Form Error??

[[Br...]]

Can someone tell me why I am suddenly getting all this form error in this cylinder I am measuring? This was not happening when I first started checking these parts and now over the last 5 there is so much form error and it reports that the hole is significantly undersized because of it. I know this is not the case because we have pins that go in smoothly so I know the reading from Calypso is wrong. I have tried slowing down the speed and taking fewer points, I initially was running with .060 on my speed and taking 450 points and it was working. Now though you can see it is skipping and not taking points? Any ideas why now?

[[Ia...]]

Have you tried re qualifying the probe to see if it is stable? Do you have another probe that can measure that feature?

I'd eliminate the possibility of stylus error before looking for a software error.

[[SH...]]

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Do you have any master sample?. If yes then run that master .you can check weather stylus is good or not.

[[Ke...]]

Just an FYI: If you right click while the feature is open, and select "Show Masked Points", you will probably see the points that it appears to be "skipping"

[[To...]]

The skipping points that Keith is referring to are from the outlier elimination settings. Is it possible that you're shanking out due to the part or stylus being slightly off-axis or from anomalies on the surface. Not sure about your stylus system but check to see if everything is tight. The earlier post regarding re-qualifying your stylus system is a good idea, too.

Assuming you're using a 50 upr filter setting, 250 points is not enough. 450 was adequate. Your form to sigma ratio is good so the results are not due to a lack of points but you need the filters to be working.

[[Br...]]

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I didn't think it was the probe because I've checked other parts and it was fine, but I re-qualified it and checked the same part again and nothing changed so it is not the probe.

[[Br...]]

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I selected this and no other points appeared.

[[Ke...]]

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What is a good general rule for Form to Sigma ratio?

[[Br...]]

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Everything seems to be tight, and I did re-qualify and nothing has changed. I went back to my original amount of points and yes I am using 50 upr filter settings, gauss, low-pass, and connected segments. My settings are all pretty much the same as what I would normally use.

Like I was saying in the first post, it is very strange to me because it was working fine for the first 10 parts or so. Then I went to check another and ever since I've been getting this problem with my form error.

[[Ke...]]

"When in doubt - reboot!"

Do a complete shutdown - Controller & software; requalify & re-check.

Sometimes, Calypso be crazy.

[[Ke...]]

...are you using a rotary table?

[[Br...]]

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No

[[Ia...]]

Do you happen to have a part that you know previously measured well?

[[De...]]

The hole appears to be on a rather large angle in X/Z, I would agree with Tom's earlier statement that the probe could be shanking.

It looks like it is removing points on only the inner path, which is generally the case when a probe shanks out.

Have you actually watched it run this feature to verify the shank is not contacting the rim of the hole when it is scanning the inner scan path?

[[Br...]]

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Yes, it does not appear to be shanking, I will try moving my circle path back a little bit though.

[[Za...]]

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I was wondering the same thing. I've never seen the two terms referenced as a ratio like that before.

[[Ow...]]

I'm going with_________________

[[Mi...]]

If you ran 10 parts and all was good and suddenly a group of parts shows bad with no actual change to sequence, remove variables until you solve the problem. Just as a test, use a different probe and rerun it. If both probes show a problem then it could be the part. If the second probe shows good, then it's something about the probe assembly. Maybe the adapter plate is dirty or maybe the stylus tip is damaged or worn.

[[To...]]

Here’s a way to visualize if you’re shanking your stylus. Open the feature. Right click in CAD window and select Curve Magnification from context menu. Select 20, 30 or 40. This will magnify the error on your actuals. If you’re shanking, the arrows where you’re shanking will be further away from the group.

[[To...]]

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It was explained to me that a 3 to 1, or better, of form to sigma is an indication of a good data set.

Added: If less than 3 to 1, add more points.

[[Ri...]]

Any chance this part is plated?
Cleaned with some type of solution?
Are you using denatured alcohol? (denatured alcohol can leave an invisible film).
It is typical that plated parts tend to have a sticky or gummy feel to them, some cleaning solutions can also leave an invisible residue.

I ask, because your "arrows" appear to slanting, more than I see as normal, to one side. This is indicative of excess drag on the stylus, speed changes wont help.
I have been washing parts with Acetone, it wont harm the vast majority of plating or metals/aluminum's materials (Look up your specific application).