Page 287 - Machinery Component Maintenance

Balancing of Machinery Components 269

In single-station automatic balancing machines, all functions of the bal-
ancing process (unbalance measurement, location, and correction) as
well as inspection of the complete process are performed sequentially in
a single station. In a multiple-station machine, the individual steps of the
balancing process may be performed concurrently at two or more sta-
tions. Automatic transfer is provided between stations at which the
amount and location of unbalance are determined; then the correction for
unbalance is applied; finally, the rotor is inspected for residual unbal-
ance. Such machines generally have shorter cycle times than single-sta-
tion machines.

Establishing a Purchase Specification
A performance type purchase specification for a balancing machine
should cover the following areas:

1. Description of the rotors to be balanced, including production rates,
and balance tolerances.
2. Special rotor requirements, tooling, methods of unbalance correc-
tion, other desired features.
3. Acceptance test procedures.
4. Commercial matters such as installation, training, warranty, etc.

Rotor Description

To determine the correct machine size and features for a given applica-
tion, it is first necessary to establish a precise description of the rotors to
be balanced. To accumulate the necessary data, IS0 2953 suggests a suit-
able format. Refer to Appendix 6C.

Supporting the Rotor in the Balancing Machine

Means of Journal Support
A prime consideration in a balancing machine is the means for support-
ing the rotor. Various alternates are available, such as twin rollers, plain
bearings, rolling element bearings (including slave bearings), V-roller
bearings, nylon V-blocks, etc. (See also Appendix 6B, “Balancing Ma-
chine Nomenclature,” and Appendix 6C .) The most frequently used and
easiest to adapt are twin rollers. A rotor should generally be supported at
its journals to assure that balancing is carried out around the same axis on
which it rotates in service.