Long Helical Involute Spline

[[Ri...]]

Hello, 

 

Does anyone have any experience with measuring super long Helical Involutes - so long that they turn into threads/screws? 

 

I just wanted to make sure that GearPro doesn't care if I measure this as one long trace, or if it would be better to break it up into segments. 

[[Ch...]]

Gear Pro should be able to do this, is this involute? or worm or rotor ??

[[Ri...]]

It is spec'd as an Involute. I've done some measurements on it previously, but I saw some really weird results that I struggled to wrap my head around. 

[[Ch...]]

make sure to measure the R/T in calypso on a feature on the part, in R/T advanced commands, can you share the 'angle to main axis' during the run? This is the usual culprit.

Feel free to PM, I can take a look at the programs if possible.

Is probe staying on the PD as it measures, or do you see some drift as it is measuring ?

Is there other evidence (gear analyzer charts, etc) that says it is a conforming part ?

 

 

 

 

 

 

[[Ma...]]

The thing people typically find unusual about parts like this is that the helix trace represents much more rotation about the axis than normal gear geometry. The result of this is that location errors of the gear teeth relative to the axis of rotation appear on the helix trace as sinusoidal curves rather than straight traces with varying slopes typical on normal helical gears. Just by looking at the trace you show it appears that the face width of the part is approximately 1.5 times the lead so you see 1.5 wavelengths of the runout sine wave in the helix trace. 

Does this explain any of what you find unusual about these, Richard? 

Edited Monday at 01:30 PM

[[Ri...]]

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Hi Mark, 

 

This might explain exactly what I was seeing when I measured one of these. It made it look like there was crowning when I don't believe there is?

I'm thinking about measuring it in sections to see if that helps instead of just one long trace. 

 

[[Ro...]]

Hi Richard, I agree with Mark, this behavior is also typical for worm shafts or screw compressors/rotor. Location deviations appear in helix/lead measurement results as sinusoidal deviations. What shows you additionally the pitch and runout evaluation? You should also have a sinusoidal behavior there?

[[Ma...]]

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The result you are seeing is real, Richard. I don't see any value in measuring the helix in sections. If the helix parameters form and total are out of tolerance you will likely have to make the production and measurement axis agree more closely with one another in order to achieve good results. I have measured quite a few similar parts for hydraulic rotary actuators. These convert linear motion of the hydraulic piston to fast  rotary motion imparted by the helical spline. Common uses are bin dumpers on garbage trucks and fork lifts.