The components produced by machine tools are essentially a combination of many simple geometric shapes such as the cylinder, cone, sphere, flat surfaces, and helical surfaces. These shapes were obtainable due to the possible movements of the machine tool parts during its operations.
Machine tool movements are made up of one or more degrees of freedom; by carefully controlling these movements relative to each other, it is possible to produce the geometric shape desired. An example of this is the production of cylindrical shape on a lathe, where the work is rotated and the tool movement is controlled so that the tool travels in a path parallel to the axis of the work, thereby producing the cylindrical shape.
The process such as the one mentioned above, where the shape of the work is controlled by a combination of work and tool movements is called “Generating”. Another good instance of generating is where the flat surface produced by the shaper is as a result of the straight-line movement of the cutting tool and the feed movement of the work. For instants;
The generating of conical surfaces, generating of helical forms-screw threads, etc. in all these instances, the shape produced is independent of the shape of the tool. If the shape of the work does depend upon the shape of the tool, then a process is known as “forming” is involved. Extrusion is an example of true forming, where the shape of the work is a direct replica of the extrusion die.
In most machining operations involving forming, some generating is also inevitable, for example, a screw thread requires a form tool to produce the shape of the thread but requires a precise linear movement of the tool for each revolution of the workpiece to produce the helix which by the previous definition is a generating shape. Other examples of forming are knurling on the lathe, using a concave tool to produce a convex surface, using a form tool to produce a conical surface on the lathe, using a form tool to produce the desired shape on shaping and milling machines.
There is one other system referred to as “copying”, it is used for the production of more complicated shapes, the shape of the work being a replica of a master component or accurately made model or template.
Coping is a special case of generating since it requires some form of copying system, which can accurately control the tool movements relative to the work movement to produce a workpiece identical to the “master” within the limits of accuracy of the copying system. A system like that is used mainly on lathes and milling machines and may use a hydraulic, pneumatic, or electrical servomechanism to control the tool movements.
It is a dream of every engineer to produce exactly what was designed and the operations mentioned above are among the various ways of achieving such dream, the machine tools operations are increasing everyday for higher accuracy and efficient due to the continuous development in the system. Previously manual, later to semi-automatic, and now automatic machine tools operated systems such as the one seen in “AUDI MOTORS” assembling line, next stage is fully robotic operated machine tools systems.