What Is A Milling Machine? Its Applications, Parts, Diagrams, Types, Operations, How It Works, Advantages, And Disadvantages
In a machine shop, milling machining is a crucial process that involves advancing a cutter into a workpiece to remove material. This process, which can be performed in various directions, is essential for the manufacturing process.
Milling machines are suitable for various operations, from small individual parts to large ones, and are ideal for machining custom parts to precise tolerances.
Milling machines are a versatile tool used in industrial workshops for various operations, including carving, threading, milling, drilling, and cutting.
These machines rotate a circular tool with symmetrical cutting edges around its axis, holding the workpiece in a vise or similar device. They are commonly used to machine irregular and flat surfaces, such as metal, plastic, and wood.
Milling machines are powered tools designed to mill or carve material using various cutting tools such as rotating blades, drills, and abrasives. The best mills feature high-quality cast iron construction, variable-speed engines, power feeds, and cutting tools moving along the x- and y-axis.
They are used in various roles from woodworking to metalworking, with self-contained electric drive motors, coolant systems, digital readouts, variable spindle speeds, and power-operated table feeds.
Milling machines are utilised in various applications, including gear making, groove and slot production, metal design, and cutting super-alloys, titanium, and tensile steel with closer tolerance, greater accuracy, and faster production rates, ensuring high-quality results.
The milling machine is a crucial component in the process of milling, requiring a strong foundation and a machine part. The base, made of cast iron, serves as the foundation and supports the machine’s weight.
The column, vertically mounted on the base, supports the knee and table and serves as housing for other driving members. The knee is a cast iron mechanism that supports the saddle and table and can be adjusted by a vertical positioning screw.
The saddle is an intermediate part between the table and the knee, providing horizontal motion to the workpiece. The table, situated over the knee, holds the workpiece during the milling process.
The overhanging arm is used to fasten the arbour support, which may consist of cylindrical bars that slide through the holes in the column. The spindle is the part that holds the tool in place, offering rotary motion and drives for arbours, cutters, and attachments.
The arbour serves as an extension part of the spindle in a horizontal mill machine, holding the tool and moving it in the correct direction. The milling head is the upper part of a vertical mill machine, consisting of a spindle, driving motor, and other controlling mechanisms.
The ram allows the milling machine part to move transversely on the column by a hand level. Milling machines are essential tools for various industries, including car parts, automotive, and aerospace.
There are various types of milling machines, such as column and knee, vertical milling machines, horizontal milling machines, universal milling machines, fixed bed milling machines, turret milling machines, C-frame milling machines, simplex milling machines, duplex milling machines, triplex milling machines, planner milling machines, special milling machines, tracer milling machines, and CNC milling machines.
Column and knee milling machines consist of a vertical column attached to the bed, gear drives that rotate the knee and saddle, and a table placed over it.
Vertical mills use a rotating cutting tool similar to a drilling machine or drill press, with a tool head speed ranging from 500 to 50,000 RPM.
Horizontal milling machines have a spindle situated horizontally and rotate at a horizontal position, using an arbour to hold the cylindrical disc-shaped cutter. Universal milling machines are similar to horizontal types but have a swing-up table arrangement.
Fixed bed milling machines can move in both vertical and horizontal directions. Turret milling machines, also known as Bridgeport milling machines, offer advanced functionality for producing different products and car parts.
C-frame milling machines are sturdier and hydraulically controlled, while simplex milling machines travel only in one direction, mostly in the vertical direction.
Duplex milling machines can travel both vertical and horizontal directions, and triplex milling machines move in all three directions along the X, Y, and Z axes.
CNC milling machines are the most versatile type, controlled by a computer, and ideal for difficult geometrical objects. Milling operations are essential in the production of various types of workpieces.
Plain milling is a common operation in milling machines, where the axis of the cutter is parallel to the surface being milled. This operation produces a flat, horizontal surface parallel to the axis of rotation of a plain milling cutter.
The work and cutter are secured on the machine, and the depth of cut is set by rotating the vertical feed screw. Face milling is a fundamental part of milling, involving a cutter mounted on a stub arbour.
This operation creates a flat surface at the workpiece’s face, perpendicular to the cutter’s axis. The depth of the cut is adjusted by rotating the cross-feed screw of the table.
Side milling involves using a cutter to create flat vertical surfaces on the side of a workpiece. The depth of cut is set by rotating the vertical feed screw of the table, ensuring accurate and efficient milling.
