[Ed Williams]

I have been chasing a problem and I can't find it. My holes are larger on top than bottom when I cut them. The top is .02 inch larger than bottom of hole on a 20mm hole. This machine has linear bearings and ball screws on all axes. There virtually no backlash on all axis's".0005" or less. This just started happening and I have used this machine 2 years. Little over a month ago I put one of these Chinese spindles on it. It worked great. But I have checked everything out and run out on spindle bit is a little over .001. The spindle seems good and tight. But could the spindle be doing something different when it’s under a load?
Thanks Ed

[eloid]

what matieral are you cutting at what feed rates etc... may be you have a resonace issue in you frame and gantry how deep are the holes?

try cuting the same material at a very slow rate and slower rpm reduce the
step over rate too.... see if anything changes and you plung rate

[Ed Williams]

If I slow everything down my holes are more even but I mean slow 10 ipm, .001 cut. And then the holes are still wrong in size. Too large. I'm cutting .5 6061 aluminum. I haven't tried slowing rpm. I'll try that.

[Ed Williams]

No matter what speed I use I still have holes larger at top and smaller at bottom. I'm using Mach3 could there be anything with that. If not the only thing that has changed on this machine is the spindle. It worked fine when I first put it on. Can a spindle have runout only under load.
Thanks Ed

[Ed Williams]

OK I changed my speed to 24000rpm and went to 10ipm and .001 cut and my hole is perfect. But I can't cut at this speed I would never finish a project. Any ideas
Thanks Ed