I suspect that your motion controller doesn't properly support probing.

It does, or at least that's what the engineers that develop the controller say. I contacted customer support and their engineers and they mentioned that the G31 command does what it is supposed to do. I have seen in other web pages and forums that people use this type controller, but there aren't many others posting details about it.

Hi,
you're lucky to get a response from XHC at all. I don't think any of the development engineers are left. The company just makes copies of what they have made before
without any detailed insight into how they work, or in this case, don't.

Craig

Hi,
I use Autoleveller, a software utility that probes the surface of a nominally flat printed circuit board blank. Then it manipulates the Gcode file to accommodate the inevitable wave and/or warp
of the blank. As such probing has to work well and accurately, say within a few um otherwise it does not work.

Initially I used Mach3 and a parallel port, and Autoleveller worked well, ie within a few um.
Then I used Mach3 and an Ethernet SmoothStepper, and that worked well also.
Then I went to Mach4 and the ESS and have used it extensively for seven years. With my new build mill, having quite good acceleration, I can get about 1.5um  accuracy/repeatability with g31 moves.
I use it daily, if not multiple times per day, so g31 works. It's something about your machine, or as John has postulated, the controller. Consider getting a US or European made controller, we know they work
and the manufacturers support them, unlike the Chinese manufacturers.

Craig

Well, those are sad news, I spent about 400 dollars on that controller thinking it was something fairly good, you know, better than the controller kits that come with cheap CNCs. I bought that one also because I read in quite a few threads that Mach4 is still quite unstable, and this WiXHC is compatible with Mach3 which has been going around for quite a while.

Hi,
you're lucky to get a response from XHC at all. I don't think any of the development engineers are left. The company just makes copies of what they have made before
without any detailed insight into how they work, or in this case, don't.
Craig

What do you mean by "I don't think any of the development engineers are left"? The company isn't up and running anymore. For what I have seen they are still active and bringing new products out there....

What are the good reliable brands then? Any recommendations? Not that I would buy it any time soon, because you know, money. I feel cheated 

Hi,
the only person who responds to any enquiry about XHC products is a guy Alex Hee, and he only replies sometimes. Further he does not answer any detailed technical questions
and I would guess he can't. Have a close look at the 'new' products, are the genuinely new or are they rehashed old products?

The only new product that I'm aware of is a supposed Mach4 ready controller, and it's absolute s*********t, it does not support Mach4s GUI, just wxMach, what a joke. XHC have no interest in
fixing it, and I don't know how many people who've bought only to have to throw them out as junk. Seems to have tailed off recently, as most people do enough research to understand they are being ripped.

Craig

 

So, the good reliable brands are?

Hi,
the reason that I am dubious about the controller is that g31 is and has to be a realtime procedure.

When a probe event occurs the motion controller must immediately decelerate the moving axis. This immediacy, measured in a few tens of micro seconds is required to avoid over travel.
The controller must have that feature built, or programmed in, in order that it can happen almost automatically.

It is not sufficient for the controller to report back to Mach, it would take some tens of milliseconds to do so, then Mach would calculate the deceleration trajectory
and communicate that to the controller whereon it will go into the motion buffer, commonly several hundred milliseconds in duration. The delays are such that overtravel would
be excessive.....and that it what you describe.

I would concur that XHC has been in the market long enough that I would have expected it to support g31, even if development has ceased this realtime support should have been
part of the controller function for many years now. Your description of what is happening rather suggests the the controller does not have that critical realtime support.

Craig

Hi,
sorry, forgot to mention the good ones:

I use an Ethernet SmoothStepper ($190) by Warp9 TD in the US. Others are:
UC300,and UC400 (about $150) by CNCDrive in Hungary
57CNC (about $150)by PoKeys in the UK (I think?)
CSMIO (about 600Euro) by CSLabs in Poland
HICON (starts at $600) by Vital Sytems in the US.

All of these devices have complete and well sorted plugins for Mach3, and all have a Mach4 plugin but in some cases a less complete set of realtime supports. All, should have g31....that's one of the most basic.
Of them the Ethernet SmoothStepper and the HICON have the most complete Mach4 plugin, with both companies committed to supporting Mach4.
The UCnnn products are made by CNCDrive, and they have their own software, UCCNC, and good it is too, but naturally they support their own software before investing too much effort in supporting the competitors (NFS)
software.

Craig

And I use a cncdrive uc100 which also supports probing.

your controller may support G31 what is enough for a "simple" probing, but am pretty sure
it is not supporting the update of the var's 2000-2002.