Process design – relation to process flow and evaluation


There is a definite relationship between the production process and process flow. For continuous manufacturing, the methods and processes must be determined before the line is set-up. The process design is built into the line. Once processing lines are established, any further changes in methods should be held to a minimum, owing to the dependency of each operation on all preceding operations. Changes usually require that the line be shut down with consequent loss of production. Changes in the line for improvement of methods are usually held up until product design itself is changed. For continuous flows, process design must be thorough and accurate and tools and equipment must be highly specialized.

For intermittent process flows, no lines are set up. The process engineer is usually required to adapt the methods and processes to the types of equipment available. General purpose machine tools and equipment are employed, as each machine may be used for varying operations on many different components of the product. Changes in methods can easily be effected without affecting the overall productive capacity of the plant.

Evaluation of the Process Design

One of the objectives in designing the process flow is to ensure that, goods and services are produced at minimum cost. A major problem confronting the process engineer is to determine when this objective has been attained.

Process design is a dynamic activity. Better tools and equipment are constantly being developed. New materials are being introduced and new uses for old materials are discovered. Every process engineer must be alert to changes in the basic factors of volume, product quality level and equipment available. Any of these changes may affect the process design.

A basic tenet of the process engineer is that, there is always a better way to make the product. There are techniques (cost reduction, value engineering, for example) to do things better. Competition makes such policies pre-requisites to success in manufacturing.

The use of the staff specialists—the process engineer—contributes to this end. A clearly though out plan of manufacturing will uncover possible pitfalls and predict the manufacturing cost. This estimate can be translated into anticipated profits. Careful planning ensures a complete coverage of all operations in manufacturing a product and of the costs involved.

The improvement of process designs cannot go on indefinitely to the exclusion of the production of the product. Production schedules must be met. Plant facilities may also limit the extent of the implements that can be made within the current manufacturing plan. All these problems are best solved by the cooperative efforts of all involved. Any solution, however, should be accepted as only one benchmark in the continuing improvement of the process design.

Many intangibles need to be considered from time to time. Among them are : the cost of larger inventories caused by the leveling of production to prevent labor turnover, the problem of overheads distribution and the nature of the customer goodwill that may be lost through late deliveries or poor quality product. These and other intangibles enter into the total evaluation of the process design.