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MILLING MACHINE PDF

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MILLING OPERATIONS. Milling is the process of machining flat, curved, or. Milling machines are basically classified as vertical or irregular surfaces by feeding. Development and improvements of the milling machine and components continued, which resulted in the manufacturing of heavier arbors and high speed steel. The basic function of milling machines is to produce flat surfaces in any orientation as well as surfaces of revolution, helical surfaces and contoured surfaces of.


Milling Machine Pdf

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One or more rotary milling cutters. • Workpiece held on work table or holding device and brought into contact with cutter. • Vertical milling machine most common. A milling machine is a machine tool that removes metal as the work is fed In milling machine, the metal is cut by means of a rotating cutter having multiple. •A universal milling machine that allows for horizontal and vertical milling. • Compact construction with economical price. • 6-step speed on horizontal spindle .

The knee is a rigid casting mounted on the front face of the column. The knee moves vertically along the guide ways and this movement enables to adjust the distance between the cutter and the job mounted on the table.

The adjustment is obtained manually or automatically by operating the elevating screw provided below the knee.

Milling Machine Books

The saddle rests on the knee and constitutes the intermediate part between the knee and the table. The saddle moves transversely, i. The table rests on guide ways in the saddle and provides support to the work. The table is made of cast iron, its top surface is accurately machined and carriers T-slots which accommodate the clamping bolt for fixing the work.

The worktable and hence the job fitted on it is given motions in three directions:. Longitudinal back and forth motion provided by hand wheel fitted on the side of feed screw. Overar m: The Overarm is mounted at the top of the column and is guided in perfect alignment by the machined surfaces.

The Overarm is the support for the arbor. Arbor support: The arbor support is fitted to the Overarm and can be clamped at any location on the Overarm.

Its function is to align and support various arbors. The arbor is a machined shaft that holds and drives the cutters. Elevating screw: The upward and downward movement to the knee and the table is given by the elevating screw that is operated by hand or an automatic feed.

Plain or slab milling. Face Milling. Angular Milling. There are two subcategories of vertical mills: the bed mill and the turret mill. A turret mill has a stationary spindle and the table is moved both perpendicular and parallel to the spindle axis to accomplish cutting. The most common example of this type is the Bridgeport, described below.

Turret mills often have a quill which allows the milling cutter to be raised and lowered in a manner similar to a drill press. This type of machine provides two methods of cutting in the vertical Z direction: by raising or lowering the quill, and by moving the knee.

In the bed mill, however, the table moves only perpendicular to the spindle's axis, while the spindle itself moves parallel to its own axis. Turret mills are generally considered by some to be more versatile of the two designs.

Milling Machine Books

However, turret mills are only practical as long as the machine remains relatively small. As machine size increases, moving the knee up and down requires considerable effort and it also becomes difficult to reach the quill feed handle if equipped.

Therefore, larger milling machines are usually of the bed type. A third type also exists, a lighter machine, called a mill-drill, which is a close relative of the vertical mill and quite popular with hobbyists. A mill-drill is similar in basic configuration to a small drill press, but equipped with an X-Y table. They also typically use more powerful motors than a comparably sized drill press, with potentiometer-controlled speed and generally have more heavy-duty spindle bearings than a drill press to deal with the lateral loading on the spindle that is created by a milling operation.

A mill drill also typically raises and lowers the entire head, including motor, often on a dovetailed vertical, where a drill press motor remains stationary, while the arbor raises and lowers within a driving collar. Other differences that separate a mill-drill from a drill press may be a fine tuning adjustment for the Z-axis, a more precise depth stop, the capability to lock the X, Y or Z axis, and often a system of tilting the head or the entire vertical column and powerhead assembly to allow angled cutting.

Aside from size and precision, the principal difference between these hobby-type machines and larger true vertical mills is that the X-Y table is at a fixed elevation; the Z-axis is controlled in basically the same fashion as drill press, where a larger vertical or knee mill has a vertically fixed milling head, and changes the X-Y table elevation.

As well, a mill-drill often uses a standard drill press-type Jacob's chuck, rather than an internally tapered arbor that accepts collets. These are frequently of lower quality than other types of machines, but still fill the hobby role well because they tend to be benchtop machines with small footprints and modest price tags.

Horizontal milling machine[ edit ] Horizontal milling machine. Many horizontal mills also feature a built-in rotary table that allows milling at various angles; this feature is called a universal table. While endmills and the other types of tools available to a vertical mill may be used in a horizontal mill, their real advantage lies in arbor-mounted cutters, called side and face mills, which have a cross section rather like a circular saw, but are generally wider and smaller in diameter.

Because the cutters have good support from the arbor and have a larger cross-sectional area than an end mill, quite heavy cuts can be taken enabling rapid material removal rates. These are used to mill grooves and slots. Plain mills are used to shape flat surfaces. Several cutters may be ganged together on the arbor to mill a complex shape of slots and planes.

