Sketching a customized spring 2

[vanleurth]

Hi Happy Solidworkers,

I have a simple question but last night I spent 3 hours trying to figure this one out together with my solidworks books (but I couldn't).

It is about sketching a costomized spring it has a 360 helix attached to straight rod extensions. So I figured how to create the helix in 3d. Now, How do I union (from AutoCAD vocabulary) two lines to the ends of the helix.

In Autocad it will be easy but I want to learn how to join lines, and other geometry to create a sketch from different exploded sketches.

I tried moving the lines to the ends of the helix but I don't seem to be able to connect tehm.

Sorry for the simple question but this is the only solidworks forum there is (in eng-tips website).

V.

 

[TheTick]

I have a torsion spring model posted at the following link:

http://rschwarz.tripod.com/CAD/TorsionSpringByTheTick.htm

It's pretty involved, the product of two years of torsion spring design in SW. Some important points:

•Don't use the helix curve as part of a feature. Copy the curve into a 3D sketch and use that. Otherwise, parts of the helix curve become inaccessible for future use (like picking endpoints).

•Lots of equations in this model. See faq559-590 for important info regarding equations and dimension names.

•Though this is a torsion spring. I believe it could readily be modified to be a variable compression/extension spring. The spring length is governed by a centerline 3D sketch. Vary the spring length by varying the sketch.

If the ladies don't find you handsome, they should at least find you handy.

 

[vanleurth]

Tick,

Thank you for your comments on this matter. I wonder if you know about a good online tutorial on how to ... equations in solidworks.

Thanks again,

V.

 

[TheTick]

I don't know of any equations tutorial. I would start by making a scratch part and playing around.

The spring model has equations that are turned on and off selectively by configuration. I recommend using a design table when doing this, as the conventional method of making equations configuration-specific is flaky.

 

[SBaugh]

Try going to the SW website and look under the model portion of the site. I know there are some models there that use equations. You can take them apart and probably figure it out from there on how equations work.

Regards,



Scott Baugh, CSWP
3DVision Technologies

http://www.3dvisiontech.com

http://www.scottjbaugh.com

faq731-376
When in doubt, always check the help

 

[vanleurth]

Tick,

I have been trying to copy the helix from the 2D sketch but it says that this can't be copied to the clipboard. How do you move a helix that was created in a 2D sketch to a 3d Sketch ?

Solidworks doesn't seem too easy for the creation of springs.

I'm trying to model a spring similar to the one you showed me with extension. Mine has just one turn and has rod extension at each ends.

I also tried to draw the helix and then sketch the extension lines but I don't seem to grab the endpoints of my helix. So, like you said I have to copy it into a 3D sketch but I can't.

I guess Solidworks is frustrating at the beginning,

Thanks in advance for any advice,

V.

 

[manxJim]

To get a helix into to a 3D sketch open a 3D sketch select the helix then select convert entities
Jim

 

[TheTick]

manxJim is right. The helix is copied into a 3D sketch, not a 2D sketch.

Spring design is actually one of those things that got much mores unnecessarily difficult in 3D (3D in general, not just SW). It really tries one's knowledge of trig and geometry every time. If I had my druthers, I would just model the spring body as a hollow cylinder. However, once they see you model a full spring just one time, they (customers, management) insist that you keep doing it!

If the ladies don't find you handsome, they should at least find you handy.

 

[sirmick]

The attached bars I believe should be tangent to the converted 3d curve. Now, when I tried to change the pitch of the helix the tangent constraint did not automatically update. I had to go back into the 3d sketch and drag a point and then the lines became tangent.

 

[macPT]

sirmick

I guess that you must add an equation that relates the pitch with the rods distance (I suppose that this is the distance that controls de spring compression/extension).

This way, when you change the rods distance, the spring will update it's length accordingly.

Regards

 

[vanleurth]

Thanks so much manxJim and all others who contributed,

It is working now !! Yeah !! good start of the weekend.

V.