Minimum Qualification coverage angle?

[[Aa...]]

I've got a 0.5 mm stylus in an inconvenient setup that keeps shanking out on the Ref Sphere. As I'm trying to qualify it, I keep decreasing the coverage angle, but I can't get it to stop shanking out. It's obvious that it's ignoring the coverage angle I've entered and substituting some default minimum value. Does anyone know anything about this?

[[Th...]]

XXT? If you're not seeing a reduction in coverage it's because the passive head always does the full helix for the scanning bit.

[[Ne...]]

I had a similar problem with .5mm when I tried to qualify it on my scanning machine. When I moved from a CMM using a TP20 tip to CMM with XXT. The probe Shanked out. It doesn't seem as though the scanning reads the coverage angle. If this is happening to you, will need to change the reverence sphere angle or go to a smaller reference sphere. I was able to solve it by changing the reference sphere angle for this one probe.

Neil

[[Mi...]]

Also betting XXT.

Assuming I'm right, You're likely using a probe with a length shorter than the radius of the calibration sphere. The solution is buy a smaller sphere. I went though this with a tiny M2 Threaded 10mm long 1mm ruby probe a few months ago.

It's the length of the probe thats screwing you, not the size of the ruby.

[[Aa...]]

Nope. XT Gold. Trying to use static Tensor mode to establish size on our 30mm ref sphere (the one that's part of the machine's calibration), and run Dynamic Tensor on our 8mm sphere to establish the dynamic bending parameters. That's generally our practice for smaller styli, where the stepped nature of the shank causes them to shank out on the 30mm. In this case, however, the direct shank is so short, as Michael points out, that it shanks out on the vertical portion of the system. It won't let me turn it down far enough to not shank out.

[[Th...]]

Is there any downside to doing the full qualification on the 8mm sphere?

[[Aa...]]

Yes. The 8mm ref sphere was not used in the calibration of the machine and provides no traceability.

[[Aa...]]

Thanks to everyone who weighed in. Our local Zeiss dealer is very good and found the answer.

[[To...]]

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Is there a difference between Sphere Coverage and Taper Angle? If so, where do you find taper angle?

When did that change? I've qualified several styli using less than 180° coverage.

[[Aa...]]

You're right, Tom. I believe they're the same thing. In the Probing System Qualification dialog, it's actually labeled "Sphere Coverage",
and in the Stylus System Management dialog, it's labeled "Taper Angle,
even though in the help for Probing System Qualification, they refer to it as "Taper Angle".
Seems almost as confusing as including a blank for entering the sphere coverage that the software is just going to ignore. 😮

[[Aa...]]

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I wish I knew when it changed. What mode were you using? Are you sure you were getting less than 180 deg?

[[Aa...]]

Does anyone here know whether entering a taper angle of less than 180 in the Geometry of the stylus in the Stylus System Management and hitting "apply" will affect the behavior in a tensor qualification?

[[To...]]

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I recall qualifying a R0.1 scribe point stylus about 2 years ago. I believe I had to use something like 30° sphere coverage. I seem to recall the angle on the graphic was wrong. I just kept reducing the sphere coverage until the S was reasonable and the radius was close to 0.1

Screenshot 2021-05-20 111323.jpg

[[To...]]

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Your screen grab shows 240° but I think you need to be using less than 180°

[[Aa...]]

And I assume that your position gave you access to the latest version of Calypso at that time? Were you using Tensor or six point mode?

[[Aa...]]

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Indeed. The screen grab is from Planner and not connected to a CMM.

[[To...]]

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If it was 2 years ago, I'd have to guess it was around 6.6. VAST-XT Gold. Tensor. I never use 6 point because my understanding is that it does not calculate bending. I've seen posts from someone who swears by 6 point when qualifying 0.5 or smaller styli.

[[Aa...]]

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That makes no sense to me. If the shank is that small, there's bound to be some deflection. Do they also reduce the probing force?

[[To...]]

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I don't recall. I believe it reduced the breakage, according to the poster. Since Tensor defaults to taking 2 points, 1 at 200mN and 1 at 800mN, I can see where breakage might be less often.

[[Aa...]]

Well, this throws a wrench in things. I was just informed that someone here successfully reduced the coverage angle to 90 degrees on our machine running 2015.

Edit: I attempted to reproduce this, and could not.

So what versions ignore it, and what versions don't!? If I hit up the help in Calypso, is it specific to the version I'm running, or is it pulling the current version from the web? It would be extremely helpful if someone from Zeiss would tell us the expected behavior, here.

[[Th...]]

The help file is locally stored. It should be version-specific, although I suppose it's possible things get missed from time to time.