Spiral Flight Auger (Unfold Command) 1

[zeroburn315]

I have made an auger spiral as shown in the image below as a surface. After i use the unfold command, everything looks fine to me, However when I cut it and pull the flat part, to match the inside pipe dia, the pitch should come same as per my model, but its not the case. The pitch is higher compared to the folded (Original) model.
Then I did the manual calculations, and it shows the same unfolded dimensions as catia. which means the problem is not in catia, but I am not able to figure out the issue, if the unfolded part dimensions are correct, why is it not matching the dia of my model when i pull it to match the shape?

Am I missing something? can someone please help me regarding this issue?

 

[zeroburn315]

Its been days now, any help would be appreciated. Thanks

 

[itsmyjob]

think about the inner diameter... if you unfold the geometry the length of the edge should stay the same... but if you keep unfolding think about the shape of that edge... it would become a line when unfolded to the max. Meaning the inner diameter will go from whatever value when geometry is flat to a null value when we pull the geometry to the maximum we can. That could explain why the inner diameter change from flat to shaped.

The length you gain going 3D, you lose in the perimeter... if the pitch is 20mm that is the 20mm you lose in perimeter..

Eric N.
indocti discant et ament meminisse periti ​