MBD simulation on Internal Geneva Mechanism
AIM: To model and assemble an Internal Geneva Mechanism and perform motion analysis on it.
INTRODUCTION
An internal/external Geneva mechanism is also called as Geneva drive or Maltese cross is a gear mechanism that translates the continuous rotary motion into intermittent rotary motion. The rotating wheel called as driving wheel has generally a pin attached that reaches into the slot of the driven wheel thus advancing it by one step.
An internal Geneva drive is a variant on the design. The axis of the driving wheel of the internal drive can have a bearing only on one side. The angle by which the drive wheel has to rotate to effect one step rotation on the driven wheel is always smaller than 180° and in an external Geneva drive always greater than 180° Therefore in an internal geneva drive the switch time is greater than the time driven wheel stands still.
PROCEDURE
Step 1) Create a driving wheel with proper dimension as shown below.
Step 2) Create a driven wheel with proper dimension as shown.
Step3) Assemble both the parts to make the desired internal Geneva mechanism.
Step 4) Go to SOLIDWORKS Add-Ins enable motion analysis there and perform motion analysis.
Step 5) Set up a rotary motor as per the desired speed and give a contact to both the part so that motion and energy could be transferred from one part to another.
Step 6) Run the simulation and plot the desired outputs.
OUTPUT & RESULTS
Internal Geneva Mechanism motion-
For case 1) At 10 RPM
The angular displacement of Driven wheel.
The angular displacement of Driving wheel.
Contact force without using precise contact
Showing setup of setting 60 FPS and using precise contact.
Contact force with using precise contact.
Comparing the plots of contact forces with and Without using precise contact
OBSERVATION
1) We can observe from angular displacement of driven wheel plot that the Driven wheel is taking about 24 seconds to have a complete rotation of 360 degrees, at 10 RPM.
2) The Driving wheel is taking about 6 seconds to complete the rotation of 360 degrees.
3) Contact forces obtained are much greater and smoother on using precise contact as compared to without using precise contact.
For case 2) At 20 RPM
The angular displacement of Driven wheel.
The angular displacement of Driving wheel.
Contact force without using precise contact
Showing setup of setting 120 FPS and using precise contact.
Contact force with using precise contact.
Comparing the plots of contact forces with and Without using precise contact
OBSERVATIONS
1) We can observe that Driven wheel is now taking about 12 seconds to complete the 360-degrees movement.
2) The Driving wheel is taking about 3 seconds to complete the 360-degree movement.
3) Contact forces obtained are much greater and smoother on using precise contact as compared to without using precise contact.
CONCLUSION
1) As the RPM increases,we got some obvious results like decrease in time taken to complete the 360-degree complete rotation of both Driven and Driving wheel and increase in the amount of contact force as we increases the speed of the motor.
2) When the value of RPM got doubled (10RPM to 20RPM) the time taken to complete the 360-degree rotation becomes approximately equal to half.
3) As the RPM increases the contact force increases hence for higher RPM situations we need to make the design more stable and stronger for better life and efficiency.