Planetary Gear Motion Analysis

Planetary Gear Motion Analysis

1. AIM:

To design and simulate a planetary gear arrangement in SolidWorks

2. INTRODUCTION:

- Motion studies are graphical simulations of motion for assembly models.

- Motion studies do not change an assembly model or its properties. They simulate and animate the motion you prescribe for a model.

- Motion study has 3 components out of which 2 are enabled by default. They are -

1. Animation - Basic animation and also can add motors and define the assembly positions at different points in time.
2. Basic Motion - Animation but with mass consideration. Effect of gravity, spring, dampers can also be turned on.
3. Motion Analysis - Proper analysis using all physics options including force, pressures. It includes powerful solvers which calculate answers accurately and also provide plot options.

- Planetary gear arrangement:

- In this type of arrangement (Epicyclic geartrain), the internal spur gear named as Ring Gear is in mesh with 4 Planetary Gears which in turn are in mesh with a Sun Gear. This type of gear arrangement is common in shoe buffing devices.

- It consists of gears mounted so that the center of one gear revolves around the center of the other. A carrier connects the centers of the two gears and rotates to carry one gear, called the planet gear or planet pinion, around the other, called the sun gear or sun wheel. The planet and sun gears mesh so that their pitch circles roll without slip. A point on the pitch circle of the planet gear traces an epicycloid curve. In this simplified case, the sun gear is fixed and the planetary gears roll around the sun gear.\

3. OBJECTIVES:

- Create 3D models for Ring, Sun, Planetary Gears and Carrier.

- Perform motion analysis by rotating different gears at 200RPM.

- Obtain the plot of Angular velocity of Input and Output Gears.

4. FLOW OF PROJECT:

1. Create 3D CAD models on the basis of gear teeth properties.
2. Assemble the CAD models using proper constraints.
3. Use the assembly in motion analysis and set-up the motion parameters like rpm, material etc.
4. Run the calculations.
5. Save the animations.
6. Plot graphs.

5. MOTION STUDY SETUP:

1. Initially, the gear properties like module and number of teeth were used to make 3D CAD models of the different types of gears like ring gear, sun gear, planetary gear as well as a carrier.
2. Those parts were imported to a new assembly and assembly was made. Both the parts were constrained to a certain degree so as to allow required degree of freedom for circular motion.
3. A new motion study having type as Motion Analysis was selected.
4. Input gear was given a rotation of 200RPM and contact between all mating gears as well as carrier was established assuming steel material(dry) for both of them.
5. In motion settings, Frames per Second was set to 60.
6. Finally, the solver of SolidWorks calculated the study and simulation video and results were out.
7. The same process was repeated for different input and output gears.
8. Graphs were then plotted.

Cases:

Sl.No	Input	Output	Fixed
1	Sun Gear	Carrier	Ring Gear
2	Ring Gear	Carrier	Sun Gear
3	Sun Gear	Ring Gear	Carrier

Given Gear data:

• Ring Gear
  • Module = 2.5 (metric)
  • Number of teeth = 46
• Sun Gear
  • Number of teeth = 14
• Input Speed of the Gear = 200 rpm.
• Number of planet gears = 4

Since we need to find out number of teeth on planetary gears, lets check out some basic parameters.

We know 2 meshing gears have same module. Thus module of planetary gear = module of sun gear = module of ring gear = 2.5

Now, PCD(ring) = m*teeth = 2.5*46 = 115mm

PCD(sun) = m*teeth = 2.5*14 = 35mm

We can say, from arrangement of planetary gears that PCD(ring)-PCD(sun) = 2*PCD(planetary gear)

So `(115-35)/2` = 40mm is PCD of planetary gear. Thus, no, of teeth = `(PCD)/m` = `(40)/2.5` = 16 teeth.

6. OBSERVATION, RESULTS AND CONCLUSION:

- In case 1, we can see that input sun gear has been given angular velocity of 1200deg/sec i.e. 200rpm and output is carrier and it is having an average angular velocity of 275deg/sec i.e. 46RPM. Since Ring gear is fixed, planetary gears move around the rotating sun gear and rpm depends upon diameter of ring gear.

- In case 2, we can see that input ring gear has been given angular velocity of 1200deg/sec i.e. 200rpm and output is carrier and it is having an average angular velocity of 920deg/sec i.e. 153.33RPM. Since sun gear is fixed, planetary gears move around the fixed sun gear and rpm depends upon diameter of sun gear. Since it is small as compared to ring gear, hence rpm imparted will be much more than case 1.

- In case 3, we can see that input sun gear has been given angular velocity of 1200deg/sec i.e. 200rpm and output ring gear is having an average angular velocity of 367.5deg/sec i.e. 61.25RPM. Since carrier is fixed, planetary gears are forced to rotate about their own axis. Thus ring gear has to rotate and speed obtained will be higher than first case but lower than second case.

Animations:

CASE - 1:

CASE - 2:

CASE - 3: (Reduced rpm because of difficulty in watching the animation even after reducing playback speed)

Why the variation in output gears angular velocity?

It is due to friction between carrier and gear shaft hole as well as gear teeth profiles meshing with another. That cause spikes in the graphs.

7. REFERENCES:

- https://en.wikipedia.org/wiki/Epicyclic_gearing