cheap?  Hobby cheap?  Tightwad cheap?  I've toyed with
> this idea as well, but obviously not gotten very far with it (other than
> cluttering up the basement with misc. tractor type drives gleaned off of
> other equipment.)

   Here in brazil I can get 4 igus rails for about Us$ 120. It is cheaper
than spending the time to use old printer parts and not getting the job done
so well. I know that myself, I have done that :-) The guides I am talking
about may not be good enough for a router or a mill but will surely be good
enough for a pick and place machine where precision is not that critical.
Picking and placing 0805 components do not require too much precision.

   If you have any more questions fell more than free to ask.

Best regards,
Alexandre Guimaraes

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2001\12\29@204317 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi,

> toaster oven? solder PASTE? wha?!?!?
>
> woefully unaware,


   Take a look on the archives to find more details, there has been a long
thread about using small toster ovens to solder SMD boards. I will explain
briefly and after checking the old messages I can answer any doubts, ok ?

   I have been using for a while a toaster oven with a comercial
temperature controller that can make temperature "ramps" for soldering 0805
SMD components with components on both sides of the board. All you need is a
toster oven that has infrared heaters, a good temperature controller, nice
clearance between components for not making shadow areas and solder paste to
put on the components pads. The paste holds the components in place. A
vacuum twezzer will also be very helpfull. With the right temperature
profile and good board layout you can get results that are so nice that no
one can tell the boards were not soldered in a big convection oven :-)

Best regards,
Alexandre Guimaraes

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2001\12\29@213347 by Aaron Blohowiak

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Thanks! (I think i will stick with my soldering gun..)

Aaron
----- Original Message -----
From: "Alexandre Guimarces" <.....alexgKILLspamspam.....IIS.COM.BR>
To: <EraseMEPICLISTspam_OUTspamTakeThisOuTMITVMA.MIT.EDU>
Sent: Saturday, December 29, 2001 8:41 PM
Subject: Re: [EE:] homemade CNC pick and place


> Hi,
>
> > toaster oven? solder PASTE? wha?!?!?
> >
> > woefully unaware,
>
>
>     Take a look on the archives to find more details, there has been a
long
> thread about using small toster ovens to solder SMD boards. I will explain
> briefly and after checking the old messages I can answer any doubts, ok ?
>
>     I have been using for a while a toaster oven with a comercial
> temperature controller that can make temperature "ramps" for soldering
0805
> SMD components with components on both sides of the board. All you need is
a
> toster oven that has infrared heaters, a good temperature controller, nice
> clearance between components for not making shadow areas and solder paste
to
{Quote hidden}

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2001\12\30@004322 by Roman Black

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Alexandre Guimarães wrote:

> > Hi everyone, has anyone built a home made
> > CNC pick and place machine to do SMD work?
>
>     I have the first one built from printer parts and it works but I am
> going for the second one with real guides.
> The design I will be using
> as the base for my new machine can be seen at
> http://groups.yahoo.com/group/Homebrew_PCBs/files/Dscn0329.jpg .

Nice picture, ouch it's 1.4Mb though...
You seem to be getting some sag in the
middle of the gantry, you could add a cross
brace or box section to the gantry and
one supported rail would be a big improvement
compared to the 2 unsupported rails. :o)

> It is not
> worth it, in my opnion and by some experience trying, to use old printe
> parts for it. It is cheap enough to make one with the proper mechanical
> parts. You can use simple plastic nuts to drive the screws. The only
> problems is that you will need access to a mill and a lathe to make the
> screws with the proper advance characteristics. You need a screw with big
> advance to make the table move fast.

I already have some large rugged (all metal)
printer chassis, good toothed belts. My current
rig gets 6rps x 56mm = 336mm/sec, and my stepper
drivers are PIC based, giving 8 microsteps, ie
1600 usteps/rev and 28 microsteps to the mm. So
it has good power, high speed and 1/28th mm
resolution is fine for 0805 SMD stuff. With a
microstep driver most belt driven printers will
perform this well. Mine has been lugging a 2.5kg
load (head) back and forth at 300mm/sec with
never a missed step. A pick and place head should
weigh less than that.

>     I prefer using the machine to put solder paste and then the components
> and use the toaster oven method. You do not need any glue !! Even if you use
> components on both sides of the board you do not need glue at all. The
> solder cauldron will probably not work, the glue could melt and the
> components will not like all that heat on them. I can assure you that the
> toster oven works great. I have more than 3000 boards on the streets done
> that way with no returns caused by bad soldering !

Yep, oven was my first idea. I'm currently doing
solder paste by hand, and toaster oven. But, after
some tests it is a LOT slower than glue and dip
technique. Modern VCRs are made this way, they use
a heatproof red glue spot, pick and place SMD, then
wave or dip solder the board. Soldering takes about
4 seconds, even with my crude test attempts. That's
much faster and easier than in a toaster oven.
You don't need paste, which is expensive and goes
off, and it's easier to build a glue applicator
than a paste one as glue flows better.

I'm really interested in what your doing, but if
i'm going to build from scratch I still think glue
and dip is going to be better.


>     The problems I have not adequately solved yet are how to control the Z
> axis of the machine cheaply and how to take the components out of the rolls.
> The Z can be controlled by a hobby servo motor and the components might be
> taken from the rolls by using the Z axis vacumm pen pulling the roll and
> getting the component afterwards. I have not tried that yet. Please tell me
> if you have a better idea on this areas.

I have a suggestion here. Get the parts loose,
not on rolls. Sprinkle them on a white tray,
then use a cheap video camera into the PC and
just get the picker to identify the part
orientation and pick it up. You only need a video
still capture board, a cheap mono one, some
VERY easy image reconition stuff which you can
get off the net from the robot soccer guys.

I think you could use a mechanical tweezer and
rotary head, just sprinkle the parts and let it
do the rest. Gluing parts holds then very secure
if the board goes through other processes before
soldering, like having some larger parts added
to the board by hand. Gluing is also safer for
double sided boards??

So do you have any pictures of the "old ugly"
unit you are actually using now? I would love to
see it. :o)
-Roman

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2001\12\30@004334 by Roman Black

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Dal Wheeler wrote:
>
> ----- Original Message -----
> From: Alexandre Guimarces <alexgspamspam_OUTIIS.COM.BR>
> >     I have the first one built from printer parts and it works but I am
> > going for the second one with real guides. The linear guides are cheap
> > enough and will give better results. The one I have built is too big, too
> > ugly and too slow :-(
>
> Sorry to horg in on the conversation, but how cheap can you get linear
> guides  --Production cheap?  Hobby cheap?  Tightwad cheap?  I've toyed with
> this idea as well, but obviously not gotten very far with it (other than
> cluttering up the basement with misc. tractor type drives gleaned off of
> other equipment.)


Tractor drives with toothed belts are cheaply
available in any old matrix printer. They are very
fast and with a 8th step microstep driver you can get
good speeds AND resolutions. It's just handy to get
the whole assembly in one, and just attach wires...
Unless you need to move a lot of weight or need
high rigidity they work great. :o)
-Roman

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2001\12\30@021053 by Alexandre Domingos F. Souza

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>Hi everyone, has anyone built a home made
>CNC pick and place machine to do SMD work?

       Hmmm, too much work for too little trouble ;o)

>I'm thinking of doing one with a couple of
>old matrix printer chassis, they have sliders,
>belts and stepper motors ready and will do good
>speeds with 0.1mm repeatability easily.

       So tell me, HOW to do that? These are fairly common in Brazil - people around here is crazy doing plotters with old matrix printers. But how to get 0.1mm repeatability? Maximum I got was something around 1mm!! :oP

>I have an idea for a new product that will
>require lots of 0805 SMD parts and I like the
>thought of using a machine to do glue spots,
>then pick and place, then once parts are glued
>I can just hold them into a solder cauldron
>(with bamboo tongs!) to solder them in one go.

       The Yellow Box will be the size of the dip switches, eh? ;o)

>The whole operation would be almost totally
>automated. Maybe it could be automated later
>by attaching the solder cualdron to the process?
>Any thoughts??

       Well, this is not a hard thing to do. Have you tried the lutcho's pages? Full of support for personal PCB plotters and engravers. I'll look for the link here on the backup (just formatted the computer...)


---8<---Corte aqui---8<----

Alexandre Souza
@spam@taitoKILLspamspamterra.com.br
http://planeta.terra.com.br/lazer/pinball/

---8<---Corte aqui---8<----

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2001\12\30@023535 by Alexandre Domingos F. Souza

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>    The problems I have not adequately solved yet are how to control the Z
>axis of the machine cheaply and how to take the components out of the
>rolls.
>The Z can be controlled by a hobby servo motor and the components might be
>taken from the rolls by using the Z axis vacumm pen pulling the roll and
>getting the component afterwards. I have not tried that yet. Please tell me
>if you have a better idea on this areas.

