Tormach / MACH3 Pause Issue.

[RTP_Burnsville]

Hi,

I have an issue with MACH3 running my Tormach that has been an issue for months but last night I think the pieces of the puzzle finally came together.

The issue is if you are running a part and then hit the pause command button on the main MACH screen. The machine stops as expected but when you hit continue the location pointers appear to get changed and the operation continues on except to the wrong location. As you can imagine this is not good!!!!

Over the past several months I have broken several tools when this happens but last night it happened in such a way that I am sure the location pointer change is what is happening. Most times I just run one off parts so the chance of a G-code error exists. However, last night I was running a program that had just run several good parts.

I know the pause - restart has been an issue with MACH just wondering if anyone has a work around. Restarting from the start of a program and cutting air would be really frustrating.

Thanks,
Robert

[howecnc]

I have found so long as you pause it on a linear move it is safe. If you stop it on a G2 or G3 it seems to loose the arc centers and can destroy parts.

[M250cnc]

Maybe a solution would be to use RUN FROM HERE starting on a linear move if you happened to have paused on a G2/G3

Then just start before the G2/G3 you paused on

Phil

[flick]

Does pause decelerate in a controlled manner? I thought loss of position was inevitable, the same as if you landed on a limit switch... please correct me if I'm wrong.

[M250cnc]

Does pause decelerate in a controlled manner? I thought loss of position was inevitable, the same as if you landed on a limit switch... please correct me if I'm wrong.

You are wrong

Phil

[Pandinus]

In the standard MACH3here is a FEEDHOLD and a STOP , the way I understand it....
Stop is like "right now" dead in the water, starting again after this "might" have unexpected results, while it allows you to rewind or change the run from here / next line...
FEEDHOLD "should" decelerate safely, no lost steps and in the middle of the current move and a start after this "should" accelerate finishing the current move, and would not allow you to change the program position.
While in either of these modes if you have stopped the spindle, START THE SPINDLE BEFORE YOU PRESS THE START MOVE...

I'm assuming Tormach would have left both buttons in...

[RTP_Burnsville]

Thanks everyone for the tips and comments...

I tried the pause and start while on a linear motion line and that appears to work as expected. That is a rather nasty bug in MACH having a loss of position during a non-linear command. It's good to finally understand what is happening so maybe there will be a few less broken tools.

Pause has always performed a controlled stopping action where as stop is just that, stop now!

Thanks again,
Robert

[flick]

In the standard MACH3here is a FEEDHOLD and a STOP , the way I understand it....
Stop is like "right now" dead in the water, starting again after this "might" have unexpected results, while it allows you to rewind or change the run from here / next line...
FEEDHOLD "should" decelerate safely, no lost steps and in the middle of the current move and a start after this "should" accelerate finishing the current move, and would not allow you to change the program position.
While in either of these modes if you have stopped the spindle, START THE SPINDLE BEFORE YOU PRESS THE START MOVE...

I'm assuming Tormach would have left both buttons in...

Thanks for clarifying, I guess I missed that distinction.

[keen]

Hi Robert - I often pause and never an issue. I am fairly sure not all my pauses have been during linear. It may not be a universal M3 software bug but something else. All the same, I will try to pause when in linear when I can from now!

[RTP_Burnsville]

Hi Keen,

Not sure if it's pausing all non-linear motions which cause the issue. I am fairly convinced that it is at least some element of non-linear motion.

Many times I have paused and resumed without a problem. However, now and then the controller would appear to get lost and drive the cutter into the part or someplace else when resuming. Being I do mostly one-off parts it took a long while to put the puzzle pieces together. As mentioned above, this time I was able to verify that all was operating as expected except for the pause and resume as there were multiple parts made with the same G-code.

Last night I tried the pause followed by a 'start from here' command and that also appeared to work. I did resume from a line with linear motion as I did not want to chance damaging the part.

Thanks,
Robert

[keithorr]

I always use "start from here" or whatever it's called. It allows mach to preprocess the file up to the chosen line and you get to see the position the cutter is moving to before you commit. I always move to the tool retract position first (998) and then try to start on a line just after a G00 with a Z axis retract so the preliminary move is to the raised Z position; off of the workpiece. Hate watching a cutter rapid toward the work even if it does stop on the nose.