MOTION ANALYSIS OF INTERNAL GENEVA MECHANISM
1.AIM :
TO PERFORM MULTIBODY DYNAMICS STUDY FOR INTERNAL GENEVA MECHANISM USING SOLIDWORKS
2.OBJECTIVE :
- To create 3D model of the internal geneva mechanism.
- To perform motion analysis by rotating the driver wheel at 10rpm & 20rpm.
- To export the results to excel and make the plots.
- To plot contact force as a function of time and compare the plot with the precise contact.
- To plot angular Displacement of the driven wheel.
- To make a plot of the driver wheel's angular velocity.
3. INTRODUCTION :
The geneva mechanism is a gear mechanism that translates the continuous rotation movement of the driver into intermittent rotary motion of the driven member.
This mechanism is mostly used for the purpose of automation such as for indexing in assembly lines, CNC machines etc. or in stepper motor.
There are 3 types of geneva mechanism external, internal and spherical which are shown below.
External geneva mechanism Internal geneva mechanism Spherical geneva mechanism
In all type of mechanisms the driving member has a pin that reaches into a slot present in the driven member and advances it by one step at a time.
Here our subject of study is Internal geneva mechanism.
When the pin touches the slot a force is exerted due to contact, we have to analyze the contact force (for precise and non precise contact) , angular displacement and angular velocity for 10 and 20rpm.
4. MODEL AND ASSEMBLY :
Using the following 2D CAD drawings the 3D model of the internal Geneva mechanism was created in Solidworks
3D solidworks model for driven wheel:-
3D solidworks model for driver wheel:-
Solidworks assembly of internal geneva mechanism:-
5. MOTION ANALYSIS :
Motion analysis for the internal geneva mechanism can be done using the SOLIDWORKS Motion feature available as an add-on in the solidworks, innside this feature the option motion analysis can be used to perform the operation.
To rotate the driver component a constant RPM motor is assigned to the component, further a solid body contact is established between the driver and driven component using the contact option also the material steel is chosen for both the parts.
There are 2 studies performed
1) Study 1 (at 10 RPM)
In this the motor speed is set at 10rpm (anticlockwise) and for precise contact 60 Frame per seconnd is used
2) Study 2 (at 20 RPM)
In this the motor speed is set at 20rpm (anticlockwise) and for precise contact 120 Frame per seconnd is used
ANIMATION
The animation video of the internal geneva mechanism made using Solidworks motion is shown below
Link for the video :- https://youtu.be/jrSviRqkcII
6.RESULTS :
The plots for both the study are given below:-
1) Study 1 (at 10 rpm)
Here the plots for contact force (with and without precision contact), angular Displacement of the driven wheel and angular velocity of the driver wheel is made for 10rpm motor speed.
i)Contact force
Contact force (between driving and the driven wheel) as a function of time is plotted.
a) Contact force without precise contact
As it can be seen from the plot the contact force varies whenever the driver wheel pin makes contact with the driven wheel slots, when the contact initiates there is a sudden jerk produced which gives a sudden increase in the contact force.
b) Contact force with precise contact (60 frames per second)
When precise contact is used with 60 frames per second it is clearly visible that the results obtained are more accurate, variation due to jerk is minimized.
ii)Angular Displacement of the driven wheel
The trend of the angular displacement of the driven wheel with time can be seen from the plot above.The Angular displacement remains constant when the driven wheel is not moving and becomes zero whenever the driven wheel completes a rotation.
iii)Angular velocity of the driver wheel
The angular velocity of the driver wheel remains almost constant i.e. 60 deg/sec with very negligible variation.
2) Study 2 (at 20 rpm)
Here the plots for contact force (with and without precision contact), angular Displacement of the driven wheel and angular velocity of the driver wheel is made for 20rpm motor speed.
i)Contact force
Contact force (between driving and the driven wheel) as a function of time is plotted.
a) Contact force without precise contact
As it can be seen from the plot the contact force varies whenever the driver wheel pin makes contact with the driven wheel slots, when the contact initiates there is a sudden jerk produced which gives a sudden increase in the contact force.
b) Contact force with precise contact (120 frames per second)
When precise contact is used with 120 frames per second it is clearly visible that the results obtained are more accurate, variation due to jerk is minimized.
ii)Angular Displacement of the driven wheel
The trend of the angular displacement of the driven wheel with time can be seen from the plot above.The Angular displacement remains constant when the driven wheel is not moving and becomes zero whenever the driven wheel completes a rotation.
iii)Angular velocity of the driver wheel
The angular velocity of the driver wheel remains almost constant i.e. 120 deg/sec with very negligible variation.
LINK TO SOLIDWORKS MODEL & ASSEMBLY AND EXCEL FILES:-
https://drive.google.com/drive/folders/1qxqjYfWms01gUcW6dD9-fYpCbXH5eyH0?usp=sharing
7.CONCLUSION :
The motion analysis of the internal geneva mechanism was completed.
Motion analysis helps to simulate the real time perfomance and give various results and plots to better understand the working.