10 Replies Latest reply on May 11, 2018 5:00 PM by Ben Mitchell

    Mating a "bumper"

    Ben Mitchell

      Hi.


      I've got a mating situation I've never run into before and I'm hoping someone can help me figure out how to model this.

       

       

       

      I have an assembly with a carriage that's pushed forward and back on a linear track by an actuator.  The carriage has a sub-carriage that can move vertically, and toward the end of the main carriage's stroke the sub-carriage is forced up a ramp that lies parallel to the track by a wheel attached to the sub-carriage.

       

      I would like to be able to model a pin that rotates under the sub-carriage to keep it elevated during the return stroke of the main carriage.  In essence, I'd be deploying a bumper that would prevent gravity from allowing the wheel to travel back down the ramp, and keep the sub carriage elevated.

       

      I can't figure out how to do this with the mates available to me in SW.  It seems to require a mate that would be aware of the relative positions of the mated parts, which I don't see how to do.  (ie: limit the range of motion of a component when another component is on one side of a line, but not when it's on the other)  Anyone have any suggestions?

       

      Thanks,

      -Ben

        • Re: Mating a "bumper"
          Kevin Chandler

          Hello,

           

          Some screens shots at a minimum would be nice, but now that the lecture is over, you'll probably will have use configs.

           

          Cheers,

           

          Kevin

            • Re: Mating a "bumper"
              Ben Mitchell

              Ok, ok...  :-)

               

              Screen Shot 2018-04-30 at 1.08.34 PM.png

               

              The "Actuator" I mentioned is the arm that the blue pin is mounted to.  It moves in a rotary manner and as it does so, the carriage it's connected to is pushed out. 

               

              Just beyond the pin you can see the somewhat hidden wheel buried in the center of the carriage.  That follows up a ramp you can't see that's mounted to the top of that track.

               

              The rotation of the bar continues over-center, pulling the lower carriage back away from the ramp.  By then, the blue pin is then in the position you see it now, beneath the boss that extends below the top plate of the sub-carriage.  As you can see, in the current model the sub-carriage isn't stopped by the pin so they're occupying the same space in this screen-shot.

               

              The goal is that the block rests on top of the pin, keeping the sub-carriage elevated when the system is rotated to one side of center, and that when it's on the other side of center the pin is out of the way and the sub-carriage can move back down the ramp.

            • Re: Mating a "bumper"
              Jim Paige

              I suggest a combination of configs and path mates.  One config with a path mate that reflects the forward motion and a second config with a separate path mate that reflects the return motion.

                • Re: Mating a "bumper"
                  Ben Mitchell

                  Interesting.  I haven't played with configurations much before.  Is there a way to have the part automatically switch configurations based on some criteria?  Per my image / further explanation above it'd be ideal to have one config active when the activator arm is one one side of center, and the other config active when it's on the other...

                    • Re: Mating a "bumper"
                      Jim Paige

                      To the best of my knowledge changing configs is pretty manual, though I believe you can utilize them in an animation.

                      • Re: Mating a "bumper"
                        Kevin Chandler

                        Ben Mitchell wrote:

                         

                        Interesting. I haven't played with configurations much before. Is there a way to have the part automatically switch configurations based on some criteria? Per my image / further explanation above it'd be ideal to have one config active when the activator arm is one one side of center, and the other config active when it's on the other...

                        Hello,

                         

                        One avenue to try for this is to create a global variable (gv) using the Measure option.

                        This will create a driven dim in the assembly, from the carriage to some fixed reference.

                        You create this gv such that it passes a certain value at the config transition point, let's say 2" (I'm using "2" for typing purposes, you'll move the carriage to the transition point and see what the gv transition value is).

                        (Be mindful that this dim is 3D so you may have to create some ref geometry to reference from if you can't pick the dim as required.)

                         

                        Also in the equations dialog, set one config to be suppressed above 2" and the other config to be suppressed below 2" (one of these should probably take equals 2" scenario).

                        Use the iff function to test which side of the transition point you're on and set the config's suppression status accordingly.

                        I'd use an iff function test for each config.

                         

                        Cheers,

                         

                        Kevin

                          • Re: Mating a "bumper"
                            Ben Mitchell

                            This is really good info.  Thanks a bunch - both of you.  I'll have to mess with it a bit since there's a lot in these suggestions that's going to be new to me, but I see where you're going with the suggestions and I'll start experimenting.

                             

                            Again, thanks!

                             

                            -Ben

                            • Re: Mating a "bumper"
                              Ben Mitchell

                              Ok.

                               

                              So I've experimented a bit with this.  For the most part it "works" but I'm not able to get across the finish line. 

                               

                              The challenge I'm having is that the re-evaluation of the equation doesn't appear to be dynamic.  In my ideal world as I'm manipulating the assembly by dragging the actuator back and forth, the sub-carriage follows the correct path depending on the measurement from the transition point.  In reality it appears that the re-evaluation of that equation - and thus the suppression/unsuppression of the configurations with different path mates - only happens on rebuild which at best occurs when you stop moving things around.

                               

                              Is there a trick to make that equation something that's being continually re-evaluated?

                               

                              -Ben

                                • Re: Mating a "bumper"
                                  Kevin Chandler

                                  Ben Mitchell wrote:

                                   

                                  Ok.

                                   

                                  So I've experimented a bit with this. For the most part it "works" but I'm not able to get across the finish line.

                                   

                                  The challenge I'm having is that the re-evaluation of the equation doesn't appear to be dynamic. In my ideal world as I'm manipulating the assembly by dragging the actuator back and forth, the sub-carriage follows the correct path depending on the measurement from the transition point. In reality it appears that the re-evaluation of that equation - and thus the suppression/unsuppression of the configurations with different path mates - only happens on rebuild which at best occurs when you stop moving things around.

                                   

                                  Is there a trick to make that equation something that's being continually re-evaluated?

                                   

                                  -Ben

                                  Hello,

                                   

                                  Sorry so long in reply.

                                   

                                  I built an assembly that adjust the linear pattern count of the cube depend on the roller slide position.

                                  I was thinking there'd be a way for SW to automatically process this, but only the calcs are automatic.

                                  I have to do a rebuild for the assembly to catch up to the equations and get the cube count correctly shown, even with "auto rebuild" checked in the equations dialog:

                                  I went looking for another setting in System Options but I didn't see anything to override and let the rebuild just happen.

                                  Perhaps others will point the way on this.

                                   

                                  Sorry if I led you astray on this.

                                   

                                  Cheers,

                                   

                                  Kevin

                          • Re: Mating a "bumper"
                            Ben Mitchell

                            No problem, Kevin!  I learned a lot in the process of failing :-)

                             

                            After messing around with that approach for a while I *just* figured out an approach that worked.  In short, I projected a bunch of surfaces describing three dimensional "planes" through which a reference point moved, and then intersected them to create a 3D Sketch I could use in a Path Mate.

                             

                            It was a giant pain getting everything positioned "just so," and the tolerancing of the Path Mate was interesting given that I had to create splines from recorded data points to describe the path, but I made it work.

                             

                            Ever onward!

                             

                            Thanks to everyone for their help :-)

                             

                            -Ben