An Engineers Guide to Cnc Machining Cad/cam

Computer Numerical Control (CNC) of manufacturing machines such as lathes and mills was the next stage of development from Numerical Control (NC). NC control had allowed the machines to be run automatically using a fixed program for the first time. This increased automation of the manufacturing processes led to considerable improvements in the consistency and quality of components. The program was, however, long winded to create and difficult to alter.

The addition of a computer within the machine allowed the program to be viewed and edited making it easy for alterations to be made to what had previously been a fixed program. This allowed operators to write programs directly into the machine and update and optimise them as they went. This required a new breed of machine operators who had the skill and training required to program the machine from engineering drawings in addition to their traditional skills.

The next stage of development was Computer Aided Manufacture (CAM), this allowed the program to be created offline from the machine, not by typing in dimensions from a paper drawing, but by taking the geometry directly from Computer Aid Design (CAD) files. A software package would be used to create the program from 2 Dimensional CAD data of the geometry and then add tool and speed/feed information. This program could then be post processed into a language appropriate to the machine being used. This development further increased the required computer skills of the machinists but made programming of complex shapes just as simple as creating simple shapes. It also reduced the chances of errors within the program as more of the programming was automated.

The current state of the art is 3D CAD/CAM, which allows programs to be created directly from the 3D solid models created by the design engineers. This technology allows parts to be machined without any from of paper drawing, as all the tool paths are derived from the 3D model. The advantages of this process are most obvious when creating development or prototype parts as not only is the programming time considerably reduced but also programs can be simulated and verified offline. Therefore no time consuming line-by-line proving of the program is necessary at the machine. A further advantage to this system is that more complex three-dimensional forms can be easily programed allowing more flexibility to the designers, and where necessary making the creation of more stylish shapes, cost effective even for very low production.

All these developments have completely revolutionised workshop practices within a generation, as machinists have evolved from skilled operators running manual machines, to computer literate programers able to drive complex 3D CAD packages that had previously been the domain of the designers.