Planetary Gear

AIM: To do multibody dynamics (MBD) analysis of Planetary gear mechanism using SOLIDWORKS

OBJECTIVE:

1. To create 3D models of all parts after calculating pitch circle diameter and number of teeth.
2. To perform motion analysis of the assembly by rotating the input gear at 200rpm
3. To obtain a plot for angular velocity for output parts and exporting the result to a spreadsheet through the following cases:

Sl. No.	INPUT	FIXED	OUTPUT
1	Sun Gear	Ring Gear	Carrier
2	Ring Gear	Sun Gear	Carrier
3	Sun Gear	Carrier	Ring Gear

THEORY:

A planetary gear also known as epicyclic gear train 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 gears and rotates to carry gears, called planet gears or planet pinion, around the other, called the sun gear or sun wheel. The planet and sun gear or sun wheel mesh so that their pitch circles roll without slip. A planetary gear train is assembled in such a way that the planet gear rolls on the inside of the pitch of an outer ring gear.

Motion studies are graphical simulations of motion for assembly models. Motion studies do not change an assembly model or properties. They simulate and animate the motion we prescribe for a model. By using Solidworks mates to restrict the motion of components in an assembly when we model motion. From motion studies, motion analysis can also be done for accurately simulating and analyzing the effects of motion elements. It can also be used to plot simulation results for further analysis.

PROCEDURE:

• Calculate the pitch circle diameter and number of teeth for designing planet gears

GIVEN:

Ring gear :

Module (m) = 2.5

Number of teeth (T) = 46

Sun gear:

Number of teeth (T) = 14

Input speed of the gear = 200 rpm

Number of planet gears = 4

CALCULATIONS

Ring Gear:

Module (m) = 2.5

Number of teeth (T) = 46

Pitch Circle Diameter (D) = Module (m) * Number of teeth (T)

D = 2.5 46

D = 115

Radius = 57.5

Sun Gear:

Module (m) = 2.5

Number of teeth (T) = 14

Pitch Circle Diameter (D) = Module (m) * Number of teeth (T)

D = 2.5 14

D = 35

Radius = 17.5

Planet Gear:

Module (m) = 2.5

Pitch Circle Diameter (D) = Radius of Ring Gear – Radius of Sun Gear

D = 57.5 `-` 17.5

D = 40

Number of teeth (T) = Pitch circle diameter / Module

T = `40/2.5`

T = 16

• After calculating the number of teeth for planet gear we will design a spur gear having required number of teeth. But instead of designing a spur gear we can also the toolbox directory present in Solidworks in which all the types of gears are pre – designed and we just have to enter some values to get our desired gear. But we have to save this gear as a separate part. As we are using the metric system we have to give the value of Module, Number of teeth, Nominal shaft diameter and Face width.

• Now we will make a spur gear for the sun gear using the metric system by providing the required values like module, number of teeth nominal shaft diameter and face width.

• After this a ring gear is created using the toolbox directory and in that metric system an internal gear. We will provide the value of number of teeth, module, outer diameter and face width.

• Now we will design the carrier by using the pitch circle diameters. Firstly we will draw the pitch circle diameter of all the gears accordingly and then use that sketch to design the carrier, four holders are made using the boss extrude command, for four planet gears. The holder’s diameter should be same as the nominal shaft diameter of the planet gear.

• After all the parts made we will create an assembly using all the parts. The first part that was imported is made float so that it can move. We will give all gears a coincident mate with the right plane of the assembly. Then draw a sketch of pitch circle diameters of ring gear and sun gear, and then give concentric mate to the gear with its pitch circle diameter. Then give a distance mate between the carrier base face and the face of ring gear. Now give concentric mate between four planet gears and carrier holders. Now give a coincident mate between the axis of the sun gear and the axis of the carrier.

• Motion analysis of the gear train is done for getting desired plots. For this a motor is provided at the input gear having a constant speed of 200 rpm. Now according to the assembly giving the gravity in downwards direction in this case in y – direction. Now establishing the contact between the gears and also providing the material as steel. Now fixing the parts and obtain the plots of angular velocity of the output part in each case:

Sl. N	INPUT	FIXED	OUTPUT
1	Sun Gear	Ring Gear	Carrier
2	Ring Gear	Sun Gear	Carrier
3	Sun Gear	Carrier	Ring Gear

PLOTS AND ANIMATION:

• Sun gear – Input : Ring gear – fixed : Carrier – Output

ANIMATION : Sun gear - Input : Ring gear - fixed

• Ring gear – Input : Sun gear – fixed : Carrier – Output

ANIMATION: Ring gear - Input : Sun gear - Fixed

• Sun gear – Input : Carrier – fixed : Ring gear – Output

ANIMATION: Sun gear - Input : Carrier - fixed

CONCLUSIONS:

• When the input is given to the sun gear and the output is obtained at the carrier keeping the ring gear fixed, the planet gears rotates about its axis as well as it rolls on the ring gear as it is fixed. The angular velocity obtained is in between 270 – 290 deg/sec.
• When the input is given to the ring gear and the output is obtained at the carrier keeping the sun gear fixed. As the ring gear is large in size as compared to planet gears, the velocity ratio is also high due to which we get maximum angular velocity ranging from 910 – 930 deg/sec.
• When the input is given to sun gear and the output is obtained at the ring gear keeping the carrier fixed, all the gear rotates about its own axis only. As planet gears are small in size as compared to ring gear, due to which the angular velocity of the ring gear is achieved is less ranging from 330 – 390 deg/sec.

DRIVE: Files on Planetary gear analysis