# Seven Simple Tips for Modeling Springs

Every so often, I’ll hear a comment about making springs in SolidWorks.  Some people say that it’s difficult, or that SolidWorks does not have adequate tools for it.  But it’s not really as hard as you would think.  With that in mind, here are a few basic tips for modeling springs in SolidWorks:

1. The Helix/Spiral curve generation tool is very powerful.Taking a quick glance at the Helix/Spiral tool, you see a few simple options:  you can define the helix by pitch and revolution count, height and revolution count, or by height and pitch.  There are a few other options (namely direction, starting position and the ability to taper the helix), but that’s mostly it.

Inspect a little closer, and you’ll see that you can choose between constant and variable pitch.  The variable pitch option will open the door for much more complicated helical paths, such as when you wish to decrease the pitch on either end of a ground end spring.  By selecting the variable pitch, you have the ability to create a table with multiple points where you can define height, pitch, revolution count or even diameter.  A good analogy for this would be that it is like creating a spline from a table of parameters for the location and tangent direction for each of your spline points.

2. It’s very easy to add on to a helical curve.You can create other sketches that refer to the endpoints of the helix curve.  In the pictured example, I created a torsion spring where the tabs are sketched on datum planes that refer to the endpoints of the helical curve.  When the sketches are complete, I can combine them with the helix by inserting a composite curve.  I added another step to the process and got rid of the tangent edges along the spring by creating a new 3D sketch and fitting a spline to the composite curve.  I find this technique easier than it is to try to use one swept feature as a parent for a second swept feature.
3. A Ground End doesn’t have to be anything more than a surface cut.
While you could design in a ground end by using a complicated swept or lofted cut, you can also create the ground end effect simply by using a datum plane as a cutting surface.  In the pictured example, I made the upper cutting datum plane a child feature to the helix by adding a datum point to the center of the end face on the helical sweep.
4. Configurations can show the spring in multiple positions.This is a pretty common use for having models of your springs:  lots of designers will want to be able to see how the spring will fit into the context of an assembly.  You might want to show one position for a no-load length of a spring, and another position to show the spring bottoming out, (perhaps including a change to the spring’s O.D).  This is a pretty natural time to make use of configurations.  A variable pitch helix will have a lot of variables to change, but you can use linked variables or design tables to simplify the process.   Shown is a compressed version of the ground end spring from above.

5. Intersection curves can let you get fancy.If you want to show a more detailed form spring, there is a fun little trick that you can use to generate coils using a variety of shapes.  To start, you just need a body (solid or surface) that represents the shape you want to wrap around.  In this example, I’ll start with a pretty basic revolved surface:

Then, you can create a spiraling swept surface (it will look like a spiral cut potato when it’s done).  The easiest way to do this is to do a simple surface sweep with a line as the profile, and the axis of your revolved body as a path.  The “twist along path” option for the sweep feature will allow you to add a spiral defined by turns, radians or degrees.  This will give you a constant pitch helix, but you could alternately add a guide curve in the form of a pre-made helix which would allow you to vary the pitch.

Once this is done, it’s a simple process of creating a 3D sketch and using the “Intersection Curve” feature to create your helix, which you can use as your sweep path for your spring.

6. You can get a length for your sweep, but there’s a caveat…If you’re on the manufacturing end, you might be curious to know how much raw wire material will be required to make your spring.  The good news is that you can use the measure tool to find the length of your sweep path.  The bad news is that this isn’t necessarily going to be a measure of wire raw material required.

Although the measure of your sweep path is accurate, this is simply a geometric measure that does not take into account the deformation of the raw material as it is bent to form the spring.  Your measurement will be at best a rough estimate for your raw material requirements.  To put it another way:  you won’t be able to use that information in the same way that you can with a flat pattern for your sheet metal components.

7. Springs in Simulation:In assemblies, the beautiful thing about a spring model is that you don’t need to include it in the study.  As long as you have the stiffness coefficient and any pre-loading information, you can easily replace it with a spring connector.  This is a simple way to free up resources for the mesher (no need to discretize the spring) and for the solver (much simpler contact conditions).

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#### jeff setzer

• There was a small utility .swb to automatically create a compressed end spring to few length if necessarily. Suddenly it works well in SW 2008 but doesn’t in next realizes. If somebody are familiar with MS Visual Basic and can spend some time to fix it – I can e-Mail this file to volunteer. This could be highly appreciated by all SW users. Contact me at vkunin@srtorque.com