Internal Geneva Mechanism

Objective : Use the given 2D CAD drawings to create the 3D model of the Internal Geneva Mechanism and perform motion analysis by rotating the driver wheel at (i) 10 RPM and (ii) 20 RPM. Calculate the results of the study with and without precise contact.

1. Introduction

1.1 Geneva Mechanism

Geneva mechanism, also called Geneva Stop, one of the most commonly used devices for producing intermittent rotary motion, characterized by alternate periods of motion and rest with no reversal in direction. It is also used for indexing (i.e., rotating a shaft through a prescribed angle).

1.2 Types of Geneva Mechanism

1) External Geneva Drive
2) Internal Geneva Drive
3) Spherical Geneva Drive

In this project, we are focusing on Internal Geneva Mechanism

2. Sketches

2.1 Driven Wheel

2.2 Driver Wheel

3. Procedure

1. Create 3D models of respective parts using 2D CAD Drawing given
2. Assemble the parts and use mates to constraint the bodies accordingly.
3. Create a motion study and select motion analysis
4. Define Contact and set motor on the axis of driver wheel.
5. Calculate the motion study and get graphs with/without the precise contact.
6. Export the graphs to spreadsheet.

Precise contact with 10 RPM Motor

Precise contact with 20 RPM Motor

4. Results

4.1 10 RPM Motor

4.1.1 Without Precision Contact

a. Contact Force vs Time

b. Angular Velocity vs Time

4.1.2 With Precision Contact

a. Contact Force vs Time

b. Angular Velocity vs Time

4.2 20 RPM Motor

4.2.1 Without Precision Contact

a. Contact Force vs Time

b. Angular Velocity vs Time

4.2.2 With Precise Contact

a. Contact Force vs Time

b. Angular Velocity vs Time

Observations:

• Precision contact offers more sensitive data and therefore the contact forces are higher when it is enabled.
• Angular velocity increases with increase in RPM
• Due to Jerk when the driver enters the driven wheel, the contact forces are initially high

Google Drive Link containing all the parts and assembly : https://drive.google.com/drive/folders/1HLB5EYkHmkC0-WTyyF9lBggpkN2edffd?usp=sharing

Animation Link: https://youtu.be/jCa9xXgaVOM