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NC software - how it stacks up.

More than 50 US software vendors produce NC software; worldwide, the total is more than 100. With such a large number of vendors producing NC software, the range and diversity of features among the various programs is huge. For example, some NC programs use a command-line prompt interface, while others offer a TABULAR DATA OMITTED graphical user interface. Four- and 5-axis surface milling support is offered by some, but not by all. All in all, there are dozens of attributes by which the quality of an NC program may be evaluated.

The methodology

In order to determine what features are most important to NC software users, CIMdata conducted a survey of 30 American users who completed a nine-page questionnaire structured to determine the features users look for in NC software and how important those features are relative to others.

Once the important categories were determined and weighted through user surveys, CIMdata went to the companies that produce NC software to determine how they view each other' products. To make this assessment, each vendor was asked to state its primary and secondary competitors for each category. By consolidating the information, a measurement of the overall competitive position of each vendor as seen by the other vendors was obtained. Thus, the 13 most important categories were determined by the users, but the company rankings within each category were determined by the NC software companies. As such, the vendors' appraisal considers not only its competitors' product capabilities but also its sales strength, market presence, marketing capabilities, and pricing practices. The rankings discussed in this article are an integration of all of these considerations.

The process used to obtain the competitive weighting factor was to assign two points for each time a vendor was listed a primary competitor and one point for each time a vendor was listed as a secondary competitor. The values were then totaled to provide a competitive weighting factor. On this basis, the top ten companies in each category was determined.

What's important

The average importance for each functional area within the survey is shown in the accompanying table. Users were asked to evaluate several aspects of each functional area listed and assign a rating of 1 to 5 for each. The "Importance Factor" thus represents an average of all responses of all users within each functional area.

It can be seen from the table that deviation control and collision avoidance are the most important functional areas among users. Along with base machining capability and 3-axis surface milling, they are the only functional areas ranking above 4.0 (between very important |4~ and critically important |5~).

Deviation control

Clearly, deviation control and collision avoidance is a key component of all machining because it directly impacts product quality, time to market, material generated, and machining costs. The individual functions within this group that are rated as having the greatest priority are: stepover control by distance, consideration for back side of tool, consideration for full-tool shape, control of scallop height, the capability to pick part surfaces to avoid, and the capability to pick check surfaces to avoid.

Base machining

The types of functions included in the base machining category include canned cycles, cutting tool support, undo and redo, associativity, and entry and exit controls, etc. These are all recognized as providing a base machining functionality that is important for all users.

The general machining group is based on 23 features including base machining capability such as canned cycles and cutter support, providing machining process plans, associativity between geometry and the toolpath, display of material to be removed, and entry and exit controls.

Users rated this group second in importance with the most important features being entry and exit and interactive toolpath editing. The least important features are support of barrel-shaped and torical tools, and automatically generating and interactively editing the process plan.

3- to 5-axis surface milling

Surface milling software is generally viewed as the most complex NC software and often most distinguishes one vendor's product from another. Although the bulk of the workload may not require this level of sophistication, it can make the difference between being able to do a job or not. Since most of the users in the survey were also the most experienced individuals in the user community, they are for the most part the ones performing the most complex machining operations. As such, they fully recognize the importance of surface milling software. Three-axis surface milling is more commonly utilized than either 4- or 5-axis surface milling, and as such, it is viewed as more important.

The most important features in this group are climb milling, machining of trimmed surfaces, and machining of multiple trimmed surfaces. The least important features are machining of untrimmed surfaces, parametric machining, and user-specified machining perpendicular to a curve.

Design features

The functional category of design features is rated at an importance level of 3.92 and is based on 37 features including general drafting, 2D wireframe modeling, 3D surface modeling, solids-based design, form feature design, integrated wireframe, surface and solid geometry, and other design functionality.

The most important features in this group are creation of surface models, blending two surfaces, creating surfaces of revolution, and creating ruled surfaces. The least important features are having the system present design alternatives, anticipate user actions, and be based on a 3D parametric design paradigm.

The overall ability to create a surface model and the capability to blend two surfaces are viewed as the most important design capabilities. Blending of four or more surfaces is viewed as somewhat less important than two surfaces, because it is a less common situation.

