Question Ghost steps/skipping steps while cutting aluminium

Hello,

New owner of SC 840/2
Setup: orginal electronics LPT controlled, running on MACH 3, china made 400w spindle

I had previous problems with skipping steps, when cutting wood, but they seem to be mach3 setup problems.

But now while cutting aluminium i encounterd that on some operations program stopped and gave me E-stop, also it had added many Z axis steps causing to cut trough spoil board and when moved to next operation broke tool and also lost some on Y axis (missed cutting line)

Now i have noticed that problem starts when spinlde hits metal, steppers go crazy and gives E-stop



It sounds like some electrical/magnetic disturbances but where do i start? SC controller, LPT cable or computer motherboard

Maybe someone had same issues or has any idea what could be issue?

I think your China spindle causes electromagnetic interference. To solve this it should be sufficient to ground the machine with the supplied ground cable..

I had a similar problems with an odd china power supply. Even with machine grounded there were false steps. Solution was replacing this piece of shit with a well made supply.

But it has nothing to do with Mach3.

If your using a DC motor from ebay running on a PWM power supply then that is one cause of noise. The motors are okay - the controllers are really really low quality items made with the cheapest of parts.

if you drive the motor with a better power supply the performance from the motor will be a lot better.

And make sure the machine is grounded. but this can still not be enough for this sort of motor controller.

for best noise immunity you want everything star grounded in a control bay. Introducing a separate DC motor controller into the system will for sure open up the possibility for ground loop noise.


Another possible issue could be as per the following

Simply - the stepper amplifiers take the frequency of the pulses to the inputs from PC and the frequency then controls the motor speed.

So for example X pulses per second equals X rpm of motor. provided the pulses are spaced equally. If the pulese have some timing issues (common with poor LPT outputs) then the motor and drives will see this as accelerations and decelerations (as opposed to constant velocity) and you will see a massive loss of torque. The clicking could be the lpt output giving spurious irregular pulses also. its hard to know.

For sure - what you need to do is get a UC100 USB controller. We have seen examples where moving form LPT to UC100 USB controller results in double the max speed of the machine. Same machine, same config same steppers - and twice as good.


One other comment - your cutting thin aluminium sheet.

Your cutter stick out is HUGE. The longer the cutter is out of the collet the larger the lever arm between the end of cutter and the collet. You want that cutter in the collet as far as it will go. So only a few mms of cutter above the material thicknes. this will greatly reduce vibration and increase the peroformance. That cutter will flex and bend and vibrate very easily like that.

also - be aware that WD40 and other spray lubricants have flahs points. So if its getting really hot it can be dangerous also.

Hello,

A little update, i tried few things.


grounded together; spindle motor housing, machine Y rail and aluminium plate (stock) - nothing changed, still ghosting
grounded machine to mains earth lead - a bit better
Plugged PC, spindle motor and SC machine trough UPS - it seemed to work all good

BUT

i had long program to cut (foam 2000mm/min) and after 15min of cutting, some of the axis would get stuck and skip steps (around 50mm) and ruin whole work. There was no mechanical problem with machine, it continued cutting like nothing happend. There seemed to be some electrical issue to cause stepper to make whining noise but not move.

This pissed me off so i bough new 4axis china controller and also updated all steppers to 0,65nm NEMA17
I tested, not fastest (3300mm/min) but no skipping and quiet operation.
Few build pics soon.

A correctly tuned STEPCRAFT machine with a UC100 USB controller will not loose steps like you have seen.

the LPT control or mechanical tuning is the cause of the lost steps.

This is like in our health system: sometimes it is easier to cure the symptoms instead of fixing the real problem.
Hopefully your problem does not lead to an increased wearout and you do not start loosing accuracy over time.

Good luck!