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Member #20956

Member Since: June 22, 2007

Country: United States

  • Ok, so I have been playing with my "new" chmt36va with varying degrees of success. Not a terrible machine, especially for the price. You can easily buy feeders for other machines that cost more than this entire setup... but I digress.

    I use this machine (for now) to produce a very, very simple board that I have in a 5 panel array (1..5) arranged on the X axis with a 3 millimetre space between the boards. I used the cool Sparkfun charm converter to get the data in the machine, and I have had reasonably good luck with it. Some days better than others..

    Some things I learned the hard way: 1) you MUST shut off the FIFO buffering in the usb-serial converter that is supplied with the unit. Admittedly I have a slow lap-top running the machine. What was happening with the default USB fifo buffer turned on was that the up-camera would end up taking a picture of the part as it was -moving- into the "center" of the camera. This resulted in it often finding the centroid of the part centimetres away from the "center" of the camera, and causing gross placement errors.

    2) sometimes the drag-pin on the feeder just plain misses the component tape, usually at the back of the machine, and continues to do so. I have found that re-starting the software fixes this. WTF? It is workable but a pain in the butt. Is the machine "loosing" steps? somehow I doubt it, becasue it has encoder-feedback -- unless the embedded software sucks. (a possibility)

    3) On one of my more fussy days using this machine, I had a hunch that the fiducial offsets don't work right. Turns out, I am pretty sure that they DO NOT work right on penalized boards... let me explain what I have found.. First my setup:

    NORMAL setup:

    {Mark1}

    { } { } { } { } { } {board1} {board2} {board3} {board4} {board5} { } { } { } { } { }

    {mark3} {mark2}

    On a “normal” day when you go into the “pcb calibrate” menu and the fiducial are very close. No problem, hit run and all is well. I noted that on some boards, when the fiducals require movement of the head, the boards on the “end” don't seem to line up as well. So, to prove this I performed this experiment, I shifted the entire panel to the right about 1 CM, just slid it over to the right away from its normal corner-circle stop:

    Experiment:

    <1cm> {Mark1} <1cm> <1cm> <1cm> { } { } { } { } { } <1cm> {board1} {board2} {board3} {board4} {board5} <1cm> { } { } { } { } { } <1cm> <1cm> {mark3} {mark2}

    I shifted the boards right 1 cm, and got some very surprising results: the components on Board1 were placed perfectly. The offset was accounted for by the machine, and all was perfect. board 2, was ok, but has a visible shift of the components being placed too far to the right. Board 3 was bad, parts were shifted quite a bit too far to the right. Boards 4 and 5 were totally un-useable. The parts had been “over shifted” too far right and were literally falling off of the board.

    So, my question is, has any one else seen this problem? Is there something that I am probably doing wrong?

    Here is a link to pictures of the board, and my DPV file..

    http://www.mediafire.com/folder/qi2k5n14ldftq/cmt36va_offset_error

    Cheers,

    ---Lou

No public wish lists :(