Analyzing GearPro helix features

[[Ja...]]

Hey all. As I get more and more involved with GearPro, I am still not a programmer, but I have to be able to analyze these features and know how they are affected. I am looking at some of our data for new splines and am noticing differences in the helix angle features and have some questions:

1) What does each line represent in the lead section? I see vertical lines, lines that look they are the lines from the scan, and purple lines.
2) Do the two lines closest to the middle (one left of middle and one right of middle) indicate the right and left side of the 1st tooth measured? Then the next two lines further out from that on both sides indicate the 8th tooth, then 16th, and then 23rd on the picture?
3) How can some of the flanks in the lead section be to the left of the line at the bottom and some are to the right of the line? If a spline was made to a helix, how could this happen?
4) Is there any documentation out there that has better explanations so I can pass this information on to management in an understandable way?
5) What are the Qa diameters in the middle?

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[[Ma...]]

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1) Vertical lines = nominal helix, lines...scan = actual helix trace lines, purple lines = LSQ best fit lines
2) Yes
3) Assuming you mean how can some of the helix traces lean to the left and some lean to the right, this typically indicates that the axis of the spline is tilted or wobbling compared to the measurement axis
4) There is a lot of information and training available for chart interpretation
5) These are the mean values of the deviations measured for the 4 teeth of each flank

[[Ky...]]

Hello all,

Mark had some good answers on his post, but there is one thing I would like to clarify at least. The "Qa" part in the middle indicates the worst tolerance grade that any of the flanks measured on that side met (depending on the standard you are using), while the diameter indicates the mean as Mark mentioned. The Qn on the outside indicates the nominal tolerance grade that you input in the program. From the looks of the chart you sent, it doesn't look like a standard was selected in the profile or lead characteristics, so those are blank in this situation.

We do have a poster online that does cover at least a little bit of the charts, which you can find here:https://portal.zeiss.com/iqr-academy/learning-documents. It's not exactly a detailed document covering it, but it might help with some things. It seems to make more sense if you think of the chart as deviation from nominal rather than the actual value, at least it does to me. It gets a bit more complicated when you throw in crowning, K charts or design profiles, but no reason to make it more difficult at this time.

I hope you find this helpful.

[[Ja...]]

Thank you for the information. Couple responses:

1) I talked to someone today and he said that the vertical lines are indeed nominal lines, the trace lines are the form deviation lines, and that the purple lines are the slope deviation lines. I am not sure what LSQ is, but does this sound correct?

3) I was basically asking how some of the flanks on the left side of the tooth be in one direction and some of the others on the left side going in the other direction. Surely if it is a helix spline, atleast the flanks on the same side of the tooth should follow the same pattern, right? Would it even be possible to have some going one way and some going another? Take the right side in the lead section for example. The 1st and 8th tooth are going from top left to bottom right, 16th tooth in the other direction, and 23rd tooth nominal. Is this even possible?

How is the form and slope deviation combined calculated?

This is coming from a splined shaft chucked into the rotary table. Do you think perhaps the alignment is off? The way the program was provided to us, we do a circle around the major diameter of the spline, then 4 points on top with a different probe, then one point on the major diameter with the 2nd probe. A suggestion was made that we do 8 points around the major diameter, 4 on top and 4 on bottom to create the axis. Does this sound correct?

[[Ma...]]

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1. The "trace" lines are just that. They represent the displacement of the stylus compared to a perfect surface as it scans across the part. LSQ stands for Least Squares best-fit. This refers to the method used to calculate the slope line. Basically a regression line according to Gauss.
3. Helix slope variation is typically caused by tilting or wobble of the measurement axis of the part compared to the production axis. This should be pretty easy to visualize if you hold the part in your hand tilted to the right. If you then rotate it 180 degrees it appears to you to be tilted to the left. The stylus sees the same error your eyes do.

The alignment you use to measure the teeth should represent the datum structure specified on the part drawing AND it should represent the function of the part in use. If the part in final use rotates on bearings you should use these bearing surfaces to construct your alignment.

[[Ma...]]

This article is quite old (1985) and the examples are from the manual measuring devices of that time, but I think the information on causes of various errors seen on gear measurement charts is still very helpful today.

https://www.geartechnology.com/ext/reso ... oderow.pdf

[[Ky...]]

Our Gear Pro training manuals also discuss effects like this in the appendix. This specifically looks like the axis you are using for the Gear Pro alignment isn't lining up with what the cutters cut to, so as it rotates, it the angle changes a bit. Without seeing the program, it's hard to say what might be a better axis, but perhaps we need to make a secondary alignment and use that for the Gear Pro macro?