       If you need only vertical moviment of the Z axis, you can use a screw driven (worm drive?) thing to move the piece up and down. It works well here.


---8<---Corte aqui---8<----

Alexandre Souza
KILLspamtaitoKILLspamspamterra.com.br
http://planeta.terra.com.br/lazer/pinball/

---8<---Corte aqui---8<----

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2001\12\30@023610 by Alexandre Domingos F. Souza

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>>     I have the first one built from printer parts and it works but I am
>> going for the second one with real guides. The linear guides are cheap
>> enough and will give better results. The one I have built is too big, too
>> ugly and too slow :-(
>Sorry to horg in on the conversation, but how cheap can you get linear
>guides  --Production cheap?  Hobby cheap?  Tightwad cheap?  I've toyed with
>this idea as well, but obviously not gotten very far with it (other than
>cluttering up the basement with misc. tractor type drives gleaned off of
>other equipment.)

       What about Deskjet encoders? It has a plastic tape inside of it that is a incremental linear position control. Anyone tried to hack that?


---8<---Corte aqui---8<----

Alexandre Souza
RemoveMEtaitoTakeThisOuTspamterra.com.br
http://planeta.terra.com.br/lazer/pinball/

---8<---Corte aqui---8<----

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2001\12\30@023843 by Alexandre Domingos F. Souza

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>toaster oven? solder PASTE? wha?!?!?
>woefully unaware,

       Look for the page of Kenneth Maxon and you will understand everything ;o)


---8<---Corte aqui---8<----

Alexandre Souza
spamBeGonetaitospamBeGonespamterra.com.br
http://planeta.terra.com.br/lazer/pinball/

---8<---Corte aqui---8<----

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2001\12\30@110039 by dpharris

picon face
Wow - blew me away at: www.users.qwest.net/~kmaxon/page/intro.htm
This guy does everything, and well.
David

"Alexandre Domingos F. Souza" wrote:

{Quote hidden}

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2001\12\30@121843 by Dale Botkin

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"Alexandre Domingos F. Souza" <RemoveMEtaitospamTakeThisOuTTERRA.COM.BR> said:

> >    The problems I have not adequately solved yet are how to control the Z
> >axis of the machine cheaply and how to take the components out of the
> >rolls.
> >The Z can be controlled by a hobby servo motor and the components might be
> >taken from the rolls by using the Z axis vacumm pen pulling the roll and
> >getting the component afterwards. I have not tried that yet. Please tell me
> >if you have a better idea on this areas.
>
>         If you need only vertical moviment of the Z axis, you can use a
screw driven (worm drive?) thing to move the piece up and down. It works well
here.
>

Hmmm...  sounds like a perfect use for an old 3.5" floppy head mechanism, or
even the head mechanism from a tape drive.

Dale

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2001\12\30@140906 by Alexandre Domingos F. Souza

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>Wow - blew me away at: www.users.qwest.net/~kmaxon/page/intro.htm
>This guy does everything, and well.

       The interesting: A friend of mine (born here in Brazil, but now he is on high school in USA) that lives near Kenneth, does the same crazy things he does. Maybe it is the air of kentucky. Sure I'll live there, hehehe


---8<---Corte aqui---8<----

Alexandre Souza
taitoEraseMEspam.....terra.com.br
http://planeta.terra.com.br/lazer/pinball/

---8<---Corte aqui---8<----

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2001\12\30@141115 by Alexandre Domingos F. Souza

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>Hmmm...  sounds like a perfect use for an old 3.5" floppy head mechanism, or
>even the head mechanism from a tape drive.

       More or less that! You can use a screw coupled to the motor, and a nut to carry the z block up and down. It works!


---8<---Corte aqui---8<----

Alexandre Souza
EraseMEtaitospamterra.com.br
http://planeta.terra.com.br/lazer/pinball/

---8<---Corte aqui---8<----

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2001\12\30@151910 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi,

> >Hmmm...  sounds like a perfect use for an old 3.5" floppy head mechanism,
or
> >even the head mechanism from a tape drive.
>
>         More or less that! You can use a screw coupled to the motor, and a
nut to carry the z block up and down. It works!

   It sounds simpler than it is in reality. The 3.5 head mechanism is very
very light and it is spring loaded. That is how they get the precision. The
head mechanism of a streamer drive is a much better option but still hard to
get it to be repeatable enough. The problems is much smaller than doing a
mill or a lathe because you do not have any forces besides the weight of the
mechanism but you still have to get everything to be perfectly square ! Even
at a good CNC lathe it is pretty hard to make 2 parallel holes if you have
to take the part out of the "holding jaws". If you have a cnc mill you still
have to make all the rails and screws adjustable. That is the main advantage
of using Roman's approach and using ready made printer mechanisms but my
experience with the mechanisms is that they have too much backslash when
they change direction and that may not be repeatable. For anyone that wants
to make that for a professional use I still recommend going from the ground
up with real machine parts. Look closely at K. Maxon design of the mill and
you will see that all the parts were put together with allen screws to make
it adjustable. Is is much harder than it looks, specially for milling. The
link I sent on the other messages is the simplest clean gantry design that I
have found. the only problem is that you have really to use good guides
because it is driven from just one side and can stop if it skews too much.
You can not get much simpler than that. Belt drive is definitely a good
option because the acme screw precision is too much for the application.

Best regards,
Alexandre Guimaraes

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2001\12\30@194522 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi,

> Nice picture, ouch it's 1.4Mb though...
> You seem to be getting some sag in the
> middle of the gantry, you could add a cross
> brace or box section to the gantry and
> one supported rail would be a big improvement
> compared to the 2 unsupported rails. :o)

   I do not thing it makes a difference for the kind of weight it is
carrying. The rails are oversized and remember that you do not have drag as
in a mill.

> it has good power, high speed and 1/28th mm
> resolution is fine for 0805 SMD stuff.

   How about the repeatability and backslash ? Those are the problems I
have seem on the printer mechanisms I used. The printing head support was
too loose without the belts being too tight. I had to put another support on
the mechanism to tighten the belt well enough. On the printers I used you
had a preset compensation for the backslash. If you go the printer way try
to modify it as little as possible. I used just the parts and made all the
mechanics again.

   Do you need just one machine ? I plan to have a solution that can scale
up with my production. That is another reason to go for comercial new parts.

{Quote hidden}

   Loctite has some nice solutions in that area and you can even use 454
gel cyanoacrilate !! It works great !! The only problem is that you need a
good dispenser for it. Dispensing paste is not that critical, specially if
you use water at the end of the system. Water does not compress so it is
easier to control the time and pressure as the syringe goes down. You just
have to control the time and pressure and it is quite repeatable.

   Wave solder is ok if you glue and have a very controlled fluxing and
cleaning of the board but I would never trust dipping a critical board ! You
will stress every component over their specs ! It is ok for toys and low
cost consumer products that do not have to work for too long or for the
twainese manufacturers that never see the end customer. Keeping the solder
clean is also a big problem and you will probably get a big number of bad
joints whenever the operator changes mood ! There are inexpensive wave
soldering machines around, there are small ones for short run productions.
There are also fast ovens but they are surely not inexpensive.

> I'm really interested in what your doing, but if
> i'm going to build from scratch I still think glue
> and dip is going to be better.

   If the production is too big I would go for the comercial machinery or
let a factory do it for you. It may not be worth the risc. My production
levels do not allow sending them out and I cannot handle it without some
automation, that is the reason I went to the house made solution. It is
dependable and repeatable but not too fast or energy efficient. You could
try making a 3 or 5 zone oven. All you would need are some pizza oven
conveyors, some infrared heaters and temperature controllers. The problems
is that a 3 zone oven gives much worse results the a well controlled toaster
oven !!! I tried that and the oven manufacturer got really dissapointed. If
you really decide to go to the dip solution make sure you can get a hold of
some xray inspection equipament to really see how the solder joints are. It
can be very dangerous to put some thousands of boards out and find out that
10% of the joints fail in 2 years !! It may happen and actually has happened
many times with trough hole components. I am sure you have already got some
of your TV's with boards full of cold solder joints. Solder paste and oven
is the most reliable way to do it, not the fastest or the cheapest.

> I have a suggestion here. Get the parts loose,
> not on rolls. Sprinkle them on a white tray,
> then use a cheap video camera into the PC and
> just get the picker to identify the part
> orientation and pick it up. You only need a video
> still capture board, a cheap mono one, some
> VERY easy image reconition stuff which you can
> get off the net from the robot soccer guys.

