Operation Sequence

The best sequence of manufacturing operations is determined by both the degree of control desired, which can be maintained throughout the process and the logical processing sequence. These in turn depend on the following considerations.

Based on Part Design

(a) Part geometry

(b) Part physical specifications

Based Upon the Process

(c) Process limitations

(d) Alternate processes available

Part Geometry

It is necessary to determine the surfaces on the workpiece which best qualify for location geometrically, dimensionally and mechanically. The dimensional control of the workpiece during process is determined by these surfaces. Thus one can determine the logical processing sequence and the number of operations which can be combined.

Some surfaces will provide better control of the workpiece dimension than the other. It is generally easier to maintain control from a large surface than from a smaller one. Similarly, better control can be achieved from a plane surface rather than from one, which is curved or irregular. The extent to which workpiece dimensional and form control can be achieved also depends on size of the workpiece.

Physical Specifications

Physical specifications of the workpiece relates both to tolerances on dimensions and the initial material condition. When certain close dimensional relationship exist between surfaces, these relationships should be accomplished as directly as possible to avoid tolerance stacking. In fact, it is desirable to accomplish the operations, which control close dimensions as early in the process as possible. Material condition however may prevent this. For example, it is difficult to machine hardened surfaces by means other than abrading.

Process Limitations

The process itself imposes certain restrictions on the order of processing.