8 Replies Latest reply on Sep 13, 2012 8:44 PM by J. Dm

    Thickening Surfaces - best practices

    J. Dm

      Hello All,

       

      I am a recent graduate and a young Junior designer. One problem that has plagued me for a while is what best practices to use when surfacing for injection moulded parts. I'm familiar with the old design-draft-fillet order of business, but I am still running into some troubles.

       

      I've heard many people say "thicken your surfaces first, then add fillets" to avoid thickening (or shelling) errors of "minimum radius of curvature" creating self-intersections on the inside of the part. My question is this: what if I'm not using fillets to create these tight radii? I often use lofts or boundary surfaces as they provide more control over the surface when creating parts. These inevitably create tight radii in some areas that fail when thickening.

       

      Am I doing things in the wrong order? Or perhaps using the wrong tools? I just spent several hours using offset surfaces, extending edges, trimming, and face filleting to thicken my parts. Very painstaking and inefficient, any feedback would be great, and I suppose I could provide a model if necessary.

       

      JDM

        • Re: Thickening Surfaces - best practices
          Lenny Bucholz

          J. Dm wrote:

           

          Hello All,

           

          Am I doing things in the wrong order? Or perhaps using the wrong tools?

           

          JDM

          J,

           

          to answer your questions above................ YES, NO, MAYBE is the final answer, I'm not being a smart A$$ but a realist.

           

          With time and experiance you will start to learn at what time you should shell then add those nice details to the outside faces that wouldn't translate to the inside using surfaces (replace face, cut with surface or split delete and patch or fill or or or), solid features like swept cut, lofted cuts, multible bodies ( shell each body combine together after).

           

          so as you can see you'll have to put the hours in and get some of those hard pull your hair jobs that will train you to when where and why you should do this over that..... every part has its own set of rules lets say, what worked on a simple one may only work 50% on another or less.

           

          been modeling in SW as a model maker for Industrial Designers since SW97 and I still am learning the best way

           

          best of luck and keep plugging away

           

          lenny

          • Re: Thickening Surfaces - best practices
            Chris Kamery

            J,

             

            I agree with Lenny on this one. Although I often do, he is good at what he does.

             

            The best practice is... (drumroll).... Trial and Error. Don't get stuck always trying to make the same tool work over and over again for every part / project. Sometimes you spend all of your time creating surfaces and trimming them together. Other times you can create a few blobs and shell them out. I can go on and on. Surfacing is often regarded as a Dark Art, those who can do it, prefer to keep it that way. What can I say, surfacing experts like to be mysterious.

             

            Just keep plugging away at it, use all the tools, use tools in ways they werent meant, sometimes it works, sometimes it doesnt. Seat time and experience will help you better predict the results of the tools you use. That is where you find your best practices.

             

            Chris

            • Re: Thickening Surfaces - best practices
              Aaron Godwin

              These guys are right every part is different. Use the tools you like till they don't work, then use differnt ones. And that's the best part, you're always learing something new.

              • Re: Thickening Surfaces - best practices
                Robert Stupplebeen

                If you know your wall thickness I would create a couple of surfaces, knit them together, then thicken. Roll back before your knit and thicken make more surfaces. Then roll forward, update the knit to include the extra surfaces and see if it works. Repeat as needed. I hope this helps.

                Rob Stupplebeen

                • Re: Thickening Surfaces - best practices
                  Jerry Steiger

                  JDM,

                   

                  You've gotten some good, though painful, advice from the others. I think you have already figured out the really basic issues, like waiting to put the 1 mm outside blends on after the shell when you have a 2 mm wall. I suspect that you are running into problems with the Sweep/Loft/'Fill/Boundary tools. Sometimes they generate tight radii near the edges for no apparent reason. It seems like this happens more wth Loft than with Boundary and is one of the reasons that I use Boundary whenever possible. Still, a case may come up where it is better to use a Loft than a Boundary. It seems like the tight radii show up more often when the mating surfaces are tangent or curvature continuous. I've actually had a few cases where I was better off to leave off the tangency conditions and just count on the profiles and guide curves to give me a "good enough" tangency. (Fortunately I was working with matte rubber parts, not polished parts.) One way to get around these issues is to build your surfaces bigger than needed and then trim them back.

                   

                  Jerry Steiger

                  • Re: Thickening Surfaces - best practices
                    J. Dm

                    Thanks for all the great reply guys, you're definitely right, it is a bit of an art. One that I'm still learning!