   Hey, that is a really cool idea ! The main problem would be to correlate
the real position of the components to the distorted camera view and to
solve the problem of refilling the trays and making sure that you do not
have one component over the other or on the back side when using SOT23
transistors ! It is pretty hard to get the components out of the rolls and
not flip half of them on their back side. I am really not sure what would be
easier, a roll feeding system or the camera.

> I think you could use a mechanical tweezer and
> rotary head, just sprinkle the parts and let it
> do the rest.

   Believe me on this one :-) It is easier with the vaccum tweezer. You
just turn the vaccum on and them rotate the component to whatever position
you need. With the mechanical tweezer you have to get the right force and
will have to rotate the head 2 times to get the job done. The first time to
grab the component and the second to put it at the right orientation at the
board.

> Gluing parts holds then very secure
> if the board goes through other processes before
> soldering, like having some larger parts added
> to the board by hand.

   Gluing is ok but if you go for the oven it is another step. By my
experience it is completely unecessary for small parts or parts that go on
the top side of the board.

> Gluing is also safer for
> double sided boards??

   I also thought that way and got glue from loctite for the components on
the bottom of the board. I still have the glue on the fridge and never used
it after the first day ! The only components that insist on falling once in
a while are the AVX surge supressors. They are pretty dense and fall once in
a while. If you get the right solder paste the surface tension is more than
enough to hold the components on the bottom side.

> So do you have any pictures of the "old ugly"
> unit you are actually using now? I would love to
> see it. :o)

   Unfortunately I have not taken any pictures and I got a small pneumonia
( is that the right spelling ) and the doctor made me promise I would stay
put at home :-( It is not being used at all ! It did not get to be good
enough and I decided to make another one before using it with components. It
can draw nice rectangles and squares but I have not finished the pick and
place part of the software. Is is an very ugly plotter with very bad
resolution :-) I will take some pictures as soon as the doctor let's me get
out of home... I will send them to you privately..


best regards,
Alexandre Guimaraes

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'[EE:] homemade CNC pick and place'
2002\01\04@083559 by Roman Black
flavicon
face
Alexandre Guimarães wrote:

THANKS Alexandre for the excellent info you provided,
and sorry I didn't reply sooner but I have been busy
in the workshop. :o)

> > it has good power, high speed and 1/28th mm
> > resolution is fine for 0805 SMD stuff.
>
>     How about the repeatability and backslash ? Those are the problems I
> have seem on the printer mechanisms I used. The printing head support was
> too loose without the belts being too tight.


It depends on the quality of the printer mechanism.
I have some 15" NEC Pinwriters from mid 80's that
are VERY rugged, full steel chassis and 2 large steel
rails. Some of the smaller printers are not good at
all. One of my 15" printer chassis cost me $5 and
has a 25mm hardened rail with PB bearings! Don't
ignore good old printers.

I just chose a chassis to make a CNC PAP (PNP?) machine,
it's a 15" unit with steel cable drive from motor
to carriage, even less backlash than a belt. Even my
belt chassis get a lot less than 0.1mm backlash, the
cable driven unit will be good for 0.05mm repeatability.
How accurate do you need for 0805 placement? I'm sure
even 0.1mm will be ok.

>     Do you need just one machine ? I plan to have a solution that can scale
> up with my production. That is another reason to go for comercial new parts.

Sure, but you are obviously doing the volumes to need
good machinery. I'm still sticking parts on boards
with tweezers and a magnifying glass! The thing i'm
making will do 300mm x 120mm, perfect for pick and
place on small boards.

>     Loctite has some nice solutions in that area and you can even use 454
> gel cyanoacrilate !! It works great !! The only problem is that you need a
> good dispenser for it. Dispensing paste is not that critical, specially if
> you use water at the end of the system. Water does not compress so it is
> easier to control the time and pressure as the syringe goes down. You just
> have to control the time and pressure and it is quite repeatable.

OK, you've convinced me to drop the glue idea and
just dispense solder paste direct to the board. :o)
How do you mix the water with the paste, what sort
of applicator nozzle, pump etc are you using?? I thought
of standard size rubber hose in a simple peristaltic
pump turned by a stepper motor. That should dispense
dots and also lines of paste quite well.

>     Wave solder is ok if you glue and have a very controlled fluxing and
> cleaning of the board but I would never trust dipping a critical board ! You
> will stress every component over their specs !

Not totally true, but i'm going to trust you and
stick to the paste and oven method for now as you
suggested. You helped me so much before with my
manual toaster oven system. :o)


>     If the production is too big I would go for the comercial machinery or
> let a factory do it for you. It may not be worth the risc. My production
> levels do not allow sending them out and I cannot handle it without some
> automation, that is the reason I went to the house made solution. It is
> dependable and repeatable but not too fast or energy efficient.

My oven system is working well, thanks in part
to your temperature charts etc. I'm approaching
that point where it's a pain to tweezer tiny parts
by hand, and a machine that does the SMD placement
will be a big help. But I don't need high speeds
or quantities.


{Quote hidden}

You don't have to buy on the roll. In 1k
quantities you can often choose loose or rolled.
I see the only real work is pouring the parts
on a tray, making sure they are right side up.
Parallex error shouldn't be too much problem if
the camera is 40cm or so from the tray. I can live
with some manual parts fiddling, anything is much
better than placing with hand held tweezers. :o)


>     Believe me on this one :-) It is easier with the vaccum tweezer. You
> just turn the vaccum on and them rotate the component to whatever position
> you need. With the mechanical tweezer you have to get the right force and
> will have to rotate the head 2 times to get the job done. The first time to
> grab the component and the second to put it at the right orientation at the
> board.

Ok, you've sold me on the vacuum tweezer. Are tips
commonly available? What type of vacuum pump are
you using? I have a vac solenoid from a bike fuel
injection system, a high speed one. Any suggestions
on how to set it up? Does it ever drop parts?

> > Gluing is also safer for
> > double sided boards??
>
>     I also thought that way and got glue from loctite for the components on
> the bottom of the board. I still have the glue on the fridge and never used
> it after the first day ! The only components that insist on falling once in
> a while are the AVX surge supressors. They are pretty dense and fall once in
> a while. If you get the right solder paste the surface tension is more than
> enough to hold the components on the bottom side.

Good information, thank you again.
Any help you can provide on the CNC PNP stuff
will be very much appreciated. :o)
-Roman

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2002\01\04@090954 by Simon-Thijs=20de=20Feber?=

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Hello,


I have a source for membrame pumps.
These are used in professional printing press /
publisher.

These are very suitable for providing air to .......
(your paste dispencer ??)
The problem would be how to turn the airflow off !?
(A valve ???)
And they work on 220 VAC.


grtz


Simon





--- Roman Black <RemoveMEfastvidEraseMEspamEraseMEEZY.NET.AU> wrote: >
Alexandre Guimarces wrote:
{Quote hidden}

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2002\01\04@222225 by 859-1?Q?Alexandre_Guimar=E3es?=

flavicon
face
Hi,

> THANKS Alexandre for the excellent info you provided,
> and sorry I didn't reply sooner but I have been busy
> in the workshop. :o)

   My pleasure...

> How accurate do you need for 0805 placement? I'm sure
> even 0.1mm will be ok.

   Absolutely... Even 0.5 mm should be ok if it is repeatable and not
cumulative.

> >     Do you need just one machine ? I plan to have a solution that can
scale
> > up with my production. That is another reason to go for comercial new
parts.
>
> Sure, but you are obviously doing the volumes to need
> good machinery. I'm still sticking parts on boards
> with tweezers and a magnifying glass! The thing i'm
> making will do 300mm x 120mm, perfect for pick and
> place on small boards.

   You are using mechanical tweeezers because you like to suffer !!!! :-)
Just get an aquarium pump and get you vacuum tweezers done with some hot
glue !!! It is very easy.. Many aquarium pumps can be altered to make
vacuum. You will need very little vacuum and the needles can be bought in
any dimension you want from http://www.smallparts.com . You can also use a
hipodermic needle number 8. works as a charm if you cut it carefuly with
small pliers and sand it afterwards. For the handle go to the medical
equipament store and by some "silicon tubing". You do not even need to turn
the vacuum on and off ! Just use the right vacuum and it will pick up the
parts without solder paste and not pick up after they are put over the
solder paste !!! It works and is fast and easy. You just have to play around
to make the "right vacuum" and a comfortable handle.

> OK, you've convinced me to drop the glue idea and
> just dispense solder paste direct to the board. :o)

   Do not drop the glue idea !! You can make it work if you go to a wave
machine, just do not fry yours boards :-) I am just not sure that it is the
best way for low volumes.

> How do you mix the water with the paste, what sort
> of applicator nozzle, pump etc are you using??

