Design Foundation

The target of the integration of technological or non-technological subject material in an effective and efficient manner is gready enhanced by having a visible operational structure ranging from field service studies to analysis by computers. Some type of visibility is a crucial factor in bringing about integration. Visibility helps everyone find out what people are doing and why. With this approach, design may be construed as having a central foundation of activities, all of which are imperative for any design.

This foundation includes product conceptual design, design specification, detail design, manufacture, and sales. All design starts, or should start, with a need that, when satisfied, will fit into an existing market or create a market of its own. From the statement of the need a specification, or equivalent, must be formulated of the product to be designed. Once this is established, it acts as the envelope that includes all the subsequent stages in the design. It becomes the theoretical control for the total design activity, because it places the boundaries on the subsequent design approaches. Fig. 2.1 provides an example of an

: 2.1 Flow chart for designing a product from concept to fabricating the product

Product

concept

feasibility

study

Apply available experience

Conceptual product layout

Set up requirements -

Apply available experience

Conceptual product layout

Study shape, dimensions, structural loads, environments, government/industry, etc.

Target quantity, cost and production schedule

Manual approach Computer approach

Apply design creativity

Engineering analysis

Formulate plan

Geometric drawings or graphic analysis

Engineering analysis

Dimensions Et tolerances image manipulation

Structural integrity

Solid Wire Surface

Mechanical simulation

Static Dynamic

Finite element modelling

Mold/die design

Set up safety factors to meet product functions -

Mold/die design

Set up safety factors to meet product functions -

Physical integrity

Fabrication analysis

Environment Minimum weight/cost Aesthetics, etc.

Material selection Process selection -Cost analysis

Melt flow analysis Shrinkage analysis

Tool thermal analysis - Cycle time -

Tool part selection

Provide detailed individual orthotropic drawings Material

Process/equipment/tools Product service performance Plant personnel capability

Data bases and/or available information

Standard parts

Nonstandard parts

overall flow chart that goes from the product concept to product release.

Use is made of the optimization theory and its application to problems arising in engineering that follows by determining the material and fabricating process to be used. The theory is a body of mathematical results and numerical methods for finding and identifying the best candidate from a collection of alternatives without having to specify and evaluate all possible alternatives. The process of optimization lies at die root of engineering, since the classical function of the engineer is to design new, better, more efficient, and less expensive products, as well as to devise plans and procedures for the improved operation of existing products.

To optimize this approach the boundaries of the engineering system are necessary in order to apply the mathematical results and numerical techniques of the optimization theory to engineering problems. For purposes of analysis they serve to isolate the system from its surroundings, because all interactions between the system and its surroundings are assumed to be fixed/frozen at selected, representative levels. However, since interactions and complications always exist, the act of defining the system boundaries is required in the process of approximating the real system. It also requires defining the quantitative criterion on the basis of which candidates will be ranked to determine the best approach. Included will be the selection system variables that will be used to characterize or identify candidates, and to define a model that will express the manner in which the variables are related.

Use is made of the optimization methods to determine the best condition without actually testing all possible conditions, comes dirough the use of a modest level of mathematics and at the cost of performing repetitive numerical calculations using clearly defined logical procedures or algorithms implemented on computers. This composite activity constitutes the process of formulating the engineering optimization problem. Good problem formulation is the key to the success of an optimization study and is to a large degree an art. This knowledge is gained through practice and the study of successful applications. It is based on the knowledge and experience of the strengths, weaknesses, and peculiarities of the techniques provided by optimization theory.

Unfortunately at times this approach may result in that the initial choice of performance boundary/requirements is too restrictive. In order to analyze a given engineering system fully it may be necessary to expand the performance boundaries to include other sub-performance systems that strongly affect the operation of the model under study. As an example, a manufacturer finishes products that are mounted on an assembly line and decorates. In an initial study of the secondary decorating operation one may consider it separate from the rest of the assembly line. However, one may find that the optimal batch size and method of attachment sequence are strongly influenced by the operation of the plastic fabrication department that produces the fabricated products (as an example problems of frozen stresses, contaminated surface, and other detriments in the product could interfere with applying the decoration).

Required is selecting an approach to determine a criterion on the basis of which the performance requirements or design of the system can be evaluated resulting in the most appropriate design or set of operating conditions being identified. In many engineering applications this criterion concerns economics. In turn one has to define economics such as total capital cost, annual cost, annual net profit, return on investment, cost to benefit ratio, or net present worth. There are criterions that involve some technology factors such as plastic material to be used, fabricating process to be used, minimum production time, number of products, maximum production rate, minimum energy utilization, minimum weight, and safety.

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