A milling machine is a machine tool that works with a milling cutter, the rotating cutting tool that removes chips from the workpiece. There are various types of milling machine today, one of which is the bed-type milling machine, also known as the vertical milling machine.
What is a bed-type milling machine?
The bed-type milling machine is also known as the vertical milling machine and is one of the many types of milling machine available today. But what is a milling machine? Milling machines are highly complex machine tools used for metal-cutting machining of parts. They use a cutting tool with several cutting edges, called a milling cutter; the cutter rotates at high speed until it meets the surface of the workpiece and removes excess material from it.
Milling machines can be classified in different ways. There are universal machines and vertical or bed-type machines, among others. There are also special milling machines, such as gantry machines, and milling machines classified by the number of axes along which the cutting tool moves. Five-axis machines are the most advanced. Milling machines can also be manual or run under computer numerical control, or CNC.
The bed-type or vertical milling machine falls within the classification of milling machines by tool position. On these machines, the tool-holding spindle is positioned so that it rotates perpendicular to the workpiece, over its horizontal axis. That is why these milling machines have a vertical movement: either the head descends towards the workpiece or the table moves up and down towards the head.
Types of vertical milling machine
Vertical milling machines can in turn be divided into two groups: fixed-bed machines and turret machines. Although similar, they are different machines. This classification is based on how the machine heads are actuated.
- Fixed bed. The head cannot move, but the cutter can.
- Turret. The head can swivel through 180 degrees relative to the horizontal axis of the workpiece.
Features of the bed-type milling machine
The bed-type milling machine is known for being very robust. Its bed is a single piece, rigid and very heavy, and supports the worktable. As mentioned above, on this type of milling machine the table moves perpendicular to the spindle, while the spindle moves parallel to its own axis. The carriage provides cross and longitudinal travel.
These machine tools are used for machining slots, as they offer a large depth of cut when moving horizontally. A bed-type milling machine can also machine cavities in moulds, cams and dies, and can drill, bore holes and mill a wide variety of surfaces. Today, bed-type milling machines that work automatically are also available.
A distinctive feature of vertical milling machines is that their base and column are made entirely of cast iron. The heads are either fixed or swivelling. In addition, workpieces can move not only vertically but also horizontally, thanks to the carriage travel.
What to consider when choosing a bed-type milling machine
If you are planning to buy a bed-type milling machine, it is advisable to consider certain technical aspects. These are:
- Table. The table surface is the first thing to consider when choosing this machine. Both its width and length are measured.
- Weight. The maximum permissible weight indicates how many kilos the machine can support.
- Table feed travel. Measured in millimetres, this parameter indicates the ranges of cross and longitudinal table travel.
- Axes. The milling machine can move along the X and Y axes.
- Speed. Measured in revolutions per minute, it indicates the milling speed levels.
- Number of speeds. Machine tools offer different numbers of speeds. On milling machines, this indicates how many processes the machine can perform.
- Power. Cutting power is a measure of the machine's performance. Harder metals require more milling power.
- Dimensions. Bed-type or vertical milling machines tend to be versatile. The simplest models do not usually take up much space since, as their name suggests, they extend upwards rather than outwards. Dimensions are measured in millimetres.
- The spindle. When choosing a vertical milling machine, it is important to consider the spindle, specifically its distance from the table and its travel. The distance determines the maximum workpiece height; the travel, the smallest workpiece size.
- Tool holder. Consider the type of tool holder fitted to the milling machine, whether cylindrical or tapered. This determines how workpieces can be machined on this machine.