I had put larger higher current steppers on the x and y axis. I was using the same A4988 stepper drivers that the Robo board used. I set the reference to 1.2v for 1.5 amp drive. I put the extra large heat sinks on and was running fine. The drivers on both machined failed about the same time, a few months. They were running hot which accelerated the thermal cycling failure time. I put in Chinese clone DVR8825 drivers and at first set to 16 micro steps for compatibility. I did the fast decay mod because I was only running 1.6 amps. I got the same results as the Robo drivers. I then switched to 32 micro steps. Did not seem to make any difference in the print, but the machines went quiet. The difference was amazing. I do not know why it makes it quiet, but it does. The DVR8825 runs much cooler the Robo drivers. It is worth buying the Partsbuilt board just for making the printer run quiet. Update: I modified the DVR8825 plugin boards because I read that they were using clone chips running at 1/2 freq (16 kHz). I ordered a current probe for my scope. to view the signal and verify nice smooth steps. I need two current probes to look at the differential current between the two windings..DUH. I did however find that the chips were running at the full 32 kHz so I removed the modification. They run fine and cool. I will find another current probe, look at the differential current and report my findings. It will take awhile.