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Subject: Re: [Homebrew_PCBs] making surface mount boards

From: Henry Liu <henryjliu@...>
Date: 2009-07-24

What's a good pneumatic dispenser? If it has an electronic on/off
switch, I hook it up to my cnc with a relay + M code switch.

I think if I do it a lot then I'll just program my cnc machine to do
it like this guy: http://www.youtube.com/watch?v=HdqVt0jCBHk

I think it's pretty easy, just move X,Y,Z down activate dispenser,
move up Z and move to next XY in a loop.

If I can source a good vacuum pump lift I can place the part too. I'm thinking:

Pick and place machine
1) put components randomly on flat white background on top of rotary
table (http://www.sherline.com/8700inst.htm)
2) mount camera on CNC spindle
3) segment image
4) detect lines using hough transform
5) rotate plate using rotary table to align lines either 90 degrees or 0
6) resegment image to find centroids of objects
7) move spindle over and pick it up with vacuum chuck
5) drop it on centroid of pcb

I write image recognition software all day long at work so the
software is no problem but not so sure about the lift/drop.

I think I'm getting ahead of myself though as I probably will only
make a few boards a year lol.

Too many projects, too little time...

Cheers,
Henry

> I tried a stencil when the board house offered it free with the PCB,
> one board turned out quite good but for the second the stencil didn't
> lie flat and it was a mess. I'll stick to the syringe in the pneumatic
> dispenser for now. If you do more than ones and twos the stencil
> probably pays off.
>
> ST