Spring modeling challenge

[krywarick6]

I am modeling an arc coil compression spring.

The basic arc seems to be rather easy to model. I set up an arc as a path and sweep a circle along the path using the twist option in the sweep feature setup.

Easy enough, or so I thought. Then the method of manufacturing comes into play. This starts to affect the response of the ground end interaction of the physical spring. The ground end is not a radial angle passing through the model center. The spring is made as a normal compression spring and then heated and stress relieved around a mandrel thus creating the arc.

During this process, the ends still have the ability to stay straight according to the initial coiling. This why the ground ends do not become an angled surface that is a radial angle.

Where is leading? To match the model to the method of manufacturing. Assuming a given starting point, a ground angle provided by the manufacturer and our design parameters, the twisted sweep doesn't quite represent the physical model. In the attached model, you can see that my first solid coil should be laying off more than what the twist is creating.

On the OD of the spring arc, there should be a coil that half of the wire diameter for that coil is absorbed by the grinding process with a pitch equal to the wire diameter. Note that this pitch does have to be opened slightly for the body to actually sweep(twist).

The rest of the spring body should take off from the first diameter at the ID of the spring arc. As you can see, it doesn't seem to create the correct pitch to avoid the first partial coil. I've tried to play with the starting point of the sweep path, but that affects the spring body's shape.

We are still using 2005, but I don't see this as an issue. Any help or suggestions are welcomed. My last and least option is to calculate a curve, which can be done, but then it will not make for a user friendly model with other designers, and they will say mean words to me even though greatness and modelling prowess have been demonstrated.

Regards,

Christopher Zona - Product Designer
Concord, Ontario

 

[CorBlimeyLimey]

Have you tried the Flex command? This should be most like the actual forming process.

 

[krywarick6]

That's a cool idea, but...

Here's what I tried. I swept a circle around a helix. This looks like a straight spring. Assume this to be the wire used for the spring.

As I apply flex, it gives an arc and it distorts body so that the "spring wire" is not round any more, as opposed to the model that I am starting with.

Am I missing some control with the flex?

Christopher Zona - Product Designer
Concord, Ontario

 

[rgrayclamps]

Hi, Christopher:

I modelled compression springs many times. I did not notice any of the difficulties you described. Maybe I missed something in reading your explaination. Could you post a picture or better still a print of the spring you try to model?

By the way, 3D models are math data. They have nothing to do with how they are made in production.

Best regards,

Alex