A manufacturing group at Brigham Young University says they have developed a machining system that combines master model CAD geometry with toolpaths in one file. It also uses DLLs (dynamic linked libraries) to drive particular machine tools in much the same way a word-processor drivers run a printer. DLLs eliminate post processing that ordinarily adjusts toolpaths for specific machine tools. “We have proven the system by milling 5-axis tool paths directly from Catia V5 and Unigraphics NX2 models,” says associate professor of mechanical engineering C. Greg Jensen.

The system works like this: “A part programmer checks-out a CAD or master model from the company PDM system, puts toolpaths on it with NC software, and associates the two,” says Jensen. The programmer then checks the file back into the PDM system. The machine-tool operator later downloads the CAD file along with toolpaths from the PDM system to his machine-tool controller. “Our DLLs open the master model and find the machining instructions. As soon as the operator pushes Cycle Start, he's running the associative toolpaths, not M&G code that comes from an NC postprocessor”. Now suppose, suggests Jensen, the operator finds a hole slightly out of position when verifying the toolpaths. The operator adjusts the CAD model, the associated toolpaths update, and the test run finishes. Releasing the model and toolpath back to the PDM system keeps the two in synch.

That is not so today, says Jensen. “ASCII and M&G codes are often edited at the machine tool, so they don't match the master model because the two aren't associated. Associativity exists to some extent with all CAD models but it's broken as soon as the NC software dumps out APT or M&G-code files,” says Jensen. His team so far has developed DLLs for three different machine tools. The researchers assume manufacturers of machine tools will develop DLLs just as printer manufacturers develop drivers.

Jensen adds that his group is closing in on generative process planning. This is a method that eliminates generating toolpaths as a separate manufacturing step.