Creating a Multi-Wire Spring

Steven Kiley

31 Aug, 2021 09:13 PM

This tutorial is intended to show you how to model a multi-strand spring. Whether you want to make a coil spring, torsion spring, or any other type of wire spring, this method will work! This tutorial will require prior knowledge on starting sketches in SolidWorks, use of 3D sketches and some surface modeling for certain types of springs.

1. Step 1: Spring Layout

   1. The first thing you want to do is determine what type of spring you are designing, where it will fit, and what wire diameter you are using.
   2. Let's start by making a 10mm circle on the right plane.

   

   • Complete this sketch and go to your 'Features' tab. You're going to look on the right end of the toolbar for 'Curves', then click the dropdown to select 'Helix and Spiral'.

   

   • There are several ways to define your helix. We're going to select "Height and Revolution. We'll make the height 80mm and the revolutions 15. Then we'll set our Start Angle to 90 degrees.

   

   We're now ready for Step 2.

   
   

   
   

2. Step 2: Spring Profile and Finish

   • We're now going to create a plane that is perpendicular to the end of our helix. On the 'Features' tab, select 'Reference Geometry', then 'Plane'.
   • Next, you're going to select the endpoint of your helix, for First Reference, then the helix itself for the Second Reference.

   

   • Once your plane is created, you can grab the handles and adjust its' size to your liking. With your plane still selected, start a sketch on it.
   • We're going to make a spring with a cable diameter of 1.5mm, comprised of three 0.7mm wires. There is no need to dimension the 0.7mm wires if you do this trick: Draw a 1.5mm circle, make it a construction line. Draw three circles inside the 1.5mm circle. Make them all equal to one another. Make all three circles tangent to each other in pairs. Tangent pairs should be (1,2) (2,3) (3,1). Then make each of the three tangent to the 1.5mm circle. You should end up with a sketch like this:
   • The last thing we want to do before we close this sketch is to trim the arcs near the center to create a closed three-lobe contour. We do this so that the Sweep command doesn't get confused and it makes our geometry slightly less complex.

   

   • Now we're going to complete the sketch and go to our 'Features' tab. Select the 'Swept Boss/Base' feature.
   • The three-lobe contour is our Profile (blue box) and the helix is our Path (pink box).
   • DO NOT CLOSE THE COMMAND YET! We're still setting things up. Expand the 'Options' dropdown. Under 'Profile Twist', select 'Specify Twist Value'.
   • 'Twist Control' will appear. Select 'Revolutions' from the dropdown menu.
   • Now move on to the 'Direction 1' dialogue box. Enter 100 for 100 revolutions. This will tell our three-lobe contour to twist 100 times as it makes its' way around our helix.

   Hint: Turn on 'Show Preview' to get an idea what your shape will look like before you accept.

   

   Congratulations! You've just created a twisted coil spring!

   

   • Now let's apply these skills to a much more complicated spring.

   
   

   
   

   
   

3. Step 3: Complex Torsion Spring

   I'm now going to take you step-by-step through the creation of a more complicated multi-wire torsion spring. Please pay careful attention to each detail in the images below. I will do my best to spell out what to do in each step, but some features may be implied through illustration. This will require some basic use of surfaces to complete this part.

   
   

   
   

   • Start with this sketch on the Front plane:

   

   • Extrude as a surface with the following parameters:

   

   • Make a reference plane offset from the front plane:

   

   • Make a circle on Plane1 and create a helix with the following parameters:

   

   • Create this sketch on the top plane (not top surface). Note, I added construction lines to show the relation to the origin. These are not necessary if you properly constrain with sketch relations:

   

   • Extrude as surface with the following parameters:

   

   • Now start a 3D sketch.
   • Use 'Convert Entities' to convert the helix to sketch lines.
   • Look for the dropdown under 'Convert Entities' and select 'Intersection Curve'.
   • Select the following surfaces:

   

   • Complete that Intersection Curve command and start a new one with the following surfaces selected:

   

   • Add the following lines and relations to connect the helix with tangent segments:

   

   • Delete this point to merge the two colinear segments:

   

   • Add these sketch fillets to all sharp corners:

   

   • Add these construction lines and relations to get setup for the next step:

   

   • Connect the two open ends with a 3-point spline. Note the 3rd point floating in space in the "center" of the spline:

   

   • Add tangent relations to each line segment with each end of the spline.
   • Create the two construction lines to lock down the "center point" of the spline
   • NOTE: Portions of your sketch may turn blue during this process. This is a glitch (at least on SW 2020) and your sketch will actually still be fully defined:

   

   • Go normal to your front plane and drag the two tangency handles on your spline to line it up on top of your circle.
   • NOTE: If doing a single-wire spring, this process can be substituted with a more precise method of 'Spline on Surface', but because we are making a multi-wire spring, we require the tangency of this less-precise method to perform our twisted sweep later on.

   

   • Once the spline is lined up to your liking, complete the 3D sketch and add the following reference plane to the end point of our sketch:

   

   • Let's make our profile the following dimensions:

   

   • Now, just like before, select Swept Boss/Base and create your twisted sweep.

   

   • Complete the twisted sweep and you should have a finished torsion spring!

   

   
   

   I hope you enjoyed this tutorial and added a new skill to your portfolio! In my next tutorial, I'll be teaching you how to create a detail drawing of this spring.