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Verify one-off programs without cutting metal.

To meet production schedules, Rockwell manufacturing is continually upgrading machining technologies to machine Space Shuttle parts. One such improvement is in verification software for NC programming. Many parts are designed on an MCS ANVIL 5000 CAD/CAM system.

Typical lot sizes are one and two parts. Compounding the need for accuracy is a wide range of part sizes and geometries. Although the majority are in the 12" x 24" range, some are as large as 4 ft x 6 ft. Over 60% are aluminum, and other metals machined include titanium, stainless steel, and Inconel.

Verifying each part has required an average of 2.1 machining tryouts. Eliminating these tryouts is highly desirable. A variety of tool-path verification techniques exist to ensure a given part will be machined as intended. Rockwell has traditionally machined prototype parts in aluminum, and extrapolated for those parts to be made of titanium and Inconel-a practice that does not always produce accurate results.

To do the same thing with software, the tool-path verification method should display a solid 3D model of the rough stock on a graphics screen, show simulated results of cutting action, and depict the remaining part when tool motion is complete.

To do this, Rockwell chose a graphic verification program, VERICUT, by CGTech, Irvine, CA. It gives the user control over the dimension, location, and orientation of rough stock, as well as fixturing and clamping. It can depict both milling and drilling operations, with three-axis through five-axis simultaneous motion. Cutter information can be developed interactively, with input using an expanded APT seven-parameter statement, or retrieved from a tool library.

Tool paths to be tested can be passed to the verification workstation via any network. Thus, CAD/CAM data can be passed directly to a workstation to visually verify an NC program without machining a prototype. A typical part that would require 8 hr of machining time can be simulated in about 20 min.

Significant improvements have been achieved in a relatively short time. The visual aid from verification shows immediately if there is any bad cutter motion that would cut through a part wall or membrane. NC verification has proven particularly useful in incorporating engineering changes in previously programmed jobs.

Tryout proofing has been eliminated completely for 25% of new jobs, and the overall proof average has dropped from 2.1 tryouts to 1.3.
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Title Annotation:Manufacturing Solutions
Publication:Tooling & Production
Date:Feb 1, 1992
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