Peculiar picking issue with a 0402 package

[Marc L]

Hi, I have a very peculiar issue with a specific 0402 package, that happens occasionally with another 0402, but never otherwise.

For that 0402 resistor, whenever I try to pick it using the Feeder pick command, or during a job, the resistor will not stick to the nozzle tip. It just stays inside the reel. Like, the tip touches down, the pump and valve actuate (tested using a small paper confetti: there is vacuum), but the 0402 will not come up. It happens with one other 0402 resistor, sometimes. In both cases, the pick location is spot on; perfectly centered with the CP40LV-N045 nozzle.

The weird part is that if I just use "move to pick location", then quickly actuate the pump and valve, then move up, the part always comes up. It works every time. Just not during the pick command.

What is the difference between the pick command and the move to pick location command? Does one use the contact probe nozzle and the other not? That's my best guess; Maybe there is something with the tape and the pressure of the nozzle makes the part stick to the bottom of the paper pocket. Is there a way I can disable the pick probing just for one part?

Regards,

Marc

[Marc L]

Ok, well, asking the question made me think about it. A workaround I found that will probably serve me well in the near future is to place the whole board,  then disable "Feeder Height Probing" in the ContactProbeNozzle actuator. That proves my theory that the difference between "auto pick" and "manual pick" is the probing part, and that there would be a problem with the tape.

I'm still interested: is there a way to not probe for feeder height for only one part? Or to recalibrate the feeder height on each pick (or see the detected value someone other than in the logs)?

[Mark]

Hi Marc,

I guess such a behavior would point to a problem with contact probing that you should solve. Contact Probing should actually make picking small parts like the 0402 more reliable, not less.

Make sure the contact probing actually works, it is easy to get wrong, both on the controller side and OpenPnP (send a log at TRACE level if in doubt).

The only other thing I can think of, would be a Final Adjustment, that is too right.

https://github.com/openpnp/openpnp/wiki/Contact-Probing-Nozzle

Another thing to look at is vacuum setup. This should not actually make a difference whether you're Contact Probing or not, but who knows what side effects that can have.

If you have vacuum sensing, see the following link, especially the Establish Level setting, that makes sure you reach a certain vacuum level before lifting the nozzle.

https://github.com/openpnp/openpnp/wiki/Setup-and-Calibration:-Vacuum-Sensing

If you do not have vacuum sensing, check the Dwell times on nozzle and nozzle tip.

_Mark

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[Marc L]

Thanks Mark, your intuition was good. After proper configuration, it is now obvious my Contact Probe Nozzle settings and Nozzle Tips settings were wrong. My probe speed was 5x too fast and my Final Adjustment was at 0.0 mm. I might have skipped that step previously, I don't know. The settings that solved the issue for my LitePlacer are:

- Probing Speed: 0.01 (down from 0.05. The probe command is now F300 instead of F1500)

- Final Adjustment: 2.0 mm (up from 0.0 mm, calibrated in steps of 0.1 mm)

- Feeder Height Probing: After Homing (to reset the height of all feeders at least once with the new settings. Might switch back to "once" later)

It's not the first time I post here, and as always I'm very grateful for your work and support. Cheers,

Marc

[Marc L]

Ah I forgot to mention that I re-calibrated the Touch Location height for each nozzle tip after changing the Probing Speed and Final Adjustment for the ContactProbeNozzle, and before re-probing for each feeder height.

Marc

[Mark]

Glad it works!

_Mark

To view this discussion on the web visit https://groups.google.com/d/msgid/openpnp/344e0221-a27b-4444-b61e-ade6fa48b773n%40googlegroups.com.