6 Replies Latest reply on Apr 14, 2015 9:49 PM by Mike Price

    How do you model soft, malleable parts?

    Koji Intlekofer

      I'm working on designing some soft protective bumpers for a device. Something that stretches over and ads some cushion, sort of a like a smartphone case. Probably to be injection molded with silicone or PP. I've only done rigid parts before. Does anyone know of any tutorials or have any best practices on how to approach this?

       

      One issue I've had is that the configuration that it would be injection molded is different than the final shape when it's mounted onto the device. Should I start with designing it around the part then change it somehow for mold design? Any insights would be helpful. Thanks!

        • Re: How do you model soft, malleable parts?
          Mike Price

          Designing the part is one thing, designing the mold tools is another.

           

          If you are wanting a consistent thickness protective cover around the part (or something close to that) you can start with offsetting the part surfaces you want to cover by 0 (make a copy).  Then if the geometry allows, you can thicken this surface to your desired mold thickness.

           

          You can do this in-context in an assy with the "cover" part inserted into that assy as a new part, copying the original part surfaces, or you can do this in a part and then insert the newly created solid body into its own part.

           

          Then you could scale the cover part, having a configuration that is "mold scale" or something like that.

           

          Do you know much about making silicone parts from molds?  Modeling mold tools for this will depend on how you go about do this.

            • Re: How do you model soft, malleable parts?
              Koji Intlekofer

              I have experience with silicone parts, but nothing that deforms or changes shape once produced. The idea here is to create a part that wraps around a hard plastic device, sort of like a rubber band. So, if I design the part around another model, it's probably going to be molded in a more splayed-out configuration. I'm not sure how to make this transition (or convey it to a mold maker as the case may be).

                • Re: How do you model soft, malleable parts?
                  Mike Price

                  You'll want other input here, but I would think some combination of scaling/offsetting surfaces (to get an interference fit of some magnitude) would be an approach.

                   

                  Are you trying to mold somewhat planar and then wrap the part to a conformal shape?  If so, why not mold it to the shape of the part itself, then stretch it onto the part you are trying to protect?  A smartphone case would be molded this way.

              • Re: How do you model soft, malleable parts?
                Christopher Sudlik

                You can't, what you do is you design the original molded shape and the final shape and do the two separately, or linked to one another via a parametric variable that is in different states in different files. What some places do is just allow the malleable part to interfere and look bad in the drawing of the phone assembly, which is plenty an option. If you know the material properties you can always run an FEA and determine the force required to stretch the part through iterations.