Good machines, good software, good cutting tools. High speed machining (HSM) is like a three-legged stool. You might think you can buy the right chair and the rest is gravy. Not so fast. While it’s clear that HSM needs top-notch technology, dropping a bunch of cash on the latest and greatest equipment won’t make you a high speed master. It also takes a good deal of know-how.
But what is HSM? The truth is there’s no industry standard. Most experts agree, however, that HSM removes material faster than conventional methods. It utilizes feedrates two to three times higher, together with light depths of cut, often less than 10 per cent of the tool diameter. And as the name implies, HSM uses high spindle speeds—40,000 rpm or more is not uncommon.
Ironically, many in the industry think this last point—spindle speed—is the defining factor for HSM. Far more important is a spindle with broad torque capability across a wide rpm range. HSM can be used in a variety of machining scenarios—mould/die work with its intricate surfaces and tool steels up to 62 Rc is a prime candidate. Another is aluminum wing spars, struts and other aerospace components. Buying a machine with the proper rpm range is critical.
Steve Bond, national sales manager for Fanuc RoboDrill, RoboCut and EDM Products at Methods Machine Tools Inc., Sudbury, MA, says a 40,000 rpm spindle by itself won’t help you machine parts any faster. “Spindle rpm is relevant to the type of part you want to cut.” For example, a 20,000 rpm spindle might be fast enough for hardened tool steel, whereas 50,000 rpm or more is warranted when machining with cutters the size of a human hair. “It really comes down to tool load. If the cutter can’t remove any more material given a higher rpm spindle, then you won’t gain anything by buying one.”
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