Home > User Area > CES Selector Documentation > Process Case Studies > Window Handle

Window Handle Case Study

The selection methodology used in CES Process can be encapsulated by developing a case study. Here, we will use the design of a simple window handle to illustrate the development of some selection criteria, we will apply them and plot them on some selection stages by using CES.

The Design Problem

For every component design there is a desired set of attributes. Consider a handle for a metal-framed window which clamps the window shut when it is rotated. It is decided to make it from a zinc-based alloy, but which process should be used to manufacture this part? The handle must have a high surface finish or roughness of 1-2mm and a tolerance of 0.2 mm and should be produced in a batch size of 1 million without the use of secondary machining operations.

Fig. 1 Window Handle

Design Requirements

First, we must identify the 'desired attributes' of our process - the Material, Process and Shape Classes, and the Physical and Economic attributes. There are approximately 40 attributes to chose from, but not all will be required to identity candidate processes for any given application.

The required attributes for the window handle are shown in Table 1. Using CES Process, these attributes can be plotted on a series of selection charts from which the processes that satisfy the design requirements can be selected.

Material Class Non-ferrous metal (Zn-based alloy)

Process Class Primary, discrete

Shape Class 3D-solid

Size 0.1 kg

Minimum Section 3 mm

Precision /Tolerance 0.2 mm

Surface Finish 2 mm

Batch Size 1,000,000

Table 1 Window Handle: design requirements

The Selection

Processes which can produce 3D-solid components with a tolerance of 0.2 mm can be clearly identified from the chart of Tolerance plotted against Shape Class (Figure 3).

Figure 3 A process selection chart of Tolerance plotted against Shape Class

The cost of manufacturing a particular component is critical in the selection of a process. The Cambridge Process Selector provides a guide in the early stages of design by ranking the most suitable methods. Economic attributes of: cost per component, batch size, tooling cost and capital cost can all be selected. Here a chart of Economic Batch Size plotted against Process Class is needed, and is shown in Figure 4

Figure 4 A process selection chart of Economic Batch Size plotted against Process Class

Results

The selection charts, in combination, indicate that the processes that satisfy all of the design requirements are:

Processes Passing All Stages

Die casting

Powder Injection Moulding

A detailed economic analysis will need to be made before a taking any final decision on the choice of a manufacturing method, but it's scope has been reduced to just two processes.