Comments from Rob Durham’s Visit September 24-25, 2007.

Comments from Rob Durham’s Visit

September 24-25, 2007


• Gage bar / length standard crucial to verify accuracy• Don’t spread global monuments too far from part – should minimize distance. Choose

monuments with a small angle as possible.• Usually use about 6-8 global points to see how much error. We use three points plus

few points on part. Should we establish more global points. Global should be on wedge or concrete – probably not both. Use same type of globals.

• Need to examine trade off in error of limiting points by field of view or angle per scan versus leap frogging tracker.

• Avoid straddling cracks in concrete.• Collect data in a timely manner to assure least environment change.

– Avoid delays but verify alignment before you resume.• Single Axis Length Check – Monument points verify alignment as you go around.

Measure the single axis distance between 2 points to validate that they are the same on the part. Should be able to view from every position. Should be as close to the working environment as possible.

– Provides sanity check and can check during the day that the device is working– Go to report manager and get distance between 2 points.– Pick one common axis and go back to it before and after measurements to assure nothing

changed.– Also provide 2 nests on part to verify position of measurements.

• Laser line of sight is most accurate axis. Encoder angular error is 10x distance error.– Try to limit encoder swing to within 45 degree. The

wider the angle the more the error – proven on Dea CMM by Rob. Is accumulative error.

• His trackers and software show similar jitter and noise. The error (noise) observed was normal BUT do not over analyze. “Standing around watching error was troublesome.”

• Take measurements as efficient as possible.


• Establish monuments on part then should we shoot all or just move around– Should collect all from first spot.– Once you get initial alignment get as many points

from that first position.• MTM tracker stands are Brunson (equivalent to

K&E) but he installed better casters for smoother rolling. – Should minimize vibration.

• Acceptable extension of stand?– Rob says he has had it full up and on machining knee

pillars 16’ high and performed measurements.


• MTM operates computers with Windows 2000 AND DO NOT update.

• Verisurf updates are also tried true before used. They are currently using an April ’07 version.

• MTM runs pointing compensation when he powers down tracker.– We shut down for weekend only.– They run front sight back sight every week.

• Do not clean CCR/SMR very often – too delicate.– Air in can or water mist with a lens brush– If you can see beam on exit surface glass it should be cleaned

• Glass on top of MTM tracker units (older model Si) is not sealed and need to be reconditioned.


• How should one assemble multiple parts?– Since coils were wound to best fit, cannot best fit any further.

Need to use that coordinate system established during coil winding.

– Be careful with best fit in Verisurf – It allows 6 degrees of freedom. We are past this phase.

– Rack the parts back to best condition – Align – maintain through assembly

– When place B on A may have to rerack A.• When bring B onto A while well supported all around flange does

not move A.• We found that A can be pre-calculated a set of shims to allow the B

placed on it.• BUT should allow for method to adjust A

– MUST plan for flexure within every part.


• Many Thanks to Rob and Major Tool for allowing him to visit!!

• Would like to definitely keep two way communication open both ways regarding trials, tribulations, and successes.


Comments from Rob Durham’s Visit September 24-25, 2007.

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