   DO NOT MIX the paste with water !! You can put water behind the syringe
and after your solenoid air valve ! I do not use it because my people prefer
to control the dispensing time by hand and I just use a solenoid air valve
and a pressure regulator set to about 20 PSI. The water will help when you
are doing automatic timed dispensing and you need as little variation as
possible. If you are dispensing by hand it is not needed.

> I thought
> of standard size rubber hose in a simple peristaltic
> pump turned by a stepper motor. That should dispense
> dots and also lines of paste quite well.

   I use a paiting air compressor. They are cheap and work very well. Just
have a big air cylinder and you can turn the compressor on just once or
twice a day. I live the air line with just 40 PSI on it so I have very low
risk. I tried many small pumps and they all make too much noise and end up
costing more than a good membrane pump. Just go to the hardware store. For
the cylinder to hold air I use disposable freon cylinders. Very cheap ( free
most of the time) and reliable enough for 40 PSI ! The solenoid air valves
should not be hard to find also.

> My oven system is working well, thanks in part
> to your temperature charts etc. I'm approaching
> that point where it's a pain to tweezer tiny parts
> by hand, and a machine that does the SMD placement
> will be a big help. But I don't need high speeds
> or quantities.

   Like I said before.... You use mechanical tweezers because you like to
suffer :-) Just go to the pet shop and select an aquarium pump that can make
vacuum, go to the medical supply store and grab different gauge silicon
tubing to connect it and make the handle and prepare a needle for it. You
should spend a few bucks and get it done with minimum effort. Afterwards
they me how it worked. It is cheap and simple...

> You don't have to buy on the roll. In 1k
> quantities you can often choose loose or rolled.
> I see the only real work is pouring the parts
> on a tray, making sure they are right side up.
> Parallex error shouldn't be too much problem if
> the camera is 40cm or so from the tray. I can live
> with some manual parts fiddling, anything is much
> better than placing with hand held tweezers. :o)

   We should talk off list about this.... Sound like a very good idea to
make the mechanical problems smaller.

> Ok, you've sold me on the vacuum tweezer. Are tips
> commonly available? What type of vacuum pump are
> you using? I have a vac solenoid from a bike fuel
> injection system, a high speed one. Any suggestions
> on how to set it up? Does it ever drop parts?

   Go for the aquarium pump. If you get the air compressor to work make a
search for "venturi vacuum pumps" and you can find an even cleaner solution.
I use both the aquarium and the venturi pumps and both work great. The vac
solenoid is not the best option in my opnion.

Best regards,
Alexandre Guimaraes

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2002\01\05@045843 by Nick Ray

flavicon
picon face
An interesting project, Roman.

I was wondering how are you going to align the head with the PCB or your
"home" datum? One of the problems I encountered in making a homebrew drill
was repeatability of the IR sensors used to detect the home position. That
may have just been due to the tolerance of the sensor itself (parts from
circa 1980) or incidental light affecting it. It wasn't a big issue at the
time as I used to drill-then-etch.

Don't forget that printers are pretty hot on relative accuracy, but in terms
of absolute positioning of the image on the paper tolerances of >1mm are
considered the norm.

You can see my 1st attempt at
http://www.mailmaster.freeserve.co.uk/ncdrill/drill.htm Boy it's hard work
without machine tools! The main problems I had were belt backlash and the
12mm rods flexing. Actually, because prototype PCBs are so cheap now I just
use it for routing cut-outs in front panels.

Nick

> {Original Message removed}

2002\01\05@062628 by Roman Black

flavicon
face
Simon-Thijs de Feber wrote:
>
> Hello,
>
> I have a source for membrame pumps.
> These are used in professional printing press /
> publisher.
>
> These are very suitable for providing air to .......
> (your paste dispencer ??)
> The problem would be how to turn the airflow off !?
> (A valve ???)
> And they work on 220 VAC.

Thanks Simon. :o)
Whats the source for the pumps?
I already have a vacuum solenoid (12v)
from a Suzuki motorcycle fuel injection
system, it is a SPDT airflow if that makes
sense.
-Roman

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2002\01\05@081845 by Roman Black

flavicon
face
Nick Ray wrote:
>
> An interesting project, Roman.
>
> I was wondering how are you going to align the head with the PCB or your
> "home" datum? One of the problems I encountered in making a homebrew drill
> was repeatability of the IR sensors used to detect the home position. That
> may have just been due to the tolerance of the sensor itself (parts from
> circa 1980) or incidental light affecting it. It wasn't a big issue at the
> time as I used to drill-then-etch.

IR sensor repeatability is fine, but you need to
reference it to the particular full step. Ie the
A+A+ full step. The belts give 56mm per rotation,
so that is:
56mm / (200 / 4) =  1.12mm per A+A+ step
if that makes sense. No problems there, but keeping
ambient light off the IR sensor is important too. :o)


{Quote hidden}

Thats a very nice machine and thanks for the
link! I like the way you built so much with just
a few simple pieces. Is this a recent project?
Are you considering modifying your machine to
do SMD pick and place too?
-Roman


> > {Original Message removed}

2002\01\05@083342 by Roman Black

flavicon
face
Alexandre Guimarães wrote:

> > How accurate do you need for 0805 placement? I'm sure
> > even 0.1mm will be ok.
>
>     Absolutely... Even 0.5 mm should be ok if it is repeatable and not
> cumulative.


>     You are using mechanical tweeezers because you like to suffer !!!! :-)
> Just get an aquarium pump and get you vacuum tweezers done with some hot
> glue !!! It is very easy.. Many aquarium pumps can be altered to make
> vacuum. You will need very little vacuum and the needles can be bought in
> any dimension you want from http://www.smallparts.com . You can also use a
> hipodermic needle number 8. works as a charm if you cut it carefuly with
> small pliers and sand it afterwards. For the handle go to the medical
> equipament store and by some "silicon tubing". You do not even need to turn
> the vacuum on and off ! Just use the right vacuum and it will pick up the
> parts without solder paste and not pick up after they are put over the
> solder paste !!! It works and is fast and easy. You just have to play around
> to make the "right vacuum" and a comfortable handle.

You are a legend Alexandre. :o) I have an aquarium
air pump and some needles I bought to use with
the solder paste syringe. Are these the right
type? So you just use the metal tube needle,
filed flat on its end, as the bit that touches
the SMD? I thought it had to be rubber or something
but your way sounds very easy to make. The aquarium
pump hose will match up to my vacuum solenoid too,
same size rubber hose.

> > How do you mix the water with the paste, what sort
> > of applicator nozzle, pump etc are you using??
>
>     DO NOT MIX the paste with water !! You can put water behind the syringe
> and after your solenoid air valve ! I do not use it because my people prefer
> to control the dispensing time by hand and I just use a solenoid air valve
> and a pressure regulator set to about 20 PSI. The water will help when you
> are doing automatic timed dispensing and you need as little variation as
> possible. If you are dispensing by hand it is not needed.

Ok, I understand now. With regulated pressure and
controlled time you can get fairly exact quantity
of paste dispensed. But is this suitable for the
repeated tiny paste spots needed to use 0805 SMD
parts?? And does the consistency of the solder
paste change over time and cause problems with
dispensing an accurate spot each time?

{Quote hidden}

It is so great to hear from someone actually
doing it. Experience is quality. :o)

>     We should talk off list about this.... Sound like a very good idea to
> make the mechanical problems smaller.

Will do. :o) But i'm hoping that people aren't
objecting too much to this SMD CNC topic? I would
think there must be a lot of us doing small
quantity manufacturing that would like a cheap
SMD pick and place machine.
-Roman

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2002\01\05@084202 by Tim McDonough

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face
>     We should talk off list about this.... Sound like a very good idea to
> make the mechanical problems smaller.

>Will do. :o) But i'm hoping that people aren't>
>objecting too much to this SMD CNC topic? I would
>think there must be a lot of us doing small
>quantity manufacturing that would like a cheap
>SMD pick and place machine.
>-Roman

Wait! How about just changing to [OT]: ? This has been a very interesting
exchange of information.

Tim

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2002\01\05@090940 by 859-1?Q?Alexandre_Guimar=E3es?=

flavicon
face
Hi,

> You are a legend Alexandre. :o) I have an aquarium
> air pump and some needles I bought to use with
> the solder paste syringe. Are these the right
> type? So you just use the metal tube needle,
> filed flat on its end, as the bit that touches
> the SMD? I thought it had to be rubber or something
> but your way sounds very easy to make. The aquarium
> pump hose will match up to my vacuum solenoid too,
> same size rubber hose.

   Hey, you make me blush :-) These crazy ideas is what I always liked the
most about the piclist.. We are not afraid of doing it in some different
way.

