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

[Attila Kinali]

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.

> 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 :-)

> 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.