On 6/24/2016 9:32 AM, Attila Kinali wrote:

Laser cut Kapton are fine for a few boards - up to 5 or so.  You start
seeing the effects of use after six or eight and steel is clearly a
value. . I use them for most protos.

If I'm doing anything really fine that would drive me to steel on
resolution alone, I pay someone else to do it.

Oshstencils are cheap, and they will do 4 mill Stainless Steel for 2X
Kapton cost.  Deal if I'm doing more than 5 boards.

--
mailto:oz@ozindfw.net
Oz
POB 93167
Southlake, TX 76092 (Near DFW Airport)

Hi

If you are doing a board with a few hundred parts on it (as earlier mentioned). And have designed
a “3D printer” pick and place that runs one reel at a time. And are running the printer slow to keep
everything from going all over the place. And have a manual reel advance (no feeder) ….

I can easily see you getting into a “put it away for today” situation. You can beat a simple system like that
(speed wise) with a good manual vacuum pickup and some modest pre-organization of parts.

Bob

Don Latham said
to Discussion
I do not see why a small pick and place assist system could not be built on
a 3-d printer.

Lots of problems to be solved...

How do you take loose parts or cut tape or tape reels and get the right
part out, and into the chuck, oriented in the right direction?
How many different kinds of parts, sizes, shapes, pin counts, IC
footprints, can you handle at once?
How do you know it is the correct part?
How do you know where the "+" end, or "pin 1" is?
How do you know that there actually is a part in the chuck?
How do you know the part in the chuck is oriented the way you expected it?
How do you know where the footprint on the circuit board is located? (to a
few thousandths.)
How do you know the part left the chuck and ended up where you intended it
to be?

Commercial systems have answers to all of these questions. In many cases
involving intelligent vision systems.

Once they are all answered, then you have a PCB unique set-up / programming
effort to instruct the placement machine all about today's specific board
and parts list to be assembled.

I can usually build one or two boards by hand about as fast as an engineer
can do the placement machine specific PCB programming and verification.

--- Graham

==

On Fri, Jun 24, 2016 at 11:52 AM, Don Latham djl@montana.com wrote:

Hi

A “low cost” auto pick and place does have some things in common with a 3D printer:

Drive is by stepper motors
Micro stepping stepper motor drivers are used
Belt drive is pretty common
Tube support and circular ball bearings are generally used
You have X, Y and Z drive
Very custom software to drive them that may or may not be open source
A setup and calibration process that may not be a lot of fun
A requirement to do some trial runs before you do anything important

There are generally a few things different between my 3D printer and a simple pick and place:

The drive is on both sides of the X / Y region
The X/Y is much larger than the Z
There is a Z rotation (4th axis) on the pick and place.
My 3D printer has one head, two heads is about as low as they go on pick and place
The parts feeders are a big part of the pick and place machine and there are a lot of them (even on a simple one).
The base plate is a lot heavier duty (more rigid)
Vacuum to do the parts pickup
Pressure to blow off a stuck nozzle
Some means to detect that a part has been picked up
Interchangeable pick heads (the head size needs to match the part size to some degree)
A “small” (“desktop”) pick and place is a meter square. Most 3D printers are much smaller.

— As you move up, the pick and place might have —

A camera to check parts on the placement head to properly align them (“up camera”)
A camera to check the board and align to it (“down camera”)
Four or more placement heads.
Enough variety in feeder widths to match the size of the reels you have :)

No matter what you do for a pick and place, you will need:

Some way to mount the board on the machine
Mounting holes (or whatever) on the board to match up with the machine
A design allowance that keeps parts out of the area contacted by the mounting setup
Fiducial marks to line things up that are of a type the machine can work with

There are lots of details….The 3D printer takes cad files and generates motion information.
The pick and place take the output of a PCB layout program and generates motion information.
It goes on and on ...

Bob

On Fri, Jun 24, 2016 at 3:32 PM, Attila Kinali attila@kinali.ch wrote:

For what it's worth, I have a manual / guided pick and place machine
available. UK pickup only unless you're really keen ! Off-list please if
anyone's interested.

