[sansbury]

Decided to upgrade my homebrew LinuxCNC control to PathPilot and am having a bugger of a time calibrating the probe. Previously I had not fully aligned/adjusted the probe because I used a custom macro for probing that had manual offsets in it to account for the probe's errors.

I am trying to follow the instructions PP gives and it feels like I am starting to chase my tail.

1. The instructions say to label each of the three screws and then tighten/loosen them sequentially. Are they referring to the socket head screws or to the set screws? I have tried doing it both ways and in neither case can I get the measurements to move reliably in either direction.

2. What is the best procedure for adjusting the SHCS and the set screws? My assumption is that the set screws are the parts which actually determine the alignment of the lower plate and the SHCS just hold it together.

3. How tightly should the SHCS be? I can't shake the feeling that a tiny difference in how much I tighten these could really alter the alignment. I am using a screwdriver-style hex driver and have been doing a little more than light finger tight--not cranking it down but enough that it feels firmly seated.

4. Leaving all this aside, has anyone figured out how to edit the PathPilot routines so that I can just add some manual offsets for the +/- errors in X and Y? That seems like a LOT less work than trying to get the probe perfectly aligned. That method seemed good to a couple thou or less before and if I need better than that I wouldn't use the probe anyway.

[keen]

Hi - I think most folk set the probe tip concentric with a light action finger dial indicator.


Cheers Cliff

https://www.youtube.com/watch?v=rAh_YFhH_V8&t=599s

[sansbury]

Thanks Keen, unfortunately that doesn't actually answer any of my questions. I can measure the probe's concentricity, but I am having a hard time adjusting it. Your probe has a different adjustment mechanism altogether.

[keen]

Thanks Keen, unfortunately that doesn't actually answer any of my questions. I can measure the probe's concentricity, but I am having a hard time adjusting it. Your probe has a different adjustment mechanism altogether.

Hi - I started with a Tormach SPU40 and made the adjustment the same way - the adjusting screws are the 3 grub screws that tip the end cap. Same end result.

Cheers Cliff

[sansbury]

Yeah, I tried doing it both ways (adjusting the set screws or the SHCSs) and neither worked. I decided to try my "when all else fails" approach and do the opposite of what the instructions said, and sure enough that worked. I got it to within about .001" across all three, and compared to my edge finder the probe is coming in within .002" on the first tests.

For clarity, what I did is the following:
1. Labeled the SHCSs as A/B/C
2. Measured each using the PP probe setup routine
3. For whichever one read highest, I slightly loosened that SHCS. For correction of more than a few thou, I also tightened the set screws to both sides. If that didn't move it enough, I also slightly loosened the set screw opposite the high SHCS, and tightened the other two SHCSs.

In terms of tightness, I tried to tighten every screw about the same, and got the best results with a medium-firm level.

[keen]

My apologies Sansbury - I rushed the reading of your first questions. My point about using a dial indicator did not fully address your questions.

Can we call the bottom screws: 3 set or grub screws and 3 cap screws .

I would back off the grubs well clear, then lightly nip up the caps. This brings the end cap in flat contact.

Touch the finger indicator to the tip eg at the front. Rotate to get the high spot at the front and tighten the front grub a little. If the amount needed is more loosen the caps each side of the grub that needs more travel, and so on.

But dont tighten either caps or grubs too much, the end cap is light and could easily distort, and this could even cause the contacts to be disloged.

Cliff