Sorry, forgot to follow up on this. This was fixed in Feb 2018. Nothing was wrong with spindle or VFD. However one of the VFD settings inadvertently was wrong. I stepped through all the settings and found a max voltage setting that was clobbered and not as was described in the Probotix guide. I don't know how that happened. The Probotix consultant said that I did not need to edit/verify these settings as they are set before shipping but I did not know that. The lesson for me here is that if the spindle has an issue to first check all VFD settings.
The other lesson I learned a month ago is about side surface quality. All my small 0.75 thick HDPE plastic parts suddenly started to show less smooth or rough side surfaces. As I was in a time bind, I tried different cutters, speeds, pass depths and feedrates and cut many of the same parts multiple times in the hope of just getting some quality parts for a toy assembly. Sometimes I would get a reasonably good part but most were not good enough. I suspected that maybe my spindle speed was not honored and really much lower than indicated as the machining/cutting noise was different and sharper. I finally called Kaden at Probotix and told him the machine was only a year old and asked for advice. He advised me that such a quality problem is often 'chatter', especially on older machines. He recommended to tighten all bolts on the side risers/sliders and try again. Most of the 24 bolts were good/tight, maybe about 5 or 6 needed a little bit of tightening, which I did. That took care of it. Lesson here is to call Probotix help much sooner, it can save lots of time and frustration!
