9 Replies Latest reply on Oct 14, 2009 1:03 PM by Jonathan Lawrence

    Press pin in plate

    Aric Tibbitts

      My question relates to a best practice of doing a drawing for a plate machined and then press in a pin.

      Typically we like to do one drawing which shows the part dimensioned and then show the pin pressed in with a nom interference and how far etc.

       

      The two methods I have found don't see to work quite right.

      1. First Method

           Have a plate and insert a part(the pin) into one file.

           Manually edit the BOM table to delete the plate and change it to describe the pin.  Not parametric. If the pin changes the table wont change.

           Or work with configurations and manually input the properties of the pin and only the pin will show.  Not parametricly linked to the pin.

       

      2. Second Methon

          Create an assembly with a plate and a pin.

          Works but we have our material listed in our drawing sheet not the BOM table. The drawing will show the part number of the plate and the pin and a shop may ask for the drawing of the plate when its already detailed on the assembly.

        • Re: Press pin in plate
          Daniel Smith
          Personally I'd go with option #2 with a note stating plate dimensions on print.... or add a column in the bom calling out print #'s
          • Re: Press pin in plate
            Ryan Grandidge

            Hello,

              What I normally do in the case of a pressed in pin or PEM would be to insert it into the part file and then call it out on the detail drawing of the part file with some dimensions and a note describing the part number of the PEM. The reason that we would do this at the part level is because the two parts will never come apart (similar to a weldment).

            • Re: Press pin in plate
              David Anderson

              to make a plate and then press in a pin actually requires 2 drawings.

               

              one is the part detail drawing having the dims, tols, material, finish etc.

               

              one is an assembly drawing showing the parts assembled.

               

              my 2 cents...i realize companies have their own "standards" but in the long run it is best to have a detail drawing that is not an assembly drawing, this is true for a number of reasons in addition to the ones you have discovered within solidworks.

                • Re: Press pin in plate
                  Daniel Smith
                  Very true, but couldn't that be done on one drawing?  We will use one drawing # for multi-sheet sets..... Technically (and probably being a PITA) :-)
                    • Re: Press pin in plate
                      David Anderson

                      sure, you can do most anything but there are standards (ASME) for drawings to help to ensure we all get what we need in the end.

                       

                      lenny mentions he will make the hole the proper size for a press fit if he knows the materials. i do not doubt for a minute that he can make a hole a press fit however, there are many interpretations of a "press" fit. if a machinist does not know  the design intent you may end up with a failure such has the pin falling out at high temp, or high stress/part distortion at low temp.

                       

                      for example, consider that you have a hardened steel dowel pin and you want a press fit into aluminum. also imagine that the service temp of this assembly is -30C to + 80C. how will a machinist know the proper size hole to guarantee a press fit at high temp, but miniize distortion at low temp without actually specifying the hole size. stating "press fit" on the drawing does not lend the machinist the nature of the environments this part/assembly will endure.

                       

                      to get around the above w/a single drawing, you could specify the hole diameter and tol and ensure the dowel pin is of the proper material and tol. BUT how does one inspect a hole that has a pin pressed into it. maybe the hole was made incorrectly and the part still fails.

                       

                      perhaps this is an extreme example, but i come across it all the time and i cannot expect the manufacturer to know these types of details.as the engineer it is my job to spec the hole. as the machinist it is my job to make the hole to spec.

                       

                      after many years of design and machining and assembly i have found this to be the most sure way that the parts will assemble and perform as engineered.

                       

                      my 4 cents (gotta account for inflation)

                       

                      peace out.

                        • Re: Press pin in plate
                          Jonathan Lawrence

                          I would have to agree with David here.  All assumptions above are that the machinist will be the one doing the assembly work.

                           

                          As the design engineer you would be the one responsible for the fit and finish of the hole.  The engineer is the only one with the knowledge of the operating environment and stress conditions of the joint, therefore should specify the hole tolerance.  For example a 0.250 H7 hole is all the machinist needs to know.  This can be checked prior to assembly, a separate process therefore a separate drawing is required.

                           

                          Are we up to 6 cents now?

                    • Re: Press pin in plate
                      Lenny Bucholz
                      as a machinist, fully detailed drawing of what you want made......use dowel pin symbols and the dia callout, depending upon the material of your part we will make the hole to the tolerance needed.
                        • Re: Press pin in plate
                          Aric Tibbitts

                          Please clarify,

                          I have not seen a dowel pin symbol.

                           

                          I tend to agree with david.  Although as I'm engineer I tend to let the machinist pick the right tool for the job. So I list the materials for each and say press in pin with a .0005 nominal interference.  Now that note I agree will depend on the machinist intrepetation of what material is being pressed into what.

                          Such as Plastic pins pressed in aluminum, steel pins pressed in aluminum and aluminum pins pressed in aluminum.

                           

                          As new solidworks user. I find the assembly method a bit longer and the BOM lists the plate and the pin.  This leads to another drawing which the machinist has to use and it seems that It might lead to paperwork. Instead of having one drawing.