Probe bending during calibration?

[[Co...]]

Hello Friends,

I've got a contura where I'm using both a XXT/RDS and a XTR. I'm having some issues getting the XTR setup and working and I'm hoping someone here can help me out!

Part of why I got the XTR was the ability to use big probes, long probes, and small probes with more fidelity than the passive XXT (maybe I was wrong in my assumption). As such one of the probes I'm trying to setup is a fairly large star with small Silicon Nitride spheres on the end. I've got a star probe with 5X 1.5mm X 81mm SN probes, and I have a probe with two super long 8mm's (8mm x 300mm) going in the Y axis, and then two 2mmx 90mm going in the X axes.

I'm trying to qualify my probes and I'm getting total garbage results on the small ones, for example I had an S value on the 1.5x81's of 0.0004" which is obviously totally unusable.

I set my measuring force to the lowest available in the dropdowns (100mN) and I set probing dynamic at 50% and I can watch the probes bend a crazy amount while calibrating. I know that they are supposed to bend some, that's part of the tensor calibration, but they are bending enough that it's uncomfortable to watch. My guess is something like 5mm?

I think my question is did Zeiss sell me a probe that isn't functional or am I doing something wrong during my calibrations? Should I be manually typing in smaller measuring force values? Anyone run into somethin like this before?

Any help is greatly appreciated!

Thank you,
Connor

[[Da...]]

What is the shaft material of your probes? Carbon probes can crack , but not fall apart. try changing probes and see if it improves.

[[Da...]]

Every supplier of probes and styli will sell you anything you want, it's your own responsibility to check if something makes sense or not. A probe bending 5 mm is certainly not making sense.

There is one possibility for very soft probes. Forget about tensor calibration. When calibrating probes with tensor calibration, a low and a very high force will be applied to the probe in order to interpolate the bending at different probe forces. With a very soft probe, you should stick to a six-point-calibration. That will give you only limited scanning capabilities and it's best to stick to single touches, but if you verify your calibration on a gauge ring at given diameters and speeds, it still might work.

[[Da...]]

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100mN is not the minimum, type in 70mN and try it out. And also lower probing dynamic to 20% or less.

[[Je...]]

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Conner,

Good choice on the XTR. It's definitely an upgrade. Put that XXT on the shelf or sell it (just my stance).

Yes, you will want to manually input values for the measuring force. As with many presettings in Calypso, the dropdown values are broad brush strokes. I use a VAST Gold, and I qualify as low as 20mN and 5% probing dynamic, especially for smaller probes in the 0.2mm to 0.8mm range. My typical qualification settings are between 50mN to 100mN and 50% dynamic.

Check the XTR documentation for the listed weight and length limits, and make sure all stylus connections are firm. Try a lower probing dynamic and see if the sigma improves.

I'm interested to hear how this situation turns out for you. Please let us know.

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[[Mi...]]

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What exactly is the Probing Dynamic?, unless I suck at searching the help files are useless at a laymen's terms explanation.

[[Je...]]

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🌟 Cinematic Version: Probing dynamic refers to how flexible or responsive the probe is when it comes into contact with the object being measured.


🌟🌟🌟🌟🌟 Boxed Set Extended Edition:

• When you use a probe to measure something, it's important that the probe can adapt to the shape and contours of the object accurately.
  .
• The term "Probing Dynamic" describes how well the probe can flex or adjust its position when it touches the object's surface.
  .
• A higher Probing Dynamic means the probe is more flexible and can bend or move easily to conform to the object's shape. This is useful for measuring complex and irregular surfaces.
  .
• Conversely, a lower Probing Dynamic means the probe is stiffer and less flexible. It's suitable for more straightforward measurements on flat or less intricate surfaces.
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• Adjusting the Probing Dynamic settings allows you to control how much the probe can bend or flex during the measurement process.
  .
• The goal is to find the right balance of Probing Dynamic for your specific measurement task. If it's too high, the probe might bend too much, affecting accuracy. If it's too low, you might miss details on the object's surface.

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[[Co...]]

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This is a tungsten carbide shaft that's directly from Zeiss! I can't get another shaft material in this specific size unfortunately.

[[Co...]]

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I'm really glad that the XTR is an upgrade! I can say I've been super impressed with the active scanning thus far.

I really appreciate the input, didn't realize how low I can go on this! I'm going to keep working on the XTR next week and I'll try this stuff out and I'll come back with an update for sure!

[[Co...]]

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I guess I would've thought that Zeiss wouldn't sell anything that wouldn't work on their own machines, but I'm thinking that this is more user error than a Zeiss problem.

That also makes a ton of sense avoiding the tensor calibration, I tried just a geometry qualification and that ran much better than the tensor calibration. Since this is such a long narrow probe (1.5x81) I wasn't really planning on scanning with it anyways so no great loss losing the tensor calibration! I'm going to try what Jeff reccomended first and if I can't get anywhere there then I'll go to a 6 point cal. Thank you!

[[Co...]]

Update:

I went back through the calibration process and adjusted the measuring force and probing dynamic values way down (50mN and 20% dynamic is what I wound up with) and played around with the different calibration modes and I was able to get some pretty darn good results, even when using Dynamic Tensor and Tensor calibrations (S values of 0.00003"-0.00006"). I want to try dynamic tensor on all the probes on the star, just didn't have time to screw with the sphere angles this afternoon. I did get a slightly better S value with the 6 point calibration but if I can scan with these probes then it'd be nice, so I figured that going with a tensor or dynamic tensor calibration was the better move. I think there's probably a bit more screwing around to be done to really figure out how to get the best results, but I'm definitely on the right track now. I find it interesting that Zeiss makes all of this probing stuff configurable, coming from Hexagon & Mitutoyo I didn't expect to have all these options! Also I think I'm starting to better understand the benefits of the active scan head, makes me wonder how much better a VAST Gold would be... Anyone have opinions on that?

Thanks for the help everyone!

[[To...]]

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I've always had the understanding that Probing Dynamic controls the speed (or more technically, the time) it takes for the stylus to reach the set probing force or in the case of a passive sensor, the set deflection value.

[[Je...]]

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Yes, Tom, I would agree. The speed deceleration is observable. I was taught that the mode of action for probing dynamic involves both the approach speed and movement during scanning, but it has been a while since I took Basic, and I can barely remember what i had for lunch today.

[[Je...]]

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Probing Dynamic directly effects the measurement speed both during approach and tactile data collection. The "Dynamic" portion of this is due to the lower speed, it is able to be more "Dynamic" in its path and follow the surface more closely while reducing the Tensor bending of the stylus system.

In machinist terms
Speeds and Feeds:
Speed - Dynamic Probing
Feeds - Probing Force

FYI - Its typically the Dynamic Probing value that breaks small styli, not the Probing Force. Typically, small styli can withstand the force of the scan but not the inertia of the complete stylus configuration before stopping the head. This is why it breaks on contact rather than during the scan.