Hi, I’ve just started building my first attempt at a small CNC router based up an Arduino Uno running grbl and fitted with a V3 CNC Shield with four A4988 drivers (Y axis cloned) running NEMA 17 2A steppers. I’m then using UGCS to send the G-Code.

I started by getting both the X and Y axis connected and running smoothly with no problems, my problems started when I fitted the Z. Jogging in X and Y gives me no problems with the Z motor unplugged and likewise running the Z up and down gives me no problems with the Y axis removed.

However with all three connected I get an issue where jogging Y in either direction also causes my Z to move negative and moving my Z in either direction causes my Y to move negative.

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I’ve tried swapping my Chinese Arduino out for a genuine Italian R3 unit and although I thought it seemed better at first it is still present. I’ve also tried turning my vRef on my X and Z back down from 1.2v to 0.6v and this seemed to reduce the severity of the problem, but it is still there and this isn’t running anywhere near the 2A limit of my motors or drivers as my A4988 are fitted with 0.1Ohm current sensing resistors. I've double checked all my connections and visually all looks okay.

Any ideas what would cause this pattern of movement? Electronics like this are very new to me so just looking for some pointers in the right direction of things to check.

Thanks