Variable Pitch Helix

[timothyryoung]

I'm having difficulty creating a variable pitch spring where several sections of the spring have a close wound pitch (i.e. pitch = wire diameter = .003"). SW yells at me and says I have to choose a value greater than .00393701. Anyone know if this is possible?

Tim

 

[Heckler]

I seems to me that SWx doesn't like to cross over on itself. This happened to me when doing some flex cables using a loft. If SWx is telling you choose a great value that would indicate you can't have pitch = wire diameter.

Best Regards,

Heckler
Sr. Mechanical Engineer
SWx 2007 SP 2.0 & Pro/E 2001
Dell Precision 370
P4 3.6 GHz, 1GB RAM
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(In reference to David Beckham) "He can't kick with his left foot, he can't tackle, he can't head the ball and he doesn't score many goals. Apart from that, he'

 

[krywarick6]

Another trick is to break down the total curve(variable pitch helix) and make a helix for each pitch, assuming that the number of turns in each pitch is less than 1, and sweep that pitch. This way the sweep will not collide with itself.

The end result is rather hack and can be horrible for FEA, but it is a way to communicate your intention.

Christopher Zona - Product Designer
Concord, Ontario

 

[adn1975]

create seperate helixes. creat the first helix, insert a plane at the end point of the first helix to create the second helix upon. besure to use the pierce mate. create the second helix. then create a composite curve from the two. then you can sketch and sweep to make your spring.

 

[TheTick]

In a position such as you state, "pitch = wire diameter = .003", there will be a zero-thickness condition (non-manifold solid) which will cause a modelling error. This is not unique to SolidWorks. Many modelers have problems with this, ncluding UG and Pro/E.

 

[MNuttall]

If you don't care if the model is exactly right or not, for the case of:
"pitch=wire diameter-0.003"
make the wire size 0.0029999" and the pitch 0.003".
If you set your dimensions to only display 3 decimal places it will round to 0.003 and the model will work.