Internal Geneva Mechanism

Aim:

To creat a 3D model of internal geneva mechanism parts and assemble it and to make a motion study on it and to obtain the following plot, are as follow

• • 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"

Solution:

Internal Geneva Mechanism:

The Geneva Mechanism 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.

Procedure for 3D part modelling, Assembling the parts and Motion study on it

Driven wheel

1. First designing the driven wheel by creating a circle in the front plane and by using smart dimension tool i made it based on the dimension given in the challenge

[note: all the parts are designed in the front plane and assembled in the front plane and all the dimensions are in mm]

2. Secondly to create a slot for the travel of driving wheel to drive the driven wheel,by using circle command create the circle in two different dimension and by using line command create a line from the center of the circle and make the line as center line and by using offset command create both side offset with caped end after completing this by using rotational translation copy those lines and paste it in the other quarters of the circle and by using power trim option cut un wanted lines and by using fillet option create the round corners in the edges of the cutted area,

3.Then by using extrude cut option cut the second sketch to complete the driven wheel and save it as Driven wheel

Driving Wheel

4.Create a new sketch and using circle command create a circle based on the dimension given in the challenge.

5.By using Extrude command extrude it as a disc

6.By choosing the front face of the disc and create a sketch and create a circle based on the dimensions given in the challenge and finally extrude it to create a pin and save it as a Driving wheel.

Assembly

7.Then by using insert command select the components and place it in the workspace

8.First verify that the driving wheel is in float condition and then moving on to mate command.

9.First Mate the front planes of the driving wheel and the Assembly,then create a sketch that represent the maximum diameter of the parts to fix the axis of the wheel.and create a Mate between them to fi the axis.

10.Secondly position the driven wheel and mate it the front plane of the assembly and then create a sketch that represent the maximum diameter of the parts to fix the axis of the wheel.and create a Mate between them to fi the axis.also aligne the parts in their position.

Motion Study

11. First give the force by means of giving motor to the driving wheel and set 10rpm as speed

12.Secondly select setting and choose or set frame rate here based on the challenge first i have made the study with 60fps and also with precise contact and without precise contact.

13.Then give contact force to the body set it in the solid body contact and choose dry steel as material.

14.Then move on to calculate.

15.After completing calculation move on to plot option and select force and select contact force and choose contact surface of the bodies.

16.Select displacement and select Driven wheel and create a plot.

All the plot are shown below and these plot are based on 60fps and without precise contact.

1.Plot on contact forces

2.Plot on Displacement

17. Setting the same things for precise contact and optain the plot for contact and displacement.

3.Plot on contact force

4.Plot on Displacement

Then for 120fps and 20rpm

18. First give the force by means of giving motor to the driving wheel and set 20rpm as speed

19.Secondly select setting and choose or set frame rate here based on the challenge first i have made the study with 120fps and also with precise contact and without precise contact.

20.Then give contact force to the body set it in the solid body contact and choose dry steel as material.

21.Then move on to calculate.

22.After completing calculation move on to plot option and select force and select contact force and choose contact surface of the bodies.

23.Select displacement and select Driven wheel and create a plot.

5.Plot on Contact force

6.Plot on Displacement

24. Setting the same things for precise contact and optain the plot for contact and displacement.

7.Plot on Contact force

8.Plot on Displacement

The below two graphs are based on the values obtained from the exported from the graph and made as graph

9.Plot from 60fps

10.Plot from 120fps

The below image show the selection of precise contact

Movement of internal geneva wheel is uploaded in youtube and links are shared

1.Internal geneva Mechanism with 60fps:https://youtu.be/C5MI-Mm3vCY

2.Internal geneva Mechanism with 120fps:https://youtu.be/-9HCVtvh4Mo

Result:

Finally I have made the assembly of the internal geneva and made a motion study and obtained the above plots.ANd also attached the .csv file which are ogtained from the plots.And the motion of internal genva wheel is saved in the form of video and they are uploaded in youtube and links are shared above.