   The parts are so small and the vacuum so little that you will never hurt
the parts not using rubber. Your description is perfect. Just file flat the
needle. If you make the vacuum small enough the parts will fall off the
needle as soon as they touch the solder paste !!! Works so good that you
might want to forget about the automatic pick and place alltogether :-(
Please don't.......

> Ok, I understand now. With regulated pressure and
> controlled time you can get fairly exact quantity
> of paste dispensed. But is this suitable for the
> repeated tiny paste spots needed to use 0805 SMD
> parts?? And does the consistency of the solder
> paste change over time and cause problems with
> dispensing an accurate spot each time?

   You can have more than 30% errors without any trouble at all. Just make
the pads for the components bigger than the ones your software tells you.
The consistency do change with temperature, pressure and number of
repetitions but not enough to cause problems.

> Will do. :o) But i'm hoping that people aren't
> objecting too much to this SMD CNC topic? I would
> think there must be a lot of us doing small
> quantity manufacturing that would like a cheap
> SMD pick and place machine.

   I am curious of how many people actually have this kind of problem... I
always fell that we are a group that basically has the hobbyist, the
independent consultors and the guys with the big companies that can spend
lots of money on equipament. Maybe I am wrong. If no one objects I guess if
on topic enough for the [EE:] tag. At least we do not have any cows involved
yet :-)

Best regards,
Alexandre Guimaraes

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2002\01\05@104413 by David VanHorn

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At 07:38 AM 1/5/02 -0600, Tim McDonough wrote:
> >     We should talk off list about this.... Sound like a very good idea to
> > make the mechanical problems smaller.
>
> >Will do. :o) But i'm hoping that people aren't>
> >objecting too much to this SMD CNC topic? I would
> >think there must be a lot of us doing small
> >quantity manufacturing that would like a cheap
> >SMD pick and place machine.
> >-Roman
>
>Wait! How about just changing to [OT]: ? This has been a very interesting
>exchange of information.

I could invite you all over to the ez_bake group at yahoogroups.
I started it for people who use toaster ovens to do SMD, but we haven't had
a lot to say lately.

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2002\01\05@120947 by Dal Wheeler

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Do you have a picture you could share of this smd needle pickup doohicky?
It doesn't have a vacuum break valve on it?
{Original Message removed}

2002\01\05@122227 by 859-1?Q?Alexandre_Guimar=E3es?=

flavicon
face
Hi,

> Do you have a picture you could share of this smd needle pickup doohicky?
> It doesn't have a vacuum break valve on it?


   I think I will even try ascii art for the first time in my life :-) It
is as simple as it can be. Just put a neddle that you have cut and filed
flat inside a silicon tube of appropiatte diameter and it is done. It is
even quite comfortable ! You do not need the break valve if the vacuum is
just strong enough to just barely hold the parts. They will fall off with
the surface tension of the solder paste. The parts are much lighter than we
can imagine. The only problem is with round parts, that we usually grab with
mechanical tweezers or use stronger vacuum and a break valve. This decision
I live for the operator, they usually use the mechanical tweezer for round
parts.


   ----------------
               ----
                   \-------
                   /-------
               ----
   ----------------


   If the vacuum is too strong and the parts are not "gluing" to the solder
paste just make a small hole on the side of the needle and you should be
fine.

   By the way... I forgot to mention that the needle eventually "glogs"
with the solder paste and you need either to change it or "deglog" it with a
small "accupunture" needle ! These needles are quite strong and
exceptionally thin..

best regards,
Alexandre Guimaraes

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2002\01\05@143042 by Alexandre Domingos F. Souza

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face
>I could invite you all over to the ez_bake group at yahoogroups.
>I started it for people who use toaster ovens to do SMD, but we haven't had
>a lot to say lately.

       I'd prefer to see this thread here, after all the SMD machines uses PIC! ;oD


---8<---Corte aqui---8<----

Alexandre Souza
KILLspamtaitospamBeGonespamterra.com.br
http://planeta.terra.com.br/lazer/pinball/

---8<---Corte aqui---8<----

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2002\01\06@035251 by Roman Black

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Alexandre Guimarães wrote:
{Quote hidden}

Hi Alexandre, this "glogging" might be a problem
when using the CNC placer. I really would like 100%
pick up reliability without glogging. :o)

Would the addition of a vacuum solenoid, as I was
planning, to turn the vacuum off before the tube
is removed from the top surface of the part, fix
this problem? Obviously there would be accurate
placement of the solder paste in MINIMUM quantity,
and hopefully accurate placement of the part
on top of the paste, surely this would keep the
paste away from the opening of the vacuum nozzle??

Since my vacuum solenoid is a SPDT type I can
feed one tube with vacuum and the other with a
small pressure from the other end of the aquarium
pump. Then when it places the part the nozzle
switches from "suck" to a slight "blow" to really
help drop the part without sucking in any solder
paste. That would be pretty easy.
Any suggestions?
-Roman

PS. And I would want the machine to be able to
pick and place round parts like SMD diodes too,
even if it means fitting a different nozzle
before doing those parts. :o)

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2002\01\06@041006 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi,

> Hi Alexandre, this "glogging" might be a problem
> when using the CNC placer. I really would like 100%
> pick up reliability without glogging. :o)

   The problem would not happen at all with a CNC setup. It is caused by
the operator misplacing the needle when putting the component on the right
place. It is also very dependent on the operator, some have to clean the
needle many times a day and others once a week !

> Would the addition of a vacuum solenoid, as I was
> planning, to turn the vacuum off before the tube
> is removed from the top surface of the part, fix
> this problem? Obviously there would be accurate
> placement of the solder paste in MINIMUM quantity,
> and hopefully accurate placement of the part
> on top of the paste, surely this would keep the
> paste away from the opening of the vacuum nozzle??

   On the CNC setup you have to have the valve and it would indeed keep the
paste away from the needle. The component can be move a little further away
from the paste and dropped over it. When you do it by hand you actually
press the component over the solder paste.

> Since my vacuum solenoid is a SPDT type I can
> feed one tube with vacuum and the other with a
> small pressure from the other end of the aquarium
> pump. Then when it places the part the nozzle
> switches from "suck" to a slight "blow" to really
> help drop the part without sucking in any solder
> paste. That would be pretty easy.
> Any suggestions?

   I do not think you would need the blow. It should fall down by it's own
weight. If you use the blow it needs to be really slight or you will blow
the paste and the component away.

> PS. And I would want the machine to be able to
> pick and place round parts like SMD diodes too,
> even if it means fitting a different nozzle
> before doing those parts. :o)

   No need to change needles. Just use a stronger vacuum and the solenoid
valve. That is how some of the operators do with the manual setup. Most
prefer to pick the round components with a mechanical tweezer and some use a
stronger vacuum and the solenoid valve.

   The manual and automatic setup are quite different beasts. In the manual
setup using a stronger vacuum is not the best way because you need to use
the valve and use both hands or a foot switch to drop the components over
the solder paste. If you use a very light vacuum the solder paste surface
tension will "suck" the component from the needle. You can get the job done
with just one hand. On the automatic setup the vacuum can be much stronger
and round components are no problem at all.

Best regards,
Alexandre Guimaraes

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2002\01\06@074627 by Simon-Thijs=20de=20Feber?=

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I can send you one if you are interested.
He is from my home town and buys his materials from
companies with over-stock or who went broke.
And he sells it to privates on Electronic bazars abd
etc.


grtz

Simon


--- Roman Black <.....fastvidspam_OUTspamEZY.NET.AU> wrote: >
Simon-Thijs de Feber wrote:
{Quote hidden}

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2002\01\06@075038 by Simon-Thijs=20de=20Feber?=

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About the vacuum tweezers .............

You can buy manual chip suckers with different heads.
Probably one those will fit.

grtz

Simon

--- Alexandre_Guimarces <.....alexgspamRemoveMEIIS.COM.BR> wrote: >
Hi,
{Quote hidden}

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2002\01\06@114619 by Roman Black

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Thanks again Alexandre. :o)
I've been checking some stuff and I'm getting pretty
keen on this machine. The problem of getting high
speeds and good accuracy I think is sorted by using the
nice 15" printer chassis with the cable drive, and
8th step or 16th step microstep drivers. I already
have 8th step drivers (1600 steps/rev) but want to get
some boards made because i'm sick of veroboarding
them.

Looks like i've decided to go the opposite way to your
machine (in the picture) and keep the travel distances
short and build a small, very light machine to try to
keep speeds high, instead of a big sturdy mill.

