Machining uses cutting tools to remove excess material from work pieces. Together with turning and drilling, milling facilitates the creation of high quality metal parts.
A Brief History
The first milling machines were developed in the 19th century with the goal of shaping wood. As technology and metallurgy advanced, those wood mills were repurposed for cutting and shaping metal.
Milling machines gained prominence during the Industrial Revolution. Many innovators contributed to this development, including James Nasmyth, the inventor of the steam hammer.
Today, milling performs a manufacturing role in numerous industries. From furniture making and automotive industry to telecommunications, people rely on this process to produce consumer and industrial goods.
Milling remains the most widely used machining process in many manufacturing settings. It typically involves the use of a workpiece, a milling machine containing a platform and a rotating cutter, and a fixture to hold material in desired positions.
A human or an automated machine feeds the workpiece into the path of a rotating cutting blade to remove chips of excess metal. This process may occur on a variety of workpiece surfaces and at various angles, depending upon the desired dimensions of a metal part. Manufacturers also vary the speed of rotating cutters, based upon the workpiece materials.
Many types of milling machines exist. In the past, experts distinguished between two broad categories: vertical milling machines (with vertical spindles) and horizontal milling machines (with horizontally-directed spindles to cut heavy items). Since sophisticated milling machines today often operate along all 3-dimensions (on an x, y and z axis), this distinction has become largely academic in some contemporary production environments.
Once controlled mainly by direct human manipulation, current milling machines often use computerized control systems ("CNC machines"). Detailed software programs direct specific automated movements of the cutter and the workpiece. They can generate complex parts in high volumes.
Machinists frequently perform specific types of milling operations. These include:
Specific Milling Operations
Milling machines perform a variety of operations. Just consider a few of the most popular:
The Main Milling Process Cycle
Milling may occur through "up milling" in which the rotation of the cutting blade opposes the feed motion or "down milling" in which the rotation of the cutting blade coincides with the feed motion. In most conventional milling operations, manufacturers use up milling.
End Milling: This milling operation allows a machinist to work on a tapered surface, with the rotating cutter typically located in a vertical position to the workpiece.
Chamfer Milling: Similar to a beveled edge, a chamfer forms a transition between two adjoining surface planes of an object. Specialized milling equipment called "chamfer mills" perform this operation rapidly in manufacturing environments.
Face Milling: During a face milling operation, a manufacturer affixes the rotating cutter on a spindle kept in a perpendicular position to the surface f the work piece. This operation will typically modify the appearance of the "face" of the surface.
Other Common Milling Machine Operations
Manufacturers also use milling machines to complete other, similar types of machining operations.
Drilling: Machinists may use a milling machine to remove extensive quantities of material from a part in order to form a hole or cavity.
Boring: A manufacturer may use a milling machine to enlarge the size of a cavity in a part.
Counterboring: This operation significantly widens the top section of a hole so that the head of an inserted bolt or cap screw won't protrude past the surface.
Countersinking: This operation changes the shape of a hole to provide a funnel-like, tapered rim capable of permitting a manufacturer to sink a rivet or a screw into the hole so the head will lie beneath the level of the workpiece surface.
Reaming: In reaming, a manufacturer shapes a drilled hole by removing additional material precisely, sometimes through the use of a milling machine.
Tapping: During a tapping operation, a machinist cuts a thread inside the interior of a hole to permit the insertion of a screw or other threaded object.
Advantages of Milled PARTS
Around the globe, manufacturers often produce milled parts. Both milling in general, and CNC milling in particular, hold great appeal in production environments. Milling offers important advantages.
- Machinists can mill many different types of materials readily, including most metals and metal alloys. This process works well with woods and most plastics, and will even permit the shaping of stone.
- Skilled milling can produce parts within a good tolerance range.
- In most manufacturing settings, companies complete milling operations comparatively quickly. The brief lead times involved in generating milled parts sometimes contribute to more efficient production costs.
- Milling enables companies to manufacture a variety of useful products, including some precision-cut implements and cutting tools.
- Within the subset of milled parts, automated CNC milling greatly assists numerous businesses. High tech milling machines conduct this process within close tolerances. A single machinist may generate a high volume of milled parts comparatively quickly with the assistance of robotic equipment, for instance. Modern CNC milling machinery typically includes automated cooling hoses, so machinists to don't need to manually cool down work pieces during the milling process by stopping production at frequent intervals and/or adding cooling liquids manually to the cutting area.
- Powerful automated milling machines in this century usually possess extensive computerized features. They often store entire libraries of programs, allowing machinists to shift production between different milled parts readily. The most recent versions of automated CNC milling machines permit precision cutting and the programming of highly complex shapes. The software allows manufacturers to generate nearly uniform parts in high volumes rapidly and efficiently.