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That's right, NC software is smarter.

NC programming software systems, offered either as stand-alone application systems or as a component in a full CAD/CAM system, have traditionally been provided as a set of software tools to be fully utilized by the NC programmer. Knowledge, expertise, and decision-making capability have been totally associated with the programmer and have not been contained within the software or the CNC hardware.

According to Alan Christman, vice president, CIMdata Inc, Ann Arbor, MI, that is changing, though there is some question about how quickly and to what extent so-called knowledge-based engineering (KBE) and one of its fundamental building blocks, generative machining, will be widely available. Here's his assessment of KBE progress:

Increasingly, leading software vendors are tailoring systems to solve specific engineering, manufacturing, and management problems. Languages and other software toolkits are readily available to develop these knowledge-based systems. Using them, the knowledge of experienced users can be captured in a software system. Constraints, rules, and models are defined, and the application software is developed to automate an operation or to provide guidance to a user.

Until now this technology has been only minimally applied to NC programming software in production environments. However, the potential of adding "intelligence" to NC programming software is at hand with some NC vendors introducing KBE-oriented product capability and a number of user organizations developing their own application capability.

Knowledge-based engineering software contains information about objects, attributes, events, situations, and courses of action that emulate the reasoning processes of human experts in a given field. As such KBE is a more encompassing term than generative machining. In addition to the input and output associated with generative machining, knowledge-based engineering may also encompass the entire tooling process including, fixturing, utilization of all machining resources, and costing. The results may be utilized to automate the process and/or to provide data for review by the programmer or operator.

Generative machining software automatically generates a machining process plan and the associated toolpaths to machine a part. Input to the system typically includes the machine tool characteristics, material of the part, the shape of the starting material, individual form-features, tolerances, and description of the final product. The generative machining codes produce the machining sequences, individual setups required, form-features to be machined in each setup, cutting tool description, feeds, speeds, depth of cut, and associated toolpaths. The system would flag a design that could not be machined with available equipment or a programmed sequence that could not performed for any reason.

Form-feature machining is typically used as a base building block for generative machining and KBE. In form-feature machining a library is developed that contains 1) the geometric definition of a series of form-features, and 2) an NC knowledge base built on experience to define the machining process used to create each form-feature. The NC part program used to cut each form-feature can be created from the information stored in the library.

Examples of form-features include through-holes, blind holes, slots, pockets, chamfers, fillets, rounds, and other features. User-defined form-features are also essential and should be part of any system. The capability should also be available to parameterize form-features. In a production environment, multiple form-features would be grouped into appropriate setups for machining. The information in this library could also be used to advise the product designer of manufacturing considerations when producing the base design.

How KBE works

KBE is generally used either to 1) automate relatively simple and repetitive operations, and/or 2) provide choices or guidance to the operator in more complex environments. In all cases an operator override capability should be provided. Simple operations lend themselves to automated operation; the greatest return to the user would likely come from providing guidance in more complex environments. The highest priority areas for KBE implementation in terms of machining operations are 3-axis milling, 2.5 axis milling, turning, and holemaking, which account for as much as 75% of machining use.

One target for KBE-oriented NC is prototype production. In this environment frequent changes are made to a base model; there is likely to be similarity with other production parts; and the timeframe to complete tasks is usually very tight. KBE opportunities for either an automated or a guidance system are significant. KBE-based NC is also appropriate in production environments and in one-of-a-kind environments in which the product has considerable complexity.

Primary focus of KBE systems in the machining process are tooling and toolpath generation; within tooling, tool optimization, preferred tooling, and tool selection functions. Users typically expect KBE technology to be provided by their CAD/CAM or NC supplier. Relatively few expect it to be provided by a KBE application vendor or a CNC hardware vendor. Also relatively few expect to fully develop the technology with their in-house staffs. Most users expect a vendor to provide a toolkit as opposed to a turnkey application system.

There is very strong support for data dependency software. In this environment the dependent data in machining can be immediately re-created when base design or process data are modified. Users overwhelmingly regard this as important. There is also substantial support for capturing non-machining attributes such as cost, schedule, resource availability, and the like to build a more complete knowledge-based system.

As with any new technological wrinkle there are a significant number of obstacles or concerns expressed with regard to implementing KBE in an NC environment. These include the extent key resources are required to implement a KBE application, the time required to implement, the availability of KBE technology, and the emotional concern that could be expressed by the NC programmer with regard to potential loss of control or their job. These obstacles are well understood by the user community. The upside is freeing them from routine programming to take on profitable new business.
COPYRIGHT 1995 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1995 Gale, Cengage Learning. All rights reserved.

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Title Annotation:knowledge-based engineering programs
Publication:Tooling & Production
Date:Feb 1, 1995
Words:957
Previous Article:Forming the fabricating future.
Next Article:Modular gaging and quality manufacturing.
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