Is There Still a Role for the Skilled Turner?
My own opinion is a definite “Yes." To qualify that opinion, let us look briefly at some of the tasks that skilled turners undertake.
After training, the average CNC machine can be programmed by almost anyone with some degree of computer literacy. However, what should be realized is that these machines, by their very design, are extremely powerful, so that they can handle the maximum capacity of material described in the machine specification. The program utilizes parameters that are developed from the properties of the materials, the tooling types, etc., and are set in the main machine program by the manufacturer. So, although these parameters are available to configure the machining dynamics for the work piece, e.g. its turning speed, depth of cut, feed rate, the required finish etc., as the parameters can be quite wide, the machine usually derives and applies a “happy medium."
The skilled Turner however, can observe the machining process and will know that, for instance, the swarf generated by the cut is wrong, the depth of cut on the final roughing cut is too heavy for the finished diameter and is causing the work to bow away from the tool, or perhaps causing “chatter," the finish is not correct, etc. By dint of his experience he can usually alter the program to produce the optimum result.
One Off and Prototyping
Unless a company is very large, with spare capacity on its production lines, normally it is taboo to take a high volume producer (like a CNC machine) off line for “one off" jobs or “prototype" manufacture. It is just not economical. With “one offs" the Skilled Turner is doing exactly what he trained for- producing high quality work on a lathe and thereby saving the production line from disruption. Similarly with “prototyping," this can enable the design engineers to test and evaluate a part, introducing any modifications, material changes etc., that may be required. When the prototype is ready to upgrade to production status, it also allows the programmer to study and evaluate the part and write the best program for the CNC machine/s that will be tasked with production.
Unfortunately, producing parts rapidly with an enclosed, automated, very powerful machine does not allow the operator to easily discern faulty production. To overcome this problem the operator is usually required to inspect, for instance, 5 pieces of every 100 produced. If he detects any faults in the production item, the machine is taken off line for the fault to be rectified. As an example, it could be a chipped tool that is producing a sub-standard finish. Further inspection will then establish just how many faulty pieces had been made. Depending on the economics of the situation, e.g. 5-10 lower cost items could justify "scrapping," whereas 99 medium-expensive items, if they could be recovered, would be given to the charge of the Turner for rectification.
The Devil that is Diversity of Production
When parts are required for high volume, complex assemblies, as for example, automobiles, the sheer number of components will normally preclude all those items being produced by the same manufacturer. Several manufacturers will be sub-contracted to produce the various components, which will then be shipped back to the assembly line. The problem that then arises is to ensure that all those components will fit together correctly. An example could be a shaft that is to be fitted into a bearing. The shaft will have been manufactured to certain tolerances. Those tolerances will dictate that the shaft must not be undersize (slop in the bearing = scrap), but may be slightly oversize. This over-sizing could be caused if the shaft had to undergo heat treatment to harden it. For whatever reason, provided the shaft is within tolerance, it is still acceptable to the assembler and will be passed to the Turner, who will finish the shaft to the correct dimensions. This is an over-simplification of the process, but it conveys the idea of how it works.