-adrian

On Fri, Jun 24, 2016 at 9:52 AM, Don Latham djl@montana.com wrote:

You are not the first to think of this.  But the problem is

1. moving the reels of parts,
2. programming the machine.  Translating the PCB design files into g-code.
3. Building a vision system.  With very small parts you really can't
   run open loop

--

Chris Albertson
Redondo Beach, California

On Fri, 24 Jun 2016 13:59:58 -0500
"Graham / KE9H" ke9h.graham@gmail.com wrote:

Most of these problems are easy:

You don't. No loose parts with any kind of pick&place machine.
As for cut tape, these can be taped on an empty reel to make
them compatible. Everything has to be in a tray, reel or similar.

Orientation is defined by the reel/tray the parts come in.
This is also documented in the datasheet, usually.

As many as there is space around the machine :-)

You put it manually in the right feeder and double check that it
fits the programming.

This comes with the orientation of the part in the reel/tray.

Your trays are guaranteed to be non-empty by manually loading them.

The manufacturer guarantees that the reels/trays are loaded correctly.

This is provided by the pick&place file. Usually its 3-5 digits after the
decimal point, when using mm. But as I wrote before, you don't have to
place part hyper exact. Being within 0.1-0.3 of the pitch of the part
is usually enough. Surface tension does the rest.

You dont :-)

The way how this is checked is either a pre-solder and/or post-solder visual
inspection. This is either done manualy or using a camera system where
computer compares the PCB to the picture of a known-good PCB.
As this is ment for a small volume and hobbyist system, doing the visual
inspection manualy is good enough and more than fast enough.

		Attila Kinali

--
Malek's Law:
Any simple idea will be worded in the most complicated way.

The ideal hobby use pick and place machine would be very different
from a commercial machine.  Lets say I want one board made.  What I
want to minimize is my time.  With a conventional machine by FAR most
of my time is spent setting the machine up.  In fact setup is so slow
that for smaller PCBs I could do it with tweezers in a fifth of the
time needed to set up the machine.

So a hobby machine must be designed such that you could get it going
in nearly zero time.  In the ideal case you drop the parts all mixed
up, (but right side up) in a small tray.  They are mixed and in random
orientation.  then you give the machine your PCB design file (not a
special pick and place file) and then a vision system IDs the parts.
Today vision is dirt cheap.

But the 3D printer needs one more degree of freedom.  It must be able
to rotate the part (or the PCB) as it is unlikely the part on the tape
or tray only needs translation to the PCB, likely ration is required
in almost all cases.

I think a hobby machine would only be successful if it could reduce
the setup time to nearly zero and for that it would need a really good
vision system that could hunt down randomly placed parts.  It would
have to work pretty much like you or I would do the job manually.  But
we have software like openCV and good "board cams" with M7
interchangeable lenses for $35.  A vision system actually saves a ton
of money because the machine need not be so precise as vision closes a
feedback loop.

Also how many hobbyists are going to have reels of parts?  I might buy
some parts by the dozen but most no more than about 4 or 6 at a time.
I don't want a large machine.  It should have a working surface, a
white melamine table about 12 inches square and I place the PCB to be
stuffed and all the parts on the same foot square table at any random
location then press the "go" button.  The camera scans the table.
This kind of machine would be horrible for production work but a one
foot cube machine that required zero setup is what most of us want.

Going a little farther.  I'd like this SAME machine to actually make
the PCB too.  A 3D printer could route the copper and drill holes and
print the solder resist plastic too.

On Fri, Jun 24, 2016 at 8:56 PM, Attila Kinali attila@kinali.ch wrote:

--

Chris Albertson
Redondo Beach, California

Many parts can't be recognised visually. Capacitors are the obvious example.

On Sat, Jun 25, 2016 at 6:11 AM, Chris Albertson albertson.chris@gmail.com
wrote: