High Speed Machining

High Speed Machining (HSM) can be defined as operating a computer numerically-controlled (CNC) machine tool at spindle speeds which dramatically increase the limiting depth of cut for stable machining. These desirable speeds occur when the tooth passing frequency of the cutting tool is equal to integer multiple of the natural frequency of the most flexible mode of vibration of the system. If the machine is operated at one of these speeds, the stable depth of cut and the material removal rate (MRR) can be dramatically increased. As the MRR is increased, machining time is reduced and productivity increased.
HSM is revolutionizing the manufacture of a wide range of products from commercial aircraft to automobiles and electronics. It is a rapidly growing area of interest for machine tool builders, users and researchers alike. HSM does not simply mean using higher speeds and feeds than in conventional machining. Instead, HSM exploits the characteristics of the dynamic response of machine tool structures to allow stable machining in regions which were previously thought to be impossible, thus allowing dramatic increases in the productivity of the machining process. In many cases, the use of HSM techniques allows for increases in the MRR of 5 to 20 times.
When coupled with appropriate CAD/CAM technology, HSM can now allow many sample parts to be produced in aluminum, bronze, or even hardened die steel in less time than most rapid prototyping machines can make a layered composite plastic mock-up. In this sense, HSM is a rapid prototyping process capable of making functional parts.
For a new part or production run to be manufactured with the use of CNC machine tools, the current procedure is to write the CNC part program using the engineering drawings, execute the part program to machine a test part or prototype, and then inspect the test part, normally with the aid of a coordinate measuring machine, to check for conformance to design tolerances. This feedback of the actual part dimensions (with an adequate degree of precision) is currently the only way to certify the performance of the CNC program. If the test part does not meet the specified tolerances, as is often the case for a first trial, the CNC program is modified, another test part is machined and the process repeated.