Geneva Drive
Aim- To study the mechanism of Geneva Drive and analyze its motion characteristics with the help of 3D contacts.
What is Geneva drive- It is the most commonly used devices for producing intermitted rotary motion, characterized by alternate periods of motion and rest with no reversal in direction. The rotor carries a pin that fits in the four radial slots in the Geneva. Between the slots there are four concave surfaces that fit the surface on the driver and serve to keep the follower from rotating when they are fully engaged. The pin is entering one of the slots, and, on further rotation of the rotor, it will move into the slot and rotate the Geneva through 90°. After the pin leaves the slot, the rotor will rotate through 270° while the Geneva dwells—i.e., stands still
Important Criteria- Once the Step file of geneva drive is imported with the help of the Import cad utility, refines its mesh rize after auto mesh and save the file. The boundary and shape of the model geometry is only good as the surrounding mesh defines it. Thus it seems like it is interfering with the geometry.
Procedure-
- The step file of Geneva drive was given and was imported with the help of Import cad utility tool.
- Once the cad model is imported, it is remeshed again to finer mesh size. Automesh geenrates the boundary and shape of the model geometry which is only good as the surrounding mesh defines it. Thus when we run the contact analysis, it is running for the mesh geometry which is completely different from the actual geometry. Thus it seems it is interfering with the geometry but actually it is making contact with the mesh geomtery.
- 2 revolute joints are created at the center of the rotor and the Geneva.
- A revolving motion is created at the center of the rotor about the global z axis with angular velocity of 10 rad/seconds.
- Spring damper is created on Geneva drive to absorb the shock durning the contact between them.
- A 3d contact with defalut setting is created between those 2 body.
- Once the 3d contact is created, an automatic force contact output is generated.
- Two more output are generated to measure the anular displacement and angular velocity.
- The final step is to run the Trasient Analysis for 4 seconds.
Results -
Contact Forces.
Angular displacment of Rotor.
Angular displacment of Geneva.
We can see little jerks on the graph of angular displacment of the geneva which is due to the contact of the pin on rotor with the geneva.
Angular Velocity of the Rotor.
Angular Velocity of the Geneva.
we see little spike at the end of angular velocity graph for geneva. This is due to the spring damper which we applied on geneva to absorb the shock due to the contact between them.
Conclusion- Thus we have studied the mechanism of the Genava drive with the help of the 3d contacts. Also for the contact modeling, automesh doesn't perform very well thus we need to remesh the geometry to finer mesh for proper contact.
Google drive link-
https://drive.google.com/drive/folders/1Ihj1LrEpkgLRiYYnOOosTTtYUYhIPbkR?usp=sharing
Youtube link-
https://youtu.be/hv7oQCLVMVY