Imagine something NOT like a gantry mill, but more
like a box on a rail. 300mm travel. The box has a short,
light unsupported arm out one side, with a head travel
of about 140mm. The arm is light and the head is lighter.
I've been toying with the idea of using long bent tubes,
one for the paste applicator tip, and a rotateable one
for the vacuum tweezer. These have small lightweight
stepper motors, (from disk drives maybe?), to lower and
lift the tubes. Have you ever seen inside a pen/chart
plotter machine? The long thin pen arms can move very
fast, and no real strength is needed for PNP, only speed
and accuracy. :o)

So I get only 300 x 140mm work area, maybe less, but
the work area is on the corner and can fit large boards
if they are partially hanging out. The advantage is
a fast action, i'm hoping for 1 to 2 PNP's per second,
from a machine basically built from junk but with
good microstep motor drivers. I don't see the small
work area as much of a sacrifice to get a fast and
portable sized machine. Something you could put on
the back seat of a car and take to a friends place,
plug it into their PC and it's running.
-Roman


Alexandre Guimarães wrote:

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2002\01\06@144646 by Robert Rolf

picon face
If you want speed, remember that you don't have to microstep your
drives until you get near your final position. And using an
acceleration profile also allows for a higher maximum step rate.
I assume also, that you are using constant current drivers which
allow for higher rates than the primative drivers typically used
with old printer motors.

And you might also want to consider adding one of those small
single board video cameras to the head to allow for continuous
inspection of the work as the parts are placed. Also makes for
easier indexing of the boards.

Robert

Roman Black wrote:
{Quote hidden}

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2002\01\06@161810 by Jafta

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Here is another link for a CNC drill

Regards

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2002\01\06@182200 by Russell McMahon

picon face
>     No need to change needles. Just use a stronger vacuum and the solenoid
> valve. That is how some of the operators do with the manual setup. Most
> prefer to pick the round components with a mechanical tweezer and some use
a
> stronger vacuum and the solenoid valve.
>
>     The manual and automatic setup are quite different beasts. In the
manual
> setup using a stronger vacuum is not the best way because you need to use
> the valve and use both hands or a foot switch to drop the components over
> the solder paste.


You could build a valve into the handpiece to keep it one handed - either a
squeeze to break vacuum or a squeeze to apply it. Breaking vacuum could be
as simple as flattening a silicon rubber tube. Or you could have a simple on
/ off valve in the handpiece - or perhaps a "vent to atmosphere" that
shunted vacuum away from the needle tip.




       Russell McMahon

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2002\01\06@190619 by Brandon Fosdick

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Roman Black wrote:
> >     Hey, that is a really cool idea ! The main problem would be to correlate
> > the real position of the components to the distorted camera view and to
> > solve the problem of refilling the trays and making sure that you do not
> > have one component over the other or on the back side when using SOT23
> > transistors ! It is pretty hard to get the components out of the rolls and
> > not flip half of them on their back side. I am really not sure what would be
> > easier, a roll feeding system or the camera.
>
> You don't have to buy on the roll. In 1k
> quantities you can often choose loose or rolled.
> I see the only real work is pouring the parts
> on a tray, making sure they are right side up.
> Parallex error shouldn't be too much problem if
> the camera is 40cm or so from the tray. I can live
> with some manual parts fiddling, anything is much
> better than placing with hand held tweezers. :o)

The video system sounds pretty easy. Some of the other students in my
lab are working on video systems using cheap components (web cam, OS
software, etc...) and based on what they're accomplishing I think what
you want to do should be relatively easy. But it seems like using a roll
would be even easier. That way the parts are all within a smaller known
area and always right side up. The feed mechanism could be similar to a
reel-to-reel camera. You would need a third wheel to peel off the cover,
and I'm not sure how you would get the first and last few parts off the
roll, but other than that it should be easy.

Sticking with the video pick-up system for a sec...instead of dumping
the parts onto any old flat white surface, you could make a series of
parallel fences on the white surface and put different parts into each
"chute". That would restrict the possible area that each part could be
in and make it easier to accomodate multiple types of parts
simultaneously.

About the vaccuum tweezers...How do you determine the position of the
part wrt to the tweezers once its been picked up? Do you assume that the
tweezer drive system always picks up the part in the same spot?

Don't you dare move this thread someplace else. I don't want to have to
sub to yet another list (YAL) just to follow this thread.

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2002\01\06@201334 by Benjamin Bromilow

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>Breaking vacuum could be as simple as flattening a >silicon rubber tube. Or
you could have a simple on / off >valve in the handpiece - or perhaps a
"vent to >atmosphere" that shunted vacuum away from the needle >tip.

Try a hole in the side of the tubing. Place finger over tube to create
suction, remove finger to relieve suction. Works in the medical profession
(making an impromtu ventilator from some tubing and an O2 supply except then
it is the other way round ie +ve pressure!).......
Also if gunging of the needle is a problem- couldn't a switch be used to
blow air down the needle instead of sucking up it. Maybe a foot pedal. Blow
out all the goo??

Ben

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2002\01\06@203358 by David VanHorn

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>
>
>Try a hole in the side of the tubing. Place finger over tube to create
>suction, remove finger to relieve suction.


I have a pro version of this which I picked up cheap.
It uses this technique, on a metal pen-shaped body, with bent syringe tips,
that have little rubber suction cups for different sized parts.

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2002\01\07@053212 by Roman Black

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Robert Rolf wrote:
>
> If you want speed, remember that you don't have to microstep your
> drives until you get near your final position.

That's ok, i'm getting 16000 usteps/sec from my
PC parallel port with no difficulties and that's
10 revs/sec or over 1/2 metre a second, it's the
mechanicals that are almost breaking up at that
speed. :o)

> And using an
> acceleration profile also allows for a higher maximum step rate.

Good point, and yes I do that. The best I can
get with crude acceleration is 1% faster every
microstep, looks pretty impressive, revs the motor
to 10revs/sec top speed getting there in about
HALF of a revolution. With a 2kg weight cariage it
makes quite a bit of G force, on accel/decel it
literally throws the entire machine side to side!
This is one reason that swung me towards making
the entire carriage and arm light, the machine
is capable of 2 PNPs/second now but it makes
a spin dryer look stable. There are a couple of
resonance spots in the accel ramp (as you expect)
but i've got enough accel now without having to
compensate them.

> I assume also, that you are using constant current drivers which
> allow for higher rates than the primative drivers typically used
> with old printer motors.

Yep. 25v. But i'm only using a low perf stepper
at the moment, a 5v 1a high inductance 1980s style
motor. It's scary to think how fast it would be
with a modern 1v 5A motor. :o)

> And you might also want to consider adding one of those small
> single board video cameras to the head to allow for continuous
> inspection of the work as the parts are placed. Also makes for
> easier indexing of the boards.

Not on the head, but now you mention it that is a
good idea!
-Roman

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2002\01\07@064113 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi, Russel

> You could build a valve into the handpiece to keep it one handed - either
a
> squeeze to break vacuum or a squeeze to apply it. Breaking vacuum could be
> as simple as flattening a silicon rubber tube. Or you could have a simple
on
> / off valve in the handpiece - or perhaps a "vent to atmosphere" that
> shunted vacuum away from the needle tip.

   We used the "vent to atmosphere" and it is incredible how small 0805
parts really are ! When you move your finger away from the hole you move the
part ! I also tried a very ligth microswitch and the operator get's tired in
one or 2 hours ! The best way, by our experiments, is still using a light
vacuum that makes the part fall when it touches the solder paste. That is
for manual pick and place, obviuosly. For automatic you can use much stronge
vacuum.

Best regards,
Alexandre Guimaraes

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2002\01\07@070914 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi,

> The video system sounds pretty easy. Some of the other students in my
> lab are working on video systems using cheap components (web cam, OS
> software, etc...) and based on what they're accomplishing I think what
> you want to do should be relatively easy. But it seems like using a roll
> would be even easier. That way the parts are all within a smaller known
> area and always right side up. The feed mechanism could be similar to a
> reel-to-reel camera. You would need a third wheel to peel off the cover,
> and I'm not sure how you would get the first and last few parts off the
> roll, but other than that it should be easy.

   The roll pick up system is simple and stable, for sure. The only problem
is that you have to remake all the mechanics for 25 times if you have 25
different components values ! You would need 25 motors or solenoids and all
the control system that goes with it. My idea on that is a little different.
I would use the pick up head to pull the roll and position the components at
the right place. This way I can stay away from 25 motors !

> Sticking with the video pick-up system for a sec...instead of dumping
> the parts onto any old flat white surface, you could make a series of
> parallel fences on the white surface and put different parts into each
> "chute". That would restrict the possible area that each part could be
> in and make it easier to accomodate multiple types of parts
> simultaneously.

   The problems is positioning the components at the parallel fences !
Remember we are talking some thousands of components a day. That may end up
being almost as hard as positioning the components directly on the board
:-( Using a small retangle for each component value and the vision system
just to tell direction and position inside each tray seems to be the most
reasonable compromise.