Of the various surface types available to users, creating a surface of revolution and creating a ruled surface are viewed as the most important. However, the capability to create all surface types is important, and none received less than a 4.0 rating. It is essential to users that the fundamental design capability be present in the design system. It is interesting to note that NURBS and Bezier are rated as equally important by the North American users.

The variance of the data for this category is greater than most categories. For an individual feature, one might have numerous inputs stating that the feature is critical (5). However, a few individuals rate it as not important (1). This, of course, is directly related to whether or not design is also done on the NC system, or whether the design is imported to the NC system from a CAD system.

Solids-based machining

Solids-based machining received an importance rating of 3.85 in the survey. The use of solids in design is in its early stages, and relatively little production machining is actually being accomplished directly on solid models. To the extent that a solid model is created in design, surfaces are usually extracted from the solid, and then the NC programming is performed on the surface model. However, it is apparent from the ratings that users recognize the potential benefits that can be obtained from working with solid models as a base.

The most important features in this group are automatic collision avoidance and extracting surfaces from a solid. The least important features are the capability to simulate tool wear and to simulate forces on a tool.

It was clear from the survey that users want to operate on solids in the same way that they operate on solids in the same way that they operate on surfaces. They want automatic collision avoidance, to extract surfaces to machine, to machine in 2-, 2 1/2-, and 3-axis, and to machine multiple surfaces on a solid. It is also important to have an integrated solid/surface/wireframe capability supported by a single data model to allow users to operate in any mode.

Visualization and verification

The capability of visualizing the machining operation and verifying that material is being removed as intended has received a 3.79 importance rating and has become increasingly important over the recent past.

The specific features that support this capability and have the greatest importance are gouge detection, display tool tip, display contact point, display entire tool, and collision detection.

Visualization of the cutting operation and verification that neither gouging nor collisions are going to occur is a very important function. If this can be accomplished on the screen without the actual machining of a test part, considerable time and dollar savings can occur.

Machine tool support

Machine tool support encompasses post-processing and other functions that generally occur subsequent to the NC machine-tool programming function. The overall importance rating for this grouping was 3.75, with the highest prioritized functions within this group going to outputting in APT source and user customization of order format.

User customization of post-processors is important to users. Users want customized post-processors and the ability to build them in their own order format and content with their own error checks. Outputs must be provided in both an APT source format and a CL file format.

This portion of the survey revealed that users have not yet accepted the geometric dimensioning and tolerancing methodology. At a 2.7 importance rating, it is the lowest rating of all functions in the grouping. Other low-rated functions are direct generation of machine control data without using an intermediate format, and outputting in a Compact II format--once heavily used with the MDSI time sharing NC service--is now fading from the NC scene.

General NC programming

Two- and 2 1/2-axis machining comprise the bulk of the machining activity that is now undertaken. The importance of 2- and 2 1/2-axis machining was rated at 3.69 with boundary profiling, milling with islands, automatic pocketing for drafted sidewalls, and automatic planar roughing judged most important within the group.

The importance factors for NC programming to support various machine types are (in order of importance): drilling and boring, wire EDM, 2-axis turning, 4/5-axis wire EDM, 5-axis laser, punch, bending, and multi-axis grind.

Multi-function machining

Multi-function machining relates to support of machine tools that provide multiple machining functions such as milling and turning. This is becoming increasingly important as the use of multi-function machines generally reduces the number of set-ups and increases machining productivity. The two types of machine tools included in this survey are mill-turning machines and 4-axis lathes. This grouping received an overall importance rating of 3.15.

The key factor in programming of multi-function machines is that the functions are integrated. The programming should be done in a single session, the toolpaths should be concurrently displayed on the screen, and the outputs should be in a single program. This is in contrast to programming each function individually, seeing only one function on the screen at a time and then merging them at the end.

Data exchange

Data exchange includes the capability to exchange information via different formats and the ability to import data. The overall importance rating for this functional area was 3.01, with the most important factors being: support of IGES, importing 3D surfaces, importing solids, importing point data, and support of DXF.

