A CNC milling machine is a form of subtractive manufacturing that begins with a block of raw material – typically metal, wood, or plastic – and the material is cut and carved as necessary to achieve the desired geometry. CNC milling is a highly versatile machining method that is known for its precision and ability to achieve complex designs with tight tolerances.
There are various CNC milling machines on the market but nearly all are comprised of the same key pieces of equipment: a work table, cutting tool, and spindle. The block of raw material is typically fastened to the work table. The cutting tool is held in place by a spindle which, for most CNC milling machines, is rotated by an electric motor during cutting operations. The cutting tool, or cutter as it is often called, is used to mechanically perform the carving. One of the most common tools is a milling cutter, which is similar to a drill bit but has many “teeth” that are designed to remove material in a specific way. Cutters come in a variety of shapes, sizes, and arrangement of teeth, each providing a unique cut. As the milling cutter contacts the work piece, the teeth of the tool repeatedly cut the material, shaving off chips from the work piece with each pass. The milling process removes material by performing many separate, small cuts. Operating conditions such as the feed rate and cutting speed can be adjusted as necessary to achieve the desired cut during CNC milling. State-of-the-art CNC milling machines may also include advanced equipment such as remote tool changers, tool carousels, and robust coolant systems to improve operations efficiency.
Proper tool selection is a key aspect of successful CNC milling. Tools are typically designed to provide a unique cut and for use with a certain raw material. Choose the wrong tool and you may damage the work piece or even the tool and CNC machine. In general, smaller cutting tools take longer to complete the desired cut but are able to deliver more complex and intricate designs. Ideally, each milling job would only require a single tool, however, most parts require multiple tools to achieve the desired design. Another component of tool selection is balancing – and in most cases minimizing – machine time in order to complete the part as fast as possible without sacrificing quality. For these reasons, it is crucial to select the right tools for each job and rely on the expertise of a trusted CNC milling partner, like ABS, that guides customers through the design process and offers a wide array of CNC machining solutions.
There are two main types of CNC milling machines that are categorized based on orientation: vertical and horizontal. As the name implies, vertical machines are oriented to perform cutting “up and down” in a vertical motion whereas horizontal machines perform cutting horizontally. There is variety within both types of milling machines; for example, spindles and work tables can either be stationary or move along a number of axes, depending on the specific CNC milling machine being used. In general, vertical mills are often considered more versatile while horizontal mills are typically used for heavier or longer parts that require deeper cuts. Some key factors to consider when deciding between a vertical or horizontal milling machine include the size and geometry of the part as well as the number of surfaces that require cutting. Additionally, universal CNC milling is another type of machine that is able to accommodate a horizontal or vertical spindle depending on how the machine is setup. Universal machines offer machine shops additional CNC machining flexibility.