> About the vaccuum tweezers...How do you determine the position of the
> part wrt to the tweezers once its been picked up? Do you assume that the
> tweezer drive system always picks up the part in the same spot?

   With the roll system you always pick up at the same spot. With the
vision system you would use the camera to decide where to pick up. With the
roll system you know the components orientation and can rotate it to the
right position on the board at once and would probably just use right
angles, with the vision system you have to deal with fractional positions.

> Don't you dare move this thread someplace else. I don't want to have to
> sub to yet another list (YAL) just to follow this thread.

   Ok ... Ok .... We are warned and will follow :-) If it is not disturbing
anyone we hang around here...

Best regards,
Alexandre Guimaraes

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2002\01\07@071112 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi, Jafta

> Here is another link for a CNC drill
>
> Regards


   You forgot to put the link :-(

Best regards,
Alexandre Guimaraes

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2002\01\07@072340 by Jafta

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Aaah...in such a hurry to share with you!  Sorry ;-\

http://www.hut.fi/~taaltio/ap/autopora_index.html

Regards

Chris A

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2002\01\07@072946 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi, Roman

> Looks like i've decided to go the opposite way to your
> machine (in the picture) and keep the travel distances
> short and build a small, very light machine to try to
> keep speeds high, instead of a big sturdy mill.
>
> Imagine something NOT like a gantry mill, but more
> like a box on a rail. 300mm travel. The box has a short,
> light unsupported arm out one side, with a head travel
> of about 140mm. The arm is light and the head is lighter.
> I've been toying with the idea of using long bent tubes,
> one for the paste applicator tip, and a rotateable one
> for the vacuum tweezer. These have small lightweight
> stepper motors, (from disk drives maybe?), to lower and
> lift the tubes. Have you ever seen inside a pen/chart
> plotter machine? The long thin pen arms can move very
> fast, and no real strength is needed for PNP, only speed
> and accuracy. :o)

   I already tried to work that idea out and all the mechanical guys that I
consulted told me to forget about it !!!! The long arm will always flex and
shake a lot unless it is very sturdy and then it gets to be too heavy for
the other driving axes ! I quoted some strong driving system to use just 2
arms, one mounted over the other and the pickup head on the end of the top
arm and the mechanical system would cost over us$ 3000 !!! The idea is great
but maybe harder to implement then it seems. I decided to go with the gantry
style because the parts are cheap and readily available and everyone knows
how to workout the design. I will spend about us$ 300 to us$ 400 in parts
that are ready available, except for the motors that I already have scrapped
from old printers. I will send you in a private msg some pictures of a very
interesting design with just 2 arms. If anyone else want's it drop me a note
and I will send the pictures. They are small and should be about 100k.

   The long bent tubes will flex and shake all over, unless they are very
strong and them they get to be too heavy. Be carefull there. A tube with 150
mm that flexes 0,5 % will put the component in the wrong position.

{Quote hidden}

   The 300 x 140 mm work area should be enough for most applications. You
may not need all the speed you are running for. It is nice to have a fast
machine but remember that if the machine is cheap enough you can just make
one more when you need more production. I prefer slow, cheap and reliable.
Working with the mechanics people for a while I lost some of my urge for
doing the best all the time, sometimes the best is the worst enemy of the
good. In the electronics we can usually make it cheaper, faster and more
reliable. On the mechanics we have to settle for one of the goals and try to
work the others out the best we can.

   You can put the gantry on the car and show friends :-) It would be
somewhat like a square 400 mm by 400 mmm. That fits my car ;-)

best regards,
Alexandre Guimaraes

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2002\01\07@073359 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi, Roman

> Good point, and yes I do that. The best I can
> get with crude acceleration is 1% faster every
> microstep, looks pretty impressive, revs the motor
> to 10revs/sec top speed getting there in about
> HALF of a revolution. With a 2kg weight cariage it
> makes quite a bit of G force, on accel/decel it
> literally throws the entire machine side to side!
> This is one reason that swung me towards making
> the entire carriage and arm light, the machine
> is capable of 2 PNPs/second now but it makes
> a spin dryer look stable. There are a couple of
> resonance spots in the accel ramp (as you expect)
> but i've got enough accel now without having to
> compensate them.

   You have been riding a byke for too long !!! :-) Slow down man.. You do
not need all that speed. The machine will shake, rattle and you will not
gain that much. Just make 2 machines if you need to put the boards out
faster. Remember that you have to "bake" them anyway, so why put the
components faster them you can solder ??

Best regards,
Alexandre Guimaraes

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2002\01\07@094620 by John Maud

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02/01/07 14:28:58, Alexandre Guimarces <alexgspamBeGonespamIIS.COM.BR> wrote:

>interesting design with just 2 arms. If anyone else want's it drop me a note
>and I will send the pictures. They are small and should be about 100k.
>
>

Yes please.  Thank you.

John

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2002\01\07@094635 by Simon-Thijs=20de=20Feber?=

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Hello All,

I've seen the discussions about moving arms / printer
mechanisms for the CNC.
But is it not easier to move your PCB on the X and Y
axis and let the pick and place part just move X and Z
axis to get parts ????

To move the pick and place part on 3 axises seems more

fragile/unstable to me.


grtz

Simon




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2002\01\07@104251 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi,

> I've seen the discussions about moving arms / printer
> mechanisms for the CNC.
> But is it not easier to move your PCB on the X and Y
> axis and let the pick and place part just move X and Z
> axis to get parts ????

   I am unable to make a mental picture of that !!! Could you sketch it for
me ? The board moving X and Y is ok but where do you get your parts from ?
Would not you end up with 5 axis to control ?

Best regards,
Alexandre Guimaraes

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2002\01\07@121350 by Brandon Fosdick

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Alexandre Guimarães wrote:
>
> Hi,
>
> > I've seen the discussions about moving arms / printer
> > mechanisms for the CNC.
> > But is it not easier to move your PCB on the X and Y
> > axis and let the pick and place part just move X and Z
> > axis to get parts ????
>
>     I am unable to make a mental picture of that !!! Could you sketch it for
> me ? The board moving X and Y is ok but where do you get your parts from ?
> Would not you end up with 5 axis to control ?

I was getting ready to suggest the same thing. My lab has a CNC mill
that basically does this. The head only moves in the Z (up,down)
direction while the table, which is long and narrow, moves in the X and
Y (horizontal) directions. The tool caddy is at one end of the workspace
and can move independantly of the table. To change out a tool the
part-in-progress is moved out of the way while the tool caddy moves into
place to do the change out. You probably don't need the complexity of a
free moving part caddy, but you could easily make the work space large
enough to hold both the board and the parts pick-up area.
I'm not sure if this method is really applicable to this case though.
AFAIK mills do this because they need everything to be rock solid stable
to get high enough tolerances. The tradeoff is that the moving
components are much more massive (which is why they're so stable under
milling loads) and therefore slower. For a mill, accuracy is more
important than speed. A PnP machine doesnt need anywhere near the same
level of accuracy but does need speed. I this case I think it really
depends on what's less-massive, the workspace or the head.

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2002\01\07@122827 by Brandon Fosdick

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Alexandre Guimarães wrote:
>     The roll pick up system is simple and stable, for sure. The only problem
> is that you have to remake all the mechanics for 25 times if you have 25
> different components values ! You would need 25 motors or solenoids and all
> the control system that goes with it. My idea on that is a little different.
> I would use the pick up head to pull the roll and position the components at
> the right place. This way I can stay away from 25 motors !

Interesting. Will the pick up head need a different attachment for
interfacing with the component roll?

>     The problems is positioning the components at the parallel fences !
> Remember we are talking some thousands of components a day. That may end up
> being almost as hard as positioning the components directly on the board
> :-( Using a small retangle for each component value and the vision system
> just to tell direction and position inside each tray seems to be the most
> reasonable compromise.

By "fence" I meant a small rectangle that happened to be rather long in
one direction. :)

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2002\01\07@133155 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi,

> I'm not sure if this method is really applicable to this case though.
> AFAIK mills do this because they need everything to be rock solid stable
> to get high enough tolerances. The tradeoff is that the moving
> components are much more massive (which is why they're so stable under
> milling loads) and therefore slower. For a mill, accuracy is more
> important than speed. A PnP machine doesnt need anywhere near the same
> level of accuracy but does need speed. I this case I think it really
> depends on what's less-massive, the workspace or the head.

   Thanks for the explanation, now it makes much more sense. I still think
that the gantry is easier in this specific case.

