Evolution & history of CNC or 5-axis milling
The success story of CNC milling and 5-axis milling actually already began in 1818. In this year, the U.S. manufacturer Eli Whitney developed the first metal milling machine. Its base body consisted of a block of wood. The milling table could be optionally moved manually or automatically by means of a worm gear drive. Around the middle of the 19th century, the U.S. national Francis Pratt designed the Lincoln milling machine. This universally usable apparatus provided the design basis for numerous other machines both in the United States and in Europe until around the year 1900.
The historical first universal milling machine was verifiably delivered to Providence Tool Co. on 14th March 1862. The manufacturer was Brown & Sharp, a mechanical engineering company operating in North America. A further ten milling machines of this type were manufactured by the end of the same year. After this time, the numbers manufactured continuously increased. The first special-purpose machines entered the market around the end of the 19th century, such as machines for the milling of gearwheels, grooves, and threads. To increase the cutting performance, several milling cutters were clamped one after the other. These relatively simple machine tools enabled relatively high dimensional accuracy. However, the machines were far inferior to today’s high-precision CNC milling and 5-axis milling machines. In addition to milling machines, milling tools also continuously improved over the course of the years. Hardened cutting steel was already introduced in the United States by F. W. Taylor around the year 1900. The cutting performance was thus tripled.
During the period from 1949 to 1952 John Parsons from the Massachusetts Institute of Technology (M.I.T.) in Cambridge (USA) set a major milestone for the development of CNC technology – and thus also CNC milling and 5-axis milling. On behalf of the U.S. Air Force he designed the first NC-controlled machine referred to as the “Cincinnati Hydrotel”. In 1954, Parson’s technology was taken over by Bendix. This company also based in the United States then designed an NC machine equipped with more than 300 electron tubes. The machine was controlled via punched cards. The workpiece carriers were moved backwards and forwards by separately operating motors. The NC programme, which contained the sequence of position or control information, is the direct precursor to the CNC programme.
In Europe’s industrial nations, the first NC machine conquered the market in 1959. From 1960 onwards, numerous milling machines were retrofitted with NCs. However, it soon turned out that special machine designs were required to make optimal use of NC technology. Therefore, NC-compliant milling machines were built which stood out due to their more stable design, more powerful, variable-speed (DC) drives, hydrostatic and roller bearing guides, as well as ball screws.
In 1965, the tool change could finally be automated. And from 1968 onwards, the controls were equipped with Integrated Circuit (IC) technology for the first time. The level of automation of the machines could be increased with the introduction of tool quick release mechanisms and pallet changers in 1970. The first NC controller with programme memory, i.e. the precursor to CNC technology, followed in 1972. From 1976 onwards, the CNC functionality could be implemented for the first time thanks to the use of microprocessors. This ultimately paved the way towards CNC milling and 5-axis milling. The hardware previously used for control purposes was increasingly replaced by software. Flexible manufacturing systems could already be implemented in 1978 and 1979 was the year of origin of the first CAD/CAM couplings.
Initially, the CNC programmes for both CNC and 5-axis milling had to be painstakingly written by hand. The programming job thus required enormous concentration. In fact, even the slightest programming error could cause severe damage to the milling machine. The era of classic programming continued until the end of the 1990s. From this time onwards, programmes were created directly from the CAD/CAM system, as is usually the case today. In future, programming will be performed via CIM with the ultimate goal of eliminating the need for any human intervention. Just a few years ago, a maximum of up to 5-axis machines could be programmed via the machine controller, whereas nowadays, CNC milling machines with up to eight axes can be implemented.