TP2 vs. TP2 vs. TP20 standard

[gage guru]

OK please look at the attached to follow the explanation below.

TP2(A) was calibrated (num 3) and the results are for parts 1-5 shown.
Same TP2(A) was taken to another CMM and run same 5 parts (num 1).
TP2(B) was calibrated (num 2) and results of 5 parts are shown.
TP2(B) was adjusted tension - different operator and results shown (num 4).

Finally TP20 was calibrated and results are shown (num 5).

From what I can tell num(1,3,4) seem to be correct as the calibration shows the Dia. is much closer than the other calibrations.

I was hoping the TP20 would give me similar results, but it was in between the others.

Does this mean that the TP20 should be the low force and then we would get better results as you cannot adjust them??

Using a PH10T for num(1,2,4,5) Num 3 is a PH6 head. All measurements used a 1 X 30 mm tip in an A0 B0 position(Tip 1 for Ph6).

I am looking to get to using the TP20 instead of the TP2 as we have operators who have "issues" with setting the tension for different probe configurations. I know this is quite the subject as everyone has there own personal preferences, but for right now I just want to be (pardon the use) "close".

Ok I will leave it at this for now, but will be in tomorrow to see what the experts say!!! Thanks in advance!!!

[John Riggins]

Need to know what you were measuring.

Was it a diameter?

A distance?

A location?

If it was a dia then the results are not too surprising since unless you try to set up for very accurate sizes (this can be done, but it takes some effort) different Touch Probes will give different results.

If it was a distance, was it 3D? 2D?
Different methods can produce different results.

If it was a location, then you have big problems.

Please give us some more info.

[T Miller]

When you used the tp20 after calibration did you run the program at the same speed you calibrate at? What prehit distance?

[gage guru]

It is a distance from 2 pierce points created from 2 different circles. The speed is the same all across the board as well. We rotate the alignment to the center of the notch and create a line from the alignment and then use the line to pierce both circles. See attached view. We are measuring the .116 dimension. Note we can only measure the circles where the tiny circles are representing points(these do not match exact points measured).

[gage guru]

Is this something that renishaw would know, because I looked at all of the specs for a standard TP20 and it should handle the 1 X 30 mm tip just fine and I would think it would give better results. Just confused as to what is truly correct???

[bw_bob]

I just saw you are using a 1x30 tip. That is about the biggest piece of crap tip you can use. The shaft is so long and thin i would not trust the deflection. I only use those when I absolutely have to....My .02

[gage guru]

In this situation we need the 1 X 30 mm as we have a best fit pin in the middle of the part and we want to run it with the PH6 head. Even so - the results are all based on the same tip, why such a difference with the TP20??

Again thanks for all the feedback, but still looks like there is no good answer on this......

[John Riggins]

I would recommend you do a similar study (same machines/tips/repetitions) with a ring gage and see what you get for results with that. Use something similar in size to the dimension you are trying to measure.