Software Validation Process - Coordinate Measuring Machine

[cbearden]

Ok.....I'm the end user of a Coordinate Measuring Machine Software (PCDMIS by Brown and Sharp).......My question is about Software/Process validation.
In my mind, I just want to know that the Software is giving me the true results from my measurements........Plus, I want to keep it Simple (K.I.S.S)
So, here is what I want to do.......Take several known standards (Class 1 GageBlocks) and measure them. If the Software tells me that a 1" gageblock checks 1.000005", then I know its giving me correct results.......Software VALIDATED!!!!!!...........
Do you think this would be acceptable to an auditor?

Thanks,
ZeissUser

[Miner]

I am far from an expert, so others need to chime in here.

What you describe should already be covered by the calibration of the CMM. Most CMM calibrations involve the use of a Ball-Bar that covers the accuracy and volumetric accuracy.

I would be more concerned about the software routines like the distance between features, a bolt circle diameter created from multiple features etc.

However, most commercial CMM software should have been validated by the CMM manufacturer. If your registrar insists that you need it, you should be able to obtain this from the manufacturer.

Most registrars that I have run into on this issue are more concerned with the validation of test software that your company has written, or with highly configurable software to verify that you configured it correctly.

What have others experienced?

[Jcowan]

We ended up buying a NIST traceable Demo Block from Hexagon...

[bradhaz]

I work in aerospace and have been up against the same requirement(s).

For validating the software I created a solid model with a selection of different features accommodating all of the ASME Y14.5M-1994 callouts. Then generate a drawing from the model with the GD & T. Program the CMM offline using the model, report against the drawing, and compare the results. Go a step further and include the feature construction points within the model.

Validation using the above approach is dependent upon how the model is brought into CMM. Any translations (Catia, UG, Iges, Sat, etc.) can introduce their own errors. You should be aware of the translation parameters in the authoring system. Translation is a topic in it's own right.

Use the artifact part for dynamically validating the CMM system. It's a good idea anyhow for interim checks between calibrations.

There was an issue some years ago when true position results of a popular measurement software was in error to some degree. I believe the requirement you ask about may be in regards to this matter. If that is the concern then validating the software algorithms without actually measuring anything may be more prudent by not introducing measurement errors.

Our procedures were the result of the AS9100 requirements combined with input from customer representatives along with personal experience. They work well for us and who we serve. Speak with your customers to see what they expect and how they expect it. Good Luck.

[prototyper]

I'm not sure where you are coming from with this question but don't forget that a part programme is also software.

PC-dmis software has been through an extensive process of testing and validation to ensure it's algorythms are correct. Your CMM will be calibrated (Usually annually by the manufacturer or a third party calibration company), with traceability to international standards.

What many people assume is that if something is measured on a CMM the results must therefore be correct. Big mistake!!!!

Poor programming can give incorrect results, excessive clamping can distort parts and give errors.

Check and double check your part programmes to ensure datums and sub datums are correct to drawing and reflect the fit and function of the part.

Conduct a Measurement Systems Analysis study. I have seen significant differences between 2 operators running the same part programme due to the way they loaded parts to fixtures and applied clamps.

If the study shows excessive variation from the same parts, different appraisers, etc., you must then investigate the whole measurement system (programme, fixtures, appraisers) to determine where the errors come from and then take corrective action.

Be thorough with this process and you will end up with a robust measurement system and will be able to demonstrate validation of your part programme.