z axes looses about 0.01mm when moving down.

I soldered all the connections directly to the arduino just to make sure there is no bad connection using the plugs.
As Christian said i tried a external powersupply to the arduino. Both without any improvements.
Tomorrow i'm gonna try a shielded USB cable and a powered USB hub.

SOLVED!!!!!!

I purchased a USB hub with external power and the problems disappeared at once..
To make sure i changed a 1.8meter USB cable with a cable of 1meter length and there were the problems again. So back to the cable with 1,8 meter.
All my problems were related to a weak USB signal and a bad USB cable.
Everything worked today 4 hours without problems and i really hope it stays that way.
Thanx everyone for your help!!

Veröffentlicht von: @nacra

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After using my stepcraft 600 for almost a year now i noticed that when i had a cutting job which took some minutes the router did not pass through the material of the last parts. So, in fact id did loos some steps after a some minute on the Z axes.
I tried different jobs and there is a pattern. It looks like moving the z axes down is loos about 0.01mm.

The Z always end up in positive position. After milling when the z axis is used about 150 times up/down it ends up 1,5mm positive
I used Estlcam 10 and 11. Different settings. Different cutting jobs. ~Disassemled the z axes and all running smooth.
Used different USB ports, usb cables, reconnected the arduino uno to the flatcable, cheched all the connectors.

Is use a arduino uno which is connected without a shield to the Stepcraft controller. So no resistors used as in the shield is done.
Could that be the problem?
X and Y are running correctly

And at last, i tried about 30 runs without cutting material. So no resistance on the steppermotors

Anyone ????

It is my Problem by now