6 Replies Latest reply on Jul 26, 2017 9:39 AM by Jim Steinmeyer

    If I am going to do dynamic analysis, should I input the weight of all components?

    Peter Cohen

      Hello, I want to plot the motor torque and torque of the joints of a mechanical system. in this case, I need to enter at least the weight and materials of the majority of the system. Am I right? Do I need to enter the weight and material of small components such as washer, nuts, screws, etc.

       

      Some body frames are made of aluminum alloy. Even so, there are several numbers and properties for this metal. I don't know the exact number. What shall I do?

        • Re: If I am going to do dynamic analysis, should I input the weight of all components?
          Ryan Dark

          Hi Peter,

          If you are looking for ballpark figure it is a fairly easy matter of applying a material to all the bodies in your setup.  Even if you have a dozen materials in use it would only take a few minutes of multiplying groups to apply materials (even including nuts, washers, and screws).  Then you have all your densities applied to account for all your weight.

           

          For the material to apply to your frame, there are a lot of varieties of aluminum to pick from.  You should become acquainted with the few that are options for your design.  Once you have the list narrowed down head over to a place like www.matweb.com and collect up all the material properties about the ones you picked.

           

          If you have concerns about missing numbers for specific properties, post those properties here and you will be able to get more specific advice.

            • Re: If I am going to do dynamic analysis, should I input the weight of all components?
              Peter Cohen

              Hi Ryan,

               

              Thanks.

               

              1. My system includes aluminum (e.g. screws, nuts, some washers), aluminum alloy, 3D printed strong plastic, copper, etc. In this case, shall I divide the materials into three groups (aluminum alloy for all aluminum, plastic, and copper)?

               

              2. I got information from the store where I bough the aluminum alloy. The sales said that it is called A5052. He then listed the chemical properties.

               

              3. For the plastic, the majority plastic components are 3D printed using ABSplus. For components bought in stores, I have no idea. What shall I enter in SW in this case?

              ABSplus, Fortus 3D Production Systems FDM Materials | Stratasys

               

              4. In regard to frictions, once I have assigned the material to the components, will SW automatically assigns frictional property to each component? I have no way to measure the friction of each component myself.

                • Re: If I am going to do dynamic analysis, should I input the weight of all components?
                  Gian Flavio Violi

                  3. For the plastic, the majority plastic components are 3D printed using ABSplus. For components bought in stores, I have no idea. What shall I enter in SW in this case?

                  ABSplus, Fortus 3D Production Systems FDM Materials | Stratasys

                  If you are doing a motion analysis, only desinty is required. But if you ever plan to do some FEA calculations beware that 3D printed parts have different mechanical properties in the Z axis, they are a bit weaker.

                   

                  Regards,

                  GF

                  • Re: If I am going to do dynamic analysis, should I input the weight of all components?
                    Ryan Dark

                    Like Gian Flavio Violi mentioned in his post for item 3, the material properties for your printed part will differ a good deal from solid ABS.  The only way to know what your machine is printing is to print test pieces to use on an Instron strength tester.  X and Y strength should be very similar; Z will likely be much weaker as it will fail to layer delamination before the material yields itself.  I haven't seen material data floating around for any of this which is why I would suggest doing your own testing at this point.

                     

                    For friction, there are likely going to be known friction coefficients for copper on aluminum but for copper (or aluminum) on printed ABS there is likely no published data.  Again, it would be recommended to do some testing to determine your friction coefficient for those interfaces.  If that is not feasible you may just want to run a zero friction analysis and a maximum friction analysis (however high you think your highest friction might be) and see how much of a difference the friction truly makes.  Also, in this way you can see an upper bound and lower bound on what your required torques might be without exactly knowing all the frictional values of the model (or knowing only some).

                • Re: If I am going to do dynamic analysis, should I input the weight of all components?
                  Peter Cohen

                  Do you mean in addition to the measured weight, I have to also manually enter the density and friction? I thought density and inertia could me calculated automatically by SW using the weight and dimensions of the component.