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A leg up on the latest in solid surface CAM.

With computer performance doubling every 18 months, today's solid-surfacing CAM systems are delivering power and performance that only a decade ago were unattainable at any price. What's more, usability has dramatically increased over the same period thanks to a number of key developments:

* the graphical user interface (GUI) standards set by Microsoft Corp for the Windows operating system;

* open architecture, allowing the acceptance of data from any source;

* dynamic visualization, providing clear and concise graphical display of parts and machining processes;

* optimization for high speed machining; and,

* new advances in verification and simulation, called "in-process" modeling.

As a result, a new generation of CAM systems is emerging today--systems that deliver considerably greater power and performance, while dramatically improving ease of use at an affordable price for most shops.

Today's new CAM systems and their solid surfacing capabilities are significantly faster and easier to use than ever before. This new generation of CAM software is, in part, the result of an evolution in part modeling. In the 1980s, wire-frame geometry was used to represent parts. In the 1990s, CAD/CAM's mathematics advanced to surfaces, utilizing nonuniform rational B-spline (NURBS) technology, which provided support for significantly more complex shapes. Today, we are clearly experiencing a rapid transition towards feature-based solid models as the technology of choice for part modeling. As a result, CAD and CAM systems will provide even greater degrees of automation, speed, and accuracy to the CNC programming process. The trend toward CAD/CAM's increased use of solid models is particularly significant because it has brought with it a host of other desirable features designed to help users leverage their productivity effectively and at a minimum cost.

Gain time, save money

With more than 75% of people involved in solid-surface-milling using the Microsoft Windows NT operating system, it's apparent that Windows NT is the platform of choice. Window NT is four times more stable than Windows 95/98, significantly less costly than Unix, and it provides an interface familiar to the vast majority of computer users worldwide. When searching for a good solid surfacing package, or any type of CAM package for that matter, users should insist upon 100% compliance to GUI standards set forth by Microsoft for the Windows operating system. This not only reduces the cost of the software solution, it also results in dramatic time savings with increased usability in addition to reduced training costs.

Open architecture

Most shops find it desirable to machine parts that were designed within any one of a number of CAD systems. Some new part designs and many of the older designs are based on wire-frame and surface geometry and are usually provided in one of the established electronic formats, such as DXF and IGES. But a growing number of shops must now be capable of working directly from solid models, which are most commonly provided in one of the emerging standard file formats, such as STEP, XT, or SAT. Open architecture, next generation CAM systems naturally accept all of the above formats, enabling shops to reliably and accurately machine parts, regardless of the source.

Advanced graphics

Computer graphics have advanced at a tremendous pace over the last few years and now provide realistic graphical representations of both part models and machining operations. These shaded images can be rotated for viewing from any angle, as if a person were to hold a part in hand and rotate it. Powerful pan and zoom capabilities allow one to instantly change the magnification of a part to view it as a whole or to view it in minute detail. In years past, these advanced graphics would have required expensive proprietary software and hardware. Today, thanks to the industry standards of OpenGL, CAM systems can deliver dynamic visualization on most Windows-based computers, eliminating the need for a costly proprietary environment. The advantages are tremendous -- gone are the days when it took a CAD/CAM expert to interpret computer graphics. Today, almost anyone can take a glance at a CAM software's solid modeling interface and immediately become apprised of what's happening with a part model, what it represents, and the machining that has been performed.

Toolpath creation

Today's CNC machine tools are cutting at much faster rates than ever before and, as a result, CNC programs must he developed to meet an ever-increasing set of demands and criteria. The leading technology for toolpath calculation that provides highly accurate, extremely smooth and highly efficient CNC programs is NURBS. Toolpath generation from NURBS mathematics is becoming a standard in manufacturing because it allows you to deal with the complex free-form movements which are necessary to machine today's parts. Due to high cutting rates, uniform cutting directions and conditions must be maintained, while many of the controls will require that CNC programs be formatted with NURBS-curve or Spline-curve output.

Animated simulation of the material removal process, usually referred to as simulation or verification, has been around for many years. The most advanced of these verification and simulation systems are further enhanced with features such as real-time dynamic graphics; comprehensive collision detection; and a full machining environment of fixtures, clamps, and toolholders. All of these, of course, are excellent tools in that they minimize the time spent at the machine tool proving out programs. However, another hot item that is not far away from being fully realized in the solid-surfacing arena is CAM's use of CNC program verification and simulation components that incorporate "in-process" solid modeling technology. That is, CAM will soon enable the user to compare a part "as-machined" vs the "as-designed" model

As it is now, users usually have no clear vision whether the part being machined is exactly the same as the part originally designed. When you perform the material removal simulation in most CAM software today, the end result is only a picture. Until recently, no method of analysis has been available. Soon, however, next generation CAM systems will be able to do a first article inspection of the "as-machined" solid model before actual machining. With these in-process modeling inspection tools--a cross between solid modeling and solid simulation--users will be able to view how the part will look once machined and examine that part as a whole or inspect any detail. Via in-process modeling, CAM software will compare the as-designed solid model with the as-machined solid model based on the CNC machine tool program, producing a colorful display of any possible gouges, clashes, undercuts, and overcuts in a "life-like" representation of the machined part. Then, at the click of a mouse, users will be able to view an d inspect these "as-machined" parts from any angle to observe deviations, the same way they would with a coordinate measuring machine (CMM).

This technology is suitable for many areas of manufacturing, particularly in moldmaking. For example, a moldmaker may ask the CAM software to use a ballend mill to cut across a set of surfaces with a certain tolerance and scallop height. The software then creates a toolpath. In-process modeling will provide a tool to verify that these calculations are accurate. The CAM system will simulate the actual machined part on a computer, versus today's much slower method of physically cutting the part and manually inspecting the part on a CMM. Without in-process modeling, the moldmaker would normally send the part through animated simulation and verification to view it as a shaded image on screen. Though this offers you a pretty good idea of the shape of the part and representation of the moving machine tool, the process may take from five to ten minutes to complete. But in-process modeling will do the same thing in about 15 seconds, with the added value that the end result is a solid model, which is an accurate repr esentation of the part as it was machined. You can then look at it with any level of magnification and rotate it in real-time, as if you held that part in hand.

With this new technology users can be certain that what is cut is comparable to what was originally designed without sacrificing time or scrapping parts. CAM's new capabilities for enhanced NC simulation of solid models now offers definitive answers to questions of accuracy, quality control, and inspection. In-process modeling is the ultimate CAM tool for reducing machining time via comprehensive dry runs and part inspections performed on the computer. The result is significant increases in the quality of CNC programs.
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Copyright 1999 Gale, Cengage Learning. All rights reserved.

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Comment:A leg up on the latest in solid surface CAM.
Author:Mathews, Chuck
Publication:Tooling & Production
Geographic Code:1USA
Date:Apr 1, 1999
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