ComputerAided_Design_Engineering_amp_Manufactur.pdf

strong reasons to support a move to 3-D CAD representation of progressive dies:
1. In an automated design environment where most of the design tasks are left to the computer, it
is important to provide the designer with an effective tool to perform the final inspection of the
die assembly. A 3-D model is the ideal visualization aid for the designer to use to check for and
correct any mistakes made by the design automation system.
2. Similarly, a 3-D model of the strip can be laid on die assembly both in the open and shut positions.
This provides a fast and effective means for the visual confirmation of the total solution. Any operational
problems that may be caused by the interference of the strip with the die can be picked up quickly.
3. An accurate CAD representation of the non-standard components can be used directly to program
the NC codes required for their fabrication.
4. Many CAD/CAM systems provide aids to produce 2-D drawings from 3-D models. Hence, traditional
die drawings can still be produced very quickly.
3-D CAD models can be produced from the engineering model in several ways, depending on the
capabilities of the knowledge-based system and the CAD system. For example, functions can be written
in the knowledge-based system to scan the engineering model and translate it into neutral file descriptions.
Macros can be written in the CAD system to read these neutral files and generate the 3-D CAD
model. Alternatively, the knowledge-based system can fire functions to generate solid modeling kernel
data files for each and every component. These files can then be read by a CAD system.
Figure 7.15 shows the exploded view of a punch plate subassembly generated using the MBR approach.
Figure 7.16 shows a partial assembly of a two-stage piercing and blanking die generated using some of
the techniques described.
7.13 Feature-Based Process Planning for the Manufacture
of Progressive Dies
There have been many attempts to automate the process planning function for the manufacture of
engineering components. Invariably, these systems involve a machining feature extraction function to
transform the geometrical and topological information of a product model held in a CAD system into
relevant machining features such as holes, slots, fillet, chamfer, etc. This approach involves the use of
complex algorithms that consume a considerable amount of computer resources.
There is no need for the feature extraction task if one adopts the MBR approach for die synthesize.
This is because the machining features can be extracted directly from the engineering model of the die
stored in the knowledge-based system. For example, the following machining features can be deduced
from the model-based description of the punch plate:
• Dowel holes are straight thru circular holes.
• Holes for screws on punch plate are threaded counterbore holes.
• Retaining holes for straight punches are non-circular thru holes.
• Retaining holes for block punches are rectangular thru holes.
• Retaining holes for circular shoulder punches are counterbore holes.
• Retaining holes for non-circular shoulder punches (i.e., with keys) are complex features consisting
of a thru hole and an irregular pocket.
• Retaining holes for pilots are counterbore holes.
Similarly, formulas for the calculation of dimensional and geometrical tolerance values for these
machining features can be programmed as methods in their object representations. In other words, the
MBR approach is able to generate sufficient information to initiate the automated process planning task.
Hence, the framework identified in this chapter can be extended to perform the process planning task if