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Z Height Setting Woes
« on: February 01, 2013, 06:20:43 AM »
Hi,

We have a few machines running mach3 and using both big tex and gerrys 2010 screens to set the Z height (we set the height using the plate manually at every tool change).

We keep having random problems on all machines whereby every so often the tools do not retract from the touch plate and push themselves down hard into the plates, this sometimes chips the end of the tool. We never have any limit errors or home errors and sure no noise exists in any of the machines, we have tried altering the debounce values however this makes no difference as the problem still randomly occurs so we leave now leave them at zero.

It is a really annoying problem and I wonder if anyone else has experienced this? The touch light is rock solid on all machines and from what we can see there's no obvious problem why this occurs. As the problem exists with both screens (only every now and then) I see the problem being elsewhere, although strange how it is on all machines.

All of the machines operate faultlessly, no missed steps on the stepper machines and no positon errors on the servo machines, just the annoying touch plate error every so often on all machines.

If anyone has any advice it would be much appreciated.

Thank you very much.

Offline Chaoticone

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Re: Z Height Setting Woes
« Reply #1 on: February 01, 2013, 06:37:20 AM »
I have never seen this but I always touch the plate to the tool before starting the routine and watch the response of the led.  Have you tried attaching a ground wire to the tool with a clip?  Tell us more about how it is all set up.  I could also see a high debounce setting or circuit going back to Mach causing some delays.  Also, the slower the z is moving while touching off the better the repeatability will be.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: Z Height Setting Woes
« Reply #2 on: February 01, 2013, 06:43:32 AM »
Hi Brett,

Likewise we always gently touch the plate to ensure the light is green, as it always is.
We have a few variants, we have a clip and plate on one machine and the others are earthed so the plate creates a circuit which completes the circuit, both setups display this fault every now and then.

We change tools anything up to 40-50 times a day depending on jobs and in this time we may see the error once or twice. I really am at a loose end as I dont kinow what else to try. The debounce values are zero now and the problem still pops up every so often, no difference if they are set hgher neither.

Really strange and really annoying as each time we probe down were waiting for a problem.

Many thanks for your prompt reply.

Offline Tweakie.CNC

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Re: Z Height Setting Woes
« Reply #3 on: February 01, 2013, 06:52:06 AM »
Could you attach a copy of the probing script that you are using please.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline Chaoticone

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Re: Z Height Setting Woes
« Reply #4 on: February 01, 2013, 06:59:45 AM »
I understand, the intermitten problems are the true pains.  They most often are due to electrical noise but I can imagine timing causing some in certain situations.  I don't know what it could be other than the things I have listed already, but others may know.  We have lots of sharp people hanging around here.  You may want to slow it down to a creep to keep from damageing tools until you can narrow it down.

Brett
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: Z Height Setting Woes
« Reply #5 on: February 01, 2013, 07:26:44 AM »
Could you attach a copy of the probing script that you are using please.

Tweakie.

Hey Tweakie,

Im uisng Gerrys screen, I havent changed the script he uses and not sure if it would be a breach of his terms if I posted it here? Would that be ok?

Offline ger21

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Re: Z Height Setting Woes
« Reply #6 on: February 01, 2013, 10:27:33 PM »
I can tell you that I've never had this reported in the two years my screen's been available, and I have a LOT of users. I've never seen it happen. The fact that it  happens on both Big Tex's and mine would point to something else?

Any chance you're in incremental mode? There was a bug in an earlier version of my screenset that caused a problem if Mach3 was in incremental mode, but I only had one person ever report it. What version of my screenset do you have?

Also, any chance you've hit escape and killed a running macro at some point during the day? If this ever happens, I'd recommend closing and restarting Mach3 immediately, as I've seen issues with macros after ending one prematurely. But again, I've never seen a tool plunge into the plate.
And last, if you change tools  that many times, why aren't you using the automated method?

Tweakie, here's the code I think he's using:

sleep(1000) ' Pause for 1 second to give time to position probe plate

Code "F" & FirstProbeFeed ' Set feedrate to 10 ipm or 300mm/min

Code "(Probing for Z Zero.....)" ' Puts this message in the status bar

ZNew = (GetOEMDro(802) - FirstProbeDist ) ' Probe move to current Z - 6 inches
Code "G90 G31 Z" & Znew

While IsMoving() ' Wait for probe move to finish
Wend

ZNew = GetVar(2002) ' Read the touch point
Code "G0 Z" & ( ZNew + FirstRetractDist ) ' Move up .05 inch or 1mm in case of overshoot

While IsMoving()
Wend

Code "F" & SecondProbeFeed ' Set feedrate to 1 ipm or 25mm/min

ZNew = (GetOEMDro(802) - SecProbeDist ) ' Probe move to current Z - .25 inches
Code "G90 G31 Z" & Znew

While IsMoving()
Wend

ZNew = GetVar(2002) ' Read the touch point
Code "G0 Z" & ZNew ' Move back to hit point in case of overshoot

While IsMoving()
Wend

Call SetOEMDRO (802, TotalOffset) ' Set the Z axis DRO to plate thickness
sleep(500) ' Pause for DRO to update.

Gerry

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

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html

Offline Tweakie.CNC

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Re: Z Height Setting Woes
« Reply #7 on: February 02, 2013, 03:11:01 AM »
Hi Gerry,

I am absolutely certain that there is no fault or problem with your Probing code - the issue I am suspecting lies with later versions of mach3.

I do a lot of engraving work which necessitates my use of a probing script after every tool change or when engraving different thickness laminates and I noticed a similar problem (to the one mentioned here) at the beginning of last year.

It appears that one of the Mach3 feed-hold flags is not cleared by the ‘Cycle Start’ or ‘Reset’ buttons, it becomes persistent but it can be cleared by the ‘Stop’ button. This particular flag does not affect the running of Program GCode but it does affect the way in which CB scripts perform.

My solution / work-around was to include the stop command within my probing script and this magically resolved the problem I was encountering.

I have no idea if the problem mentioned in this thread will be resolved by the same course of action but CNCjunky now has ‘DoOemButton(1003)’ added to his script and I await the results of his tests.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline ger21

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Re: Z Height Setting Woes
« Reply #8 on: February 02, 2013, 07:38:46 AM »
Hmmm. I use 3.42.020 on my router.

But I do a lot of testing away from the machine using 3.43.062 with an emulated input, and haven't seen it not stop. But, I've probably never used feedhold before a probe move.
Gerry

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

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html