Motion analysis of Internal Geneva Mechanism using Solidworks

MOTION ANALYSIS OF INTERNAL GENEVA MECHANISM USING SOLIDWORKS

AIM: To create a 3D model of the internal Geneva wheel mechanism and performing a detailed motion analysis using Solidworks

OBJECTIVES:

• Prepare 3-D model driver and driven part of internal Geneva mechanism.

• Create the assembly of a Geneva mechanism.

• Simulation of the Geneva mechanism at 10 and 20 RPM

• Compare the graph for the precise contact and non-precise contact force.

• Compare the graph of the angular velocity of the driver and driven at 10 and 20 RPM

• Plot the graph of angular displacement.

INTRODUCTION

GENEVA MECHANISM

The Geneva mechanism is a gear-driven mechanism that converts a continuous rotation to intermittent rotary motion. The rotating drive wheel is usually equipped with a pin that reaches into a slot located in the other wheel that advances it by one step at a time. Some types have a main wheel with an elevated circular blocking disc that "locks" the rotating driven wheel in position between passes. Early motion-picture projectors used Geneva mechanisms to give the film a quick advance while the shutter was closed, followed by a dwell period with the shutter open.

THEORY

• Angular displacement: Angular displacement of a body is the angle in radians, degrees or revolutions through which a point revolves around a centre or line has been rotated in a specified sense about a specified axis.

• Angular velocity: Angular velocity refers to how fast an object rotates or revolves relative to another point, i.e. how fast the angular position or orientation of an object changes with time.

• Contact force: A contact force is any force that requires contact to occur. Contact forces are ubiquitous and are responsible for most visible interactions between macroscopic collections of matter.

3D MODELS

1)Geneva driver wheel

2) Geneva driven wheel

3)Assembled model of the internal geneva mechanism

ANIMATION OF THE WORKING OF THE INTERNAL GENEVA MECHANISM(10 RPM):-

ANIMATION OF THE WORKING OF THE INTERNAL GENEVA MECHANISM(20 RPM):-

MOTION ANALYSIS RESULTS

Motion analysis is performed at:

• 10 rpm with 60 frames per sec without precise contact.
• 10 rpm with 60 frames per sec with precise contact.
• 20 rpm with 120 frames per sec without precise contact.
• 20 rpm with 120 frames per sec with precise contact.

The following results were obtained:

1. 10 RPM

a) Angular Displacement of Driven Wheel

b)Angular Velocity of the Driver

c)Contact Forces(Without precise contact)

d) Contact Forces(with precise contact)

2. 20 RPM

a) Angular Displacement of Driven Wheel

b)Angular Velocity of the Driver

c)Contact Forces(Without precise contact)

d) Contact Forces(with precise contact)

Precision contact switched on

RESULTS & OBSERVATIONS

The Geneva Mechanism model was created and its motion was analysed. Further, three plots were plotted, being the contact forces w.r.t. time, angular displacement of the driven wheel & the angular velocity of the driver wheel. The motion analysis is conducted to determine the critical area or part (due to the stresses developed) and to validate a design. This analysis helps to get much more efficient & reliable design. Additionally, this project led to a great learning including the know-how & capabilities of motion analysis.

By increasing the RPM, the contact forces also increases. By using precise contact, SolidWorks calculate contact approximately using the geometry of many-sided polygons. Through precise contact, the computed contact is analytically more correct. Increasing the frames per second makes the simulation very smooth & reduces the incremental steps. For angular displacement & velocity plot, there are no such difference to mention in the case of default & precise contact.

CONCLUSION

The motion analysis of internal Geneva mechanism was performed and graphs are plotted accordingly.