Internal Geneva Mechanism
AIM : To study the dynamics of internal Geneva Mechanism.
INTRODUCTION AND THEORY :A Geneva Mechanism is a mechanism that converts the uniform rotary motion into an intermittent rotary motion. The Geneva mechanism consist of two main component, the first one is the driving wheel/component and the second one is the driven wheel/component .
WORKING PRINCIPLE : The working of geneva mechanism can be understood as ,when the driving wheel is given some angular displacement by the help of some external motor, the extruded material on the top of the driving wheel (the knob) which is fitted in the slot of the driven wheel tends to push the driven wheel. Since the driven wheel is pivoted about its centre thus it undergoes a circular motion. Now when the knob comes out of the slot of the driven wheel the driven wheel stops for a while, as soon as the knob enters the second slot of the driven wheel the whole mechanism is repeated once again. In this way we get the continuous intermittent motion from the continuous rotary motion of the wheel.
MAKING OF INTERNAL GENEVA MECHANISM
PARTS
First of all make the CAD parts of the geneva mechanism i.e. the driving wheel and the driven wheel of the mechanisms , the drawings of both the parts is provided in the challenges.
To draw the parts go to SolidWorks part
Choose the units systems and then choose a plane to sketch , than sketch the parts using the sketch tools using the drawing details provided . When the sketch get completed exit the sketch and use extrude boss features to make sketch a 3D part .
When both the parts are made save them by giving any name you wanted ( I saved as driving wheel and driven wheel).
ASSEMBLY
Now open the new file in SolidWorks choose assembly.
Here open the both the components of the geneva mechanism and make both of them float . Firstly mate the driving wheel of the component so that it becomes fixed in space and do not move in space. It will only rotate about it's axis only. Now fix the second component i.e. driven wheel w.r.t. the driving wheel such that the knob makes a tangent contact with the surface of the slot of driven wheel. Now save the assembly.
MOTION STUDY OF INTERNAL GENEVA MECHANISM
Go to command ribbon and choose SolidWorks Add Ins and select SolidWorks Motion.You will see that the motion analysis control manager will be opened, if not then go to right side corner and click on the arrow facing upward. Now go to left side hit the dropdown and choose Motion study.
Go to Motion Study Properties, drop down to Motion Analysis, and fill the various parameters such as frames per second ,animate during simulation ,use precise contact, accuracy high as given the details of the challenge.
Now go to contact, choose solid bodies and select both the components and apply contact between them.
Provide a rotary motor to the driving wheel , located at its axis. It can rotate in CW as well as ACW direction, choose as per the details given in the challenge.
Go to result and plot and choose, forces>> contact forces>> magnitude, and then select both the component and then drop down to plot results and choose time .Choose calculate and then run the motion study. Similarly by changing the parameters do other motion study.
OBSERVATION AND RESULTS
Here two plots are shown
The plot 1 shows the results of magnitude of contact forces between the two component, when the rpm is 10 and fps is 60.
The plot 2 shows the results of magnitude of contact forces between the two component, when the rpm is 20 and fps is 120