Ever since the first tools for milling metal parts were introduced, the quest to improve the process has been an ongoing one that, today, has resulted in a procedure known as CNC machining. Not confined to the factory floor, dental surgeons also now employ a near identical technique in order to create prosthetics such as veneers, crowns and inlays at the chairside while the patients look on.
Originally such processes were strictly manual and made use of hand-operated levers and wheels to set the desired dimensions and to perform the shaping process. Often a part would need multiple operations such as sawing, drilling and filing so these manual devices needed to be constantly reconfigured to perform each task.
Early Attempts at Mechanisation
The first successful attempts at automating the milling process made their appearance in the ‘40s and ‘50s and made use of an emerging technology known as numerical control. In fact the new breed of machines was little more than an adaptation of the manual precursors in which control was passed to electric motors that, in turn, operated servomechanisms to position the milling tools. The major advance, however, lay in the fact that the positioning phase was executed according to a specific set of instructions encoded on a punched paper tape just like that used for the input and output of data by early analogue computers.
Into the Digital Age
Since their humble beginnings computers have developed almost beyond recognition. CNC machining or, to give it its full title, Computer Numerical Control, now leverages modern digital computing technology that has served to revolutionise the entire milling process. In fact computers and specialised software programmes now govern the entire manufacturing process right from the design stage.
Today, engineers no longer work from technical drawings on paper but utilise powerful computer aided design (CAD) software to create accurate 3-dimentional models and display them on a screen. In order to transform the digitized concept into a physical component, the codes required to direct the milling process must first be generated. For this a computer aided manufacturing (CAM) utilises the CAD data to generate two sets of control code that will later guide the milling process.
The code sets, known as the G and M codes, provide the means to control different function sets of the automated equipment. The G code carries the instructions relating to the various turns and cuts that are required by the design while the M code controls support activities such the control of fluids and the selection of tools.
Fine Blanking, a Johannesburg-based company in Devland, is able to advise or support companies with all aspects of CNC machining.