Rotating Shaft With Unbalanced Mass

Title : Rotating Shaft With Unbalanced Mass

What is Vibration motor?

Vibration motors are totally enclosed 3 Phase motors with adjustable, eccentric weights mounted at both the ends of the shaft, to set up vibrations during rotation. The selection of bearings has been carefully done to withstand heavy radial loads.

General Unbalanced Motors Features :

• Range: 0.25HP to 10HP
• In 2,4,6,8, poles
• 3 phase supply volts 220/415/440, 40/50/60HZ
• Centrifugal force: 250 to 10000kg
• Mounting Type: Base, Flange, Wedge

Unbalanced Motors design:

Unbalanced Motors is a three-phase synchronous motor that has eccentric weights (unbalance weight) mounted at the ends of the rotor shaft. The rotating shft causes centrifugal forces, which can be adjusted by moving the weights it create a vibration.

Unbalanced Motors Winding:

Insulation class F enhances the safety under continuous operation conditions and at high ambient temperatures. Motor are tropicalized and designed for an extended voltage range.

Unbalanced Motors earing & Lubrication:

The right type of bearing for every application guarantees long service life even continuous operation. All vibratory motors are permanently lubricated for normal operation. Large capacity motor can be re-lubricated for average application.

Unbalanced Motors Protection Systems:

Motor are completely sealed and meet the requirements of safety class IP55 or IP65.

Centrifugal Force Setting:

The centrifugal forces can be regulated with the easily adjustable eccentric weights with graduations to suit practical applications.

Unbalanced Motors Application:

Unbalanced Motors are used in various material handling equipments such as vibrating screens, conveyors, and feeder. They are also used on hoppers, silos to prevent congestion of material flow. Foundry shake outs and compacting machines use these motors for fast and efficient operation.Motor use in Pharmaceuticals, construction, chemical industries, food equipment, Ceramic industries.

For this project - Solidworks ( 3D Modeling ) and ansys workbench ( Simulation ) software are used.

This whole assembly is rotating at 3-Different RPM, its effect on shaft is being monitored in terms of defection and stress.

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What is Rigid Dynamics ?

• It considers the large motion of bodies in the model.
• the displacements and rotations are due to the body inertias, loads and joints.

What is Flexible Analysis ?

• It Includes both rigid and flexible bodies, Part flexibility, stress and strain.

What is Rigid-Flexible Dynamics Analysis ?

• also known as multi-body dynamics
• connections of parts via joints to simulate mechanisms
• the response is based on the kinematics of the mechanism

Features of workbench Rigid-Flexible Dynamics

• reduce complexity and minimize run time by assigning rigid parts
• range of motion in a mechanism
• loads in each join or contact interface
• effects of spring and dampers
• part accelerations and velocities

If all parts are rigid, the analysis can run as pure rigid body dynamics anlysis

• uses the ansys rigid body dynamics solver
• Explicit dynamic soolver
• very fast
• Very robust - noconvergence issues
• calculates forces, moments, displacements, velocities and accelerations
• Does not calculate any stresses or strains

Once we add a flexible body, it uses the standard implicit solver but rigid bodies still save time!

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3D Model of this whole setup is generated is solidworks and saved in Parasolid format. Here we are Cutting the geometry into half to save computational time.

we import the geometry in Rigid Dynamics Ansys Workbench and to verify for error geometry opened in space claim.

Material Assigning :

Shaft - C50

Unbalanced Masses : Mild Steel

Rotor : Nickel - Copper Alloy

Connections Settings :

Ansys Software will automatically generates connections. But we make sure that On contact Side Bodies - Shaft selection is there and Contact type is set to No separation rest settings are by default.

Joints Settings :

For Both Unbalanced Masses and shaft Fixed joint is used, Connection type is Body to Body

Joints : Revolute Joint is Between rotor And shaft Connection type is Body to Ground

Bearing Joints : Joint is on shaft, Connection type is Body to Ground & in Y-Z Plane

Mesh settings are by default No need to put any Method Unless it is Necessary and in Rigid Dynamics we can only create mesh on face.

Analysis Settings : By Default timings are used

Joint Input : Rotational Velocity 1000/2000/3000 RPM is set.

Rigid Dynamic Analysis Result :

Connecting Transient analysis to Rigid Dynamics

Changing Behaviour of shaft to flexible

Mesh Setting : Non-Linear Mechanical Element Size : 25mm

Mesh Method : Patch Independent Method

Analysis Settings :

By Default timings are used, Weak Springs are program controlled, Large Deflection is on.

Drag Joint Setting from Rigid Dynamics to Transient Analysis

Rigid Dynamic - Transiebt Analysis Result :

Case 1

Case 2

Case 3

Conclusion :

We can say that as RPM is increasing also Total Deformation is increasing. But how to cross check these values whether they are right or Wrong?

In Any Machine Practically there are some limitations where all parameter should work in safe range. Here in our case Permissible Shaft Deflection Whlie Rotating is 6mm, we are in safe range.

To further reduce of Shaft deflection we can use more stiff material with High tensile strength such as High Carbon content steel ( Hot Rolled Steel ).

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