Configuring Mach3

[hub]

I have been setting up and configuring Mach3 mill for my 3 axis CNC machine.
Some problems/questions/notes..

- I had to do the 'axis calibration' for each axis VERY many (more than 20) times. Now it's accurate enough, but why did it take so many times? Move axis; check measurement; enter value.. Over and over. Got closer and closer each time. Is it something in the software or something in my measurement technique? I measured using a digital caliper fixed to the axis to be measured.

- I had the E-Stop input on in Mach, but after some time running the machine it would say E-Stop has been pressed, even though it hadn't. Disabled the input in Mach and now it works fine. I'm guessing some sort of noise triggered to input..? The E-Stop is connected to the stepper drivers and spindle, it will stop them but the problem is Mach3 doesn't know E-Stop has been pressed so it continues to run the GCode happily thinking nothing is wrong.. Any ideas?

- Spindle RPM is not constant. Mach is controlling it. I'm guessing the pulse rate varies a bit.. Any way to fix this?

- Otherwise, works pretty good

[ger21]

I've heard about the calibration issue ,but have never used it. Just do the math to get your steps/unit, make a cut and measure. If it's off, do the math and enter the correct number. Done.

Sounds like noise is triggering the E-Stop. A band aid fix is to increase the debounce in general config. Try a value of 2000 to start.
As for Mach3 not stopping, get a switch with another set of contacts and wire it to an input pin to mach3, so it knows to stop.

What are you controlling your spindle with? The pulse rate shouldn't vary much at all. If it does, you'll notice it in your steppers too.

[hub]

Thanks for the reply

I used the calibration in this case because I have on the X and Y axis plain threaded rod for now. Yes, they have a pitch, but it's too inaccurate I think so I thought I would try the calibration.. Worked ok in the end but I agree the math would be a better way.

Band aid fix? With a value of 2000? I'm totally lost.. What do you mean, sorry..
I know how to make Mach3 stop, I have just disabled it for now because of the issue.

I'm controlling my spindle with Mach 3, it send a PWM signal to my break out board, which converts it to analogue 0-10V, which is connected to my VFD analogue input.
I haven't noticed the same with the steppers. I can't confirm it but they sound to do constant RPM..

[hub]

I checked the 'General Config' and could not find a setting for band aid fix.. I found 'Debounce Interval' and 'Index Debounce'. Would it be any of those? (Currently both are 0).

[ger21]

I said band aid because it doesn't fix the noise issue, but it makes it better. It's the Debounce, (not the index).

Measure the voltage coming out of the breakout board, and see if it's steady. I use pwm with my spindle (Super-PID) and it's rock solid. It could also be the VFD maybe?

[hub]

Ok, thanks a lot! Will try that tomorrow & see if it helps..

[Grebbo]

Hi hub,

I had lots of trouble with intermittent “noise” with my machine when I first set it up, it would trip the “E Stop” half way through a job etc, here a some things you may consider and are ones I did and eventually gotten rid of noise, or at least to a level where it’s not a problem:
1. Shield your wires that you have running to your limit switches, use shielded computer wire etc.
2. Separate your wires e.g. stepper motor supply from your limit switches wires, don’t have them touching etc.
3. Move your BOB as far away from your drivers, I put mine in an aluminium box to further shield it from noise, just turn your radio on and turn your drives on and you will see or hear how much noise drivers and power supply can produce!!
4. My VFD probably caused some of the “noise” as well, if you are using one, isolate those wires as well.
5. Increase your Debounce, I have heard of some going as far as 5000?? (this is a “band aid fix” as Gerry mentioned in his post, but might get you going until you work out what is actually causing your noise.
6. Slow down your machine, e.g. do not go over 100% feed rate.
Some might work and some might be totally irrelevant, however when you are stuck at 2.00am and pulling your hair out, they might just work,

Good luck,

Mel

[hub]

Thanks a lot Mel,

I haven't had a chance to test the "debounce" setting yet, I have done some mechanic work on the machine. When it's done I can do some tests..

Reading your helpful suggestions, I have several things "wrong":
- My stepper cables are not shielded, neither is the E-Stop cable (but the wire from VFD to motor is shielded)
- BOB is very close to the drivers (I'm using the cables supplied with the kit, which are short...)

I'll try your suggestions when the machine is ready to run again

Yes, the machine totally kills my radio signal! Probably the neighbors too...

I have already slowed down the machine, because I have some stalling issues at higher speeds, still trying to resolve that problem.. But for now I'm just going slower to be safe until I get it fixed somehow.

Hub

[Grebbo]

Hi hub,

Below is the shielded cable that I’m using to run my limit switches, I got it from the local electronics supplier, I actually doubled up the wires (tied 2 wires together) and then connected the shield to earth. From memory I did not use shielded cable for the stepper motors but did separate them away from the limit switch wires.

Hope that helps.
Good luck,

Mel

[hub]

Thanks Mel
Did you connect the shield wire only? Or the wire + "shield foil"? I'm guessing connect to ground in one end only?

Hub

[Grebbo]

Correct, just connect the wire at one end, the foil is already connected within the cable, I also left the foil as long as I could around the contacts of the limit switches, ( I was desperate!!) where I made the connection between cables, I also put them in a small aluminium box that’s bolted to my gantry which is metal, I think I have spent more time stuffing around with noise then actually wiring my machine up..

[hub]

An update on this; thanks a lot for the help
The debounce setting fixed my problem on the E-Stop, works perfectly now!!

I'm still having trouble with the spindle RPM though..
I'm guessing it's a computer issue with not stable enough pulse rate. But in saying that, it's very strange that the steppers seems to have pretty constant RPM..
I'll next try shielded cables; test and see if that helps.

Hub