High speed machining is a hot topic. But, what is ‘high speed” machining really? Is it simply running at maximum feed rates and taking multiple shallow passes? This strategy is often less efficient than taking few passes at slightly greater depths! Achieving the shortest cutting time is related to feed rate, but the relationship is not necessarily ‘fastest feed rates = most efficient.” High-efficiency machining, cutting a part in the least amount of time, is the real goal. The key to achieving high-efficiency machining is to vary the feed rates to achieve the result each cutting condition encountered.

 

‘Typically, high-speed machining is accomplished with very small axial cut depths in order to achieve good surface finish and avoid damage to the cutter, workpiece or spindle. Feedrate optimization software can be employed to achieve better cutting efficiency with greater axial depths at the high feed rates of HSM and protect the cutter, etc., in those few places where the chip load momentarily increases. Constant chip load tool paths allow optimum use of the cutter’s strength and the machine’s speed and power. The software detects conditions where the chip load is too great and adjusts the feedrate to a more reasonable level. It then returns the machine to the higher feedrate when the chip load permits.”      Alan Christman, CIMdata      Software Trends Enhance Moldmaking Industry      MoldMaking Technology, November 2002

 

Cutting at maximum feed rate, with very light cuts, small step-down and step-over can actually require many, often inefficient, passes and can defeat the goal of reducing time. Cutting at a greater depth (in this example .500"vs.100") is more efficient. But the cutter may encounter an overloaded condition causing breakage or exceeding the horsepower on the machine.