   But that gave me the craziest idea I have had in months !!! It is hard
to explain in words but if you make the XY table a polar table you get a
design that has only circular parts and can be made using just a lathe !
Anyone that likes unconvencional ideas can take a look at
http://freeandeasy.sourceforge.net/ and imagine that table as the XY that
moves the board and the components tray and a fixed stand over it that holds
the video camera and the Z pickup head that has to move up and down just a
few milimeters. This should be the easiest and cheapest hardware setup
possible ! No precision parts at all and all round design that can be made
on a simple lathe.

   I like that idea very much... I would love if the more mechanical
inclined could take a look at it and comment on the posible pitfalls that
this dumb mechanical "unexpert" can not see.

Best regards,
Alexandre Guimaraes

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2002\01\07@133401 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi,

> >     The roll pick up system is simple and stable, for sure. The only
problem
> > is that you have to remake all the mechanics for 25 times if you have 25
> > different components values ! You would need 25 motors or solenoids and
all
> > the control system that goes with it. My idea on that is a little
different.
> > I would use the pick up head to pull the roll and position the
components at
> > the right place. This way I can stay away from 25 motors !
>
> Interesting. Will the pick up head need a different attachment for
> interfacing with the component roll?

   I was planning on just making guides for the rools and using a strong
needle that serves the double purpose of pulling the rools by the guiding
holes and picking up the components with vacuum

> By "fence" I meant a small rectangle that happened to be rather long in
> one direction. :)

   That is what I understood. The components are really small and
incredibly light, when you pull the rool cover it is very common to have
them flying out if you are not very gentle. It would not be easy to arrange
them nicely on the "fence" by hand.

best regards,
Alexandre Guimaraes

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2002\01\08@130615 by Peter L. Peres

picon face
Of course you all know that the best vacuum valve is one's finger held (or
not) over a small (1mm is enough) hole in the handle/tube/needle. I am
sure that you already knew that ;-) (for manual placement).

Peter

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2002\01\08@140450 by 859-1?Q?Alexandre_Guimar=E3es?=

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Hi,


> Of course you all know that the best vacuum valve is one's finger held (or
> not) over a small (1mm is enough) hole in the handle/tube/needle. I am
> sure that you already knew that ;-) (for manual placement).

   If you are using an assisted handpiece with a guiding arm it is ok but
if the handpiece is free in your hands you move too much to take the finger
from the hole and endup misplacing many parts. Besides that operation is
much more "anti-ergonomic" then you can think, the operator get's tired
pretty fast. It is easier and more productive to leave a small hole in the
handpiece open all the time and very light vacuum. Just enough to lift the
part and let it fall when it touches the solder paste.

Best regards,
Alexandre Guimaraes

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2002\01\08@210859 by Brian Kraut

picon face
It can sometimes be a lot easier to move the workpiece.  Since you are
not worried about the workpiece lifting like on a milling machine you
can have a table that rolls on a flat surface or uses two sets of rails
or drawer slides.  With a gantry table you are moving something heavy on
three axis.

Brandon Fosdick wrote:

{Quote hidden}

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2002\01\09@111634 by Roman Black

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Alexandre Guimarães wrote:
>
> Hi, Roman
>
> > Looks like i've decided to go the opposite way to your
> > machine (in the picture) and keep the travel distances
> > short and build a small, very light machine to try to
> > keep speeds high, instead of a big sturdy mill.
> >
> > Imagine something NOT like a gantry mill, but more
> > like a box on a rail. 300mm travel. The box has a short,
> > light unsupported arm out one side, with a head travel
> > of about 140mm. The arm is light and the head is lighter.

>     I already tried to work that idea out and all the mechanical guys that I
> consulted told me to forget about it !!!! The long arm will always flex and
> shake a lot unless it is very sturdy and then it gets to be too heavy for
> the other driving axes !
Actually it's the *short* arm, only 140mm travel.
The longer 300mm travel is the main gantry rail. :o)

{Quote hidden}

Thanks for the pictures, the 2 arm thing in
the picture was not well thought out. It might
be rigid enough for drilling but won't be suitable
for high lateral loads like milling or fast PnP.
It does look quite precise, but slow. :o)

>     The long bent tubes will flex and shake all over, unless they are very
> strong and them they get to be too heavy. Be carefull there. A tube with 150
> mm that flexes 0,5 % will put the component in the wrong position.

What I was suggesting would need about 100mm
long tubes, but these only have to hold the
SMD part and solder paste. Weight is very low
and the strength to weight ratio of a small
stainless round tube would be fantastic,
compared to most materials. :o)

My goal is to make the main sled the biggest,
the arm is small and light, made from a really
light 11" printer chassis which I have. it uses
pressed steel, one rail and plastic ends. Quite
light and strong. Extra bracing, and keeping the
arm close to the main carriage, brings that arm
travel down to about 140mm. The head, on the arm,
is very light and has tiny steppers which in
motor rotation actually lift the tubes. With
3200 usteps there will about 5 usteps to each
vertical mm lift. And VERY fast lifting/placing.

To keep the X and Y speeds high the head is very
light, i've even looked at keeping the up/down
motors off board and using teflon sheathed cables
to the head, so the head is lighter still.

Almost as good, is to mount the 2 lift motors back
on the head, over the main travel rail so the
triangulation drag is kept minimal. Imagine the
whole thing as a box over a rail, and the box has
the lightest "projections" sticking out which
do the solder paste app and the PnP. I should take
some pictures of the two rails, and draw a diagram of
the basic plan.


{Quote hidden}

Those are wise words Alexandre, thank you. As
much as I would like the thing to be fast, it can
be turned down, and the real running speeds will
probably be much slower. :o)


>> good microstep motor drivers. I don't see the small
>> work area as much of a sacrifice to get a fast and
>> portable sized machine. Something you could put on
>> the back seat of a car and take to a friends place,
>> plug it into their PC and it's running.

>     You can put the gantry on the car and show friends :-) It would be
> somewhat like a square 400 mm by 400 mmm. That fits my car ;-)

Sounds like a good size!
-Roman

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2002\01\09@111845 by Roman Black

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Alexandre Guimarães wrote:
>
> Hi, Roman
>
> > Good point, and yes I do that. The best I can
> > get with crude acceleration is 1% faster every
> > microstep, looks pretty impressive, revs the motor
> > to 10revs/sec top speed getting there in about
> > HALF of a revolution.

>     You have been riding a byke for too long !!! :-) Slow down man..
Ha ha ha!! :o)

> You do
> not need all that speed. The machine will shake, rattle and you will not
> gain that much. Just make 2 machines if you need to put the boards out
> faster. Remember that you have to "bake" them anyway, so why put the
> components faster them you can solder ??

Sure, but I like to make my software perform
at max speed, why not other projects?? You haven't
seen my 0.1 second SMD soldering machine made from
an old oxy cutter torch...
;o)
-Roman

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2002\01\09@114222 by Roman Black

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Alexandre Guimarães wrote:
>
> Hi,
>
> > >     The roll pick up system is simple and stable, for sure. The only
> problem
> > > is that you have to remake all the mechanics for 25 times if you have 25
> > > different components values ! You would need 25 motors or solenoids and
> all
> > > the control system that goes with it. My idea on that is a little
> different.
> > > I would use the pick up head to pull the roll and position the
> components at
> > > the right place. This way I can stay away from 25 motors !


Hi Alexandre, what about just having TWO spools,
each with a stepper motor. You can change a reel
while the other is working. And maybe a strong vacuum
tip would be enough to pull the part reliably from
the reel.
-Roman

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2002\01\09@160405 by Gary Crum

picon face
I used to work for a small circuit board assembly shop that had a nice line
of pick-n-place machines

When I first started they were using a manual solder paste screen dispencing
unit
It was basically a flat piece of metal the was unique to each PCB that had
the SMT pads milled out (probably lazer ethed)

Then you place the pcb under the "screen".  On the top was a big pile of
solder paste.  Then you just "squeegee" the paste over it. Only one pass was
needed.

The thickness of the metal screen determined how much past was on the pad.

Unless you are doing REALLY fine pitched devices, I think you could make the
solder paste screen on a home-brew CNC MILL

if you are doing a larger run of PCB's, that would decrease the time it took
to make the boards, instead of having the a CNC machine place each solder
paste pad

They eventually purchased a nice machine that automated it (for LOTS of
$$$$)
but that should be just as easy to make.

That's my two cents  (for now)
g

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2002\01\09@162946 by Peter L. Peres

picon face
> hole covered by finger to control vacuum

Usually a fourth finger (pinky or ring finger) is used to do this, three
fingers are required to hold the part. A footswitch will also work. I use
very sharp claw tweezers for all the parts but I do not do 'production'.

Imho vacuum sucks for p&p manual work ;-).

Peter

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2002\01\25@040040 by Simon-Thijs=20de=20Feber?=

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Hello All,

Did any of you came accross this site :

http://www.geocities.com/majosoft/

Check it, it is worth it !


grtz

Simon

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