Information Technology Reference
In-Depth Information
2.3 Machine table, chip removal and coolant system
The table and chassis of the machine are very important considerations in SPMs. Based on
technical considerations and machining properties of the workpiece material, the table
and chassis are properly designed or selected from the standardized SPM chassis. Due
to high machining forces resulting from machining operations the machine table and
chassis should be sufficiently rigid to avoid vibrations. It is also very important to
consider appropriate coolant and chip removal mechanisms in design of machine table
and chassis.
3. Design and manufacturing
Because production process is systematic, planning for design and manufacturing has an
effective influence on the success of any project (Lutters
et al.,
2004). The flowchart shown in
Figure 8 represents all necessary steps for proper analysis, design and manufacture of SPMs.
These steps should be followed in order to achieve feasible results in SPM design and
manufacturing.
3.1 Technical and economic analysis
As the cost of SPM design and manufacturing is relatively high, critical technical and
economic justification of utilization of these machines should be made before any attempt
to design and manufacture them. This includes an analysis of machinability of the
workpiece, and a comparison of the production costs with other production alternatives
considering production volume and machine amortisation period. For technical feasibility
analysis a number of questions will be asked and the user needs to answer these questions
interactively. These questions investigate quality of workpiece material and its physical
and geometrical characteristics to determine whether or not it can be machined with
SPMs. The flowchart shown in Figure 9 describes the type of questions asked for technical
feasibility analysis. If the answer to any of the questions is “No” then the workpiece is
considered to be “Not Suitable” for machining with SPM and its processing will be
terminated.
Upon completion of technical feasibility analysis, an economical feasibility
analysis is performed. To do so a detailed computation is needed in order to determine
the cost of machining a unit of product using SPM. Then the same computation is
repeated for traditional and CNC machines in order to achieve a unit cost comparison for
different methods, and to find the one that results in a lower cost. For determination of
unit cost so many factors are taken into consideration including machining time,
production volume, machine cost, cutting tool cost, labour cost, overhead
costs, depreciation cost, interest rate, etc. A case study is presented in Section 5 that
provides a detailed economic analysis for a sample part. It is noteworthy that sometimes
it is necessary to repeat the economic analysis before the final approval of SPM
design. This happens when more accurate information on the cost of SPM and
required accessories become available. This is represented by a dashed line in the
flowchart of Figure 8.