Special cutters can also cut grooves, bevels, radii, or indeed any section desired. These specialty cutters tend to be expensive. Many different types of cutting tools are used in the milling process.

Milling cutters such as endmills may have cutting surfaces across their entire end surface, so that they can be drilled into the workpiece plunging. Milling cutters may also have extended cutting surfaces on their sides to allow for peripheral milling. Tools optimized for face milling tend to have only small cutters at their end corners. The cutting surfaces of a milling cutter are generally made of a hard and temperature-resistant material, so that they wear slowly.

A low cost cutter may have surfaces made of high speed steel. More expensive but slower-wearing materials include cemented carbide. Thin film coatings may be applied to decrease friction or further increase hardness. There are cutting tools typically used in milling machines or machining centres to perform milling operations and occasionally in other machine tools.

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They remove material by their movement within the machine e. As material passes through the cutting area of a milling machine, the blades of the cutter take swarfs of material at regular intervals. Surfaces cut by the side of the cutter as in peripheral milling therefore always contain regular ridges. The distance between ridges and the height of the ridges depend on the feed rate, number of cutting surfaces, the cutter diameter. The face milling process can in principle produce very flat surfaces.

However, in practice the result always shows visible trochoidal marks following the motion of points on the cutter's end face. These revolution marks give the characteristic finish of a face milled surface.

Revolution marks can have significant roughness depending on factors such as flatness of the cutter's end face and the degree of perpendicularity between the cutter's rotation axis and feed direction. Often a final pass with a slow feed rate is used to improve the surface finish after the bulk of the material has been removed. In a precise face milling operation, the revolution marks will only be microscopic scratches due to imperfections in the cutting edge.

Gang milling refers to the use of two or more milling cutters mounted on the same arbor that is, ganged in a horizontal-milling setup. All of the cutters may perform the same type of operation, or each cutter may perform a different type of operation. For example, if several workpieces need a slot, a flat surface, and an angular groove , a good method to cut these within a non- CNC context would be gang milling.

All the completed workpieces would be the same, and milling time per piece would be minimized. Gang milling was especially important before the CNC era, because for duplicate part production, it was a substantial efficiency improvement over manual-milling one feature at an operation, then changing machines or changing setup of the same machine to cut the next op.

Today, CNC mills with automatic tool change and 4- or 5-axis control obviate gang-milling practice to a large extent. Milling is performed with a milling cutter in various forms, held in a collett or similar which, in turn, is held in the spindle of a milling machine. Mill orientation is the primary classification for milling machines. The two basic configurations are vertical and horizontal.

However, there are alternative classifications according to method of control, size, purpose and power source. In the vertical mill the spindle axis is vertically oriented. Milling cutters are held in the spindle and rotate on its axis.

There are two subcategories of vertical mills: Turret mills are generally considered by some to be more versatile of the two designs. However, turret mills are only practical as long as the machine remains relatively small.

As machine size increases, moving the knee up and down requires considerable effort and it also becomes difficult to reach the quill feed handle if equipped.

Therefore, larger milling machines are usually of the bed type. A third type also exists, a lighter machine, called a mill-drill, which is a close relative of the vertical mill and quite popular with hobbyists. A mill-drill is similar in basic configuration to a small drill press, but equipped with an X-Y table.

They also typically use more powerful motors than a comparably sized drill press, with potentiometer-controlled speed and generally have more heavy-duty spindle bearings than a drill press to deal with the lateral loading on the spindle that is created by a milling operation. A mill drill also typically raises and lowers the entire head, including motor, often on a dovetailed vertical, where a drill press motor remains stationary, while the arbor raises and lowers within a driving collar.

Other differences that separate a mill-drill from a drill press may be a fine tuning adjustment for the Z-axis, a more precise depth stop, the capability to lock the X, Y or Z axis, and often a system of tilting the head or the entire vertical column and powerhead assembly to allow angled cutting.

Aside from size and precision, the principal difference between these hobby-type machines and larger true vertical mills is that the X-Y table is at a fixed elevation; the Z-axis is controlled in basically the same fashion as drill press, where a larger vertical or knee mill has a vertically fixed milling head, and changes the X-Y table elevation.

As well, a mill-drill often uses a standard drill press-type Jacob's chuck, rather than an internally tapered arbor that accepts collets. These are frequently of lower quality than other types of machines, but still fill the hobby role well because they tend to be benchtop machines with small footprints and modest price tags.

A horizontal mill has the same sort but the cutters are mounted on a horizontal spindle see Arbor milling across the table.

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Many horizontal mills also feature a built-in rotary table that allows milling at various angles; this feature is called a universal table. While endmills and the other types of tools available to a vertical mill may be used in a horizontal mill, their real advantage lies in arbor-mounted cutters, called side and face mills, which have a cross section rather like a circular saw, but are generally wider and smaller in diameter. Because the cutters have good support from the arbor and have a larger cross-sectional area than an end mill, quite heavy cuts can be taken enabling rapid material removal rates.

