Product development and computer aided design

Work undertaken by a drawing office will vary considerably with different branches of industry. Generally, work of a 'design and make' nature will follow a plan which sets out stages in development from the time a potential client makes an enquiry until the completed product is delivered. The function of the product will dictate many of the associated activities.

A vehicle manufacturer will not design and make all of the parts used but subcontract components from specialists. The engine incorporates electrical and mechanical components and these need to conform to agreed specifications. They must also be designed for installation in specified areas and be suitable for operation in well defined conditions. Component manufacturers strive to improve quality and performance in conjunction with end user.

The stages in design and development for components in this category are shown typically, step by step, in Fig. 2.1.

1 A client requiring a certain product is often not completely familiar with specific details and needs the experience and advice from a specialist producer to clarify initial ideas. When a range of viable alternatives is presented, opinions can be focused and firm decisions made.

2 The Chief Engineer in a company has the responsibility of producing the company specification for a product. He will no doubt seek advice where aspects of the total design are outside his range of experience, and where design is involved on the fringes of Technology. However a top executive plan needs to be carefully prepared because at the outset the company must know whether or not it wishes to entertain, or get involved with, design proposals to satisfy the client. For example, while rewards may well be great the firm may not be able to cope with the scale of financial and labour demands and delivery requirements in view of current work. They simply may not wish to take the risk and, in view of available production capacity, the firm may prefer not to tender for a possible order.

1 Clients requirements

2 Company specification

2A Preparation of top

produced by chief engineer

executive plan

3 Intial design concept

3A Consultation with interfacing specialists: design and production engineers, quality controllers, metallurgists, etc.

3 Intial design concept

4 Agreed design concept

5 Preparation of working drawings

7 Prototype manufacture

9 Test results


Production drawing and




Make product and confirm

production specifications



Development program

for field trials

15 Design release for manufacture

16 Production plant and tooling

17 Production sample

18 Full scale production

3A Consultation with interfacing specialists: design and production engineers, quality controllers, metallurgists, etc.

3B Allocation of specific activity requirement

4A Provisional customer acceptance regarding installation: space etc.

5 Preparation of working drawings

6 Design review

6A Manufacturing and costing economics, future repeatability guarantees


7 Prototype manufacture

8 Confirmation and testing

8A Verification and development

10 Design review

10A Audited technical analysis

14 Final product design input review

14A Final design verifications

15 Design release for manufacture

17A Verification of manufacturing production processes

3 Drawings at this stage should be regarded only as provisional. The exercise is needed as an aid to thinking around the problem, with contributions being made by specialists within the firm to ensure feasibility.

CAD has many virtues at this stage of primary design. All information, defined in mathematical terms, can be stored in the system and manipulated on the display. After the basic geometry is established, design variations can be kept and in redrawing alternatives, sections of the previous proposals which were found to be acceptable can be used repeatedly. At any point in development the designer can take a printout, so that suggestions and comments can be made by other technical staff.

It is essential that the Company should appreciate the extent of their commitment if a firm order is accepted at a later date. This commitment includes not only the technical ability to complete the design and manufacture a satisfactory product but also the financial issues relating to its introduction on the factory production line.

4 With the completion of preliminary design work an agreed design concept will have been established, but it is necessary to obtain customer approval before work continues. If our product is to be used in conjunction with others in a large assembly, then, for example, expected overall dimensions and operational parameters need to be confirmed with the client before money is spent on further development.

5 If all is well, working drawings will be prepared. These are not production drawings—at this stage, we as a company have only ensured that our proposals are in line with requirements and that hopefully we shall be able to deliver. The object now is to prepare working drawings to formulate construction methods.

6 A design review is necessary to check the feasibility of manufacturing, to ensure that all aspects of design requirements have been incorporated in an economic manner and to guarantee future supplies.

7 A prototype or a small batch may now be manufactured. The ultimate production methods of manufacture will not be employed here. For example, components which may be moulded could be machined from solid to eliminate casting costs.

8 Prototypes are used for testing to make certain that operational requirements of the specification can be achieved. As a result design changes may be necessary. Product tests cover all areas where the component will be expected to function without failure, and these could include use in extremes of temperature and humidity, also when subject to shock, vibration and fatigue.

9 Proven test results are vital to confirm the validity of these tests.

10 A design review and analysis ensure that progress at this point will be acceptable in every technical aspect to each responsible member of the team.

11 Production drawing can commence now that the performance targets from the prototype have been confirmed. Drawings of the prototype will be reviewed and modifications made to use full scale production processes during manufacture. For plant to be used efficiently plans need to be prepared for loading and progressing work through the factory. The necessary documentation now commences.

12 Manufacture of the final product following production of the prototype has involved modifications and different manufacturing processes. It is therefore prudent to check that the specifications can still be kept.

13 Following trials where the equipment is used in its operational environment and its performance exhaustively checked, the design details can be released for full scale production.

14 Production involves not only the use of machines, but many jigs, fixtures, tools, gauges, inspection procedures need to be planned, and auxiliary equipment designed to move materials on and off production lines.

15 Inevitably teething troubles occur and samples are taken to verify that all plant and equipment operates as planned. Economic production requires that downtime is eliminated before full-scale production commences.

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