[time-nuts] pick and place problems/design (was: OT stuffing boards)

[Bob Camp]

Hi


> On Jun 24, 2016, at 11:56 PM, Attila Kinali <attila at kinali.ch> wrote:
> 
> On Fri, 24 Jun 2016 13:59:58 -0500
> "Graham / KE9H" <ke9h.graham at gmail.com> wrote:
> 
>> Lots of problems to be solved...
> 
> Most of these problems are easy:
> 
>> How do you take loose parts or cut tape or tape reels
> 
> 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.
> 
>> and get the right
>> part out, and into the chuck, oriented in the right direction?
> 
> Orientation is defined by the reel/tray the parts come in.
> This is also documented in the datasheet, usually.

If the part is oriented top-bottom and you have it on the board both 
top-bottom and left-right .. you need to be able to re-orient it after 
you have picked the part. 

If it is a diode or semiconductor , you have four obvious orientations for the part. Doing
four reels for every diode or semi just isn’t the way it is done. You 
buy one reel and let the machine deal with it. 

If you add in things that are oriented at a 30, 45, or 60 degree angle, you
simply can not have a reel for all the orientations. 

The Z axis needs to rotate.

> 
>> How many different kinds of parts, sizes, shapes, pin counts, IC
>> footprints, can you handle at once?
> 
> As many as there is space around the machine :-)

If it is a moving table design (as many if not most are) that really does 
not count. You can’t get the head there.

Bob


> 
>> How do you know it is the correct part?
> 
> You put it manually in the right feeder and double check that it
> fits the programming.
> 
>> How do you know where the "+" end, or "pin 1" is?
> 
> This comes with the orientation of the part in the reel/tray.
> 
>> How do you know that there actually is a part in the chuck?
> 
> Your trays are guaranteed to be non-empty by manually loading them.
> 
>> How do you know the part in the chuck is oriented the way you expected it?
> 
> The manufacturer guarantees that the reels/trays are loaded correctly.
> 
>> How do you know where the footprint on the circuit board is located? (to a
>> few thousandths.)
> 
> 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.
> 
>> How do you know the part left the chuck and ended up where you intended it
>> to be?
> 
> 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.
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