SEED Guides Selecting Manufacturing Processes < >

2. Introduction

The need to provide the design activity with information regarding manufacturing process capabilities has been recognised for many years (2) and some of the work that has been done to address this problem will be touched on below.

There is relatively little published work in this area; the texts on design rarely include relevant data and while a few of the volumes on manufacturing processes do provide some aid in terms of process selection and costs (3-7), the information is not sufficiently detailed and systematically presented to do more than indicate the apparent enormity of the problem.

Typically, the facts tend to be process specific and described in different formats in each case, making the engineer's task more difficult. There is a considerable amount of data available but precious little knowledge of how it can be applied to the problem of manufacturing process selection.

The available information tends to be inconsistent: some processes are described in great detail, whilst others are perhaps neglected. This may give a disproportionate impression of the processes and their availability.

Information can also be found displayed in a tabulated and comparative form on the basis of specific process criteria (M4). While useful, the design related data tends to be limited and no or very little detailed data is included. Such forms may be adequate if the designer has expertise in the respective processes, but otherwise gaps in the detail leave room for misconceptions and may be a poor foundation for decision making.

Manufacturing catalogues and information can be helpful, however, they tend to be sales orientated and again, data is presented in different formats and at various levels of detail. Suppliers rarely provide much on design considerations or information on process capability. In addition, there are often differences in language between the process experts and the users.

As mentioned previously, selecting the right manufacturing process is not always simple and obvious. In most cases there are several processes that can be used for a component and selection depends on a large number of factors. Some of the process selection drivers are listed below:

Figures 1 and 2 provide a guide to the range of materials and processes that are widely available, and which compound the problem stated above.

As can be seen from the above, to be competitive the identification of technologically feasible manufacturing process and the determination of processing cost and quality issues are a vitally important aspect of concurrent product development. The benefits of picking the right process can be enormous (see Figure 3).

The placing in the design cycle of process selection and detailed design for processing is illustrated in Figure 4. The first step is to analyse the design with the aim of simplifying the product structure through the identification of those components which are candidates for elimination or consolidation with mating parts. This must be done with due consideration for the feasibility of material and process combinations. In the case of materials selection, a number of useful approaches are available and the reader is directed to references (8)(9).

The next step is to study the problem of component handling and insertion, and ensure that the components are designed to suit the manufacturing process selected. The estimation of component and assembly processing costs is important in the trade-off analysis. The left hand side of Figure 4 can be facilitated by Design for Assembly (DFA) techniques (11-13) while the right hand side is addressed by work including (1)(14)(15).

Figure 1 General classification of materials

Figure 2 General classification of manufacturing processes

Figure 3 Contrast in component cost benefits for different processing routes

Figure 4 Outline process for design for manufacture including process selection