Taking the design of cam mechanisms as an example, its design guidelines are given below:

& The working stroke shall not exceed 20 mm.

& The working direction of cam mechanism shall be per-pendicular to the side-punching hole.

& The maximum punching force shall not exceed 10,000 N.

Figure 4 shows its design specifications.

In the standard parts design stage, the standard parts are determined, which include the type, quantity, and size for the socket head cap screws, dowel pins, stripper blots, guide posts, and plain guide bushings. At the same time, the design engi-neer needs to assemble the standard parts into the main parts.

Taking the design of socket head cap screws as an exam-ple, its design guidelines are given in Fig. 5.

Figure 6 shows its design specifications.

3 System components

After receiving all the required design information from the user, this system is able to finish the design of the progressive

die based on the design guidelines and specifications. The design of the proposed system, as shown in Fig. 7, includes a user interface, an inference engine, a design knowledge base, a design database, and CAD software. Each section is de-scribed in the following subsections.

3.1 The user interface

The user interface is responsible for the communication be-tween the designer and the system. The user interface of the proposed system allows users to input both alphanumeric and graphic information. The interface for inputting alphanumeric information is used to type the sheet thickness, progressive pitch, and path of stored files, while the interface for inputting graphic information is used to select 3D drawing files for strip layout, blanking lines, die face, punch open line, piercing lines, bending lines, side-punching lines, and cutting lines.

3.2 The inference engine

The inference engine is the core of our system. It is responsi-ble for generating the solid design of the structural parts of progressive dies based on users’ inputs. The inference engine consists of four units: a part selector, a shape calculator, a model generator, and an inference coordinator. After the de-sign information is inputted by the user using an interactive method, the types of structural parts and their parameters of solid models are automatically selected and calculated, respec-tively, by the design system based on the design procedures. Therefore, solid models are generated by the 3D CAD system automatically. In case any error occurs during the modeling process, the system will send an error message to the user.

The function of the inference coordinator is to moderate the other three units in the inference engine. Starting from the input of the design information of the user interface, the inference coordinator will design each structural parts of the progressive dies based on their design processes. For each of

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the parts, the type, quantity, position, direction, and size of the part are determined by the part selector. Then, the shape calculator starts to calculate the shape of the part and trig-gers the model generator to finish the solid model design of the part.

The part selector provides the data of the type, quantity, position, direction, and size related to the structural parts. For each of the parts, the type of part is determined by either design guidelines for the main parts or hole identification rules for the standard parts of the part selector. The part selector is also responsible for determining the quantity, position, and size of the part. Therefore, when the system is designing parts, this selector would select the type, quan-tity, position, direction, and size of the parts according to the constraints and formulas derived from the design informa-tion, design guidelines, and hole identification rules.