Calypso CNC User Forums

Hi
Working with the pro version as a trial.
Mach 3 with a new intel atom mini itx running a UC300 motion control device http://www.cncdrive.com/UC300.html and a CNC4PC C32 breakout board. I have the probe running through the C32.
IM Service probe
Debounce is set to 10 but have tested from 0 to 250.

Probing works great most of the time but every 5 or 10 probes it will over travel even though the probe LED on MSM is lit. It looks to me like it's in the .125" range. Sometimes it will do it on the first probe movement and other times it will do it in the middle of a routine. I know this may be an issue with the UC300 but have you ever seen this behavior before?

Thanks
Derek

Hi,

Here is what info I have to offer of the top of my head:

If the prove led is on in the MSM screen then Mach knows that the probe is triggered. MSM only gets probe state information from mach. Therefore, if the probe is still traveling after being triggered, I would suspect (as you noted) a bug in the UC300 operation.

If you had not said the above, I'd have thought about an electrical interface issue. Not noise (which usually manifests as false triggers during a movement) but perhaps a pull up issue at the probe line input to the breakout board.

When the probe is inactive, internally it is a closed switch - so the probe is shorting the input signal at the breakout board to ground.
When the probe is activated, the internal switch opens and the input signal is supposed to go to +5. However, if there is no (or an inadequate) pull up resister in the breakout board, the signal may not go clear to +5 (it floats) - or perhaps the rise time to +5 is slow... that would show up as either delay of trigger input (which could cause larger overrun) or the trigger state just not being seen by mach (which would prob crash the probe as it keeps moving after is was triggered. If this is happening and the input signal happens to be at the logic threshold, it might show as intermittent missing of probe trigger signals.

Some items that may or may note be clues:
When you say if overruns by approximately 0.125, does that happen to be a value that you have set for the MSM probe operation? Like maybe the back off clearance distance you have set?
If so, I'd also suspect the UC300 operation... When MSM sees the probe triggered, it back off in two steps after the trigger event: first to take out overrun from the probe move (typically a few tenths), this move puts the probe right on the surface that caused the trigger.
The 2nd move is the to back off the surface by the clearance amount.
I have noticed that some motion devices only implement probing correctly in G90 and not in G91. MSM issues both G90 G31 and G91 G31 commands when doing probe operations.

If want to track this further, I can provide you some instructions re how to get a detailed trace log of a probing operation - but that's usually only useful if you can make the problem happen on demand so we can get it logged.

Dave

Hi Dave
Thanks for the prompt response.

I'll do some more testing with it and see if I can get more familiar with whats going on and then post back. It's really intermittent so it's going to be challenging. I may end up getting a whole new probe from CNC4PC as this ones been a bit finicky since the day I bought it.

Derek