DESIGN FOR MANUFACTURING:DRAWINGS

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DRAWINGS

Drawings represent the heart of design for manufacturing because they are the principal means of communication between the functional designer and the producer of the design. They alone control and completely delineate shape, form, fit, finish, and interchangeability requirements that lead to the most competitive procurement. An engineering drawing, when supplemented by reference specifi- cations and standards, should permit a competent manufacturer to produce the part shown within the dimensional and surface tolerance specifications provided. It is the engineering drawing that should demonstrate the most creative design for manufacturing thinking.

Certain product specifications may not be included on the drawings in view of space constraints. Product specifications such as quality assurance checkpoints, inspection procedures, and general de- sign criteria may be separately summarized but should always be cross-referenced on the engineering drawing. At all times the design engineer must remember that the end product drawing is the com- munication medium between the design engineer and the producer. It is the basis for interchangea- bility for repair parts; it provides the form, fit, and function to the manufacturing function.

Too often the language of drawings is incomplete. For example, chamfers may be indicated but not be dimensioned; worse yet, they may be desired but not even be shown. Frequently the finish desired is omitted. Complex coring may be incorrectly shown. The principal errors common to many designs are as follows:

1. Design is not conducive to the application of economic processing.

2. Designer has not taken advantage of group technology and creates a new design for an already existing item.

3. Design exceeds the manufacturing state of the art.

4. Design and performance specifications are not compatible.

5. Critical location surfaces have not been established.

6. Design specifies the use of inappropriate items.

7. Design specifications are not definitive.

8. Inadequate consideration has been given to measurement problems.

9. Tolerances are more restrictive than necessary.

10. Item has been overdesigned.

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