Design - BEng 2 - DSGN 205


Two types of cost are of interest:

a) The cost of actually carrying out the design work - this may include the costs of developing manufacturing procedures and writing documentation for customers and service engineers, etc.

b) Estimating the cost of manufacturing the product so a selling price can be established. This must obviously include some amount towards the recovery of the design costs from (a). Once a selling price is selected the company can assess how competitive the product is likely to be.

The use of computers in assisting with design work has been a major factor in improving the quality of manufactured products since the 1950s. Computers now carry out a huge range of design tasks from routine repetitive analysis using spread sheets, to highly sophisticated analysis to simulate behaviour under a wide variety of loading, including inadvertent overloading, such as crash test simulation of automobiles. This has meant that fewer people are needed to carry out routine calculations, however there is a great need for engineers to be able to critically appraise the results provided by computers.

a) Organisations with experience usually have historical data from which reasonable estimates can be made for: design hours, computer time and production of documentation. However late changes in specification will lead to cost increases, which may be considerable.

b) Working out the cost and the selling price of a product is difficult as there will be some time delay between the cost calculations and putting the product on the market, during which time a whole range of costs will probably have changed to some extent. It should be noted however that most of the product costs are substantially 'fixed' at an early stage of the design when the general outline of the product, materials and production processes are decided. Hence it pays to plan carefully at the earliest stages of a project.

Further information - 'Total Design', by S Pugh, chapter 5 and

'Case Studies in Engineering Design', by C Matthews, chapter 17.

Return to Module Introduction David J Grieve, August 1998.