General Mechanical

General Mechanical

Defining Contact between follower and CAM

    • Hira Verma
      Subscriber

      Here I am analyzing motion generated from CAM rotation. There are four bodies viz. CAM, Follower, Lifting Block (highlighted in green), and Lifting Lever. All bodies made Rigid.


      Joints applied among bodies here:



      • CAM is Ground Revolute for the rotation

      • Between CAM and Follower -- Slot

      • Between Follower and Lifting Block -- Revolute

      • Between Lifting Block and Lifting Lever -- Fixed

      • Lifting Lever is Ground Revolute


       



       


      Here I am getting problem with the joint/contact between follower and CAM. As we can see follower is merging with the CAM on one side and losing contact another side while animating. 



      Kindly suggest the joint between CAM and Follower. What joint should be applied here?


      Here I have suppressed all the contact connections made by default (bonded) and only using joints. Also, Is there any difference between No Separation contact and Fixed joint?

    • peteroznewman
      Subscriber

      Delete the Slot Joint.


      Make two Cam-Follower Frictional Contacts. One for the inner Cam face, one for the outer Cam face. Make the follower the Contact side of each pair, not the Target side.

    • Hira Verma
      Subscriber

      I have applied Frictional contact between cam and follower surface and deleted Slot joint. Other joints I kept same.



       


      Still, after analyzed with the above-mentioned conditions, the follower is merging with CAM and shows the following error. Also, the follower is not rotating due to the rotation of CAM. Kindly suggest what can be done to resolve this?


    • peteroznewman
      Subscriber

      Under the Connections folder, Insert a Contact Tool, Evaluate Initial Contact Status. Are both Frictional Contacts Closed or Near Open? Please show the table. If the contact shows as Far Open, then corrective action is required such as adding a Pinball Radius.

    • Hira Verma
      Subscriber

      Here it is showing Closed, Inactive and Near Open. Here contact required is perfect, to get revolution of the follower with the rotation of the CAM. I have also made Interface treatment as Adjust to Touch in geometric modification.


       


    • peteroznewman
      Subscriber

      Under the Analysis Settings, what are the Initial and Minimum and Maximum Time Substeps?


      Try reducing all the substeps by a factor of 100 and see if that helps. Yes, it will take 100 times longer to solve, but we are troubleshooting here.

    • Hira Verma
      Subscriber

      I am using this analysis setting for full rotation of CAM. Kindly suggest what should be done. If I increase number of steps it gives more errors and also CAM is not rotating fully.


       

    • Hira Verma
      Subscriber

      Dear Mr. Peter,


      I have uploaded the step file and project file. I am not getting desirable motion from this. Kindly suggest what should be done in connections and analysis settings. I did not get it. I really appreciate your suggestions. Thanks

    • peteroznewman
      Subscriber

      What is the goal of this analysis? What data do you want to get out of the simulation?


      Do you have access to a Rigid Dynamics license, is it in your toolbox?  That will give you the velocity and acceleration of the follower for a uniform rotational velocity of the cam.

    • Hira Verma
      Subscriber

      I wish to see the deformation and stress of each of the parts. Due to 360 degree rotation of the CAM, I am not able to see follower rotation its own axis, and this motion is transferred to the lifting block and lifting lever. I don't know why follower merging with CAM and unexpected motion is showing.

    • peteroznewman
      Subscriber

      In a Static Structural model, there are no inertial loads created by the acceleration of mass. To get that information, you need to solve the problem using Transient Structural. In this case, it is not the angle of the cam, but the rotational velocity.


      A missing feature of this mechanism is the springs that might be on the follower linkage and the masses attached to the follower. You don't seem to have any springs or additional mass on the follower. Those will have a significant effect on the stress in the follower parts.


      Also, you set all the parts to be Rigid, so there is no stress calculated in any of the parts.


      ANSYS 19.0 archive attached with a Rigid Dynamics model that rotates the cam one revolution in one second with a 100 lbf load on the follower arm to keep the follower touching one cam face.

    • Hira Verma
      Subscriber

      Thank you for your suggestion about it. First, I'm doing analysis with considering bodies as rigid (to get desired motion) then I'll make them flexible. I have applied the same Analysis Settings in Transient Structural but Ansys not able to solve it. Kindly suggest for it.

    • peteroznewman
      Subscriber

      I recommend you obtain the maximum force from the Rigid Dynamics model and apply that to a Static Structural model.


      It will be much faster than making a Transient Structural model run.

    • Hira Verma
      Subscriber

      Hello Mr. Peter,


      Thanks for making it better. Can you suggest to me about getting maximum force from the Rigid Dynamics model?


      I also have doubt about the remote force for this assembly. How do we come to know that this would be a remote force or simple loading force in the cam assembly? And how does it make difference from Joint Rotational velocity to the Rotational velocity applied directly?
      Kindly clear this doubt with reference to the Ansys(In Transient Structural model).


      Thanks in advance.

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