5 ax, center of rotation.

[PROBE]

The functions that use #19700 parameters are G43.4 TCP, G68.2 TWP and G54.4 Work Piece Setting Error Compensation. I've often wanted to do what you have done with the probing of a sphere, however my thought would be to set the pivot points with mechanical means (dial indicators) then run the probe routine to verify the probe results coincide with the mechanical check such that the operator can run the probe routine anytime for verification. The reason I say set the pivot points with dial indicators it can be way more accurate than a probe with less uncertainty. Then from there do your circle, diamond square test cut or better yet, machine a 5-sided block with various features using TCP & TWP that isolates the pivot points better than the Circle Diamond Square test and that can be inspected using surface plate, height gage and dial indicators with extreme precision, make your final adjustments to #19700's and then verify the test cube on the CMM as a reference. This way you have a solid static mechanical check that is backed up by probing and the 5-sided test piece will give you a dynamic look at the volumetric accuracy.

 

Back in mid 80's I was involved with the installation & commissioning and was the operator on the 1st 5-axis machine in the US. We didn't have probes back then. One of the first jobs was a drill jig with true position of .001 on compound angled holes. The 1st part came out about .020. We went back to the old method of setting the spindle angle, pick up a tooling ball and bored the hole on location. After that job we re-vamped the machine and it got about 10 times more accurate. Here we are in 2016 and we still need to be about 10 times more accurate than where we are today IMO.

 

I used to work for the Mori dealer and was involved with their 5-axis machines when they 1st came out. Mori had no clue on how to get the pivot points down to a tenth or less. Up until a just a couple years ago they still had no clue. At the same time we also sold high end Euro machines like Jobs and Fidia. If you have a chance, check out how Fidia sets their pivot points. Its' amazing there is no industry standard for this and customers are left to the expertise of the machine builder.

 

Cheers!

Len Dye

Hi Len,

Thank you very much for information regarding the relevant G functions. I will have to explore this topic deeper.

As to the decision if one should use the probe or indicators - I as probe guy would prefer the probe.

Back in early seventieth  I worked as maintenance engineer for aircraft industry, and cope with the problem of center of rotation on Sundstrand Omniimil  OM-5 with Bunker Ramo 3000 control. Bunch of special tools and indicators helped me to find the discrepancies. The data was passed to programming department, and they updated the parameters of postprocessor to output the compensated G-code file.

 

Regards,

Stefan Rubin

[taperlength]

That is what I was figuring... end result would be compound angle.

 

Fixture is mounted...casting secured on fixture. Surface (W) to be flat is in (parallel to table) has to be rotated in B and A . Therefore when (Surface is parallel to table) A may be 5 degrees and the X axis is now skewed to whatever B (10 degrees lets say) became to make (W) flat.

 

If A is "zeroed" at said 5 degrees... the entire program would have to run skewed to the 10 degrees the B has been rotated.

 

Does that make sense?

I did a casting job similar to that recently, where the cast datum needed to be level.   We made a fixture with some adjustment in it.  Each casting was probed in 4 places  and then the fixture was tweaked a calculated amount and then probed again to check the adjustment.   Once the part was parallel to the table, it was easy to probe the angle in the B-axis and offset it.