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Rennishaw OTS not outputting tool radius correctly

Rennfab

Plastic
Joined
Jan 6, 2013
Location
New York USA
Recently had to pull the table off my machine for service work to the rails and trucks. In doing so I removed the OTS from the table to prevent damage. Machine is back together, all aligned, squared, and working properly in that regard. For reference, this is a 2011 VF3SSYT classic controller.

Reinstalled the OTS to the table today in the exact same position, and ran the calibration procedures as I normally have in the past using a precision ground calibration bar in the spindle(Maritool). After doing so I pulled up a tool that had been in the machine and previously calibrated prior to the OTS removal and ran the probing cycle as a test. The cycle ran as it should, however the OTS is calculating the tool diameter(or radius in this case)incorrectly. Tool measured out length wise within .0001" from previous measurement, but the radius was WAY off. The tool is a 1/4" diameter 4 flute endmill, and had a previous radius measurement of .1247" The OTS repeatedly records it now at .0327-.0328" instead. We're not talking a few tenths or even thousandths. I have run the calibration process a handful of times today and nothing changes. I pulled the batteries out and reinstalled them today in the OTS as well and did not touch the stylus during the startup procedure.

What else should I be looking at here? Could something have changed without my knowledge while the probe was off the table? I had the probe stored upright tucked into the corner of the cabinet behind the controller, so it wasn't getting bumped around in a box or drawer somewhere. I am not that familiar with the actual macro(s) itself, nor the parameter settings on the machine so is there a specific data set that I should be looking at to see if something changed? It just has me stumped as the way I see it if the OTS was damaged it wouldn't be reading the Z axis length correctly, but it is.

Anyway, any help would go a long way here because it's either that or calling a tech back here
 
Should also add that I tried the calibration process with two different calibration bars. one the MAritool piece and the other was a cat40 shrink fit holder with a 3/8 gauge pin installed. Both different lengths and diameters, yet both yielded exactly the same results number wise.
 
Find the renishaw manual for the exact macros, but somewhere in the upper 5-600 you'll find the xy for the ots and verify its real position. In my recollection the probe cal doesn't really find center but expects you to start it at center.
 
No chance you put in the wrong diameter for the calibration master?

Well, no but yes. So I ran two different calibration bars in my tests, both different diameters and both measured and entered into the controller to .0001". However here is the catch. Today I messed with this for a few moments.
In the calibration setup on the screen the controller asks for the radius of the calibration bar end, which when entered as such yields an incorrect radius measurement of the tools when probed. Now if I entire the actual diameter of the calibration bar and run the calibration process in the same manner, the tools now read and measure correctly.

Something is definitely off somewhere, but for whatever reason it seems to be "working". I generally only use the OTS for rough diameter measurements of tooling like larger cutter heads or roughing cutters and not anything that requires utmost accuracy, so I can get by this for now and futz with it later. I just haven't had the time to sift though the tables and macro code yet.

The thing that I just can't seem to get out of my head is the math end of this screw up. When using a 3/8" calibration bar and entering a radii of .1875 in the calibration setup, and 1/4" diameter tool would probe out with a .0392" calibrate radius in the tool offset page. That's a rough .085" error from where it should roughly be. Now if I changed the calibration radius to .375" and re-probed the same tool it would now list the tool radius as .1248". I don't see how an increase in calibration radius of .1875" yields an approximated increase in calibrated tool radius of +.085". I tested the tool calibration on multiple tools of varying diameters today and they are all back now within a couple tenths of where they were prior(I think I still need to tweak the stylus parallelism a bit more).

Meh. Fricken machines and their pesky computers.....
 








 
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