YOU REALLY CAN HAVE IT ALL IN A MILLING PACKAGE

For those of you who do production milling of prismatic parts, you might wonder what you could possibly have in common with the moldmaker, one-off prototype shop, or short-run orthopedic device maker. Glad you asked . . . because there are more similarities than you might think.

In contrast to bygone days, everybody now starts with a CAD file that either gets massaged in a CAM program, directly input into a high-level CNC (which is possible, if you?ve read our past columns here in Fabricating & Metalworking) or run through an intermediate post-processor. From the basic contour or convex free-form surface with symmetric curvatures on a prismatic part that can be done in three axes, to the more complex three-plus-two world with rotary table/trunnion setups, to true five-axis programs for deep cavities and frequent changes in curvature, all milling processes see part quality, cost efficiency and speed.

On today?s top line CNC, you can realize optimum surface quality through the established NURBS technology, whereby the old G1 linear moves of block calculation, which resulted in that unnecessary faceted look, are replaced by true curve calculations with the NC data compressor function. This transition has advantages, whether you?re in the tool/die, mold, automotive, aerospace, medical or heavy equipment industry, because the result is immediately apparent on the workpiece surface.

Moreover, through the achievement of a truly uniform CAD/CAM/CNC process chain, all three-axis, three-plus two and true five-axis workflow improves as well. This results from the combined and simultaneous abilities of the CNC to improve surface quality plus execute more efficient machine motion, metal removal volumes, cutting speed variations, faster look-ahead functionality and, the ultimate goal for most every shop, reduced cycle times with no compromise in part quality.

New algorithms, developed in the NC kernel of the CNC, now make it possible for such achievements as a swivel cycle with Z-axis orientation to the workpiece in direct, axis-by-axis, angle of projection or solid angle orientation, as well as an operator being able to recalibrate all pivot and swivel points with a probe and sphere mounted to the worktable for precision measurements, quicker restarts after tooling changes and, best of all, the elimination of expensive laser trackers or CNC service calls after a breakage or other work stoppage. With the tool length compensation software in the onboard CNC library, substantial reposting time can be saved, too.

When the materials and machine run time are premium, modern CNC simulation software allows you to visualize 3D for instant and accurate checks on the programming or the CAM transitions.

In essence, whatever job you do, you can have the post-processor function, set-up, programming, automatic measuring function, high-speed cutting calculations, advanced surface finishing and all HMI parameters displayed on a single screen in the CNC. Additional user memory is as easy as a Compact Flash (CF) card insert plus, when necessary on the highest level or largest workpieces, kinematic transformations and volumetric/temperature compensation software is available. This means neither variations in the tooling, the workpiece material, machine-to-machine nor even the ambient conditions in the plant can substantially upset your accuracies.

Who says you can?t have it all when you?re milling? With today?s CNC, it?s more possible than ever before.

Special Note: I?ll be attending IMTS (where else would I be?), so stop by the Siemens booth (E-4933) and say hi. Bring your CNC questions, too. See you in Chicago and thanks for reading!

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Randy Pearson is the sales support manager for U.S. dealers and OEMs of Siemens Industry, Inc., Drives Technologies, Motion Control ? Machine Tool Business, 390 Kent Avenue, Elk Grove Village, IL 60007, www.siemenscnc.com. A veteran of the machine tool industry, his interest is the training aspect on CNC machine tools, which he conducts through seminars and classes at votech schools and shops, and at Siemens training facilities. For questions or comments on this column, contact Randy at 847-640-1595 or randy.pearson@siemens.com.