Although there is considerable dissatisfaction with IGES and its implementation by some vendors, it is the clear de facto industry standard for the exchange of geometric information. Also, the IGES specification continues to expand to encompass more data types. As such, it is an extremely important functional capability that must be fully supported by all vendors. DXF, the AutoCAD standard format, was rated as less important, but still high enough to warrant vendor support.

Direct importing of data and models is becoming increasingly important. Of greatest importance is the capability to import 3D surfaces, which received a 4.6 rating. The increased importance of solid models is also evident, as most users indicated a need to import them. The ability to import point data via an ASCII file, and then automatically create geometry, is particularly important in the automobile industry.

User interface

The user interface area includes six sub-groupings. They are graphics support, data entry and documentation, user maintainable libraries and parameter sets, application support and interfaces, languages, and hard copy output.

A modern graphical user interface is essential and includes dynamic pan, zoom, and rotate; support of icons and pop up/pull down menus; and a windowing capability. It must be fast, consistent, and have a manageable number of levels and commands. Pen and electrostatic plotter output as well as screen dumps to dot matrix printers are also important.

The overall importance rating for the user interface category was surprisingly low, though easily explained. While support of English language rated 4.9, foreign language support rated low. These include French, German, Spanish, and Japanese. Each language rated in the range of 1.2 to 1.4. Since the survey is based on North American users, the results are not totally unexpected. However, they do drag down the overall user interface rating.

Other user interface functions viewed as important include a macro programming capability, interactive editing of the job control file, providing tool libraries, and support of a DNC function. Each of these functions had a rating of 3.7 or 3.8, which better reflect the importance of the user interface.

Knowledge-based engineering

The application of knowledge-based engineering (KBE) to NC is relatively new. Only a few companies provide this capability. In KBE, operator knowledge of programming and machining operations is captured. The captured knowledge is then used to automate specific machining operations or to provide guidance to other programmers on tooling, establishment of machining parameters, or determining the cutting instructions. Form-feature machining and generative machining are usually viewed as components of KBE.

The overall importance of KBE was 2.95, which is the lowest importance rating for the functional areas measured in the survey. This may be due to the newness of the technology and the general lack of familiarity with KBE by NC users. Or it may be that many users believe that this is not yet practical technology.

Still, there is support for further automation of the NC programming operation. This includes automatic generation of toolpaths, machining parameters, and machine tool characteristics. Also high on the list is the use of KBE to provide guidance for cutting tool optimization.

Providing a KBE tool kit is viewed as important in that it would allow individual users to generate their own KBE database. Users would also like to see KBE integrated with NC software, as opposed to being a separate product.

The application of knowledge-based engineering, user interface, and data exchange were ranked as having the lowest level of importance. Knowledge-based engineering is probably low because it is a relatively new technology, few vendors have incorporated the functionality into their product, and most users are not yet familiar with the potential benefits of the technology.

Speak out on NC

Following this article is a much abbreviated survey that Tooling & Production is conducting in order to determine how closely its readers agree with the CIMdata survey results. Having read the opinions of some users and software experts, we would be interested in learning how you evaluate your NC software.

Please fill out the survey and mail or fax it to Tooling & Production. Results of the survey will be reported in the October issue, along with the name of the lucky reader whose survey form was selected at random to win a prize for participating in the survey.

The study

The survey results appearing in this article represent only a portion of the 696-page NC software market study conducted by CIMdata and published in March 1993.

NC Software Buyer's Guide, The Authoritative Guide to Numerical Control Software and Systems includes extensive information on 38 NC software products from 30 vendors. More than 250 specific pieces of information on each product are reported. A full lineup of NC software products encompassing a wide range of product functionality and price points are in the guide. Mainframe, workstation, PC, and Macintosh software systems are covered.

For further information about the guide, which is priced at $795, contact CIMdata at 3893 Research Park Drive, Ann Arbor, MI 48108; phone: 313-668-9922; or fax: 313-668-1957.
COPYRIGHT 1993 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1993 Gale, Cengage Learning. All rights reserved.

Article Details
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Title Annotation:evaluation of numerical control software packages
Author:Stovicek, Donald R.
Publication:Tooling & Production
Date:Jul 1, 1993
Previous Article:Setting standards of manufacturing excellence.
Next Article:Machine accuracy by the numbers.

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