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For CAD/CAM, is Windows just another pretty face? - computer-aided design/computer-aided manufacturing - Scanning the Horizon

Jon Perry

This, from Jon Perry, a senior applications engineer at Solutionware Corporation (San Jose, California), a noteworthy vendor of CAD/CAM software written for operation in Microsoft Windows:

A graphical user interface is the most obviously visible thing about Microsoft Windows and it does make life more pleasant for most people. But is that all? Is it just a pretty face with no real substance behind it for people - like machinists - who actually work for a living?

There is, in fact, another benefit that's even more important: Thanks to the way Windows handles memory, it allows software developers to do more with their applications. With DOS limited to 640 K of memory, you can only cram in so many features before you run out of room. Prior to Windows there were ways of getting around that barrier, but there was no standard way of doing it. Each software developer took a different approach which resulted in incompatibilities.

Windows changed all that with a standard way to go beyond 640 K, giving software developers more room to work. Take, for example, Solutionware's Geopath for Windows CAD/CAM system. Application code for CAM software that can cut 3D surfaces takes a large amount of memory no matter how you do it. With the added memory of Windows, you can build in full 3D surface support - everything from basic entities up to splines and NURBS surfaces - but also take an approach that's more advantageous to the user.

For instance, most CAM systems create 3D cuts by approximating the surface in a series of short straight line segments. Rather than compromise the geometry this way, however, it's possible to maintain full accuracy and cut true arcs. In order to do so, the shape being programmed and cut must retain its original math form, and the same form must be used to generate the CL file, and finally the form can be output from the postprocessor in the form of true arcs. The result is shorter NC programs, more accurate parts, better surface finish, and less handwork for mold makers. This is the approach taken with the Geopath system.

Another example is the integration of high speed machining capability, which requires the ability of "look ahead" in a program to slow down or accelerate feed rates for accurate cuts at corners and radii. Some CNCs have their own look-ahead capability, but others require special G-codes to do it. For the latter, it's possible to apply look-ahead functions in CAM and modify feed rate appropriate to conditions to optimize each section of the cut for maximum speed.

Another area where Windows shines, quite literally, is in its standardization of graphics display drivers for video cards. This allows the use of large, high resolution monitors, and allows software developers to let users take full advantage of these big screens. The same is true for printer and plotter drivers, and helps insure applications can accommodate just about any commonly used output device. Standardization of the interface also makes it easier for Windows users to learn new applications, whatever they be, and that applies to CAD/CAM software as well.

In fact, the ability to run multiple applications on the same computer is still another advantage. Multitasking capabilities allow users to program one part while using a DNC function to cut another at the same time. It's even possible to cut a part while checking into another application, such as your accounting software.

To take full advantage of these new possibilities brought on by Windows, however, it's necessary for developers to write applications for it from scratch. If you merely adapt a DOS application, it's basically still the same thing with a bunch of added boxes and menus, which can look fancy but can actually get in the way. That puts more burden on the software developer since DOS is somewhat more forgiving of minor variations in application programming. In our case, we felt that starting from scratch was worth the effort, and gave us a chance to completely rethink our algorithms and procedures, allowing the software to work more the way that machinists work.

The true advantage of Windows is that it gives software developers the opportunity to create applications that fit more naturally into the shop environment and let people do the things they want faster and more efficiently, if the software is well designed. And that means a good deal more than just a pretty face.