MBD Project 1 : Internal Geneva Mechanism

Objective :

1. Create 3D models for driver and driven wheels of the Internal Geneva Mechanism according to 2D CAD drawings. Create assembly of Internal Geneva Mechanism.

2. Perform motion analysis by rotating the driver wheel at 10 rpm and 20 rpm.

3. Obtain the following plots

3.1 Contact force (between driving and the driven wheel) as a function of time.

3.2 Angular Displacement of the driven wheel.

3.3 Compare the contact forces with and without "Precise contact" and Show image for precise contact selection

4. Export the results that you get to Excel and make the plots over there

Use 60 Frames per second for 10 rpm and then 120 Frames per second for 20 Rpm

Theory :

The Geneva Mechanism or Maltese cross is a gear mechanism that translates a continuous rotation movement into intermittent rotary motion. The rotating drive wheel is usually equipped with a pin that reaches into a slot located in the other wheel ( driven wheel ) that advances it by one step at a time. The main wheel also has an elevated circular blocking disc that "locks" the rotating driven wheel in position between steps.

2D CAD Drawings :

3D Model Created In SolidWorks :

1. 3D Internal Geneva Driving Wheel

2. 3D Internal Geneva Driven Wheel

3. 3D Internal Geneva Assembly

Motion study in SolidWorks :

In solidworks software motion feature is use to analyse the motion of the models.

According to there use in solidworks they are diveide into three categories.

1. Animation

2. Basic Motion

3. Motion Analysis

Animation creates simple visuals of model movement by considration of mass and gravity effect. Basic motion use for considration of extra layer of complexity by taking effects of mass, spring and physical collision detection. Motion analysis is use for more advance and wider range by consideration of various forces and there effects i.e. impact effect, damping effect,momentum etc.

Motion Analysis Steps :

1. Active motion analysis Add-on from solidworks add-ons.

2. After that select 'Motion Analysis' from 'Type of study'.

3. Then provide motor to the driver axis by using motor feature.

4. After that provide contacts between driver and driven wheel using Contact feature. In this feature, material for both wheel is also provide.

5. From motion study property frame per second for the study is can be adjusted according to requirement and from this feature we can enable 'precise contact'.

6. After including all the required settings, the calculation of motion analysis is done by clicking on calculation button.

7. 'Result and plots' option is then use to generate various plots and result of the analysis at various points of model.

Plot and Result :

1. Plot of Contact force between driving and the driven wheel as a function of time at 10 R.P.M. (With Precise contact)

2. Plot of Contact force between driving and the driven wheel as a function of time at 10 R.P.M. (Without Precise contact)

3. Angular Displacement of driven wheel at 10 R.P.M.

4. Plot of Contact force between driving and the driven wheel as a function of time at 20 R.P.M. (With Precise contact)

5. Plot of Contact force between driving and the driven wheel as a function of time at 20 R.P.M. (Without Precise contact)

6. Angular Displacement of driven wheel at 20 R.P.M.

7. Driven wheel's Angular velocity at 10 R.P.M.

8. Driven wheel's Angular velocity at 20 R.P.M.

image for precise contact selection

Excel Data Export Screenshot

1. Compare the contact force with and without precise contact at 10 R.P.M (Using Excel Data)

2. Compare the contact force with and without precise contact at 20 R.P.M (Using Excel Data)

Conclusion :

By this analysis we get various motion analysis plot. From those plot can see that how contact force, angular velocity, angular displacement are changes with respect to time. from this modelling and motion analysis of Internal geneva mechanism is learned. from last two plot we can see the effect of precise contact and without precise contact.

Animation Youtube Link :