Pick and Place Project
To develop a low cost, reproducible, open-source pick and place system for automated SMT electronics assembly.
Progress so far:
Successfully controlling a cartesian table through EMC2 via a Python script on a remote machine.
Preliminary on-paper design of a variable-width T&R feeder
(mostly-) fabricated vacuum / rotation / optics head
Vacuum pump (hacked aquarium pump) works for 0603/0805 without suction cups
Some optical tests: image segmentation (determine what parts of the image constitute a “part”), and some optical derotating schemes.
Requirements and “nice to haves”
--Standard 3axis CNC-like machine that can accept the required head
--Realtime motion controller that can be driven by described pick-n-place software (EMC with emcrsh/halrmt + python via telnetlib)
--USB camera following a grabbable standard (UVC, WIA?)
Had a brief look and couldn't find any in size, cost range of interest. WB-7142 ...2MPx optical webcam with autofocus. Too good to be true? Also found the "Cubeternet" which mounts easily via 4 mounting holes once the case is removed :-) Also, word on the street is that auto/software-adjustable (e.g. voicecoil) focus is unreliable, especially in motion and when the camera is not facing horizontally.
----Fixed (user-set) focus -- probably set pretty near
----Active lighting - LED source
------May need multiple, switchable angles to show partnumbers clearly for feature matching
----Calibration table (paper/printout)
-SURF for discrete feature detection Processing implementation did not work well in my tests; loves micro-features (paper grain) and ignores macro features, e.g. part legs or corners of text
------Abstracted interface of (points / transformation matrix / stats); hoping to simplify switches to new feature detection engines due to improvements and/or patent encumberances
----Stitching for 'big picture' of close-cam images for possible fiducial finding, board auto-array
------Hugin commandline / autopano provides this
----(optional) positive pressure capability to ensure part releases - needed?
Paste Dispense Head
--Needed? Or is everyone using stencils?
Glue Dispense Head
--Needed? Probably not a priority for hobby circuits; KISS (keep it single sided).
----Accept T&R of any width/depth (8mm+); standard and (eventually) mega (right-side elongated hole)
----Advance tape a computer-controlled amount per placement
------May not be terribly accurate; this is (part of) why the camera is needed
----Pull and dispose (spool or eject) tape cover; dispose empty tape
----(optional) Attempt to detect feed pitch and/or mispicks by detecting light through part wells?
----Accept tubes of all reasonable dimensions (there must be a standard; what/where is it?)
----Liberate parts from tube in a controlled-ish manner:
------Long screw to poke them out from the other side?
------Lift one end and vibrate them out; use 'loose' method to pick??
------'Catcher' endstop positioned exactly matching the length of one part?
----No special hardware; tray support will probably be a software task
----Match centering and rotation to a known reference (hand-placed and autophoto'ed?)
----(optional) Detect parts beneath preset 'matchedness' threshold and avoid/warn (upside down or wrong part?)
----(optional) Attempt to flip upside-down parts by dropping repeatedly (may require enclosed 'drop tank' and cushioning; not suitable for all parts)