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Author Topic: Probe not matching with edge finder when measuring Y  (Read 2978 times)

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Offline jevs

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Probe not matching with edge finder when measuring Y
« on: October 27, 2019, 10:39:46 PM »
I am using a Wildhorse Econoprobe
I adjust the tip with a dial indicator and get it pretty much dead on.
Then I put a new 1.0937" ring gage in the vice.
With a dial indicator in a collet, I center the ring gauge up and zero out x and Y.
Switch to the probe.
Go through the calibrate xy offset and radius.
After that I measure the bore of the ring gauge and it measures right on the money at 1.0937. A couple times I got 1.0936 after calibrating, but this is still excellent I think.

Next I probe the X edge and then load the edge finder and I was getting within .0001 of each other which is again really good.

Then I try to do the Y edge and keep getting about .0036 difference from the probe and the edge finder.

Not sure why this is happening, but I am not sure I can trust the probe or use it with it being this far off.

Offline jevs

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Re: Probe not matching with edge finder when measuring Y
« Reply #1 on: October 28, 2019, 12:02:14 PM »
Not sure if this helps, but after many cals and tweaking, the Y axis always comes out with more offset.
Here are the current calibrated settings from the machine.ini (which have been about the same any time I have ran through the cal and re-adusted the centering of the probe tip etc.).

XOffset=-0.000213
YOffset=-0.001520
Radius=0.056210 (actual radius of tip is .0625)

I do wonder how/if backlash amount using compensation affect this?


Offline dws

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Re: Probe not matching with edge finder when measuring Y
« Reply #2 on: October 28, 2019, 04:20:28 PM »
If you rotate the probe 90 degrees, does that change your results?
David

Offline jevs

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Re: Probe not matching with edge finder when measuring Y
« Reply #3 on: October 28, 2019, 05:15:38 PM »
No. Same measurements at 90.  (Without recalibrating at 90)
« Last Edit: October 28, 2019, 05:18:02 PM by jevs »

Offline dws

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Re: Probe not matching with edge finder when measuring Y
« Reply #4 on: October 28, 2019, 05:55:59 PM »
I was thinking that the error could be due to the probe. My Wildhorse probe has a very stiff spring. It appears that the stiffness varies depending on the angle to the 3 axis of the probe. The stiffness appears to be strong enough to cause the probe shaft to deflect slightly. I never actually measured it though.

David
Re: Probe not matching with edge finder when measuring Y
« Reply #5 on: October 28, 2019, 06:13:34 PM »
Hi,

Quote
I do wonder how/if backlash amount using compensation affect this?

Backlash comp is a realtime process and is handled by the motion controller not Mach4. If indeed backlash comp is screwing it up
you need to take it up with the manufacturer of the motion controller.

Craig
'I enjoy sex at 73.....I live at 71 so its not too far to walk.'

Offline jevs

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Re: Probe not matching with edge finder when measuring Y
« Reply #6 on: October 28, 2019, 06:40:20 PM »
Right now I am not sure what it is. I am trying to narrow down and understand what Mach 4 is doing better.

It is strange that it reads a bore within .0001, but has trouble with edge finding accurately. If anyone has some suggestions on methodically narrowing it down to where the issue is that would be great.

At this point I am not sure if it is in the probe, the machine (the amount of real backlash), the motion controller (ESS), or something else. 

I do have a second wild horse probe that is being used as a tool setter. I hate to mess with it because I have it all dialed in and the height set. If I don't figure something else out, I guess I could set that one up as a 3D probe and see how it differs in results.

Or, I could buy another probe that might be better than a Wildhorse and try that, but I am not sure what would be better and within a reasonable price frame?
 

« Last Edit: October 28, 2019, 06:42:16 PM by jevs »

Offline jevs

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Re: Probe not matching with edge finder when measuring Y
« Reply #7 on: October 28, 2019, 06:43:37 PM »
I was thinking that the error could be due to the probe. My Wildhorse probe has a very stiff spring. It appears that the stiffness varies depending on the angle to the 3 axis of the probe. The stiffness appears to be strong enough to cause the probe shaft to deflect slightly. I never actually measured it though.



Wouldn't the calibration account for the flex (if you don't rotate it)? I have a mark on mine so I put it in the same spot each time. It is also in a dedicated collet tool holder. Since it calibrates in X and Y at that position, you would think they would be pretty much right on if always used in that position?
« Last Edit: October 28, 2019, 06:46:12 PM by jevs »

Offline dws

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Re: Probe not matching with edge finder when measuring Y
« Reply #8 on: October 28, 2019, 06:59:29 PM »
Yes, if you do it that way. I calibrated mine by rotating the probe against an indicator, so that the probe is centered in the collet. I should also then calibrate as you describe , to compensate for any variance in flex. That would compensate for the amount of deflection before the probe is triggered.
« Last Edit: October 28, 2019, 07:06:40 PM by dws »
David

Offline jevs

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Re: Probe not matching with edge finder when measuring Y
« Reply #9 on: October 28, 2019, 09:26:41 PM »
I also calibrated mine with an indicator before doing the Mach 4 calibrations. I am just not sure yet why I get the discrepancy when edge finding, yet it measures a bore right on (using ring gage for cal and checking).