New toy… economical 3D probe

[John HaineParticipant @johnhaine32865]

That's a bit puzzling Martin! I assume that ProbeIt uses the standard G31 command, which is executed at a very low level in Mach3 – either in the PC with a parallel port or in the actual motion controller – so the wizard shouldn't be able to affect the timing at all. Did you also raise this with Eric?

[Martin ConnellyParticipant @martinconnelly55370]

Based on my communications with Eric, the ProbeIt originator, both my macros and ProbeIt use G31. The operation takes place in the Smooth Stepper I use. The only thing I can imagine is that there is either something in or not in one of the macros that is causing the issue. My macros do a "while ismoving() wend" loop directly after the G31 is called so that nothing else happens until the G31 finishes. Without this it is possible the lookahead is doing something in ProbeIt that delays the response to a G31 move and so causes an over-run.

My probe is a Ø16 piece of ground steel with a thread on the end to suit an ER collet or a Posilock collet. The other end is drilled out Ø10 and a piece of acrylic is fixed in place with anaerobic adhesive. This is then drilled and reamed Ø6 and a Ø6 hardened and ground dowel is pushed in. Nice and cheap and accurate but not immune to over-run damage.

Martin C

[John HaineParticipant @johnhaine32865]

Thanks Martin, I'll have a play. We had a long exchange over on Mach3 Support about how Mach does probing, and it isn't to my mind very sensible. Basically as I understand it the G31 movement starts decelerating when the probe triggers and the axis value it stops at is registered as the trigger point, so will always be slightly over the correct value by an amount which depends on your acceleration profile. I wonder if ProbeIt modifies the profile in some way?

In UCCNC though the axis value is registered immediately on trigger as well as deceleration starting, which seems the right way to do it to me.

[Author]

Posts