Planetary Gear MBD using SolidWorks

AIM:   

To run the motion analysis on the planetary gear with a sun gear, a ring gear, a carrier and four planet gears.

• To access the gears from the toolbox in SolidWorks present in the ANSI Metric system.
• Provide the required parameters for defining each and every gear.
• Designing the carrier, depending upon the shaft diameter of the planet gears.
• Assembling them in SolidWorks and giving correct constarints to all the parts so that the assembly is perfect for running the motion analysis study.    

Theory:

A Planetary gear (also known as epicyclic gear train) consists of a larger Ring gear, planet gears and a sun gear. The sun gear is mounted at the center around which the Planet gears are mounted which can revolve around them. The planet gears are meshing internally with the Ring gear which is an internal gear.  A carrier is mounted to the planet gears as shown in the image. The combination of epicycle gear trains with a planet engaging both a sun gear and a ring gear is called a planetary gear train.

Problem Statement:

• Ring Gear
  • Module = 2.5 (You must use the metric system in design modeler)
  • Number of teeth = 46
• Sun Gear
  • Number of teeth = 14
• Input Speed of the Gear = 200 rpm.
• Number of planet gears = 4

The dimensions of the carrier depend on the shaft diameter of the planet gear.

With the above input parameters, you are going to run a simulation on the following cases,

Calculation:

Diameter of the Planet gear :

Radius of Ring gear= Diameter of the Planet gear + radius of sun gear

        Rr = Dp + Rs

Therfore, 

        Dp =Rr - Rs

        Dp=115/2  -  35/2   =   40mm

Number of teeths of Planet gear:

Pitch diameter, D=m*T

where m=module

          T= Number of teeth

therefore, T=D/m = 40/2.5 = 16

3D Models:

The created models are as shown.

Pressure angle = 20 degree

Face Width = 20 mm

Ring Gear;

Sun Gear;

Planet Gears;

Carrier;

Final assembly

                 The ring gear, planet gears, sun gear and the carrier are assembled as shown in the below image. The assembly is done using mate option by properly aligning all the componets in such a way that no component overlap on each other. Here we are not using mechanical gear mates as we have to analyse the motion for 3 cases.

Motion analysis

In the motion study make contacts between the followings.

• Carrier and the Planet gears
• Sun gear and the Planet gears
• Ring gear and the Planet gears

The material for each contact is Steel (Dry).

There are 3 Cases;

The input speed to the motor in each case is 200 RPM. The motion analysis is done for 5 seconds.

Case 1:

Ring gear fixed. Motor - sun gear.

The plot of an angular velocity of the carrier against time.

Case 2:

Sun gear fixed. Motor - Ring gear.

The plot of an angular velocity of the carrier against time.

Case 3 :

Carrier fixed. Motor - Sun gear.

The plot of an angular velocity of the Ring against time.

Observation and conclusion :

• In the first case when the input is given to the sun gear and output is obtained at the carrier keeping the ring gear fixed, the planet gear not only rotates about their axis but are also forced to roll on the inside of the ring gear along with the carrier as the Ring gear is fixed. The angular velocity obtained for this case is between 235-313 deg/sec.
• In the second case when the input is given to the ring gear and output is obtained from the carrier keeping the sun gear fixed. The angular velocity achieved is maximum since the internal gear is big and planet gears are small comparatively so when a large gear meshes with a small gear the velocity achieved from the small gear is high because the velocity ratio is high. The angular velocity obtained for this case is between 800-1017 deg/sec.
• In the third case the carrier is fixed and output is to be obtained from the ring gear with the input given to Sun gear, all the gears rotates about their axis. The planet gears rotate only about their axis and transmit motion from sun to the ring and since the ring gear is big in diameter the angular velocity achieved is less.The deviations that are visible in the graphs show that there are points where sliding is occurring between the gears. For making the graph more smoother we can use precise contact. The angular velocity obtained for this case is around 340-402 deg/sec.

Animations:

Drive Link:

https://drive.google.com/open?id=1FYeA3jUgON37ckFPHmoGP5Yv1EgrdAE8

References:

Google and Skill-Lync