Whether hogging out a prototype engine block for Chrysler’s next-generation K-car, or machining a mold cavity for the newest Barbie doll, staying competitive often equates to fast chipmaking.
High-quality cutting tools and advanced CNC equipment help in this endeavor, but equally important is a machining strategy that best fits a shop’s processes. With unprecedented ease of use and highly efficient toolpaths, today’s CAM systems give shops the ability to maximize tool life, part quality and metal-removal rates.
ABCs of Endmilling
There seem to be as many milling techniques these days as there are endmills. Which technique is best depends on a number of factors, including workpiece geometry and material, machine rigidity and cutter selection.
One such technique is trochoidal milling, which uses a continuous circular motion to remove material. Old-timers may remember the Spirograph, a classic child’s toy in which a ballpoint pen is inserted into a plastic gear-like disc and guided around a piece of paper to generate geometric drawings. Replace the pen with an endmill and the cutter will follow a trochoidal toolpath. This technique excels at milling deep slots, where a high percentage of cutter engagement and challenging chip evacuation is the rule.
Helical ramping, a process similar to thread milling, utilizes center-cutting endmills to corkscrew into a workpiece when beginning a pocketing operation, saving the time needed to drill a starter hole.
Other milling techniques include roll-in milling, which avoids the hammering seen with a conventional head-on facemilling approach and uses an arced entry path to climb into the workpiece. This method creates a thick-to-thin chip, which efficiently transfers heat and extends tool life. In addition, slice milling cleans the corner leftovers that remain after roughing tools have done their work, and spiral morph milling takes the roll-in technique a step further, generating a spiral-shaped toolpath to quickly machine pockets and avoid the sharp corners that can cause chatter and tool breakage.
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