Planetary Gear

AIM:

Design and Motion Analysis of Planetary Gear System using Solidworks.

THEORY:

A planetary gear set is made up of three types of gears; a sun gear, planet gears, and a ring gear. The sun gear is located at the center and transmits torque to the planet gears which are typically mounted on a moveable carrier.The planet gears orbit around the sun gear and mesh with an outer ring gear.Planetary gear systems can vary in complexity from very simple to intricate compound systems, depending on the application.

Planetary gears are often used when space and weight are an issue, but a large amount of speed reduction and torque are needed. This requirement applies to a variety of industries, including tractors and construction equipment where a large amount of torque is needed to drive the wheels. Other places you will find planetary gear sets include turbine engines, automatic transmissions, and even electric screwdrivers.

Planetary gear systems are able to produce a lot of torque because the load is shared among multiple planetary gears. This arrangement also creates more contact surfaces and a larger contact area between the gears than a traditional parallel axis gear system. Because of this, in the load is more evenly distributed and therefore the gears are more resistant to damage.

GOVERNING EQUATION:

1) `m = p/N`

2) D_R = 2D_P + D_S

where,

m = module of gear

p = pitch circle diameter of gear

N = Number of teeths

D_R = pitch circle diameter of ring gear

D_P = pitch circle diameter of planetary gear

D_S = pitch circle diameter of sun gear

OBJECTIVE:

The main objective of the project is:

1. To create the CAD models of ring gear,sun gear,planetary gear and the carrier.
2. To calculate the 'Pitch Circle Diameter' and 'Number Of Teeths' of the Planetary Gear.
3. To perform the motion analysis of the Planetary Gear System.
4. To plot the angular velocity of the various outputs.

Given:

Ring Gear

Module(m) = 2.5

Number of teeth(N_R) = 46

Sun Gear

Number of teeth(N_S) = 14

Input Speed of the Gear = 200 rpm.

Number of planetary gears = 4

CALCULATION:

For ring gear:

m = D_R/N_R

2.5 = D_R/46

∴ D_R = 115mm

For sun gear:

m = D_S/N_S

2.5 = D_S/14

∴ D_S = 35mm

For planetary gear:

D_R = 2D_P + D_S

115 = 2D_P + 35

2D_P = 80

∴ D_P = 40mm

So the pitch circle diameter of planetary gear is 40mm.

also,

m = D_P/N_P

2.5 = 40/N_P

∴ N_P = 16

So number of teeths for planetary gear is 16.

The below table shows us all the properties of the gears:

Sr. No.	GEARS	PITCH CIRCLE DIAMETER(mm)	NUMBER OF TEETHS
1.	Ring Gear	115	46
2.	Sun Gear	35	14
3.	Planetary Gear	40	16

PROCEDURE:

1)Initially we open the new solidworks assembly file and then from design library we select metric system and from that we upload internal spur gear(ring gear) as per the specified dimensions.The screenshot of CAD MODEL of ring gear is shown below.

Module - 2.5 : Number Of Teeths - 46 : Width - 10mm : Outside Diameter - 130mm

2)Then in the same way we upload the sun gear with the specified dimensions.The screenshot of the CAD MODEL of the sun gear is shown below.

Module - 2.5 : Number Of Teeths - 14 : Width - 10mm : Shaft Hole Diameter - 15mm

3)Now again in the same way we upload 4 planetary gear from the design library by assign the dimensions that we have calculated earlier.The screenshot CAD MODEL of planetary gear is shown below.

Module - 2.5 : Number Of Teeths - 16 : Width - 10mm : Shaft Hole Diameter - 22mm

4)After finishing all this we design the carrier as a seperate part file having it's dimension similar to the shaft diameter of the planetary gear.The screenshot of the CAD MODEL of the carrier is shown below.

5)After designing the carrier we insert it into the assembly file and then assemble all the components by giving them the desired mates.The screenshot of the CAD MODEL of the assembly of the 'PLANETARY GEAR SYSTEM' is shown below.

6)After finishing with the assembly we do the motion study analysis of the system.

MOTION STUDY ANALYSIS:

For motion study analysis initially solidworks add-ins is clicked and in the left hand corner motion analysis is selected.Then we do motion analysis for all the 3 cases.

CASE 1: INPUT - SUN GEAR : OUTPUT - CARRIER : FIXED - RING GEAR

The motor of 200 RPM is applied at the sun gear and the ring gear is kept fixed.Then we apply the contacts between the ring gear and the planetary gear,sun gear and the planetary gear,carrier and the planetary gear.Then we click on calculate to get the motion study analysis.The input and the output plot of the case 1 is shown below.

INPUT PLOT:

The angular velocity of the sun gear remains constant due to smooth engagement of the gears and no fluctuation.

OUTPUT PLOT:

The angular velocity of the carrier increases rapidly due to force provided by the gears and then it remains almost constant with minor peaks at some point due to variable power transmitted between the gears and the carrier.

After we finish with the motion study and obtain the results and plots we make the animation of the motion study.

The animation link for the case 1 is shown below:

https://youtu.be/IdDhT5SY_70

CASE 2: INPUT - RING GEAR : OUTPUT - CARRIER : FIXED - SUN GEAR

Here the motor of 200 RPM is applied at the ring gear and the sun gear is kept fixed.The contacts applied will be same as case 1.Then we click on calculate to get the motion study analysis.The input and the output plot of the case 2 is shown below.

INPUT PLOT:

The angular velocity of the ring gear remains almost constant due to smooth engagement of the gears and due to an efficient power transmission.

OUTPUT PLOT:

The angular velocity of the carrier increases suddenly at the start and then we can see some peaks at some points due to variable power transmission between gears and carrier.

After we finish with the motion study and obtain the results and plots we make the animation of the motion study.

The animation link for the case 2 is shown below:

https://youtu.be/y7SUqV3mVe4

CASE 3: INPUT - SUN GEAR : OUTPUT - RING GEAR : FIXED - CARRIER

Here the motor of 200 RPM is applied at the sun gear and the carrier is kept fixed.The contacts applied will be same as case 1 and case 2.Then we click on calculate to get the motion study analysis.The input and the output plot of the case 3 is shown below.

INPUT PLOT:

The sun gear shows constant angular velocity with minimal variations.

OUTPUT PLOT:

The angular velocity of the ring gear increases rapidly initially and after that there are small ups and downs at some point due to fluctuation in power transmission between gears.

After we finish with the motion study and obtain the results and plots we make the animation of the motion study.

The animation link for the case 3 is shown below:

https://youtu.be/knPRQkAAZ5I

CONCLUSION:

Thus we have made the 3-D CAD MODEL of all the gears and carrier and assembly was also done.Also the motion study analysis of the 'Planetary Gear System' was done and their input and output plots were also obtained.The Motion Study provides a clear insight about the functioning of the Planetary Gear System.With the variation of the parameters, the output can be varied and thus optimization can be done in the system

REFERENCES:

A reference book of Machine Design by R.S.KHURMI

https://gearmotions.com/fundamentals-planetary-gear-systems/

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

APPLICATION AND USES:

Automated guided vehicles (AGV),Axis drive for laser cutting machines,Conveyor systems etc

LINK FOR SOLIDWORKS PARTS AND ASSEMBLY FILES IS SHOWN BELOW:

https://drive.google.com/drive/folders/1S-vYNQ9NEQlUPUPa4rh0zOqzrQXXOrmU?usp=sharing