Motion Analysis of Internal Geneva Mechanism using SolidWorks

AIM

To analyse the multi body dynamics for internal geneva mechanism using SolidWorks.

OBJECTIVE

• To create 3D models for driver and driven wheels.
• To perform motion analysis by rotating the driver wheel at 10 rpm.
• To obtain a plot for contact force between driving and driven wheel.
• To obtain a plot for Angular displacement of the driven wheel.
• To compare the contact forces with and without “Precise contact”.
• To obtain a plot for Angular velocity of the driving wheel.
• To create motion study for two conditions-

1. 60 frames per second and 10 rpm motor speed.
2. 120 frames per second and 20 rpm motor speed.

• To export the results to a spreadsheet.

Introduction

The Geneva drive is a gear mechanism that translates a continuous rotation into an intermittent rotary motion. The rotating drive wheel has a pin that reaches into a slot of the driven wheel advancing it by one step. The drive wheel also has a raised circular blocking disc that locks the driven wheel in position between steps.

External Geneva mechanism-

In this type of mechanism, the Geneva cross is connected with cam drive externally which is the most popular and can withstand higher mechanical stresses.

Internal Geneva mechanism-

In this type of mechanism, the Geneva cross and cam drive are connected internally in the closed box. The driver and driven wheel rotate in same direction.

Application and Uses-

• It is applicable in the production industries and in automobile industries for mass production.
• Modern film projectors may also use an electronically controlled indexing mechanism, which allows for fast-forwarding the film.
• Geneva wheels having the form of the driven wheel were also used in mechanical watches, but not in a drive, rather to limit the tension of the spring such that it would operate only in the range where its elastic force is nearly linear.
• Indexing tables in assembly lines, tool changers for CNC machines, and so on.

3D Models and Dimensioning

Driven Wheel

Driving Wheel

Study 1 - When we calculate after putting 10 RPM as motor speed and frame rate at 60 fps, the plots obtained are:

Now, with precise contact

Study 2 - When we calculate after putting 20 RPM as motor speed and frame rate at 120 fps, the plots obtained are:

With precise contact-

Excel Charts

Study 1 – Frame rate of 60FPS with 10RPM rotor speed

• Contact force between driving force and driven wheel

• Angular displacement of driven wheel

• Angular velocity of driving wheel

Study 2 – Frame rate of 120FPS with a rotor speed of 20RPM

• Contact force between driving force and driven wheel

• Angular displacement of driven wheel

• Angular velocity of driving wheel