0402 tape pickup location issue

[sebastian]

I am using a white paper tape with 8mm width and 2mm pitch. 0402 components.

The weird issue I notice is that just going 3.5mm left from the hole center (as liteplacer does by default to pick up components) gets us into the component of even part numbers center location pretty well.
But going 3.5mm left from the hole and 2mm down (for odd part numbers) the center is pretty far off.

I am evaluating whether this issue is caused by the tape being slightly off angle from the vertical machine axis.

Anyone else noticed this issue?

0402-tape-01.PNG (632.83 KiB) Viewed 2254 times

0402-tape-02.PNG (644.07 KiB) Viewed 2254 times

0402-tape-03.PNG (644.28 KiB) Viewed 2254 times

0402-tape-04.PNG (591.02 KiB) Viewed 2254 times

[JuKu]

> I am evaluating whether this issue is caused by the tape being slightly off angle from the vertical machine axis.

Could be, but doesn't seem to be so. The images don't show any off-angle, and the error is rather big. Do you have slack compensation on or off? Do you see the same if you go first to hole and then manually 3.5mm left and 2mm (or 4mm) up? How about 4, 6, or 8mm down?

A workaround for the problem (whatever it may be) could be to use part coordinated directly: When setting up or editing a tape (right click a tape brings up the dialog), you can set the first and last part coordinates directly. The method finding the parts will then account for any skew on the tape placement.
http://www.liteplacer.com/edit-tape-parameters-dialog/

[sebastian]

> I am evaluating whether this issue is caused by the tape being slightly off angle from the vertical machine axis.

Could be, but doesn't seem to be so. The images don't show any off-angle, and the error is rather big. Do you have slack compensation on or off? Do you see the same if you go first to hole and then manually 3.5mm left and 2mm (or 4mm) up? How about 4, 6, or 8mm down?

A workaround for the problem (whatever it may be) could be to use part coordinated directly: When setting up or editing a tape (right click a tape brings up the dialog), you can set the first and last part coordinates directly. The method finding the parts will then account for any skew on the tape placement.
http://www.liteplacer.com/edit-tape-parameters-dialog/

Slack compensation is turned on.

I made a screencapturing for showing the manual movement results from hole center: https://www.youtube.com/watch?v=bW78ud93hes

The first/last part positioning approach is very interesting but I have similar issues with part positioning errors. Sometimes moving to parts works fine, sometimes its part off...
I made another screencapturing (sorry the tape edit window moved out of the captured area what I did is set first/last position by clicking "get current"):
https://www.youtube.com/watch?v=7CNJoW_j9DE