THE DESIGN PROCESS, DECISION MAKING AND NEW PRODUCT DESIGN 2 (continue..)

1.2.5 EVALUATING ALTERNATIVES

What is it?

The purpose of evaluating alternatives is to help the Planning Committee make sound decisions about which design strategies they will advocate in the design plan. Alternatives are evaluated to determine their effectiveness in addressing the concerns, taking advantage of  opportunities, and meeting objectives in the planning area.

When do we do it?

It is the fifth step in the basic steps of design process.

How do we do it?

After alternatives or strategies have been identified, the Design Planning Committee and Technical Advisory Committee evaluate the acceptability of the alternatives. A facilitator is used during this step, and technical advisors are available to provide information and answer questions.

Evaluate alternatives by examining the benefits and drawbacks of each alternative. During the evaluation of alternatives, careful consideration is given to social, economic, and ecological factors that influence the predicted outcome. Encourage discussion and use visual aids to help explain alternatives. Technical advisors can prepare technical specifications and a short concise narrative for each alternative. For each alternative include costs, and positive and negative benefits.

The Planning Committee considers the “effects” and the “impacts” of each alternative. The alternatives are compared to benchmark conditions to evaluate their ability to solve problems, meet quality criteria and meet the Planning Committee’s objectives. Technical advisors can help the committee evaluate the effects of each alternative and describe the impacts. The effects are outcomes or results of the management strategy. Impacts are the differences between initial conditions and the effects of the alternatives.

Public review or comment may be needed during the evaluation of alternatives. This will help inform the Planning Committee about the various effects and acceptability of the alternatives.

After alternatives have been evaluated, the next step is to make decisions as to which alternatives are the most acceptable to the Design Planning Committee.

 1.2.6 Communication:

      Communication in the design process involves the sharing and communicating the design requirements, design specifications and the designed data for the relevant purpose. The communication resembles the important space in the design process, as it is one of the major step in the design and synthesis in the design process.

      Communication is accomplished by the various means such as drawings, graphs, charts etc. The drawing includes either hand drawing or CAD drawing. Drawings are mostly used in design process, as it possesses all most all information about the component to be designed or designed. The other drawing software also used to communicate the design processes. Communication also involves the plotting and sharing of graphs, charts in the form of information. These materials also are the major modes of communication as a single graph can describe much data and information required for the further process. Drawings are mostly used in design process, as it possesses all most all information about the component to be designed or designed.

1.2.7 Feedback from Manufacturer and User

In design process, the feedback from the manufacturer and the user about the final design is very important. The manufacturer comments on the feasibility of the design, availability of the components of the design, availability of the raw materials, cost of production, possibility of mass production. Based on the comments of the manufacturer the design might have to be altered. A perfect or ideal design is most often modified to meet the manufacturer’s needs. For example, to reduce the cost of production by use of cheaper material the life of the product may be compromised. However, if the higher cost of production outcomes better performance as in efficiency of a vehicle, there is nothing to comment in the design.

The feedback from the users is also an important aspect in the design process. The users may not comment on the details of the design but their complaints on durability, ease of maintenance, ease of operation are of good help in making the product user friendly. Most often the feedback from the users is gathered through prototype of the design manufactured in a small quantity. Based on their feedback, modifications in the design are made and the new product is launched that meets the demand of the users. Also the feedback is being gathered from time to time. If bigger issues regarding the product arise, the design is further altered.

1.3 COMMUNICATING THE DESIGN:

1.3.1 DRAWING AND CAD:

Almost everything around us has been created by or is influenced by engineers. Buildings, vehicles, roads, railways, food growing and processing, books, medical care, recreation, so on. Hence, drawing and CAD plays important role in design process. A designer needs to have the skills to generate and work with this model in order to communicate ideas and develop a design. Computer-aided design (CAD) is the use of computer systems to assist in the creation, modification, analysis, or optimization of a design.CAD software is used to increase the productivity of the designer, improve the quality of design, improve communications through documentation, and to create a database for manufacturing.CAD output is often in the form of electronic files for print, machining, or other manufacturing operations.Its use in electronic design is known as Electronic Design Automation, or EDA. In mechanical design, it is also known as computer-aided drafting (CAD) or computer-aided design and drafting.

1.3.2 Charts and Graphs

This is a measure of actual performance and the theoretical performance. An outline is specified and workers are guided to work as per this outline.

Gantt chart is an example of this. It is a scheduling technique that helps is immediate comparison between planned work and the actual process of work. This helps management to take corrective measures if improving the company’s performance.

Similarly, graph may me another way of representing the ongoing progress of work. This may be used to show a two dimensional study of data and facts. Comparison of an entity with another or comparison between various entities may be done by the help of graphs.

2. Material selection:

 Material selection is a step in the process of designing any physical object. In the context of product design the main goal of material selection is to minimize cost while meeting product performance goals. Systematic selection of the best material for a given application begins with properties and costs of candidate materials. For example, a thermal blanket must have poor thermal conductivity in order to minimize heat transfer for a given temperature difference.

Systematic selection for applications requiring multiple criteria is more complex. For example, a rod which should be stiff and light requires a material with high Young's modulus and low density. If the rod will be pulled in tension, the specific modulus, or modulus divided by density , will determine the best material. But because a plate's bending stiffness scales as its thickness cubed, the best material for a stiff and light plate is determined by the cube root of stiffness divided by density . For a stiff beam in bending the material index is An Ashby plot, named for Michael ashbeyof Cambridge , is a scatter plot which displays two or more properties of many materials or classes of materials. An Ashby plot useful for the example of the stiff, light part discussed above would have Young's modulus on one axis and density on the other axis, with one data point on the graph for each candidate material. On such a plot, it is easy to find not only the material with the highest stiffness, or that with the lowest density, but that with the best ratio . Using a log scale on both axes facilitates selection of the material with the best plate stiffness .

The first Ashby plot on the right shows density and Young's modulus, without a log scale. Metals are represented by blue squares, ceramics by green, and polymers by red. It was generated by the Material Grapher.

Plot using Ashby's own CES Selector software.

The second plot shows the same materials attributes for a database of approx 100 materials. Materials families (polymers, foams, metals, etc.) are identified by the larger colored bubbles. The image is created using Prof Mike Ashby's own CES Selector software and data from Granta Design.

2.1 Information on material properties

Material selection is a part of design process which seems most important. Preference may be given to strength but what property of material is most essential is to be prioritized. Selecting a material requires information about its strength, stiffness, hardness, impact load bearing capacity, temperature effects, fatigue strength and cost of the material.

Among all properties, some of them are most important and they are given more priority. Information about single material does not suggest the selection, different materials are to be studied taking full information and compare the properties. The information will help listing all available materials and rank them in order beginning with the best material.

Strength is not the only property that will fulfill all requirements. A durable design may be done with the balanced properties of material suitable for the design. Next part of selection is related to economy. Information about the cost of material plays vital role. An economic design is preferred over costly durability.

Properties requirement varies with design. Handbooks are available with specifications of material properties. Alloys, Cold drawn, hot rolled, forged and other mechanically deformed materials and other verities of material with their properties make confusion. This is the reason for requirement of detailed information over material properties. For completeness of available materials this might require a large source of material data. As mentioned earlier, once the list is formed, select a manageable amount of materials from top of list and find out the best material with economic and balanced properties as per the design requirements.

Compiled by:

Name  :        Pradip Pantha