Electronics for New Machine + Chinese Spindle + VFD

[mturneruk]

Just had my first oh shit emergency stop.

For some reason during a multipass cut of 18mm Birch plywood, the machine lost about 10mm in the Y direction during pass number 4.
I was cutting 4mm passes at about 1500 mm / per min.

As i was towards the end of the cut the cutter was already 16mm into the wood, so when the Y lost 10mm the cutter started to plow into the full depth plywood.

After slamming the Estop. I jogged the machine back to what should of been the Zero start point but the Y was 10mm behind where i started. The gantry still seemed square.

It buggered up my very nice piece of ply, but Jazzes Estop circuit worked perfectly! Anyone got any ideas what might of happened?.
I thought i set a fairly conservative feed rate / multipass depth to be honest.

Thanks
Martin

[mturneruk]

I just ran it again at a slower feedrate and it completed ok. Not happy though. Would love to understand what happened.

Also I noticed that when I was surfacing my table the other day (using Jog), every now and again the jog would stop while I still had my hand on the key.
However no reason was given as to why by Mach3. No limit switches tripped etc. I had to reset the machine before i could continue. This must of happened 10 times during my table surfacing.

Do you think this could be down to Noise ?
Anyone got any suggestions ?

Thanks Martin

[JAZZCNC]

Do you think this could be down to Noise ?
Anyone got any suggestions

Nope it's dodgy keyboard happens often. Change keyboard at try it again think you'll find it's ok.

The losing position could be number of things.? Most common is slipping coupler or pulley. Mark them and keep an eye to see if move.

Could be you have over tuned the motors and it's losing steps on rapid moves between positional moves.? What Velocity and Accel do you have set for each Axis.?

[mturneruk]

I was thinking slipping couplings. My ball screws don't have any flats on them so they are effectively only held by the tightness of 2 M4 screws in the coupling, where as the steppers do i think.

I would of thought if it had slipped, it would of been one side or the other rather than both Y and A.

As you say - I will mark and see what happens.. Do you think my 1500mm per min feedrate / 4mm depth cut was fairly conservative with a 6mm cutter ?
My cutter is only a straight two flute and it was screaming a little. Might be time to invest in some better cutters.

I read compression bit for plywood and cut the whole 18mm at once! Sounds like that might cause me a problem.

Cheers
Martin

[JAZZCNC]

I would of thought if it had slipped, it would of been one side or the other rather than both Y and A.

But are you sure it both screws lost position together.! Did you check.? After you homed the gantry would square back up so unless you checked then won't know without marks.

Do you think my 1500mm per min feedrate / 4mm depth cut was fairly conservative with a 6mm cutter ?
My cutter is only a straight two flute and it was screaming a little. Might be time to invest in some better cutters.

Unless cutter was Knackerd it should easily handle that feed rate and DOC. What RPM.?

[mturneruk]

Thanks Jazz. Hmmm. I hadn't homed the machine today. Also my Y / A currently only has prox sensor on one side e.g. Y. Are you saying I should have sensors on both sides e.g Y and A?
Makes sense when i think about it. Now i think i understand why Y and A decouple during homing.

I dont know if both screws lost position or not. Will measure tomorrow. I suspect there is some slippage going on on one side or the other. Would a small drop of loctite be sensible on the coupling bolts ?

RPM was around 14,000. I tried faster and slower and that sounded most comfortable.

[njhussey]

My machine started losing position, it was a loose pulley on the stepper...I hadn't put enough loctite on it!

[JAZZCNC]

Would a small drop of loctite be sensible on the coupling bolts ?

Not sensible more Essential. I'd also file a flat on the Ballscrews.

Regards Homing to separate switches then Yes you want them so can reset gantry square if start losing steps. If not then over time if you lose steps on the unswitched side it will never get reset so error builds over time and eventually racks the gantry and stalls one of the motors while other keeps going. Often this happens at high speeds when torque is lowest and you can imagine the results.!!

[mturneruk]

OK. It did it twice more this morning, and i am certain that the couplings are not at fault. I marked them and they haven't moved.
I homed the machine this morning before i started.

The first time the Y was 250mm off where it should of been when it started cutting along the x direction, and the second time I have no idea what it was doing, but basically it appeared to slow right down and then start cutting in the wrong direction. I was profile cutting 18mm lightply.
In all instances the feedrate has dropped from what i set (1500) to very slow when the problems have occurred, although Mach3 did not show this on the screen.

I have tried going back to the default Mach Screen layout as i was previously using 2010 screenset, and it still did it.

I am trying now a mid air cut, to see if i can reproduce it, and to film what actually happens without any danger.

[JAZZCNC]

You have got the steps per setting right haven't you.? Have you checked it's moving the correct distance.?