Spindle faulting

[levelzero]

I'm having a really strange problem that has just started (I've been running these parts for over a year). I'm using a .25" spot drill to do some engraving. Normally I feed at 20 ipm with a 0.02" step down full width. RPM is 4450.

There is a strange clicking/crunching sound and after about a second the spindle will stall.

I've tried reducing the DOC to 0.01" and I've tried feeds ranging from 10-36 ipm, with little to no difference. I've calibrated the VFD using the instructions on the website multiple times with no change. I've swapped tools, I've swapped holders. Tool over hang is roughly 1".

This only happens with this specific tool and if I remember correctly it started when I had to replace the computer last week.

Any ideas anyone has would be great.

[BlueFin]

New computer, XML tweak?

[levelzero]

If it was a setting issue then I'd expect the problem to happen with other tools/cuts.

[saabaero]

Does the spindle/motor appear to spin freely by hand (without any noises). Does the drive actually fault out or is it just that the spindle stops. The clicking/crunching defenitely sounds like a mechanical issue.

You could probably try running the program cutting air or with he belt removed to see if the problem is in the spindle or motor/drive.

[levelzero]

It might just be stopping.

Everything appears to be fine. It's something specific to the spot drill. I ran the machine for 8 hours with a 4 flute .25 and for another 2 hours afterwards with a different cutter. It only happens when I try to chamfer using the spot drill.

I also tried stalling the motor by hand and could not do it so the slip comp is set right. This is a relatively light cut and as I said I've been making these parts for over a year with no problems.

[keithorr]

if you run the same program without the tool installed or with the Z axis reference raised to cut air, does it still happen?

[levelzero]

if you run the same program without the tool installed or with the Z axis reference raised to cut air, does it still happen?

No it doesn't. It also doesn't always happen at the same spot/depth.

[philbur]

I don't have a clue what your problem is but have you tried to trace the source of the "There is a strange clicking/crunching sound and after about a second the spindle will stall.". Also I think the original VFD has a reputation of being a bit flaky, especially stopping at random occasions, during speed changes and also failing to start.

For me there are only two ways the machine can have any idea what cutter is in the spindle and that is either motor load or g-code/tool table. A light cut gives no appreciable load so as impossible as it sounds it must be the g-code/tool table, well that's the theory anyway.

I assume that it's happen enough times that there is no chance it is just luck that it is always the spot drill.

Phil

[levelzero]

The sound is coming from the tool/lower spindle area but I can't make it happen for long enough to get a stethoscope and listen to the various areas.

Yes the original VFD seems to be very flakey and prone to dieing from what I've heard. I've been meaning to buy the spindle upgrade but I'm hesitant to randomly start replacing things without knowing what the problem is, especially as I have a limited budget to throw at repairs right now.

I just swapped in a brand new computer and ran the program in the air with no problems. I'm going to throw a piece of metal in and try again but I'm not really all that hopeful as it's never had a problem cutting air, just metal.

It's happened 25+ times now but only with a spot drill. I can bury a .500" cutter and have no problems so I find it hard to believe it's a load issue. I think it has something to do with the side load the spot drill is seeing/transmitting into the spindle.

[philbur]

But surely you had equal or even bigger side loads with:

" I ran the machine for 8 hours with a 4 flute .25 and for another 2 hours afterwards with a different cutter."

Phil

I think it has something to do with the side load the spot drill is seeing/transmitting into the spindle.

[levelzero]

But surely you had equal or even bigger side loads with:

" I ran the machine for 8 hours with a 4 flute .25 and for another 2 hours afterwards with a different cutter."

Phil

I would agree, the only reason I would be tempted to think otherwise is that a spot drill isn't really designed to cut on it's side and this could have an effect of things. I'm really just grasping at straws at this point as I've tried everything I can think of.

[philbur]

How about a flaky VFD combined for a dodgy lower bearing. Why not put a blank rod in the spindle, run it at full rpm and apply some side load while listening to the lower bearings.

Phil

I would agree, the only reason I would be tempted to think otherwise is that a spot drill isn't really designed to cut on it's side and this could have an effect of things. I'm really just grasping at straws at this point as I've tried everything I can think of.