These are used to mill grooves and slots. Plain mills are used to shape flat surfaces. Several cutters may be ganged together on the arbor to mill a complex shape of slots and planes.

Special cutters can also cut grooves, bevels, radii, or indeed any section desired. These specialty cutters tend to be expensive. Simplex mills have one spindle, and duplex mills have two. It is also easier to cut gears on a horizontal mill. Some horizontal milling machines are equipped with a power-take-off provision on the table.

This allows the table feed to be synchronized to a rotary fixture, enabling the milling of spiral features such as hypoid gears.

The choice between vertical and horizontal spindle orientation in milling machine design usually hinges on the shape and size of a workpiece and the number of sides of the workpiece that require machining. Work in which the spindle's axial movement is normal to one plane, with an endmill as the cutter, lends itself to a vertical mill, where the operator can stand before the machine and have easy access to the cutting action by looking down upon it.

Thus vertical mills are most favored for diesinking work machining a mould into a block of metal. Prior to numerical control , horizontal milling machines evolved first, because they evolved by putting milling tables under lathe-like headstocks.

Vertical mills appeared in subsequent decades, and accessories in the form of add-on heads to change horizontal mills to vertical mills and later vice versa have been commonly used.

Even in the CNC era, a heavy workpiece needing machining on multiple sides lends itself to a horizontal machining center, while diesinking lends itself to a vertical one. A milling machine is often called a mill by machinists.

The archaic term miller was commonly used in the 19th and early 20th centuries. Since the s there has developed an overlap of usage between the terms milling machine and machining center. The distinction, when one is made, is that a machining center is a mill with features that pre- CNC mills never had, especially an automatic tool changer ATC that includes a tool magazine carousel , and sometimes an automatic pallet changer APC. In typical usage, all machining centers are mills, but not all mills are machining centers; only mills with ATCs are machining centers.

Most CNC milling machines also called machining centers are computer controlled vertical mills with the ability to move the spindle vertically along the Z-axis.

This extra degree of freedom permits their use in diesinking, engraving applications, and 2. When combined with the use of conical tools or a ball nose cutter , it also significantly improves milling precision without impacting speed, providing a cost-efficient alternative to most flat-surface hand- engraving work. CNC machines can exist in virtually any of the forms of manual machinery, like horizontal mills.

The most advanced CNC milling-machines, the multiaxis machine , add two more axes in addition to the three normal axes XYZ. Horizontal milling machines also have a C or Q axis, allowing the horizontally mounted workpiece to be rotated, essentially allowing asymmetric and eccentric turning.

The fifth axis B axis controls the tilt of the tool itself. When all of these axes are used in conjunction with each other, extremely complicated geometries, even organic geometries such as a human head can be made with relative ease with these machines.

But the skill to program such geometries is beyond that of most operators.

Principle and Working of MILLING MACHINE

Therefore, 5-axis milling machines are practically always programmed with CAM. The operating system of such machines is a closed loop system and functions on feedback. A set of instructions called a program is used to guide the machine for desired operations. Some very commonly used codes, which are used in the program are:.

Various other codes are also used. A CNC machine is operated by a single operator called a programmer. This machine is capable of performing various operations automatically and economically. The accessories and cutting tools used on machine tools including milling machines are referred to in aggregate by the mass noun "tooling". There is a high degree of standardization of the tooling used with CNC milling machines, and a lesser degree with manual milling machines. To ease up the organization of the tooling in CNC production many companies use a tool management solution.

Milling cutters for specific applications are held in various tooling configurations. CAT tooling was invented by Caterpillar Inc. This gives BT tooling greater stability and balance at high speeds. One other subtle difference between these two toolholders is the thread used to hold the pull stud.

Note that this affects the pull stud only; it does not affect the tool that they can hold. Both types of tooling are sold to accept both Imperial and metric sized tools.Milling cutter. Many horizontal mills also feature a built-in rotary table that allows milling at various angles; this feature is called a universal table. Approximately Pratt , Elisha K. In peripheral milling, also called plain milling, the axis of the tool is parallel to the surface being machined, and the operation is performed by cutting edges on the outside periphery of the cutter.

One of the important processes involving a non-chemical change to the fullest extent is that of reducing the harvested grain to flour. But during the s and s, NC evolved into CNC, data storage and input media evolved, computer processing power and memory capacity steadily increased, and NC and CNC machine tools gradually disseminated from an environment of huge corporations and mainly aerospace work to the level of medium-sized corporations and a wide variety of products.

Discharge Chute 4. Hammer 6. This was the Bridgeport milling machine, often called a ram-type or turret-type mill because its head has sliding-ram and rotating-turret mounting.