Milling machines are common CNC machines. These devices are used in the shaping of metal and other solid materials. It is basically a rotating cutter and a table. Milling machines are capable of complex toolpaths as the cutter is not limited to a sideways movement but allows for an in and out motion. This movement is precisely controlled by moving the table and the cutter relative to each other. Cutting fluid is then pumped in to lubricate and cool the cut and to remove any swarth that is generated by the cut.
Lathes are machines that perform different operations such as sanding, cutting, knurling, deformation, or even drilling. These machines work by spinning various solid objects and then using tools that are symmetric to the axis of rotation. A lathe machine has a single tool in which the workpiece is worked against the tool. The tool is then worked alongside or into the workpiece in order to generate the feed.
Lathes can be used for different operations.
These are more complex CNC machines that combine milling and turning. As milling was described earlier, turning will be the focus of this section.
Turning is the process by which a central lathe is used in conjunction with the rotation of the material to be turned. The cutting tool is then moved along the two axes of motions to produce accurate dimensions.
Combining turning and milling can produce extremely precise components. And that is what these machines are used for. However, due to the complexity of these machines, operators have to be specialists in order to be able to operate with maximum efficiency.
Electrical discharge machine
An electrical discharge machine (EDM) creates cavities in metals by emitting electric sparks. This process requires an electrode, coolant, a power source, and a tank. The cycle is accomplished by connecting the workpiece to one side of the power supply and then placing it in the tank. An electrode (made in the shape of the cavity required) is then connected to the other side of the power supply.
The tanks is then filled with coolant and the electrode is lowered until a spark jumps between the work and the electrode. As the coolant is a dielectric substance (resists electric currents), it requires a smaller difference in distance in order for a spark to jump through. This means that when the spark appears, the dielectric property has been overcome. The spark then dislodges material thereby creating a cavity in the shape of the electrode.
CNC systems are complex machines that transfer and store data regarding the operation mechanism of the machines. Motion programs include point to point control, straight cut control, and contouring control.
Point to point control means the control of the tools from one point to another in the coordinate plane. This method of control is commonly used in drilling and boring operations.
Straight cut control is the method by which a tool is moved in all axes of the machine. The tool also has the ability to move in a 45 degree angle.
Contouring control is the means to create a toolpath. It moves the tools by interpolating points or coordinates that make up the path for the tool to follow.