GRBL milling stopping randomly

[m_c]

Sounds like a USB lock up issue due to interference.
Try a good quality USB cable with ferrites at both ends, or an opto-isolating USB cable. You've not said what kind of spindle you have, but it could be worth adding some noise suppression to that, as it's most likely the additional current under load that is causing the problem.

[Datulab]

What you are telling sounds quiet plausible. I am in fact using a shielded USB cable but it doesn't have ferrites. The spindle I'm using is just a random 500w air cooled thing from China with included PSU. Do you think it will help to use shielded wires to the spindle? I don't have a USB cable with ferrites on hand but I should be able to find some shielded wires.
The only weird thing about this is that it doesn't happen when the spindle is on but only milling air.

[Datulab]

Sounds like a USB lock up issue due to interference.
Try a good quality USB cable with ferrites at both ends, or an opto-isolating USB cable. You've not said what kind of spindle you have, but it could be worth adding some noise suppression to that, as it's most likely the additional current under load that is causing the problem.

You are right, I found a shorter shielded cable and it worked far better, I only had a freeze one more time after like 20min. I'll probably replace the wires with shielded ones and get a even better USB cable in the future but for now it works!

[m_c]

USB is not the best choice of interface in noisy environments, but those tricks usually solve the problem.

What you'll find, is even though the USB device shows as still being connected, it becomes unresponsive, with a disconnect/reconnect being the only option to get things responding again.