The various process capabilities

Manufacturing Process Selection

The selection of appropriate processes to apply to a particular material is based upon the matching of the required attributes of the product to the various process capabilities. Others factors also influence process attributes, such as cost, production rate, flexibility, part quality and the lot size of the parts to be produced, and the material's physical properties. A list can be prepared giving the essential geometrical features, material properties, and other attributes that are required, when the overall function of a part is determined [11, 19, and 20].

The systematic selection of manufacturing processes to meet quality and cost requirements has been given considerable attention. Systematic material and process selection aims to influence this initial decision on which combination to use, before the detailed design of the part is carried out and before detailed process planning is implemented. Selection of the process deals with geometric design and material, and fulfils the design requirements. A variety of supplementary sub-processes may be needed in a process to achieve the design requirements, which complicates the problem of process selection.

Selection Criteria

The following factors have a primary influence on the selection of a manufacturing process: geometry, materials, accuracy, surface finish, productivity, lead time, minimum part count and non-geometric quality measures [8, 11, 13, 19]

The geometric shape of the product has a significant effect on the selection of processes. The determination of geometric parameters must be taken into consideration before any secondary processes are chosen.

Choosing one material from the many available is the general problem of material selection. In the design process, this proceeds from the initial consideration of broad classes of materials to the testing and evaluation of specific materials. It is essential that the material requirements be specified in terms of product function and end use.

In some cases where the material properties requirements and needs are strict, it may be practical to set up specific material alternatives prior to the consideration of processes. But it is generally recommended that process alternatives should be developed before materials alternatives. It is usually easier to fit a material to a process than to fit a process to a material, unless the requirements limit the number of acceptable materials. The fact that materials requirements are normally not generated prior to process selection does not mean that material parameters do not influence process selection [8].

There are some other factors which can have an effect, such as lead time requirements which can greatly affect the economic feasibility of a process. Minimum part count criteria are a further aspect of process selection. This criterion ensures that joining and assembly considerations are taken into account if necessary.

In addition, non-geometric quality measures will be involved the measurement of functional quality and may, for example, be concerned with electrical or thermal properties.

Significantly, general information on manufacturing processes is available in a wide range of resources such as textbooks and manufacturer's handbooks. Analysis of each process can be conducted to determine the range of its technical capabilities in terms of the attributes of the parts that can be made.

Selection Processes

Selection processes are step by step methodologies that must be followed by designers in order to make decisions efficiently.

There are a wide number of tools and techniques literatures for manufacturing process selection, as shown in table.... The methodology which has been adapted here as a baseline in assessing the suitability of the candidate process, is shown in Figure... [8, 11, 13, 19]

A systematic approach, in which the concurrent design of products and their related processes, including their manufacture and support, are integrated.

Analysis of the design or prototype to simplify the structure of the product and optimize part count. Selection of material and investigation of the possibility of joining (assembly). Next, consideration of the problems of component handling and fitting processes, and then selection of the appropriate manufacturing processes.

Quality Function Deployment (QFD) [8, 13]

A systematic technique for identifying those product features which contribute strongly to product quality, and thus where engineering effort is needed. The QFD technique consists of matrices that represent customer requirements, engineering characteristics, process planning and production planning. Selection of manufacturing processes is based on the result of component design of the product.

Process Information Maps (PRIMA) [11]

This technique presents knowledge and data on areas including material suitability, design considerations, quality issues, economics, process fundamentals and process variants. It starts by outlining the process itself (how it works, its capabilities and limitations, and quality). From this point, the technique can be used to estimate the cost of manufacturing and assembly.

Failure Modes and Effects Analysis (FMEA) [13]

Preventive quality method involving the examination of design and production drafts for possible weak points in the planning stage. This technique starts by assuming a failure and focuses on the modes that could cause the failure to happen. Preventive or corrective measures can be taken after assessing the effect of possible failure modes at all levels, by drawing the effects of component failures through sub-systems to system failure modes. The results can be used to analyse appropriate manufacturing process choices.

Selection Processes of Manufacturing Process. Adapted from [8, 11, 13, 19].

The structure of this methodology was developed in accordance with a phase to phase product development process, so that the designer can understand easily how and when the process started and what factors must be considered in the selection processes of the manufacturing process. It can be seen that the selection criteria (as described in section ...) are composed closely to (alternatives) manufacturing processes. This relationship is purposed to show that all criteria must be considered to select the appropriate (candidate) manufacturing process gradually. In the next step, factors involving cost estimates, components and assembly are also measured regarding with product design specification (PDS). In addition, some alternative business strategy be considered before conclude the selected process.

A reasonable number of possible alternatives will normally be available when selecting manufacturing processes. The procedure used for selecting manufacturing processes is to examine the alternatives against economical and technical aspects of the selection criteria. This is a decision making problem. Thus, the problem of manufacturing process selection can be defined as follows: From the evaluation of a set of alternatives, an alternative is selected that can satisfy customer needs, meet design requirements and fit the technical capabilities.

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