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Uncommanded rapid Z plunges!
« on: June 22, 2014, 12:37:36 PM »
Ok, this is getting really scary. I've now had two rapid Z plunges into the work, one while manually entering a Z coordinate which it ignored and went down. The second one I've taken a screenshot of. Look at the positions shown on the program and look at the DRO!
Once my heart rate got back to normal and I was brave enough to get out of E-Stop and reset it, I did a G01Z0F100 move which it happily did, so it clearly hadn't lost where zero was.

So please, can someone tell me what this is all about. I'm using an Aqua screen that I understand is a common one but now I'm wondering if it's full of holes.
Maybe it's because I'm using the computer for other things at the same time as Mach3? Surely that wouldn't result in something like that?
I'm getting to the point where I'm scared to use it. This is a powerful machine, not a toy, and it's capable of causing serious damage.
I've switched to the default screen and set the Z backlash compensation value back to zero in case that's got something to do with it.

Has anyone else experienced anything like this?

Offline ger21

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Re: Uncommanded rapid Z plunges!
« Reply #1 on: June 22, 2014, 12:55:12 PM »
SO, at that line of code, it just started plunging 25mm too deep?
No, I've never heard of or seen anything like that.

You should never use the computer for anything else while Mach3 is running. It can definitely cause issues, but I wouldn't expect it to do what you're seeing.

And no, the screenset has no effect on Mach3 operation. The only thihg different is the look. Everything "under the hood" is the same Mach3. I created the Aqua screenset, btw.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Uncommanded rapid Z plunges!
« Reply #2 on: June 22, 2014, 01:24:10 PM »
SO, at that line of code, it just started plunging 25mm too deep?
No, I've never heard of or seen anything like that.

You should never use the computer for anything else while Mach3 is running. It can definitely cause issues, but I wouldn't expect it to do what you're seeing.

And no, the screenset has no effect on Mach3 operation. The only thihg different is the look. Everything "under the hood" is the same Mach3. I created the Aqua screenset, btw.

It seems to be related to the high speed movement when it lifts, repositions for the next cut and then plunges again. Yes, your interpretation is correct. It seems to react violently to the F1000 feedrate and then plunge another 12mm or so before happily carrying on with the program running in the window and the DRO updating to the wrong position. If I then stop the program and tell it to go to Z0, its correct. In other words, this is not a case of the machine losing pulses, it agrees with the DRO. It's the DRO that's lost position compared to the program that generated it.

I've slowed the F1000 down to F400 and that seems to resolve the problem. This looks like an issue to do with the rate at which the DRO is capable of keeping up with the program. Maybe there's someone I could send these files and my setup file, I'm sure it would reproduce without a machine connected, after all, it's a dumb open loop system?

I'm using an ESS by the way.

This has nothing to do with the computer doing other functions. It does this regardless of whether the computer is standing idle or not. I thought the whole point of the ESS was to offload the work done by Windows. I've been happily surfing the internet, creating other 3D jobs and all kinds of things while another job has been running without a hiccup.

I'll switch back to the aqua screen since that doesn't affect anything. It's an awful lot better than the default one which is a nightmare in my opinion. I do wish things like the Home buttons weren't dangerously close to the Zero on the DRO's that's an accident waiting to happen.
Re: Uncommanded rapid Z plunges!
« Reply #3 on: June 22, 2014, 02:06:50 PM »
Ok, I can get this to repeat just from the MDI.
All I have to do is to set a feedrate of say F2000, do a move in X or Y and then type Z to a new position and it plunges straight down. This is something peculiar to the setup of Z, nothing else. Remember, this has nothing to do with the machine, the machine is doing exactly what it's told.
The feedrates I mention are not at all fast, I've been using F3000 (3000mm/min) for years on this machine with a different controller.

Offline ger21

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Re: Uncommanded rapid Z plunges!
« Reply #4 on: June 22, 2014, 02:27:39 PM »
You didn't say you had an ESS. So yes, with an ESS, you can do other things while Mach3 is running.
My guess is that your problem may be related to the ESS.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: Uncommanded rapid Z plunges!
« Reply #5 on: June 22, 2014, 04:18:55 PM »
I would have thought that Mach3 would be in control of interpreting the program and displaying the DRO? Surely the ESS only creates the steps?

Offline Hood

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Re: Uncommanded rapid Z plunges!
« Reply #6 on: June 22, 2014, 04:48:11 PM »
ESS will update the DROs.
Attach your xml and I will take a look.
Hood
Re: Uncommanded rapid Z plunges!
« Reply #7 on: June 22, 2014, 05:41:55 PM »
ESS will update the DROs.
Attach your xml and I will take a look.
Hood

Thanks, I appreciate your help. It's always a problem with a split product like this, it's hard to know who to ask and what part of the system is responsible for each part.
I've attached the xml file and the program I was having trouble with so you can try it. I've set the rapid to F2000 and the following plunge to F500, both within the setup parameters of the machine. Hopefully you will see what happens when it does the lift and then start of each cut.
Cheers,
Roger

Offline Hood

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Re: Uncommanded rapid Z plunges!
« Reply #8 on: June 22, 2014, 06:49:40 PM »
I will have to look at your xml on the lathe tomorrow as it is the only machine I have an ESS on and I cant look at certain info without an ESS hooked up
BTW just downloaded the  plugin version you have and it has a config page for Backlash, so you may want to look at that for your previous issues, maybe a setting or two there. Again afraid I can not see that page due to not having an ESS here, so maybe it doesnt have much relevance.
Hood
Re: Uncommanded rapid Z plunges!
« Reply #9 on: June 23, 2014, 02:23:28 AM »
Thanks, hopefully that will show the same fault. What's weird is that if I perform a rapid move in X/Y & Z together, it's smooth and trouble free. It seems that it might be something to do with the fact that the Z moves on its own that it doesn't like. I suspect that there's a problem in the Z motor setup that it uses to initialise the Z only move. The Z axis uses a different resolution to the X & Y axis because there's a toothed belt giving a 2:1 reduction on that axis whereas the others are direct drive.