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ComputerAided_Design_Engineering_amp_Manufactur.pdf

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Depending on the type of feature to be machined, the machine-tool, material, cost and machiningsetup<br />

experts are also activated. The activation of these experts is controlled through the control<br />

expert.<br />

3. For each one of the machining processes, the machine-tool expert determines the number of<br />

setups and the setup times required for machining the feature on a machine tool capable of<br />

generating that feature; the material expert estimates the tool life of a standard cutting tool for<br />

machining the feature; the cost expert determines the production cost for machining the feature.<br />

4. Next, the surface-finish expert estimates the amount of surface roughness zone that can be achieved<br />

by the machining process for a desired surface quality. This expert also establishes the machining<br />

cost required by the finishing process in order to achieve the desired surface roughness zone after<br />

the feature has been machined using a roughing operation.<br />

5. The control expert then determines the machining index, which is a weighted sum of the inputs<br />

provided by the machine-tool, material, cost and surface-finish experts. Subsequent to this, the<br />

control expert selects the machining process with the best machining index. The setup expert<br />

determines the setup face to be used for machining the feature.<br />

6. After establishing the machining processes for each one of the features, the control expert passes<br />

control from the phase 1 BB to the phase 2 BB. The setup expert sequences the setups so that the<br />

maximum number of features can be machined in one setup. The sequence-planning expert then<br />

studies the setup sequences and determines the sequence in which the different part features would<br />

be machined. The phase 3 BB is next activated by the control expert.<br />

7. For each one of the machining processes to be used for machining the features, the surface-finish expert<br />

determines the amount of material to be removed in the individual machining processes. The different<br />

experts from the machining, machine-tools, cutting-tools, and machinability domains determine the<br />

machinability parameters using standard data handbooks and machining process models. On the basis<br />

of the data posted on the phase 3 BB data base, the control expert determines if the features require<br />

any additional finishing operations. In the even that the feature does not require any additional finishing<br />

operations, control is passed over directly to the phase 5 BB. On the other hand, if the feature requires<br />

additional finishing operations, then the phase 4 BB is initiated.<br />

8. The surface-finish expert determines the finishing operations to be used for generating the desired<br />

surface roughness zone of the form feature. This selection is based on the capability of the finish<br />

machining processes. Next, the machinability parameters for the finishing operations are determined<br />

using standard data handbooks and machining process models in conjunction with the machinetools,<br />

cutting-tools, and machinability experts. These data items are posted on the phase 4 BB,<br />

and the control expert then activates the phase 5 BB.<br />

9. Depending on the desired surface hardness of the part, the heat-treatment operations expert<br />

estimates the depth of hardening and the heat-treatment operations that can achieve it.<br />

10. After the successful generation of the process plan, the NC tool path planning module is activated in<br />

order to generate the NC tool path to be adopted for machining the features on an NC machine tool.<br />

The NC tool path planning module requires the following input information: (a) feature geometry<br />

information as obtained from the FBDS system, and (b) feature processing information as obtained<br />

from the BBPP. The four stages involved in the generation of the NC tool path (Figure 1.10) are<br />

• Selection of appropriate machining approach (either contour or edge-based), depending on the<br />

type of feature to be machined<br />

• Generation of the NC path depending on the type of feature to be machined, geometric configuration<br />

of the feature base surface, and cutting-tool specifications for both contour and edgebased<br />

machining approaches<br />

• Generation of machining volumes that represent the volume of material to be removed from<br />

the raw stock for generating the specific form feature, depending on the NC path, machining<br />

criteria, and cutting-tool specifications<br />

© 2001 by CRC Press LLC

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