In CNC machining, there are two primary types of milling machines: the vertical milling machine, with a Bridgeport milling machine being an excellent example, and the horizontal milling machine. Although the milling operations on the two styles of milling machines might vary, the milling machine parts that make them up have much in common.
We’ve created a list of the essential parts of a CNC milling machine that you should know and understand, starting from the floor and moving up.
Milling machines, whether manual machines or CNC machines, are essential to the modern manufacturing process. They remove metal from workpieces, getting the desired shape and dimensions using a spinning tool called a milling cutter. Unlike a CNC router or CNC lathe machine, on which a workpiece spins and the cutting tool moves into it to create cylindrical shapes, the milling machine employs end mills, face mills, dovetail cutters, and various other milling cutters to machine flat and irregular surfaces, including those that are concave or convex.
Milling machines are not all that complicated in theory: A machine operator fastens a workpiece to the machine tool’s work table using a work holding device, such as a clamp or vise. The workpiece is moved through the X and Y-axis as the milling cutter removes the material and a skilled worker or CNC program directs it on a manual or CNC milling machine.
At the heart of a CNC mill is the CNC controller, a sophisticated computer system that converts a digital design into commands that drive the machine’s movements. The controller interprets G-code or other programming languages, outlining the tool paths and movements necessary to create the desired part. It precisely controls aspects such as speed, feed rate, and coordination of the spindle and tool changer. The CNC controller is the interface through which operators input data, monitor the milling process, and make adjustments as needed. Advanced CNC controllers also offer features like real-time feedback, error detection, and adaptive control, enhancing the precision and reliability of the milling process.
The cast iron column and base support the other parts of the milling machine operations. The column rests on the base and typically houses the oil and coolant system. The base is the foundation carrying the weight of everything on the machine, while the column takes the direct weight of the knee and work table. The weight of these two components ensures there is minimum vibration and better surface finishes even after the heaviest cuts.
The control panel on a CNC mill is where the operator runs the machine. It has buttons, switches, and usually a screen to show information. The operator uses it to start and stop the mill, control how fast it moves, and pick different ways to use the machine. The screen shows important details like the path the tool is taking and if there are any problems. In modern CNC mills, the control panel can be quite advanced, letting the operator program the mill, see what’s happening as the machine works, and even try out the milling process virtually before actually starting.
The tool changer is a critical component of a CNC mill, serving as the mechanism that automatically switches between different tools during the machining process. This feature is essential for complex operations requiring multiple tools, such as drilling, milling, and tapping. The tool changer operates under the control of the CNC system, allowing for seamless transitions and minimizing manual intervention. It typically consists of a magazine or carousel that holds a variety of tools and a robotic arm or other mechanism for selecting and changing the tools. The efficiency and capacity of the tool changer are crucial for high-volume production, as they significantly reduce setup time and increase the overall efficiency of the milling process.
The knee is attached to the column by dovetail ways and is supported and adjusted up and down by an elevating screw, also called a vertical positioning screw, running vertically from the base. The vertical movement can be achieved by either a hand crank or power feed. The handle to move the saddle in the transverse direction (cross feed, or in and out) is also located on the knee, while the gearing mechanism is enclosed within the knee. Some milling machines have power table feed in the transverse direction, and that unit is on the knee, as well.
The saddle is on top of the knee moving transversely to the column and providing motion in a horizontal direction to the workpiece. It is also made of cast iron.
The power feed mechanism is contained in the knee. The power feed mechanism is used to control longitudinal (left and right), transverse (in and out), and vertical (up and down) feeds. Feed rates are changed for some knee milling machines by turning the speed selection handle. Most milling machines have a rapid traverse lever to provide a temporary increase in the speed of the longitudinal, transverse, or vertical feeds.
As its name suggests, most of the machining work happens on the work table. The table is a rectangular piece of cast iron with T-slots for clamping a workpiece directly to it or fastening a vise or other work holding device to hold smaller parts and machine them safely and efficiently.
The longitudinal variable speed power feed and handles are part of the work table. In addition, an X-axis leadscrew under the table engages with a nut and assists the table in moving horizontally, either under power or manually.
