Internal Geneva Mechanism

AIM:-To create 3-D model of Internal Geneva Mechanism using SOLIDWORKS and analyze its motion study.

OBJECTIVES OF THE PROJECT:-

1. To analyze motion study of Internal Geneva Mechanism at various input rpm for the driving wheel.
2. To plot various graphs,calculate reaction forces and importing the same to EXCEL sheets.

PRINCIPLE:-Geneav Mechanism is a gear mechanism that transforms continuous rotation motion into intermittent rotary motion.It consists of two parts crank(driving) wheel,geneva(driven)wheel.When crank is rotated with help of external mechanical power it makes the geneva wheel to have intermittent rotary motion.

APPLICATIONS OF THE MECHANISM:-

1. It is widely used in movie projectors,cameras to pull the film.
2. It is also used as indexing head in lathes etc.
3. It is used in watches.

BODY OF THE CONTENT:-

CREATING THE 3-D MODEL OF THE DRIVING WHEEL:-

1. First select the front plane and select sketch command.
2. Draw the driven wheel and make it as a reference so that the centre to centre distance between them can be known exactly and can be used for creating mates in the assembly.
3. Draw a perimeter circle which is tagent with the reference lines of the slots,and make the drawes circle as reference circle.
4. Draw a circle of given diameter such that its centre coincides with the cicumference of the above drawed circle and on extruding the circle from the surface having value of 40mm.This serves as pin which helps in driving .
5. With respect to the reference circle centre sketch the driving wheel according to the given dimensions and extrude it to 20mm.
6. This ends up with creating 3-D model of driving wheel

CREATING THE 3-D MODEL OF THE DRIVING WHEEL:-

1. Select front plane and start sketch the model.
2. with origin as centre draw 3 circle as per given dimensions and make intermediate circle as refernce circle.
3. Now draw a vertical line which cuts all the 3 circles ,make it as a reference line.
4. Use the above created reference line offset the lines on either sides of width 20mm each.
5. Now select the 3 point arc and sketch it such that it makes a tangent relation with the intermediate circle.
6. Use trim option and remove unnecessary sketch.This results in creating the slot for the pin for driving it.
7. Use the circular pattern command and replicate the slots to required number with help of created slots.
8. Use fillet command to make sharp edges into curvy shape.
9. Now exit the sketch and extrude it to 20mm from midplane on either sides.
10. This results in creatong 3-D model of driven wheel and slots.

ASSEMBLING THE MECHANISM:-

1. No wwe have to select assembly instead of part model.
2. After entering into the assembly mode we have to insert the individual components.
3. The first imported part model we will be automatically fixed so we have selected float option by right clicking the mouse button so that the part will not have any constrains initially.
4. Now give mates/constrains so that the component/part will have desired ouput motion.
5. following mates are give to get desired combined ouput.

MOTION ANALYSIS:-

1. Now click on SOLIDWORKS ADD-Ins and select SOLIDWORKS MOTION.
2. Now at the bottom of the SOLIDWORLS window we have Motion study option ,when we click on it the dialogue box pops up.
3. Now at the extreme left corner of the dialogue box click on drop down arrow and select motion analysis.
4. Now click on motor option and select the part of the assembly to be given input motion ,and slect the required constant speed to be given as input.
5. Now create solid contact with the components so that motion which will be transmitted and also assign kind of materials .
6. Now click on results and plots to plot various graphs and slect corresponding component of whose graph has to be plotted.
7. Now click on motion study properties and select the frames per seconds , precise contacts between the components so that more accurate plots, motions can be captured.
8. Now select the period of time for which the stimulation has to be run.
9. Now click on calculate so that it calculates all the forces ,displacements etc and display the same in terms of graphs/plots.
10. After completion of motion analysis the plots ,results can be exported to EXCEl sheets ans can be saved for future reference.
11. Following conditions are applied to the geneva mechanism for mmotion study

ANIMATION OF THE INTERNAL GENEVA MECHANISM:-

PLOTS WHEN INPUT IS 10rpm and 60frames/sec with precise contact:-

IMAGE OF MOTIONSTUDY PROPERTIES:-

COMPAIRING THE GRAPHS WITH AND WITHOUT PRECISE CONTACT:-

1. With precise contact we can fet more precise values because of precise contacts while without precise contact we are unable to obain the results as given with precise contact.

PLOTS FOR VARIOUS CONDTION AND COMPONENTS:-

CONCLUSION:-

1. Plotted graphs of various contact forces,angular displacement,velocity,acceleration.
2. The reacton forces increases by using precise contact command because of more precise contacts.
3. As the number of frames/sec increases we will be able to analze the mechanism more clearly and obtain plots of greater accuracy.
4. As the rpm increases the driving wheel rotations /min increases.
5. Analyzed the contact forces .