Axis drfit

[Ne3M]

Hi all,

I bought the ZEN 12x12 DIY kit with Mach3 but cant get it properly going. When I try to cut PCB isolation traces everything will work perfectly and then suddenly the axis' will randomly drift and after a couple seconds work fine again.I have tried so many configurations and dont know how to solve this problem. What I have done.
1. Switched from Laptop(I hoped it was the powersave chipset issue which Mach3 reported with laptops) with LPT to Desktop PC and bought a MOSCHIP9865 PCI LPT card (Other users report great success)
2. Tried fresh install of WinXP and Win7
3. Tried different settings with the TBA6560 CARD such as 8 micro steps/16 microsteps, 50% and 75% current, 0,25,50,100% decay current.
4. Modified the Motor tuning file extensively (Tried the Zentools examples, tried a lot of different configs)
5. Tried 25, 60, 100kHz switching rate
6. Checked and rechecked all connections, PSU is stable at 12V.

Does anyone have any other suggestion of what I can look at? I really dont know what to try next...

Attached is an example of what would happen when the axis would drift and not close the isolation properly.

Also attached is the current config for 16 micro steps on Nema23 Motors as supplied by Zentools. Note that 8 micro steps gave the same results.

[ger21]

1) Decrease acceleration and velocity in motor tuning by 50%.
2) Use a 24V power supply instead of 12V.

[Ne3M]

Tried it, still the same.

Resoldered the bad for bad connection. Checked for a floating earth to the PC side, nothing.

At this stage I'm thinking that it might be the switch levels, the PCI card is 3.3V. Does it need to be stepped up to 5V?

Can anyone recommend an alternative PROPPER controller, like the smooth stepper or other?

[neilw20]

I suspect 2400 is way too high for the speed setting for 12v supply
Try 600 to start with.
Follow this in post #2
http://www.cnczone.com/forums/mach_s...or_stalls.html

[Ne3M]

Originally Posted by neilw20 I suspect 2400 is way too high for the speed setting for 12v supply Try 600 to start with. Follow this in post #2 http://www.cnczone.com/forums/mach_s...or_stalls.html

Reduced it to 600 and used a 24V supply. Same sudden random drifting. I'm suspecting noise here on these cheap boards...

Dammit!

[neilw20]

SINGLE Common point negative for all the drivers to main filter capacitor.
No daisy chained commons. Use single point common.
Strategy is to treat all wires like resistors, albeit low values, and make sure any voltage drop across a wire has no affect on other wires.

Opto coupled? Probably not.

[Ne3M]

No optocoupling, board was included in the kit. Is there any opto isolation circuit for the parallel ports?

[neilw20]

1. Take some clear photos of your wiring etc.
2. Measure one of the lines on the parallel port, to PC ground. 3.3v or 5v?

[neilw20]

Before looking too far, I just noticed your PCB picture.
Do you have a loose coupling in one axis giving backlash?

It always is the same axis, so this appears to be a mechanical problem.

Just load the axis by hand, and use the cursor keys to change direction and ensure there is no mechanical backlash.

If backlash, fix the mechanical problem. Mase sure Mach3 backlash compensation is turned off.

Try plotting some circles using MDI

F100
G0 X0 Y0
(you set Z where you want it)
G1 X-8
G3 I0 J0 (do a circle)
G1
M30
(did it finish where it started at X-8 Y0 ? It should)

[Ne3M]

Thanks for your help. Parallel port output pins are 3.3V, even found to datasheet online MOSCHIP 9865 to see if I cant change the output values to 5V. I've disconnected all the I/O pins from the board and are only driving the Stepper motors now. I am suspecting the Limit switches' wiring are acting as antennae/EMF. I an now busy with a trial run to see if anything "drifts". When an axis starts to drift it sounds like rocks falling(noise from stepper jumping around). Mannualy moving all axis in every direction is via Mach3 works fine.

There are no mechanical issues. I've clamped the screws with my hands and boy those stepper deliver a lot of torq!

My steppers are at 45C is this fine?

[neilw20]

The low level input spec is 0.8v or less.
The high level is 2v or more (from Toshiba data sheet)

That being the case, 3.3v should be OK.

It looks like you have a noise problem.
Try setting the step and direction pulse time to say 2-5 uS in motor tuning.

At worst nothing will change from what you have now.

Again, some pictures may help to solve your problem.
Many times, this sort of problem can be as simple as changing a wire a few inches.

There is only 1.6v margin between high and low on the inputs, and spikes can easily be induced in input wiring from the stepper power side. Be aware that circulating currents amounting to amps can be flowing into and out of a supply filter cap, and also drops in longish wire due to self inductance.

Photos, photos, photos....

[Ne3M]

Some pictures

I think some back EMF is introduced on the Z limit axis switches located at the spindle since I'm running those wires for both the limit switches as well as the spindle(PWM) together!