Balancing machines

chandra ghimirey

Basics

The process of providing the second mass in order to counteract the effect of the centrifugal force of the first mass is called balancing by doing so the centrifugal forces are reduced, minimizing vibration, noise and associated wear.

The more the unbalance ,the greater the force and thus the greater the amplitude of the vibration.

Unbalances

.

Principal Inertia Axis

CG

Geometric Centerline

• Static unbalance – where the PIA is displaced parallel to the geometric centerline.

• Dynamic balance - sometimes called two plane balance

The sum of forces must be zero

And the sum of moments must also be zero

 

Types of balancing machine

Hard-bearing In a hard-bearing machine, balancing is done at a

frequency lower than the resonance frequency of the suspension.

Versatile and suitable for the parts having different weights.

Requires one time calibration.

Soft bearing

In a soft-bearing machine, balancing is done at a frequency lower than the resonance frequency of the suspension.

Non versatile, time consuming

How it works

• a vibration sensor is attached to the suspension. In most soft-bearing machines, a velocity sensor is used

• (proximity sensor) or encoder is used to determine the rotational speed, as well as the relative phase of the rotating part, determine the amount of movement, or force, in one rotation of the part. Also, the time difference between the phase and the vibration peak gives the angle at which the unbalance exists. Amount of unbalance and angle of unbalance give an unbalance vector.

• Calibration is performed by adding a known weight at a known angle. In a soft-bearing machine, trial weights must be added in correction planes for each part.

AdvantagesMinimize vibrationMinimize noiseMinimize structural stressMinimize operator fatigue and annoyance Increase machine life Increase bearing life Increase product qualityIncrease personnel safety Increase productivity