Welcome to MCAD Central

Join our MCAD Central community forums, the largest resource for MCAD (Mechanical Computer-Aided Design) professionals, including files, forums, jobs, articles, calendar, and more.

Register Log in

Flexible o-ring modeling


New member
Has anyone ever defined an o-ring as a flexible component? We use round gasketing all over the place at my company, and I'm sick of ignoring those part interferences during my interference checks. What I'd like to do is model the o-ring as a flexible component, so when it's installed in the assembly, it compresses itself. If possible, I'd like a part which a) has inherent diameters defining the free shape (knocks ellipses out of the running), and b) takes groove side walls into account. Thanks!


What your asking for sounds great but I think it is beyond the capabilities of flexible components at this time. I'd love for someone to prove me wrong. We use a lot of o-rings. I model them with three unrelated features, one for the free state, one for axial compression and one for radial compression. Family tables take care of the rest.


I saw a flexible o-ring model back in about 1998 that involved relations that would squash the o-ring down (axially) and even reduce the cross-sectional area if the o-ring was stretched.

I would think that with an eval feature or two and a creative cross-sectional sketch, you could easily create an o-ring that could be squashed axially, radially, and even stretched.



New member
They way I have done what you are asking is create the model in the assy, using the grooves as a reference in your sketch, and selecting the groove as the sweep path. Since you squash the O-ring into some shape, if you are concerned what you can do is figure out the cross-sectional area of the free state and use the perimeter option in sketch to drive a dim to make sure that you have the right cross area in the squashed state.

Than in the model I would create a nice simple O-ring and use a family table to drive the model. Not the best practice since you end up with solids outside but a way to relate the purchased part to the flex one. I had always thought about making a simplified rep, but never got that far..

This is a perfect place to use external references even though many do not like to do so.

As for Using Flexible Components in wildfire this is not what it was intended for, where you can vary dims is more up its alley, though I heard that they are addressing gasket ideas.


Here's a simple example of an O-ring that can be made flexible in a WF assembly

There are 4 dimensions

- DIAM --> diameter of oring installed

- UNSQUASHED_THICKNESS --> free thickness of o-ring

- SQUASHED_THICKNESS --> installed thickness of o-ring

- SQUASH_ANGLE --> 90=axially squashed 0=radially squashed

X-sec area adjustments not taken into account, but this will prevent unwanted interferences and make cross-sections look nice.


Here it is installed three times in a WF2 assembly 'flexibly'

View attachment 406


New member
Hey guys, don't forget that most o-ring materials do not compress. I had to modify an old design for a company that forgot this. They had an o-ring that was the same shape and size as the gland.



New member
The way we have done it is to make the ring sketch an ellipse, dimensioning the minor and major axes, and the ID (or theOD depending on what you want to do), and have a plane on the botton of the ring.

When you put it in your assembly, locate it by the axis and the plane. Then you can make it flexible.

Gary B