He built a CNC plasma cutter that survives high-frequency start by ditching USB for WiFi
How to make a CNC plasma cutter with high-frequency start
High-frequency start plasma cutters throw off enough electromagnetic interference to disconnect a CNC controller's USB serial link, even though the motion controller keeps running. The author accidentally won a Parkside PPS 30 B2 on eBay for £80, then switched to FluidNC on an ESP32 and talked to it over WiFi to keep the connection alive. The frame is box-section steel and 3D-printed parts, with Leadshine servos running on 12V despite an 18V spec. Cutting parameters, he admits, are still harder than they look.
So the issue isn't that the HF start actually prevents Grbl from working, it's just that it disconnects the USB serial connection.