For decades, batch production was done by skilled workers using machine tools such as milling machines and lathes. Today, CNC (computer numerical control) machine tools -- machine tools that can be programmed to make parts of different dimensions automatically - bring the benefits of automation to batch production.
CNC machine tools have two major components: An electronic controller (computer) and a machine tool. The controller directs the mechanisms of the machine tool through the positioning and machining described in the computer program for the job. A program, for example, could contain commands that cause the controller to move a drill bit to certain spots on a workpiece and drill a hole at each spot. Although the machining is done automatically, CNC machine tools must be set up and used properly in order to obtain the maximum benefit from their use. These tasks are the job of CNC machinist. There are many variations in a machinist duties, but they generally involve the tasks described below.
Working from written instructions or directions from supervisors, the machinist must load the program into the controller, attach the necessary tools, and position the workpiece. The way a program is loaded into a controller depends on how it is stored (i.e.: Disk or Tape). During the setup and running of a job, machinists
must install the proper tools in the machine. Many CNC machines are equipped with automatic tool changers, so machinists have to load several tools in the proper sequence. Because the machine tool cannot "see" the workpiece--it moves and operates in relation to a fixed starting point on the piece - it is critical that the machinist position the workpiece correctly or all subsequent machining will be wrong. Machinist also must secure the workpiece to the worktable correctly, so the piece does not move while it is machined. The time an operator needs to load the tools and position and secure the workpiece may be only a few minutes or several hours, depending on the size of the workpiece and complexity of the job.
Machine shops usually are well lighted and ventilated, and the machines on which they work have guards and shields that minimize the machinist's exposure to moving parts. Although CNC machinist generally work 40 hours a week, overtime is common during periods of high manufacturing activity. CNC machinist may advance to supervisory positions. Machinist who becomes proficient in programming can move to the higher paying job of tool programmer.