German CNC skipping step

Hello!

I’m trying to troubleshoot a German-made CNC router (Isel DaVinci) that is skipping steps. I removed the original (late 1990s) controller and replaced it with an Arduino Uno and gShield. The power supply puts out 38 volts, so I’m using a 24 volt supply until I get a regulator that will step that down without losing too much amperage (most I’ve found are limited to 2.5 amps total). I’ve heard that higher voltage supplies tend to help resolve skipping steppers, but it seems like 24 volts should be plenty for these motors. I’ve only tested with a 1/16″ v-bit at 0.010″ depth of cut per pass so far, so there’s very little load.

The z-axis audibly and visibly misses, slightly more when inclining than declining, but it does in both directions. The x and y axes don’t noticeably skip, but over time what it’s cutting drifts.

Since the z was the most obvious I dropped the microstepping to 1x and that made it perfectly repeatable when I jog in 1 mm or 0.1 inch increments. If I go up to 1 inch it almost always jogs just fine, but occasionally skips a little. But with larger jogs and during an actual run all axes are skipping.

This is my first CNC, but I have plenty of manual machine tool experience (lathe, mill, surface grinder, and others), including setup and maintenance. I am confident when I say that this machine had VERY little use before I received it. Others who have purchased these (educational benchtop machine) have shown sawdust packed inside the controller and power supply enclosures. Mine was almost dust-free, even around the greased linear rails and ballscrews. Anyway, I don’t believe that this is a case of worn or cheap components. I’m confident that it’s something that happened since I removed the original controller. The vast majority of the threads I’m finding online on this subject go back to cheap ebay controllers, people using 12V wall warts instead of real power supplies, etc. I’m having trouble finding information for the troubleshooting process for a reputable controller and high quality machine. Please guide me, point me to existing resources, or whatever may help.

Thank you!!

– Jon