INTRODUCTION

Geneva mechanism, also known as Geneva Stop, is one of the most widely used methods for the development of irregular rotary motion, distinguished by alternating motion and rest periods with no spatial reversal. This is often used for indexing (i.e., rotation around a specified angle of a shaft).

Application of the Geneva drive used in mechanical watches, the pen shift mechanism in plotters, automated sampling systems, banknote counting machines and several types of indexable equipment used in manufacturing. The pins and slots of the system shape the combustion chambers used to drive the Geneva wheels to transform linear movement into rotating movement capable of driving cars.

The angular displacement of a body is the angle in radians (degrees, revolutions) by which a point rotates around a center or line in a given sense around a defined axis. If an object is in contact with some other entity a contact force occurs. If there are two bodies in contact with one another, there are reciprocal interaction forces that fulfill Newton's Third Law of Motion. The angular velocity refers to how rapidly an object rotates or spins relative to another point, i.e. how rapidly an object's angular location or orientation varies over time.

Constraints:

• Perform motion analysis by rotating the driver wheel at 10rpm.
• Obtain the following plots
  • Contact force (between driving and the driven wheel) as a function of time.
  • Angular Displacement of the driven wheel.
• Compare the contact forces with and without "Precise contact"
  • Show image for precise contact selection
  • Export the results that you get to Excel and make the plots over there.

• Use 60 Frames per second for 10 rpm and then 120 Frames per second for 20 Rpm
• Once you have completed the previous study, change the rpm to 20
• Make a plot of the driver wheel's angular velocity and discuss the results.

PROCEDURE FOR DOING INTERNAL GENEVA MECHANISM MOTION STUDY IN SOLID WORKS

Step 1: Creating the cad model for driving and driven Geneva wheel.

Step 2: Create new assembly select the parts

CONSTRAINTS:

1. Coincide1-driven and Front Plane
2. Coincide2-driven and Top Plane
3. Coincide3-driven and Right Plane
4. Coincide4-driven and driving (face coincide)
5. Coincide5-driving and Sketch (the path of the driving wheel pin sketched initially and then the pin axis is coincide with the one point of that sketch)

NOTE: Suppress the constraint or else there will be over constraint notification at end of the assembly.

6. Distance mate 1 - driving and Top Plane
7. Distance mate 2 - driving and Right Plane

Now the assembly is ready

Step 3: click on assembly at the tools and select rotate component (In move component session). On selecting the part and rotate the motion of driven wheel can be seen so that we can make sure the constraints are given perfectly based on motion what we needed.

Step 4: Click the SOLIDWORKS add-in and enable motion study.

Step 5: Now create the new motion study and change animation to motion analysis.

Step 6: Select the motor option to give the torque to the driving wheel (we can give the rpm, time)

Step 7: Select the contact option to give the materials (we can assign material here)

Step 8: Now we can use calculate options to calculate the results.

Step 9: Now we can plot the graph using plot option. To save in excel (Right click the plot and click the save as CSV option).

Step 10: For getting precise click on settings and we can enable precise contact and no of frames.

Step 11: Now we can plot the graph using plot option.

Step 12: We can save the results.

GENEVA MECHANISM MOTION STUDY IN SOLIDWORKS

Figure 1. CAD model of driven and driving wheel for geneva mechanism.

Figure 2. Assembly constraints.

OUTPUT FIGURES:

(a)

(b)

(c)

Figure 3. (a)Contact force plot, (b)Displacement plot and (c)Angular velocity

RESULT AND DISCUSSION:

(a)

(b)

Figure 4. Contact force plot (a)for simple contact and (b)for precise contact.

(a)

(b)

Figure 5. Angual displacement plot (a)for simple contact and (b)for precise contact.

On comparing the plots from figure 4 we can infer that the contact force is equally distributed at a regular interval in precise contact where it is not found in the simple contact output. From figure 5, the plots are similar but there is minute variation in degree.

(a)

(b)

Figure 6. Angual Velocity plot (a)60 Frames per second for 10 rpm and (b)120 Frames per second for 20 rpm.

On comparing the plots from figure 6 we can infer that the angular velocity of the driving wheel has more frequent peak values at 10rpm.

CONCLUSION:

The analysis of motion gives an angular output ie.,. From the resulting rotational displacement and rotational speed, it is possible to determine whether this geneva assembly achieves the desired values for certain applications. We can find the load exerted on the pin from the contact force, to rotate the driven wheel.