Stylus Accuracy

[[Jo...]]

I'm having a debate with my management team as to which styluses are more accurate to use when inspecting parts on the CMM. I told them that there are many variables to deciding which styluses are more accurate to use and it's not just about the stylus itself or the type of material it's made of. But they want to know, in general, which styluses tend to be the most accurate to use (brand, material, grade, etc.).

Unfortunately, I was not able to give them the simple, straight forward answer they were looking for, so I thought I'd check in with you all to see if you can help me out.

Thanks in advance!

-Joe Barajas

[[Ma...]]

Main argue will be cost.

Material comes for specific reasons - soft materials tends to buildup on the probe sphere. Shaft will have different rigidity and thermal expansion.

To have the most precise probe, it should be as much round as it can be and rigid.

All comes with your tolerances which you are dealing with.

[[Da...]]

What Martin said.

I strongly believe in styli you get what you pay for. I mostly get Zeiss or Renishaw. I have gotten custom styli from Q-Mark, they are great to work with and turned it around quickly, that said I don't think they're stuff holds up as well, I've had the rubies fall off after a short time. Don't cheap out on extensions either, I'm looking for repeatability.

If you're getting a lot of broken styli, you need to look at your work habits and or who you're allowing to run your CMMs.

    

[[Ri...]]

Standard styli, the sphere, are the most common used. You can opt to purchase more expensive high precision styli which have roundness control similar to a Reference Sphere.

I work with diametral tolerances as low a .0003" with common styli, I have not seen a difference using a high precision stylus.

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[[Ch...]]

As Martin already mentioned: It strongly depends on the material of your components and the length of your probes. Are you experiencing temperature-weight issues (carbon fiber shaft)?

Are there any local suppliers with whom you might be able to negotiate prices? 

A sample: We measure polished steel parts with a diamond probe.

 

[[Je...]]

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,

The one that is clean, undamaged, has a correctly tightened connection to the shaft, and is qualified regularly.

The shaft and connection points are much more significant sources of error than a spherical probe, regardless of material.