Z Issue After Tool Touch Off <resolved>
Posted: Sat May 08, 2021 9:59 am
Hi Folks,
I am having an issue with my tool touch off macro. I think this really a problem with G30/G28/G53 moves but I will explain in detail with some background info to see if anyone has some insight. My machine can Z home in a repeatable manner and typically does so well under .0005". I have my Acorn configured for a tool probe and tool touch off device and have been using Probe App V2 for my probing functions. My tool touch off device is one of the common knockoffs similar to the link below and it performs very well.
When manually touching off tools using the WMPG jog wheel the TT repeats within .0003" from the readout in CNC12 so I am very confident that my TT works as it is supposed to. I have cut programs using the manual touch off method and the tool offsets sync up to the the locations probed by my TP perfectly.
My issue is that when doing an automatic tool touch off cycle, after the tool is probed, the spindle head does not return to its true Z home. Each iteration of the probing cycle it returns about .14" shy of the true home location. If I do multiple offset measurements with the same tool in a row I can watch each offset drop roughly that amount each time i.e. 7.3", then 7.16", then 7.02" etc. I can also see it stop well before touching its homing switch. The first tool offset probed after homing z is always exactly as it should be. If I home z between each tool touch off the values come out as they should. At first, I thought this might be a mechanical problem but I have checked that all connections between the ball screw and the stepper are tight and free of play. The z axis is moving as it should (tested with an indicator) and the part I just cut came out to the correct dimensions. I have also run a test program multiple times to rapid up and down in z then settle to an indicated location. This test rules out slippage from the ball screw to the spindle shaft as each time it returns to +/- .0002" of the original location as measured with an indicator. I am using Stepper Online closed loop steppers with the error output monitored by acorn so I so I am confident I am not loosing steps. I have also been checking the error logs and do not see anything that would indicate that I am having signal interference issues.
I think this has something to do with the G30/G28/G53 commands since I am assuming that is the last command in the probing cycle macro. I am also curious where the macro for this is as I could not readily identify it when browsing the cncm folder. When issuing G30 and G28 commands via MDI this problem also presents itself. I can't imagine why any of those commands would cause the Z to stop short of its accurate location. When jogging with the handwheel the z axis returns to the correct home each time (as long as I do not issue a G28/G30/G53 command).
I have attached my report and recorded a video of the issue at the link below:
If anyone has some time I would love to hear any ideas on how to possible fix this.
Thanks!
I am having an issue with my tool touch off macro. I think this really a problem with G30/G28/G53 moves but I will explain in detail with some background info to see if anyone has some insight. My machine can Z home in a repeatable manner and typically does so well under .0005". I have my Acorn configured for a tool probe and tool touch off device and have been using Probe App V2 for my probing functions. My tool touch off device is one of the common knockoffs similar to the link below and it performs very well.
When manually touching off tools using the WMPG jog wheel the TT repeats within .0003" from the readout in CNC12 so I am very confident that my TT works as it is supposed to. I have cut programs using the manual touch off method and the tool offsets sync up to the the locations probed by my TP perfectly.
My issue is that when doing an automatic tool touch off cycle, after the tool is probed, the spindle head does not return to its true Z home. Each iteration of the probing cycle it returns about .14" shy of the true home location. If I do multiple offset measurements with the same tool in a row I can watch each offset drop roughly that amount each time i.e. 7.3", then 7.16", then 7.02" etc. I can also see it stop well before touching its homing switch. The first tool offset probed after homing z is always exactly as it should be. If I home z between each tool touch off the values come out as they should. At first, I thought this might be a mechanical problem but I have checked that all connections between the ball screw and the stepper are tight and free of play. The z axis is moving as it should (tested with an indicator) and the part I just cut came out to the correct dimensions. I have also run a test program multiple times to rapid up and down in z then settle to an indicated location. This test rules out slippage from the ball screw to the spindle shaft as each time it returns to +/- .0002" of the original location as measured with an indicator. I am using Stepper Online closed loop steppers with the error output monitored by acorn so I so I am confident I am not loosing steps. I have also been checking the error logs and do not see anything that would indicate that I am having signal interference issues.
I think this has something to do with the G30/G28/G53 commands since I am assuming that is the last command in the probing cycle macro. I am also curious where the macro for this is as I could not readily identify it when browsing the cncm folder. When issuing G30 and G28 commands via MDI this problem also presents itself. I can't imagine why any of those commands would cause the Z to stop short of its accurate location. When jogging with the handwheel the z axis returns to the correct home each time (as long as I do not issue a G28/G30/G53 command).
I have attached my report and recorded a video of the issue at the link below:
If anyone has some time I would love to hear any ideas on how to possible fix this.
Thanks!