Process Limitations

The process itself imposes certain restrictions on the order of processing. The most important factors are discussed below :

Limitations Imposed by the Manner in which the Material is Received

For example, the sequence of handling and machining a forging in chucking machine would differ considerably from the manner in which it would be performed if the material were received as bar stock and machined in a bar machine.

Limitations Imposed by the Flexibility of Machines

The operation sequence can be arranged in different orders when a general-purpose machine is used. Where as in case of a transfer machine there is a fixed sequence of operations. Also it requires that special qualifying operations to be performed on the workpiece to permit use of the same seat of registry throughout the process.

Limitations Imposed by Process Capability

When heavy cuts are required, machines often vary in their capacity to produce accurately; thus more or fewer operations may have to be performed for the completion of the job.

Limitations Imposed by Machine Availability

A desired machine, for an operation, may not always be available as several jobs may be waiting to be scheduled on certain machines. This results in a change in the operation sequence or even additional operations.

Limitations Imposed by the Cutting Tool

In order to simplify the problem of tool replacement and the changing of spindle speeds for operations such as turning, the cuts on large diameters are grouped together in the sequence rather than being grouped with cuts on smaller diameters, which can be turned at faster speeds.

Limitations Imposed by the Volume of Production

More sophisticated and efficient tooling is used for high volume production. Because this often results in combining certain operations with others, hence the operation sequence is shortened. The operation sequence is influenced by the rate of production and it is closely related to volume of production.

Alternate Process Available

When alternate ways of producing a part are available, the process sequence is first determined by selecting those methods, which will produce good pieces. The decision is taken based on comparative economy after developing the appropriate operational sequence.