M ATERIAL R EMOVAL P ROCESSES

For industry to operate effectively, the material that produces the final product must be machined and formed quickly and accurately. The key factors that affect the efficiency of a metal-removal process are the machine tool, the controller, spindle, toolholder, cutting tool, and CNC programming. High Speed Machining (HSM) uses high spindle speeds, high feed rates, and light depths of cut to increase productivity, reduce lead time, reduce warping, increase part accuracy, and improve surface quality.

In virtually all metal-removal operations, manufacturers are trying to reduce the amount of time a part is moved from machine to machine and perform more operations in a single workpiece setup. This has led to the development of new machine tools such as the turning center with live tooling and special workholding fixtures where both turning and milling operations can be performed in one part setup.

H IGH -S PEED M ACHINING

(Steve Krar, Consultant—Kelmar Associates)

High-speed machining (HSM), in order to be most effective, must involve the correct selection of machine tools and controls, cutting tools, and programming. HSM uses high spindle speeds, high feed rates, and light depths of cut to increase productivity, reduce lead time, reduce warping, increase part accuracy, and improve surface quality. High-speed machining begins at 12,000

surface feet per minute (sf/min.) and may be as high as 18,000 sf/min and feed rates of 600 in/min. when machining aluminum. This requires a machine that can produce a spindle speed of 8,000 revolutions per minute (r/min) or higher.

The speed in High Speed Machining (HSM) is the speed at which CNC machining can replace the operations of polishing, assembly, unused shop capacity, and other manufacturing delays. Run fast enough, and machining centers become an economical alternative to more dedicated systems for a variety of production parts. If after careful evaluation, the cycle time of each operation can be reduced even by a small amount, it could produce big savings in production time and cost.

The goal of High-Speed Machining should not only focus on the speed of machining but also the flexibility it provides. Batch jobs can be run with little advance notice, streamlining inventories, Fig. 2-1-1. The speed can let CNC machining centers compete effectively for parts that would once have required a more dedicated manufacturing process. The key factors that affect the efficiency of a HSM system are the machine tool, the controller, spindle, toolholder, cutting tool, and programming.

Fig. 2-1-1 High-speed machining focuses on speed and flexibility. (Cincinnati Machine, a UNOVA Co.)