DESIGN OF INTERNAL GENEVA MECHANISM USING SOLIDWORKS

AIM

1) Create 3D models for driver and driven wheels of Internal Geneva Mechanism.

2) Creating Assembly of Internal Geneva Mechanism.

3) Motion Study of the whole Internal Geneva mechanism assembly by rotating the driver wheel at given condition

4) Plot a graph of Contact force (between driving and the driven wheel) as a function of time according to given condition.

5) Plot a graph of angular Displacement of the driven wheel according to given condition.

GIVEN

1. Use 60 Frames per second for 10 rpm and then 120 Frames per second for 20 Rpm

2. Once you have completed the previous study, change the rpm to 20

3. Make a plot of the driver wheel's angular velocity and discuss the results

INTRODUCTION

Geneva mechanism, also called Geneva Stop, one of the most commonly used devices for producing intermittent rotary motion, characterized by alternate periods of motion and rest with no reversal in direction. It is also used for indexing (i.e., rotating a shaft through a prescribed angle).

The Geneva drive or Maltese cross is a gear mechanism that translates a continuous rotation movement into intermittent rotary motion.

The rotating drive wheel is usually equipped with a pin that reaches into a slot located in the other wheel (driven wheel) that advances it by one step at a time. The drive wheel also has an elevated circular blocking disc that "locks" the rotating driven wheel in position between steps.

WORKING

In the most common arrangement, the driven wheel has four slots and thus advances by one step of 90 degrees for each rotation of the drive wheel. If the driven wheel has n slots, it advances by 360°/n per full rotation of the drive wheel.

APPLICATION

• It is applicable in the production industries and in automobile industries for mass production.
• Modern film projectors may also use an electronically controlled indexing mechanism or stepper motor, which allows for fast-forwarding the film.
• Geneva wheels having the form of the driven wheel were also used in mechanical watches, but not in a drive, rather to limit the tension of the spring, such that it would operate only in the range where its elastic force is nearly linear.
• Indexing tables in assembly lines, tool changers for CNC machines, and so on.

PROCEDURE

Create the Geneva driving wheel first according to the dimension given below

Go to file menu and select new after that one dialog box will appear and choose part option for drawing.

1. Create a circle of given dimension of 420 mm of diameter and make a smile circle of 40mm diameter.
2. Now extrude the base circle of 20mm of thickness and after that extrude the small circle.
3. Put the color if you want.

Now the driving wheel looks like as shown in fig

Create the Geneva driven wheel first according to the dimension given below

1. Create a circle of given dimension of 1120 mm of diameter and make a rectangular shape of length 525mm and width of 40mm as shown in figure.
2. Make a circle of radius 120 mm at the center and give fillet of 50 mm radius as shown in fig.
3. Now extrude the design
4. put the color if you want.

Now to make the assembly first Go to file menu and select new after that one dialog box will appear and choose assembly option for doing assembly.

Go to insert option and insert the part to be assemble

Choose mate option in order to complete the assembly, for this design the mating of the assembly is given in the fig. below

After that go for motion study which is present at the bottom for understanding motion analysis and simulate the design after giving the right position of the component.

RESULTS

CONDITION1:

1. Speed pf the motor is 10rpm of constant speed.
2. Frames per Second is 60 as given.
3. Precise contact is not considered.

1. Contact force between driving and the driven wheel without precision with respect to time

2. Angular displacement of driven wheel without precision with respect to time

3. Angular velocity of driver wheel without precision with respect to time

CONDITION 2:

1. Speed pf the motor is 10rpm of constant speed.
2. Frames per Second is 60 as given.
3. Precise contact is considered.

Fig. for representing use of precision

1. Contact force between driving and the driven wheel with precision with respect to time

2. Angular displacement of driven wheel with precision with respect to time

3. Angular velocity of driver wheel with precision with respect to time

CONDITION 3:

1. Speed of the motor is 20rpm of constant speed.
2. Frames per Second is 120 as given.
3. Precise contact is not considered.

1. Contact force between driving and the driven wheel without precision with respect to time

2. Angular displacement of driven wheel without precision with respect to time

3. Angular velocity of driver wheel without precision with respect to time

CONDITION 4:

1. Speed of the motor is 20rpm of constant speed.
2. Frames per Second is 120 as given.
3. Precise contact is considered.

1. Contact force between driving and the driven wheel with precision with respect to time

2. Angular displacement of driven wheel with precision with respect to time

3. Angular velocity of driver wheel with precision with respect to time

5. Results

• The angular velocity plots show a linear trend for the driving wheel,
• The angular displacement plot for driven wheel describes curves during motion.
• The peaks of contact forces increase linearly with RPM as expected.
• Precision enabled study shows higher contact forces as compared to without precision.

Google drive link

1. https://drive.google.com/file/d/18bt4apHL074cDFgpc09nRqCwsO_tT36m/view?usp=sharing,
2. https://drive.google.com/file/d/1C4spbh4ahC05ra_kBMSs-zIiGQvDEWwr/view?usp=sharing
3. https://drive.google.com/file/d/1qfIARVr97lejlqw0IoRI9qWnLA9Mj3z1/view?usp=sharing

Youtube link