3 Replies Latest reply on Aug 20, 2015 9:41 AM by Mike Price

    Adding fillet to a part with undercut

    John Munroe

      Hi

       

      I have this part with an undercut and I wonder how fillets should be added.

       

      Capture.PNG

       

      The split line is colinear with the top of the boss, but after adding fillets, the fillet extends above the split line. With the fillet pushing the split/parting line up, this isn't desirable - right? Does anyone know what the proper position of the split line or the proper way of filleting might be?

       

      Thanks

       

      John

        • Re: Adding fillet to a part with undercut
          Mike Price

          John,

           

          As you can see, your parting line cannot be along the upper tangency of the boss.  It has to be coplanar with this surface

           

          8-5-2015 1-57-27 PM.jpg

           

          The fillet above can be in your upper mold (it will be negative in the tool)

           

          You can always create the mold quickly by creating a solid and subtracting out your part, splitting it about your parting surface.  You can then see if there are going to be any undercut issues if you aren't used to visualizing this inside/out.

           

          EDIT:  Do you have draft on your "clip" for your pull direction?

            • Re: Adding fillet to a part with undercut
              John Munroe

              Hi again,

               

              Actually, do you mean that the fillet above can be in the upper mould and the rest is in the lower mould? That is, the parting line depicted should only be lowered by a mm or so. Or even, just slice across the top of the hook in the middle?

               

              Thanks

                • Re: Adding fillet to a part with undercut
                  Mike Price

                  Hi John,

                   

                  Depending on where you would be ok with parting line flash is where you would want to put the parting line.  For example, you could have your parting line be coplanar with the top of your "clip" which would put it at the tangency point of the fillet at the clip (I can't open your part, but it looks like this is where you have it).  You could also have your parting line be half way into the thickness of the clip as well.....I would personally put it where it would be easiest to clean flash, but not sure what exactly you need.  What is the material you are molding/casting?

                   

                  Maybe others can weigh in too?