The Design Process

Jensen, Cecil, Helsel, Jay and Short, Dennis. “The Nineteen Chapter.” Engineering Drawing & Design. Mc Graw Hill, 2008. 686-701. Print. 

Creativity has been defined as the exercise of imagination combined with knowledge and curiosity. Although more commonly associated with the arts _ painting, sculpture , music, dance,literature - Creativity is equally important in all fields of technology. The combined affords of scientists, engineers, technicians, and skilled trade-persons have been largely responsible for the high living standards presently enjoyed by the Western civilization.  

The Design Process

The purpose of any design department is to create a product that not only will function efficiently but will also be the financial success. In the design process, consideration should be given to each of the step below:

The Engineering Approach to Successful Design 

Each field of engineering has its techniques and rules - and its standards for the use of the construction materials peculiar to that field. The steps from the idea to production are based on logical and well-known design principles. These principles apply equally to the manufacturing of gears, optical systems, industrial components, consumer articles, or rockets regardless of material of construction. These steps are not necessarily in order, but all are essential for successful application.

Defining the End-Use Requirements

As an initial step, the product design must anticipate the conditions of use and the performance requirements of the product. Consideration must be given to such things as environment, load, speed of production, life expectancy, optimum size, maintenance,  shape, color, strength, and stiffness. 

These end use requirements can be ascertained through market analyses, surveys, examinations of similar products, testing, general experience, and frequently, material suppliers. A clear definition of product requirements leads directly to choice of the constriction material.

Selecting the Material

Material is a very importance factor to consider in designing a part. Perhaps plastics are the better choice of material over wood or metal. Would one choice of metal be better than another? What elements will come into contact with water? If the part is to immersed in an oil solution, will the choice of plastics be minimized or rules out? Is strength a factor/ If so, what materials will meet the stresses required?What material is in stock or easily obtainable? Is the material the correct choice if a plating or coating is required?

There are thousands of engineering materials available, yet no single one will exhibit all desired properties in their proper relationships. Therefore, a compromise among properties, cost, and manufacturing process determined the construction material. Even within one series, material differ because of varying formulations. Just as still compositions vary -  tool steel and stainless steel, for example - so do the plastics. 

The designer needs a firm set of properties and engineering data upon which to base the first design. The data can come from handbooks or, more likely, from the published literature provided by the manufacturer of materials. 

Drafting the Preliminary Design

The designer blends the end-use requirements and the properties of the selected material into a preliminary design. Engineering techniques and formulas are used to achieve the three requirements of design success:

The production method to be used will often set limitations on design. The designer should be aware of the strengths and weaknesses of the method selected. The material supplier and the processor, with their experience in hundreds of application, can assist here. 

Prototyping The Design

The prototype is the opportunity for the designer to see the product as a three-dimensional object. This, too, is the first opportunity for checking the engineering design. The quality of the prototype is quite important. The method used in producing the prototype may not be the same as that planned for the final production line - otherwise tests may be misleading and analysis false.

If the search for the right material has been narrowed to only two or three, prototyping will help spotlight one.

Testing the Design

Every design should be given an actual or simulated service test while in the prototype stage to ensure that the obvious is not overlook and the the not-so-obvious is is taken into account. The end-use requirements dictate the design testing program. An engine part might be given temperature, vibration, and hydrocarbon-resistance tests, a luggage fixture might be subjected to abrasion tests; and a toaster knob might be check for electrical and heat insulation. Other tests, such as field testing or consumer reactions. are part of the necessary procedure for completely evaluating any design.

Taking the second look

The second look at the design provides an answer to the basic question, "Is the product doing the right job at the right price?" At this point. most products can be improved by redesigning for better production economies or for the importance functional or aesthetic changes. Weak sections can be strengthen, colors changed,a new features added. Substantial changes in design will require retesting, Now is the time to set up production.

Writing Meaningful Specifications

The purpose of the specification is to eliminate any variations in the product that will not satisfy the functional, aesthetic, or economy requirements. The specifications for the part should include such things as the material of construction by brand and generic name, method of fabrication, dimensions, color, surface finish, packaging, printing and other detail of production to which there could be more than one possibility.

Setting up the production

How many parts are required? When a large quantity is required, the number of methods of producing the parts increases. Perhaps of a casting, a forging, or a stamping may be the most sound choice. If only a few parts are require, prefabricating or machining may be the better choice.

Production Should the part be manufactured in the plant or sent out to be produced? In many cases company policy may be to produce within the plant.

After the specification is written but before the production line can start, tooling must be design, built, and integrated with the processing equipment.( In some cases, dies and molds can be started while testing in progress.) Production efficiency and economy can be realized through proper design tools. The processor is an important sources of aid in this area. 

Time factor In some instances, such as when a breakdown of a machine is holding up production within the plant, the best method of producing a part may take second place if it involves too much time.

Workforce This factor ties with time. A machine breaks down at 2 p.m. It is essential that the machine be back in operation by 8 a.m for the following day. What personnel are available to produce part, with overtime, or is there a night shift.

Controlling Quality 

Good Inspection practice requires a checklist to maintain a consistently good product. The inspection checklist, for the most part, will conform to the end-use requirements set forth in the specifications. It is beneficial to consult with the supplier or the molder, who knows the processing and finishing characteristics of the material chosen.