Axis oscillates after Mach3 estop

[bhauser]

Hi Tom,

While doing some macro development for Mach3 I discovered another issue my system. When I am doing a rapid move and hit escape in Mach3 the axis in motion oscillate uncontrolled then faults (I think due to an over current fault). It also seems to be ignoring the max following error durring oscillation. Any idea how to fix this?

Thanks,

Brian

[TomKerekes]

Hi Brian,

What kind of motor/drives do you have?

Do you have an enable/disable interfaced to the drives?

[bhauser]

Thanks Tom,

They are servo drives, running through a Kanalog module. There is an enable/disable IO line hooked up to the drives.

-Brian

[TomKerekes]

Hi Brian,

I'm not sure what Esc does in Mach3. Its behavior can probably be changed. But I suspect it just Stops motion abruptly which could cause a big overshoot and then oscillation based on how your axes are tuned.

I'm not sure why Max Following Error wouldn't disable the axes. What is it set at?

I think you would need to do Feedhold to come to a controlled stop.

Consider using KMotionCNC instead.

[bhauser]

Hi Tom,

Max following error is set to 10000, which is just a shade under half an inch on my system. Maybe that's a bit too high? I think that hitting the escape key is the same ad triggering hitting the big red reset button in mach. I'm a little (ok a lot) uncertain about using KmotionCNC, because my post file is set up for mach and I'm not certain I have enough knowledge to make a post file for KmotionCNC.

Thanks,

Brian

[TomKerekes]

Hi Brian,

Yes most system when properly tuned always follow within a few thousands of an inch normally. See step 4 here.

Another option is Max Error. See here. Again as errors are only normally a few thousands of an inch this can be set to a small value. In the event of an abrupt stop causing a huge error this can treat the huge error effectively as a smaller error and may not result in a violent response and oscillation.

I don't know what type of system you have or any special requirements but typically KMotionCNC works with GCode very similar to Mach3.

[bhauser]

Thanks Tom,

I think I will start by reducing the following error and max error... which hopefully eliminate the problem. My hope was that Mach would send a e-stop notification to the KFlop that I could then handle the way I want to... ie try to feed hold then if that fails disable the axis. If the doesn't work then I may need to look into KmotionCNC. I have a Tree Journeyman 250 that I replaced the control on... so a crash has a lot of force behind it. Definitely something I want to avoid.

-Brian

[bhauser]

Hi Tom,

On further investigation it looks like there is an e-stop message... but the message pump for mach is in the spindle control program (EX_ESTOP). I suspect that there can only be one message pump reader running. Is there a way that I can set a variable in thread 3 and take care of handling it in in thread 1?

Thanks,

Brian

[TomKerekes]

Hi Brian,

I don't think EX_STOP is ever being sent to the Spindle Program and I don't see how that would help.

[bhauser]

Thanks Tom,

I thought it ex EX_ESTOP... I changed the Max Following error to 10 thousands and that helped a lot. The axis still jitters by about 50 thousands (a guess), but at least it doesn't do anything too insane.

Since I'm in problem fixing mode... When I hit feed hold from mach, it takes a while to stop the system. Is there a way to speed up the response time? I seem to remember some buffering variable for the number of g code commands to buffer. Does this effect feed hold response time? Is there a way to maybe add a hardware IO line to do this?

Thanks,

Brian