Milling Machine Types

Milling Machine Types Milling machines are a very versatile machine tool. Milling machines are capable of machining one or two pieces as well as large volume production runs. The milling machine can produce a variety of surfaces by using a circular cutter with multiple teeth that progressively produce chips as the cutter rotates (Figure 1). Figure 1. Carbide face mill used on a vertical milling machine. The advantage of having a circular milling cutter with multiple teeth has led to the design of a large variety of milling machine types. These different milling machine types can be classified as Knee and Column, Fixed Bed, Bridge Type, and Special. All of these classifications can have either a vertical or horizontal spindle configuration. Further classifications of milling machines are made on the basis of the type of computer numerical control the machine uses. Knee and Column Type Milling Machines The knee and column type milling machine is a very versatile machine (Figure 2). This type of milling machine is found primarily in job shops and tool and die shops. Figure 2. Vertical Knee and Column type milling machine. Figure 3. Horizontal Knee and Column type milling machine. The most distinguishing characteristic of this type of machine is the knee and column configuration (Figure 3).This type of milling machine is unique in that the table can be moved in all three directions. The table can be moved longitudinally in the X-axis as well as in and out on the Y-axis. Since the table rides on top of the knee, the table can be moved up and down on the Z-axis. There are several different types of knee and column type milling machines, but they all have the same characteristic. The knee slides up and down on the column face. Universal Knee and Column Milling Machine The universal knee and column milling is very similar to the plain knee and column milling machine. The largest difference being the swiveling table housing. The swiveling table housing allows the table to be swiveled at an angle to the axis of the spindle (Figure 4). Figure 4. Universal Horizontal Knee and Column Milling Machine with the swivel table. Vertical Knee and Column Type Milling Machine A vertical type knee and column milling machine has the spindle located vertically, parallel to the face of the column, and perpendicular to the top of the table.The ram style knee and column type milling machine is a light duty milling machine (Figure 5). This type of machine is well suited for a variety of tool room work as well as other light duty operations. The head is mounted on a ram that can be swiveled or brought forward. This allows the head to be brought into an operating position over most of the table. Figure 5. Ram Style Knee and Column Type Vertical Milling Machine. Fixed Bed Type Milling Machines The most distinguishing aspect of the fixed bed type milling machine is the absence of the knee (Figure 6). Figure 6. Fixed Bed Horizontal Milling Machine. Figure 7. CNC Vertical Spindle Bed-Type Milling Machine. The fixed bed construction of this style of milling machine minimizes deflection and allows very heavy cuts to be taken. Fixed bed style milling machines can be used for general purpose work although many people look upon them as high production machines. The table can move in a longitudinal and a transverse direction. The vertical position of the spindle, with respect to the work table, is obtained by moving the head up and down along the column of the machine (Figure 7). Bridge Type Milling Machines The construction of the Bridge Type milling machine resembles that of a bridge (Figure 8).The table is mounted on the bed. On either side of the bed are two vertical columns connected at the top by a brace. A cross rail is mounted on the brace. The cross rail houses the spindle head. Bridge type milling machines are typically used to machine large pieces such as castings, machine tables and housings. Figure 8. CNC Vertical Bridge-Type Milling Machine. Special Milling Machines There are a number of types of special milling machines. Special milling machines are designed specifically for one particular part or family of similar parts. Specialty milling machines are used extensively in the automotive and aeronautics industry. The specialty milling machine in Figure 9 is used to mill screws used in large extruding machines. Figure 9. Extrusion Screw milling Machine.

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