Motion analysis of Internal geneva mechanism using Solidworks MBD
Aim:- To model & do motion analysis of Internal Geneva Mechanism and to find the contact forces.
Theory:-
The Geneva Mechanism is a gear mechanism that translates a continuous rotation movement into intermittent rotary motion. The rotating driver wheel is usually equipped with a pin that reaches into a slot located in the driven wheel that advances it by one step at a time.
External geneva mechanism Internal geneva mechanism
Draft and 3D models
Driven wheel
Features used:- Boss extrude, Extrude cut.
Driver wheel
Features used:- Boss extrude
Assembled model
Mates used:- Surface mate (coincident mate), Distance mate.
Both the parts just have 1 DOF (i.e. rotational motion about there axis)
Motion Analysis:-
- First the rotary motor is set at the axis of driver and rpm is set.
- Then the solid body contacts are given and material is selected.
- Then the motion analysis is calculated and required plots are obtained.
Contact surfaces selected for contact force analysis:-
Study 1:- The driver wheel is rotated at 10rpm and results captured at 60 fps
- Angular displacement of driven wheel
We can see after every 4sec rotation of driven wheel followed by 2sec of dwell period during which pin leaves one slot and enters the next slot.
- Contact force without precise contact.
We can see a small force at end of 2seconds its when the pin leaves the one slot and force of around 10KN at 4th second its caused as the pin enters the next slot. This pattern repeats after every 6seconds.
- Contact force with precise contact.
The precise contact is used by turning on the pecise contact option as shown in below figure.
The force pattern is same as that of observed without precise contact but the value of force is more i.e. 15KN as its calculated more precisely.
Study 2:- The driver wheel is rotated at 20rpm and results captured at 120 fps
- Angular displacement of driven wheel.
We can see after every 4sec rotation of driven wheel followed by 2sec of dwell period during which pin leaves one slot and enters the next slot at 20rpm.
- Contact force without precise contact.
We can see a small force at end of 2seconds its when the pin leaves the one slot and after 1sec from this a force of around 6.5KN its caused as the pin enters the next slot. This pattern repeats after every 3seconds.
- Contact force with precise contact.
The precise contact is used by turning on the pecise contact option as shown in below figure.
The force pattern is same as that of observed without precise contact but the value of force is more i.e. 9KN as its calculated more precisely.
- Angular velocity of driver wheel.
- We can see the angular velocity of driven wheel is constant i.e. 120rpm
Project related links:-