[Murphy_ia]

Hi after getting my machine up and running I have been testing different cuts, and have found a problem with my z axis. When running some text engraving programs it just keeps getting deeper and deeper. I have tried some 3d milling running for an hour or more with no errors, running a 20minute engraving profile crashes the tool every time.
Set up a program to test the z axis and ran 1500 lines with G0 moves on the z axis and ended up with a drop of 5thousands when it was done. Tried the engraving program and just ran it in air without the spindle on and zero was the same before and after the run, ran the same program (17minutes) still in air but with 2500rpm on the spindle and ended up 163thousands lower than when I started.
Any ideas where to look for my error, I have turned the motor tuning way down and now have 40IPM on the Z with an accelleration of 10. I am using a 570 oz stepper with direct drive.
Could the problem be a too small ball screw, I am using a 1605 on the Z axis also, and if that is the problem do you think I can solve it temporarily by using the original acme screw instead?

[IN-WondeR]

Sounds more to me, like you have some form of RF noise...

[awerby]

Yes, if the errors only show up when the spindle's turned on, that points towards noise thrown off by the spindle leads. Try putting a braided wire shield around them, grounded at the VFD end . , ,

[AVRnj]

Have you ruled out tool pullout?

[Murphy_ia]

Thanks, the noise sounds like a plausible explanation, hadnt tought of that. Noise could also explain a few intermittent jumps in the Y axis that I have thought came from to high motor speed as I havent seen it after I turned the speed down.
It is not tool pullout, the last test was cutting in air and used an indicator before and after to measure from the spindle head to base so no tool to worry about.
I have now shielded the motor wires and grounded the shield, test program is running right now so will have an idea if it worked or not in about 20 minutes.

[Murphy_ia]

Preliminary tests turned out ok, will run a few full scale tests tomorrow and see, but so far it seems the problem is solved. :banana:

[Acctek CNC]

Hello Murphy
if you test , still with problem , you can try to removed inverter from control box , because inverter have many magnetic field , interference the driver , inverter and driver separate , problem will solve .
Frank

[Murphy_ia]

Problem is back, turned out after I put the shield on the motor wires the leads were somehow reversed to the r/f switch so with the switch in F as usual the spindle ran in reverse which I didnt notice until after the aircut testing was done, all of the tests turned out perfect by the way. Then it was time for the real testcuts, engraving looked a little rough but came out perfect dimension vise. Slotting with the cutter in reverse makes for some funny looking cuts. When I saw this and switched back so the switch and the rotation direction matched again, the problems were back in forward, turn the switch to reverse and it runs perfect again.

[mduckett]

Is any of the VFD wiring running near the stepper motor wiring? Noise still seems to be a likely cause. Re-position cabling, and shielding the step/direction signals from your BOB to the stepper controllers might help--simply twisting each with a ground wire might help. Another thought is that maybe the Forward state is somehow loading down the logic voltage supply to the point where the Step/Direction levels are not meeting their timing requirements for rise times. Can you provide more details on your BOB, stepper and VFD setup to help with trouble shooting? --md

[Murphy_ia]

The VFD and motor controller is the original (the same as the G0704 but 220V) I am using shielded wires for all the steppers but havnt gounded the shields, will try that. The BOB is C10 and Nema23 570 oz steppers, The closest the wiring for the spindle motor is to the steppers wires are about 8 inches and usually when it runs it is much more. When running in forward I get about 1000RPM more than in reverse will try to run the spindle motor from a different circuit and see if that helps.

[Murphy_ia]

Tried running the spindle motor from a different circuit but that didnt make any difference still got between 10 and 30 thousands error after a 20min run.

[SCzEngrgGroup]

The VFD and motor controller is the original (the same as the G0704 but 220V) I am using shielded wires for all the steppers but havnt gounded the shields, will try that. The BOB is C10 and Nema23 570 oz steppers, The closest the wiring for the spindle motor is to the steppers wires are about 8 inches and usually when it runs it is much more. When running in forward I get about 1000RPM more than in reverse will try to run the spindle motor from a different circuit and see if that helps.

Your problem will be in the Step/Dir wiring, or the BOB wiring, NOT the motor wiring. No amount of "noise" can cause the motor to move, but it can easily create false step pulses that will cause the motor drive to move the motor..

Regards,
Ray L.

[Murphy_ia]

But then how come the error is only with the spindle running one direction, there is no errors when running in reverse or doing testruns without the spindle running.

[LongRat]

If you have the original motor and speed controller, then it isn't a VFD. It's a brushed motor with a basic and temperamental drive. If you are getting massively different speeds F/R, look at your motor's commutator and you may see a ton of arcing especially when running in the 'slower' direction. I suspect this is generating loads of RF noise and is, as has been said, interfering with your step/dir signals causing the errors.
I have the 30-size machine but the motor controller is basically the same, I opened mine up to find loose wires and washers rattling around inside the box, touching the circuit board and generally causing havoc. I switched to an AC motor and VFD and junked the original stuff. Been happy ever since!

[Murphy_ia]

Found it!!

I got my estop switch wired up to stop both the spindle motor and Mach, and have been using the same 4pin plug for the estop wiring and limit switches, and this is where the noise got to the BOB. Disconnected the plug and ran without estop and limit switches and no errors. So now there will be separate plugs for limit switches and the estop and hopefully that will work better. Might also have to rewire the estop to get the stop for the BOB and spindle motor separate.