13 Replies Latest reply on May 10, 2014 12:11 PM by Jerry Steiger

    Mechanical Linkages in Assemblies

    Carl Dahm

      I am looking for timps to make my mechanical linkages perform better in SW. I am currently running SW 2014 SP 3 and am having a lot of crashing going on when I attempt to articulate a design. It seems like my computer is really having a hard time (bogging-down) when I move a single piece. This is more than frustrating because I know my computer has more than enough power to complete these actions.

       

      Also, pretty much everytime I move a sub-assembly, parts from another sub-assm seem to move in correspondence to the movement of the first sub-assm and they are not mated to do so.

       

      In another instance I have a grate lid sub-assm that will blow apart when I move an unrelated sub-assm, and CTRL+Q won't rebuild the lid. In fact, the lid stay blown apart until I actually move it and then it will reassemble correctly.

       

      I am looking for anything that will help to eliminate these rebuild, calculation and mate errors that I seem to be experiencing. Again the assembly I am working with is rather large but I feel my computer should be able to keep up.

       

      My system is:     Intel i7 CPU @ 3.4 GHz

                               32 GB RAM

                               NVIDIA QUADRO K4000 VIDEO CARD

                               1 TB HARD DRIVE

                                RUNNING WIN 7

        • Re: Mechanical Linkages in Assemblies
          Patrick O'Hern

          While I typically dislike using them, have you tried inserting a Layout Sketch to control your motion?

           

          http://help.solidworks.com/2014/english/SolidWorks/sldworks/c_Assembly_Layout_Sketch.htm

            • Re: Mechanical Linkages in Assemblies
              Carl Dahm

              Patrick,

               

              I am not too fond of using layout sketches either. I already have this assembly complete (aside from setting up approval drawings with alternate positions and maybe a design study showing how the assembly should operate) and do not think I can utilize a layout sketch at this point. I understand a layout sketch can be useful but mates that solved correctly, or rather the way I want them to, would be more beneficial.

            • Re: Mechanical Linkages in Assemblies
              Jerry Steiger

              Carl,

               

              You might want to check out this thread: https://forum.solidworks.com/thread/80540?tstart=0 It could have some bearing on your problems.

               

              Jerry S.

                • Re: Mechanical Linkages in Assemblies
                  Carl Dahm

                  Jerry,

                   

                  I appreciate the help, but I am not having a problem with mates needing to be reassigned. The main problem I am having involves assemblies that are constrained in way where degrees of freedom are limited to show functionality (so I can make sure everything is operating as it should) and demonstrative purposes.

                   

                  The second problem I am having is when I have an assembly with a lot of parts (although very simply mated (coincident, distance and parallel and concentric)) in the scenario described above; the automatic rebuild functionality is not working. I will try CTRL+Q and that also will not work. When this happens I cannot move the blown out parts individually but the 'explode' is consistent enough to even show up in drawings. The only way I can make the subassy go back to the way it should be is to attempt to move the subassy in the assy and have it recalculate itself.

                   

                  That seems like it would be hard to follow after re-reading it.. but basically I encounter the problem when a subassy is articulated in an assy; and the subassy will only rebuild itself (correctly) when it is moved for a second time.

                   

                  This is frustrating when you are trying to create approval drawings showing alternate position view set up as configurations and supressing/unsupressing mates 

                    • Re: Mechanical Linkages in Assemblies
                      Jerry Steiger

                      Carl,

                       

                      Is this happening when you have subassemblies set to Flexible? That makes it harder for SolidWorks to handle the mates, since all of the mates in the subassembly are (temporarily) moved to the top level. I'm grasping at straws here, as I don't really understand what is happening. Could you share some screen dumps?

                       

                      Jerry S.

                        • Re: Mechanical Linkages in Assemblies
                          Carl Dahm

                          Jerry,

                           

                          Here are a couple of screenshots showing the 'not able to rebuild' issue.

                           

                          I am using flexible subassemblies to control the position of rigid subassemblies (cylinders controlling pitch of grate and hopper).

                           

                          I am having a hard time getting the mates to display what my issue is. One reoccuring problem I have with assemblies that have a lot of mates is once in a while they will show yellow because the assembly claims to be over-defined. After rebuilding (or picking one mate suppressing and then unsupressing said mate), the mates solve themselves and don't throw up any errors until after I save or I articulate the model.Capture 1.PNGCapture 2 THE WAY IT SHOULD LOOK.PNG

                            • Re: Mechanical Linkages in Assemblies
                              Carl Dahm

                              And another screenshot of the rebuild issue showing up in drawings EXAMPLE OF REBUILD ISSUES SHOWING UP ON DRAWINGS.PNG

                                • Re: Mechanical Linkages in Assemblies
                                  Carl Dahm

                                  Upon rebuilding several times in a row, I noticed that the symbol showing DOF ( - ) in the feature tree would occasionally toggle. Meaning when I rebuilt, the DOF symbol wasn't there and without doing anything (not even panning) other than pressing CTRL+Q, the symbol would appear; after another CTRL+Q, the symbol would disappear...

                                    • Re: Mechanical Linkages in Assemblies
                                      Jerry Steiger

                                      Carl,

                                       

                                      I haven't seen this behavior in mates, but I have seen it in parts themselves. I've had several parts with features that would toggle between broken and OK each time I did a control-q. I even had one that had a cycle of three. (I don't remember now whether it was good, good, bad or good, bad, bad.) The common feature was that the features seemed to be on the hairy edge of working/not working. On one Fill Surface, I could change the location of a spline point on a Constraint Curve by 0.01 mm and go from good to bad. I was finally able to tweak all of the spline point locations so that the part would consistently rebuild with a good enough looking shape to make me happy. Unfortunately, I have no idea what would cause mates to be so touchy, unless it would be geometry that switched between parallel or perpendicular or somesuch and not quite parallel or perpendicular. Another likely suspect is having mates that are overdefined, but usually consistent; such as the location of two parts being defined by 3 coincident planes (meaning 9 degrees of freedom tied down) versus a plane (3 DOF), line (2 DOF) and a point (1 DOF).

                                       

                                      Jerry S.

                                    • Re: Mechanical Linkages in Assemblies
                                      Patrick O'Hern

                                      Unless you just REALLY need to be able to move your assembly around on a daily basis, I would suggest just creating some Open/Close (or Position1, Position2, etc.) configs of your sub assemblies and set them all back to rigid.  Your rebuild times will probably be much faster, and you will have a LOT less problems when working on things. 

                                       

                                      If you need to be able to show your boss/customer how it moves (or just test it out), then you can temporarily set things back to flexible.