Internal Geneva Mechanism
Motion analysis of internal Geneva mechanism using solidworks
Aim
1.To create 3D models of driving and driven wheels
2.Setup motion analysis for 10 rpm and 20 rpm with 60 frames/sec and 120 frames/sec respectively
3.Generate plots for contact forces between driving and driven wheels
4.Generate plots for angular displacement of driven wheel and angular velocity of driver wheel respectively
Introduction
The Geneva drive or Maltese cross is a gear mechanism that translates a continuous rotation movement into intermittent rotary motion. There are two types of Geneva mechanism.
- External Geneva mechanism
In this type,the Geneva cross is connected with the cam drive externally and when the driver pin mates with the driven wheel’s slot a motion is generated.The driver and the driven wheel rotate in opposite direction.
- Internal Geneva mechanism
In this type, the Geneva cross is connected with the cam drive internally. Unlike the external type, here both the driving and driven wheels rotate in the same direction.
Applications
Filim projectors and cameras
Tool changers in CNC machines
Indexing heads of turret lathes
Pen change mechanism of plotters
Animation of the model
CAD Models
Driver part
Driven part
Assembled 3D Model
Material used
Driver wheel- Steel dry
Driven wheel- Steel dry
Motion analysis results
Analysis at 10 rpm with 60 frames per second
(Contact force between driver and driven wheels without precise contact)
(Contact force between driver and driven wheels with precise contact)
(Angular displacement of driven wheel)
(Angular velocity of driven wheel)
Analysis at 20 rpm with 120 frames per second
(Contact force between driver and driven wheels without precise contact)
(Contact forces between driver and driven wheel with precise contact)
(Angular displacement of driven wheel)
(Angular velocity of driven wheel)
Precise contact selection
Observation and results
- The value of contact forces is higher when they are calculated using precise contact. Also the results are more accurate when precise contact option is chosen.
- Contact forces are higher at the entrance of the slots.
- It is observed that as the speed of the driver wheel increases, the angular displacement of the driven wheel increases.
- The angular velocity of the driven wheel increases with the increase in speed of the driver wheel. A jerk is observed when the driver wheel enters the slot.
- Due to the intermittent motion of the driver wheel, the angular displacement and velocity remains constant for a particular period of time and again start to increase.