End milling is a process that produces a flat surface that can be horizontal, vertical, or at any angle using cutters like end mills. This process is suitable for producing slots, grooves, or keyways and is performed using a vertical milling machine.
Gang milling is a machining process where multiple milling cutters are mounted on an arbour to perform multiple operations simultaneously. This method saves time and is commonly used in repetitive work.
The cutting speed of a gang of cutters is calculated from the cutter with the largest diameter, allowing for efficient and accurate machining of multiple surfaces of a workpiece.
Form milling is a process used to create irregular contours, such as curves or straight lines, using convex, concave, or corner rounding milling cutters. It produces irregular shapes, such as convex or concave, and is inspected by a template gauge after machining.
The cutting rate for form milling is 20%–30% lower than plain milling. Groove milling helps in producing grooves on the surface of the workpiece with the use of a saw-milling cutter or end-milling cutter.
T-slot milling is done by using a T-slot milling cutter on the workpiece. Gear-cutting is a milling process used to cut gears on a workpiece using involute gear cutters.
Straddle milling is an operation carried out on both sides of a workpiece, creating a flat vertical surface. Helical milling is a process used to create helical-shaped objects like helical gears and twisted drills on the periphery of a cylindrical workpiece.
Thread milling is a process used in special machines to produce precise threads in small or large quantities. Cam milling is used to open and close IC engines’ valves.
Groove and Slot Milling is a process used to create keyways, grooves, and slots on a workpiece using various tools such as a plain milling cutter, a metal slitting saw, an end mill, or a side milling cutter.
Special cutters are used to create dovetail slots or T-slots, while standard keyways are cut on the shaft using side milling cutters or end mills, set at the workpiece’s centerline.
Angular milling, also known as angle milling, is a process used to create flat surfaces that are neither parallel nor perpendicular to the milling cutter’s axis.
Profile milling reproduces the outline of a template or complex shape of a master die on a workpiece using various cutters, with an end mill being a widely used milling cutter in profile milling work.
Saw milling is a process that creates narrow grooves or slots on a workpiece using a saw-milling cutter.
Milling is a process that involves holding a workpiece on a worktable, controlled by the table’s movement against a rotating cutter. The cutter moves against the workpiece to remove metal from the surface, producing the desired shape.
The milling process includes several phases, including milling cutters, surface finish, and gang milling. End mills have a special cutting surface for drilling and extended cutting surfaces for peripheral milling, with small cutters at the end corners.
Surface finish is achieved through regular intervals of cutting area with regular ridges on the sides, depending on the feed rate, cutter diameter, and number of cutting surfaces.
Gang milling involves multiple milling cutters in a horizontal milling setup, often used for duplicate parts. Before starting a cutting job, ensure the workpiece, table, taper in the spindle, and arbour are free from chips, nicks, or burrs.
Feed the workpiece in a direction opposite the rotation of the milling cutter (conventional milling) and use recommended cutting oil liberally. In a workshop, safety precautions are crucial for operating a milling machine.
These include not touching the revolving cutter, placing a wooden pad over the table surface, using the buddy system when moving heavy attachments, and not tightening arbour nuts using machine power.
When installing or removing cutters, hold them with a rag to prevent cutting hands. Never adjust workpieces or work mounting devices while the machine is operating, and use splash guards when using cutting oil.
A milling machine offers advantages such as the ability to produce complex shapes with multi-tooth, moderate operation costs, and is suitable for key-way making.
However, it is expensive and not suitable for mass production. The machine requires less experience and requires time for speed changing. Overall, a milling machine is a valuable tool for small batches and individual pieces.
FAQs
What is a milling machine?
A milling machine is a machine used for milling work, removing material from a workpiece by rotating a cutting tool. It is commonly used for flat and irregularly shaped surfaces, drilling, borering, and cutting gears, threads, and slots.
What are the five main uses of a milling machine?
A milling machine of various types is utilised for various purposes, including milling flat surfaces in vertical, horizontal, and inclined planes, making slots or ribs of sections, slitting or parting, producing surfaces of revolution, and creating helical grooves using proper cutting tools.
What is the function of milling?
Milling involves using tools in a rotary motion to cut material, requiring a high rotational speed to achieve a clean finish. This process is possible with various tools with varying diameters and hardnesses, similar to drilling.
What is the difference between a lathe and a milling machine?
Milling machines and lathes are machines used to remove material from a stationary workpiece. Milling machines rotate a multi-bladed cutting tool against a stationary workpiece, while lathes rotate a single-bladed cutting tool against a workpiece.
Related: Drilling Explained!
Source: mechlesson.com/milling-machine