Detail design

This section covers the key stages of transforming the chosen concept design into a fully detailed design with all the dimensions and specifications necessary to make the product specified on a detailed drawing.

The detail design process

The detail design phase lies between the concept design and manufacturing phases of the design process; it is principally concerned with the process of transforming a product concept into a set of manufacturing drawings and documentation. It should be noted that, as the design process is an iterative one, there are no neat demarcations between the sequential phases and, in reality, many of the activities will overlap or be undertaken in parallel.

The detail design process consists of five basic steps:

Step 1: Product subdivision

The preferred design concept is broken down into a number of smaller units and, as the detail design phase progresses and the product becomes more defined, this subdivision is continued down to component level. The form of subdivision decided at this stage will be mirrored in the structure of the complete manufacturing drawing set. This process enables the designers and design engineers to identify how parts will be sourced and manufactured.

Step 2: Design and selection of components and sub-units

This stage involves the designing, selection, and sourcing of the component parts and assemblies that make up the product. New components may have to be designed from scratch, and existing components may be utilized or redesigned if required, in order to successfully produce an integrated design for manufacture.

Step 3: Integration of parts

Following on from the design and selection of components, this stage sees the integration of these parts into the final configuration of the product. The design team will produce definitive whole product layouts that identify the form of each component, and will have commenced work on the general arrangement and major assembly manufacturing drawings.

Step 4: Product prototype testing

This stage involves the final prototyping and testing of the design. While the design team may have already produced large numbers of mock-ups, appearance models, and test rigs for development testing, as described in Chapter 3, it is only at this stage that the product in its final form, as intended for production, can be prototyped and tested.

Alpha prototypes are produced to represent the aesthetic design and/or function of the final product, but are not necessarily manufactured using identical processes or materials. This enables the designer to evaluate the design in detail, and avoids costly mistakes when moving toward manufacture. These alpha prototypes are tested and refined through a series of iterative steps before being signed off, when the design engineers can begin to produce what are known as beta prototypes, which evaluate the actual processes or materials intended for manufacture.

The value of prototyping and testing cannot be underestimated, and, as Chapter 3 explained, prototypes enable designers to undertake user testing and market evaluation as well as aid in the preparation of test specification and manufacturing procedures. The aim of this stage is to further define the evolving product and to modify components, parts, and drawings in order to address any issues that emerge through the testing process.

Step 5: Completion of release drawings

The final stage is the completion and signing off of the manufacturing data and the approval to commence full-scale manufacture. During the detail design stage, the design team develop the design in increasing detail, ensuring that all changes and drawing modifications are systematically recorded, with each change or “issue” controlled by the design manager/team leader. The release drawings, or release package, will contain final instructions in the form of drawings, diagrams and digital data about the product’s form, dimensions, manufacturing processes, tolerances, materials and surface properties of each non-standard part and assembly. It will also contain information regarding the overall arrangement and the sourcing of standard and proprietary parts. The structure of these release drawings will reflect the product subdivision of Step 1 and will be uniquely numbered in accordance with national standards, procedures, and conventions such those set by the American National Standards Institue (ANSI), British Standards Institution (BSI), or the International Standards Organization (ISO).