Manufacturing & Function of rotary table in Vertical Milling machine

ABSTRACT

We will study about rotary table of Vertical milling machine and the role of the Rotary plate(rotary table). The vertical milling machine is a precision tool used for shaping and fabrication by the removal of stock typically from metallic work pieces. Plastics and other materials can also be machined on the milling machine depending upon tooling and material.

A rotary table is a precision work positioning device used in metalworking. It enables the operator to drill or cut work at exact intervals around a fixed (usually horizontal or vertical) axis. Some rotary tables allow the use of index plates for indexing operations, and some can also be fitted with dividing plates that enable regular work positioning at divisions for which indexing plates are not available.

OBJECTIVE:

·         To create (make) a rotary table plate by working on the concept of the rotary table.

·         Study the function of rotary table in Milling machine.

·         Study about the vertical milling machine.

Rotary Table:

A rotary table is a precision work positioning device used in metalworking. It enables the operator to drill or cut work at exact intervals around a fixed (usually horizontal or vertical) axis. Some rotary tables allow the use of index plates for indexing operations, and some can also be fitted with dividing plates that enable regular work positioning at divisions for which indexing plates are not available. A rotary fixture used in this fashion is more appropriately called a dividing head (indexinghead).The rotatry table is shown in the Fig 1.

 

Fig 1.

APPARATUS:

·         Vertical milling Machine  (for the facing of the work-piece)

·         Drilling  (for the internal diameter/hole)

·         Rotary table  (for the grooving of work-piece)

Fig. AFTER

Fig. AFTER

Vertical Milling Machine Description:

 

Fig

The vertical milling machine is a precision tool used for shaping and fabrication by the removal of stock typically from metallic work pieces ,shown in the following Fig. Plastics and other materials can also be machined on the mill depending upon tooling and material. Mill controls may be manually operated, computer numerical controlled (CNC), or a combination of both.

Mill machining and material removal is typically made by a rotary cutter held in a spindle. Cutting options are more sophisticated and variable than a drill press by virtue of a moveable table and/or vise (x and y-axes) and vertical spindle movement (z-axis).

Many vertical mills also have a rotatable turret for the upper cutting head which provides even greater machining options (b-axis). A diagram is included in this procedure to help illustrate the varying axes.

Some of the common operations that can be performed on the mill include:

• Milling– These operations provide a flat surface or spot on a work piece, typically with a specific orientation to other work piece features, surfaces, or another piece. Facing is sometimes used on an irregular shaped work piece to “true” one surface at a time to ensure that all surfaces have appropriate specific geometric relationships with each other.

• Slotting or keyways – Slots, flats, or keyways can be cut with proper fixturing.

• Drilling or boring – Where specific orientations are required between work piece features, the        vertical mill provides the means to accurately index and machine holes.

Vertical Milling History:

Milling machines evolved from the practice of rotary filing—that is, running a circular cutter with file-like teeth in the headstock of a lathe. Rotary filling and later,true milling were developed to reduce time and effort spent hand-filing. The full story of milling machine development may never be known, because much early development took place in individual shops where few records were kept for posterity.

 In 1795, Eli Terry began using a milling machine at Plymouth Connecticut in the production of tall case clocks. With the use of his milling machine, Terry was the first to accomplish Interchangeable parts in the clock industry. Milling wooden parts was efficient in interchangeable parts, but inefficient in high yields.

In 1816, Milling machine invented to reduce hand filing of intricate shapes. Later, in 1818, Whitney invented the first milling machine. A bit later in the year 1818 Eli Whitney (inventor of the cotton gin) invents a milling machine in New Haven Connecticut. Prior to the milling machine, a machinist’s tools were primarily files and required a highly skilled operator. The milling machine allowed a less skilled operator to make the same quality of parts as the skilled operator with the file. This milling machine found use making rifles for the government. The CNC (tape) machines started to show up around 1953, in the earlier past the wood milling machine made in England that was used in making patterns in a foundry. This machine had more axis than an octopus. The table had X-Y-Z, would rotate, tilt. All this motions were made by gear changes.

Description of Rotary Table:

Rotary tables are most commonly mounted "flat", with the table rotating around a vertical axis, in the same plane as the cutter of a vertical milling machine. An alternate setup is to mount the rotary table on its end (or mount it "flat" on a 90° angle plate), so that it rotates about a horizontal axis. In this configuration a tailstock can also be used, thus holding the work-piece "between centers."

With the table mounted on a secondary table, the work-piece is accurately centered on the rotary table's axis, which in turn is centered on the cutting tool's axis. All three axes are

thus coaxial. From this point, the secondary table can be offset in either the X or Y direction to set the cutter the desired distance from the work-piece's center.

This allows concentric machining operations on the work-piece. Placing the work-piece eccentrically a set distance from the center permits more complex curves to be cut. As with other setups on a vertical mill, the milling operation can be either drilling a series of concentric, and possibly equidistant holes, or face or end milling either circular or semicircular shapes and contours.

A rotary table can be used:

·         To machine spanner flats on a bolt.

·         To drill equidistant holes on a circular flange

·         To cut a round piece with a protruding tang

·         To create large-diameter holes, via milling in a circular toolpath, on small milling machines that don't have the power to drive large twist drills (>0.500"/>13 mm).

·         To mill helixes.

·         To cut complex curves (with proper setup).

·         to cut straight lines at any angle.

·         to cut arcs.

·         with the addition of a compound table on top of the rotary table, the user can move the center of rotation to anywhere on the part being cut. This enables an arc to be cut at any place on the part.

·         to cut circular pieces.

Additionally, if converted to stepper motor operation, with a CNC milling machineand a tailstock, a rotary table allows many parts to be made on a mill that otherwise would require a lathe.

Description of Work-piece:

All the dimensions are taken in millimeters (mm)

Scale:

1inches = 12ft

1ft = 25.4 mm

·         Length of the plate is = 250mm

·         Inner Diameter or Circle is 25mm

·         Total grooves = 3

·         Groove Size 2mm

·         Clamping Gap =4

·         Clamping Gap Length =10mm

·         Clamping Gap Width =10mm

·         Work-piece Thickness =10mm

Working: