Z axis making odd sound

[ivars211]

Nice, forum crashed when I tried to upload video first time, so here is a second attempt.

I am experiencing some really nasty noise from Z motor (Motor 3), tried different speeds and acceleration, but it seems to only go away at very low speeds (200). All other axis seem to work just fine with reasonable speeds. If I turn the motor off and move Z axis by hand, all goes smoothly without any sound, so it seems like it is not a mechanical issue.

In the video below, you can see me doing "Test Z" first (it seems that acceleration/deceleration is making that sound), and then "Home Z" which is really loud.
http://sendvid.com/n3blvdr5
Any ideas what is causing that? Motor? Driver?

On different note, why is turning vacuum pump on moving axis as well? Is that like that by design, or is something wrong with my board?

Thanks.

[mucek]

Recheck all connections! I guess you might have something connected wrong. For Z motor test you can connect it to x/y output on tinyg and see if it is ok.

[ivars211]

Problem was solved by turning down power for that motor.

[mawa]

On different note, why is turning vacuum pump on moving axis as well? Is that like that by design, or is something wrong with my board?

Thanks.

That nasty movement is because it is, as Juha documented somewhere, to avoid a bug in the tinyG firmware when turning the switched output for the pump on and of.

@juha: Does this bug still exist and is there no other way to circumvent it?

IMHO it takes away time and could cause precision problems if you have slew.