[EvilSpeeder]

Hi!

I've got a 2nd gen joes machine, 4x4 bed, R&P, NEMA23, G540, 48V 12.5A PS,Ethernet smooth stepper, a computer that's plenty fast, and I'm running Mach3..

My problem is random e-stops. I've been fighting this problem for a while and some fixes seem to help but it's gotten worse and my machine is unusable. The now machine will be running along happily and then Mach3 will perform/detect an E-stop in the middle of the cut, and occasionally when it's just sitting still with the drives on. It's so random I haven't been able to fix it though super systematic troubleshooting so now I'm just replacing parts that I think might be involved and praying something works.

Thus far I've replaced:

Router motor, steppers, motor cable, G540. Shorted the e-stop on G540. I was using a parallel port interface and switched to the Ethernet Smooth Stepper. I formatted my computer and reinstalled XP and the latest version of Mach3. I replaced the 4-year old router thinking that the brushes might be worn and causing an issue with noise. I've tried air cutting and cutting material. I've changed all the settings in mach that I thought might have an effect. There have been instances where it will e-stop when sitting idle, but these are rare.

The only things I haven't physically replaced are the 48V supply to the drive and it's huge cap. The PS seems like a red herring to me in my limited expertise. With such a huge cap it should be pretty immune to voltage drop and my multimeter readings seem to confirm it (+-200mV max). Agree? I'm using a multimeter and not a scope though.
I'm out of ideas and out of money to keep throwing at it. Does anyone have any other ideas?

Thanks,

John

[mactec54]

EvilSpeeder

You say you have replaced some cables, but have not said anything about the cables being shielded, you need shielded cables, & they need to be installed correctly, you can also increase the Debounce in the General Configuration, this can help with false E-Stop & limit switch triggers

[EvilSpeeder]

The new cables are shielded and rated for hi-flex applications. What do you mean by 'installed correctly'.

[ger21]

Most likely noise or ground loops are triggering the estop or limits.

Is your estop and limit wiring shielded? What mactec means is that the shield must be properly grounded.

A quick workaround would be to increase the debounce setting in the Smoothstepper. I'm not sure where it's at or what it's called.
Increasing the debounce for the parallel port probably would have got rid of the issue without replacing anything.

[Al_The_Man]

The main reason I have found is not conforming to a star ground point and something called equi-potential bonding, this is making sure that all metallic parts of the machine, and motor frames are connected to the star ground point, also in some cases grounding the commons of all power supplies will help.
http://www.cnczone.com/forums/phase-...se-issues.html
http://www.automation.siemens.com/do.../emv_r.pdf?p=1
Al.

[Eldon_Joh]

i read somewhere else that the voltage limit for the g540 is 67vdc, which implies 70 or 80 volt components..

anyways... i did buy a G540 in 2012 i think it was.. and recently took it apart. i found out that the mosfets were pressed against the aluminum shell.. and there was no insulation other than the anodized aluminum oxide layer for voltage isolation.
i also found an aluminum chip inside the damn thing.. at the time i put the case together i thought that would be impossible.

so i placed a wd-40 soaked piece of paper between the fets and the aluminum and put the drive back together.
I never had any problems before or after but i suspect the al oxide failing and the fets shorting out is a potential failure point that would manifest exactly as you describe...

[LeeWay]

Have you looked at the diagnostics screen when this happens?

[davy182]

i second Al's post and add in to also put a separate 5v power supply for the drivers as this has helped me in the past.

[EvilSpeeder]

I have looked at the diagnostic screen and don't see anything unusual. It's got plenty of buffer. When it e-stops the indicator for that lights up.

I've separated the router and G540/PS,

I have not grounded the DC supply common to the star ground. I've heard good and bad about that.

What's the separate 5v supply for? The Smoothstepper? It's got it's own power supply but is on the same mains circuit as the PS for the G540.

I thought they put the MOSFETS against the case for thermal reasons. Could this design introduce noise issues in and of itself? They suggest putting a heat sink on it (which I have, and a fan).

I don't know if I mentioned, I have two G540s and have switched them out and gotten the same results.

[davy182]

Try having two separate ps from you g540 and the smoothstepper is what i mean, so in essence isolating them completely.

[Eldon_Joh]

I think you should make sure that you cannot have any dangerous voltages (static or line volts, doesn't matter) between the g540 ground and the computer ground. i haven't dug up the g540 schematic but i'd be presuming everything is optically isolated.

someone else mentioned static discharges while machining foam.. if you've got anything similar going on and you don't have the power supply grounded then if you get a static discharge to the motor its going to arc through the wires in the steppers and into the g540 and work all sorts of wonders in there.

[CNCMAN172]

Evil Speeder,
Use 24VDC going through your limit switches and had them activate a relay that provides the ground to the enable lead on the G540. You are picking up noise so by using a higher voltage running through the limits it will make your machine more noise immune. The limit switches should be normally closed when not activated, so the 24VDC power flows to a 24VDC relay. The common contact on the relay will be connected to a ground at the G540. The NO contact of the relay will be a wire going to the enable lead on the G540. I think you will find this simple solution will stop all the unexpected estop errors. Good Luck
Russ

[EvilSpeeder]

CNC Man: That makes total sense and I agree. The only catch is, I'm not running limit switches. I have an e-stop button but it's in a metal box that's grounded to the shield of the shielded wire that goes to the G540.

[CNCMAN172]

CNC Man: That makes total sense and I agree. The only catch is, I'm not running limit switches. I have an e-stop button but it's in a metal box that's grounded to the shield of the shielded wire that goes to the G540.

You need to explain how you have your e-stop switch wired. Do you have e-stop wired to the parallel port? What are you using as home sensors? We need a little more info to help you man.


Russ

[EvilSpeeder]

My setup is currently as simple as you can get with the addition of an e-stop button instead of a jumper. The G540 has the motor cables, parallel cable, power, ground, and the e-stop wired into it. That is all. No limit switches, no home switches.

The e-stop switch is wired with one end at the common ground point and the other is attached to the input on the G540. I have tested with a jumper as well and that did not solve the problem.

Right now I'm working on putting everything in a proper enclosure. Hopefully that will solve it. It also forces me to re-wire things, so maybe I'll find something I missed? I don't know. If I had a dollar for every time I've been sure I had located the problem and then was wrong, I'd buy a real nice router that has people to come fix it so I don't have to. For instance, I found that one of the motor wires had been snagging on a bracket and it was torn through the outer insulator and the shield exposing to the insulation of the individual conductors. There was a small cut that went though all the way to copper on one wire. I thought, "That HAS to be it." Wrong....

[mactec54]

EvilSpeeder

How have you grounded the shields, that you do have, some photos would be good

[CNCMAN172]

EvilSpeeder,
As Mactec54 requested a few pictures might help. Here is what I think might be going on with your system. I am assuming you are using MACH3 with a parallel port setup, sounds like you are new so my guess is you used the default setup. You need to look under Configuration at the top of the page and then Ports/Pins and then look under inputs. The E-STOP function is my default assigned to a input pin, normally pin 15 if I remember correctly. Since you are just using an E-stop button or switch that disables the G540 stepper driver MACH3 knows absolutely nothing about that switch. You need to disable the E-stop function on the inputs page. It is probably looking at your parallel card and seeing the inputs floating, since they are not wired to anything in your situation for the E-stop pin. Check that out and you will probably resolve your problem. I would highly recommend you implement limits switches / home switches as well. Depending on your machine a few mistakes can be costly if you command the hardware to do something wrong by accident and you have no protection.
Russ