Internal Geneva Mechanism
MOTION ANALYSIS OF INTERNAL GENEVA MECHANISM
AIM: To perform the motion analysis of Internal Geneva Mechanism using solidworks with the given dimensions.
BASIC: solidworks offers three types of motion study which are Animation, Basic motion and Motion analysis. Motion study is basically a graphical representation of an assembled parts or models. By this we can simulate, animate & do the motion analysis of a model.
- In animation model there is the motor tool available and they are animated by adding properties and when we add the motor to the assembled model we can do the animation on it.
- In basic motion there are different kinds of physical quantities like motor , springs , contact and gravity.
- Motion analysis is used for accurate simulation of model and analysing various effect on our model by getting the output in the form of graph.
OBJECTIVE:
- To Create 3D models for driver and driven wheels.
- Perform motion analysis by rotating the driver wheel at 10rpm.
- Obtain the following plots:
- Contact force between driving and the driven wheel.
- Angular Displacement of the driven wheel.
- Compare the contact forces with and without "Precise contact."
- Use 60 fps for 10 rpm and 120 fps for 20 rpm and show the result obtained.
INTRODUCTION ABOUT GENEVA MECHANISM
The Geneva drive or Maltese cross is a gear mechanism that translates a continuous rotation movement into intermittent rotary motion. the difference between Geneva Drive mechanisms and other gears is that Geneva Drive mechanisms have unusual teeth.
COMPARING INTERNAL GENEVA MECHANISM AND EXTERNAL GENEVA MECHANISM:-
In an internal Geneva drive the axis of the drive wheel of the internal drive is supported on only one side. The angle by which the drive wheel has to rotate to effect one step rotation of the driven wheel is always smaller than 180° in an external Geneva drive and is always greater than 180° in an internal one. The external form is the more common, as it can be built smaller and can withstand higher mechanical stresses.
Fig 1 geneva mechanism
Motion of the Model: -
Fig2 motion of the model
PROCEDURE:
To do the motion analysis of internal geneva mechanism first we need to design a 3D model of this mechanism. Hence we have to built a driven wheel and driving wheel based on the dimension given.
Internal Geneva Mechanism Driven Wheel
Fig3 internal genva mechanism driven wheel 2D model
Fig 4 internal Geneva mechanism driven wheel 3D model
Internal Geneva Mechanism Driving Wheel
fig 5 internal Geneva mechanism driving wheel 2D model
Fig6 internal Geneva mechanism driving wheel 3D model
Assembling procedure:
To do the motion analysis we are going to select assembly in solidworks and then going to bring out the part driving wheel and driven wheel. The first part that is imported it is always fixed so for making it unfixed we have to make it float and the second part that is imported it will be always unfixed.
We are going to select temporary axis which will enable us to see many axis. We are going to select front plane of driving wheel and assembly and make it coincident. Now by selecting centre axis of the driving wheel and top plane of the assembly going to make it coincident. By doing this are driving wheel is fully constrained.
Driver axis selected and right plane of the assembly is selected and make it coincident. By using trial and error method we have to calculate the distance between the two parts.
After this step we must make sure that the solidworks motion is enabled to do the motion analysis of assembled model, next step will be selecting the type of motor and edit the constant speed to 10 rpm; now select the contact option and select both the parts and make sure it is perfectly positioned. Then calculate it, and check whether it perfectly mating.
Fig 7 assembly of internal Geneva mechanism
Graphs:-
Analysis at 10 rpm:
Contact force without precise contact:
Contact force with precise contact:
Angular displacement of driven wheel
Analysis at 20 rpm:
Contact force without precise contact
Contact force with precise contact
Angular displacement of driven wheel
Angular velocity of driven wheel
Comparing the contact forces with and without “Precise Contact”
As we have seen in contact force without precise contact , the contact force is same in magnitude in constant interval of time. While precise contact of contact force, the contact force is precisely changing in every interval of time.
CONCLUSION
When the driving wheel starts to rotate the driven wheel also starts to rotate as there is contact between them. As we increase the RPM of the driver wheel the driven wheel RPM is also increased. This result is also displayed in the graph.
RESULT:
https://drive.google.com/drive/folders/1zQGn8fmb9tWPbs2D00JjJ_2TdP0a-5cY?usp=sharing
note: link of the solidworks file and motion animation.
REFERENCE:
https://skill-lync.com/projects/internal-geneva-mechanism-61