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Variable pitch helical curve inacurate?

Hi all,

 

After doing a bit of research on helical curve accuracy, I am starting to doubt the geometry created by my variable pitch curve. We are going to be driving cutter paths on CAM software with these models so the helix needs to be accurate.

 

We are making a constant diameter helix where the pitch varies linearly between the start and end of the helix.

 

I have done some extensive calculus to derive some equations that define the start and end pitch, and the curve itself in a polar coordinate system.

 

When I enter my start and end pitch into the helix parameters, the finish angle is not correct by enough to cause the design to not work.

 

Please see attached the first picture, which shows the equations for the curve, start and end pitch. The curve should rotate 100° during 100mm of vertical travel.

 

The second picture shows that over 100mm of travel, the curve on Solid Edge rotates 94.67°.

 

If anyone has any info, on how to make this work, please let me know.

18 REPLIES 18

Betreff: Variable pitch helical curve inacurate?

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

Hi @The_fat_Hobbit

 

 

 

which SE version and MP are You using?

 

I remember problems with the helix curve a few versions ago (ST9)

There You defined a 0.5 turns, but the curve itself opened about 200 degrees which definitively is more than a half turn

 

regards
Wolfgang

Betreff: Variable pitch helical curve inacurate?

Hi @hawcad

 

Using ST10, not sure which maintenance pack. How do I find this out?

 

All the best,

Betreff: Variable pitch helical curve inacurate?

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

Hi @The_fat_Hobbit

 

 

just go to the Learning Solid Edge tab and there with About Solid Edge You will find the necessary info

 

20180807_1216.png

regards
Wolfgang

Betreff: Variable pitch helical curve inacurate?

Thanks @hawcad

 

My version is 110.00.07.003 x64 so that would make it MP 07 in that case.

 

All the best.

Betreff: Variable pitch helical curve inacurate?

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

Hi @The_fat_Hobbit

 

 

so at least You can try to install the MP9 and see wether this will change something

 

 

regards
Wolfgang

Betreff: Variable pitch helical curve inacurate?

Thanks for the reccomendation @hawcad, I am now version 110.00.09.004 x64.

I opened up the part file again and unfortunately the angle error is still present.

I do appreciate your help with this matter.

Betreff: Variable pitch helical curve inacurate?

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

I created one in NX for comparison. Saved it as step then overlaid it in SE2019.

Looks exactly the same so I suspect it is correct.

NX_Helix.PNG

LMGi
www.TLMGi.com

Betreff: Variable pitch helical curve inacurate?

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

@JasonTitcomb, what SE version was that part created in? I can't open it.

Bruce Shand
SE2019 MP8 - Insight - Win10 - K4200

Betreff: Variable pitch helical curve inacurate?

Solution Partner Phenom Solution Partner Phenom
Solution Partner Phenom

Sorry,

Forgot I was on 2019.

Here is the step from NX.

LMGi
www.TLMGi.com