ABOUT MACHINES.

By :D.JOTHILINGAM

Metal Working Metalworking is the process of

working with metals to create individual parts, assemblies, or large scale structures.

It therefore includes a correspondingly wide range of skills and the use of many different types of metalworking processes and their related tools.

PRE HISTORY Metalworking predates history. No

one knows with any certainty where or when metalworking began.

The advance that brought metal into focus was the connection of fire and metals.

Not all metal required fire to obtain it or work it.

Metalworking was being carried out by the South Asian inhabitants of Mehrgarh between 7000–3300 BC

Around the date 2700 BC, production of bronze was common in locales where the necessary materials could be assembled for smelting, heating, and working the metal.

Iron was beginning to be smelted. Iron began its emergence as an important metal for tools and weapons.

The Iron Age was dawning.

Metal Forming processes

Sand casting Forging Sintering Sheet metal

OTHER PROCESSES Cutting Drilling Tapping Grinding Broaching Shaping Welding Brazing Soldering Filing Milling Turning Honing

TURNING PROCESSES.

Turning is the process whereby a single point cutting tool is parallel to the surface.

It can be done manually, in a traditional form of lathe, which frequently requires continuous supervision by the operator, or by using a computer controlled and automated lathe which does not.

This type of machine tool is referred to as having computer numerical control, better known as CNC. and is commonly used with many other types of machine tool besides the lathe.

Turning operations

Turning is one of the most basic machining processes. That is, the part is rotated while a single point cutting tool is moved parallel to the axis of rotation.

Facing is part of the turning process. It involves moving the cutting tool at right angles to the axis of rotation of the rotating workpiece.

Turning operations

Parting is used to create deep grooves which will remove a completed or part-complete component from its parent stock.

Grooving is like parting, except that grooves are cut to a specific depth by a form tool instead of severing a completed/part-complete component from the stock.

Drilling is used to remove material from the inside of a workpiece. This process utilizes standard drill bits held stationary in the tail stock or tool turret of the lathe.

Turning operations

Screw cutting both standard and non-standard screw threads can be turned on a lathe using an appropriate cutting tool. (Usually having a 60, or 55° nose angle) Either externally, or within a bore.[1] Generally referred to as single-point threading

Workholding Methods Three-jaw chuck: Used with a variety of

diameters of round stock. Four-jaw chuck: Used mainly for holding

irregular shapes. Collet chuck: Primarily used for small round

workpieces. Faceplate: A faceplate, drive dog, and

mandrel may be used to turn workpieces such as gearblanks.

Drive center: Use hydraulic or spring-loaded teeth that "bite" into the end of workpieces and can be used when the entire length of the workpiece must be machined.

Tooling

The various angles, shapes, and sizes of a single-point cutting tool have direct relation to the resulting surface of a workpiece in machining operations.

Different types of angle such as rake angle, side rake angle, cutting-edge angle, relief angle, nose radius exist and may be different with respect to the workpiece.

Also, there are many shapes of single-point cutting tools, such as V-shaped and Square. Usually, a special toolholder is used to hold the cutting tool firmly during operation.

Dynamics of turning

The relative forces in a turning operation are important in the design of machine tools.

The machine tool and its components must be able to withstand these forces without causing significant deflections, vibrations, or chatter during the operation.

There are three principal forces during a turning process: cutting force, thrust force and radial force.

CUTTING FORCE

The cutting force acts downward on the tool tip allowing deflection of the workpiece upward. It supplies the energy required for the cutting operation.

THRUST FORCE

The thrust force acts in the longitudinal direction. It is also called the feed force because it is in the feed direction of the tool. This force tends to push the tool away from the chuck.

RADIAL FORCE

The radial force acts in the radial direction and tends to push the tool away from the workpiece.

WHY AUTOMATE COMES…,

Although it requires less-skilled labor, the engine lathes do need skilled labor and the production is somewhat slow.

WHY AUTOMATE COMES…,

Moreover, it can be accelerated by using a turret lathe and automated

machines.

About AUTOMATE machines In a turret lathe, a longitudinally

feedable, hexagon turret replaces the tailstock.

The turret, on which six tools can be mounted, can be rotated about a vertical axis to bring each tool into operating position, and the entire unit can be moved longitudinally, either manually or by power, to provide feed for the tools

HOW AUTOMATE COMES…,

Machine tools of the "automatic" variety had already reached a highly advanced state by the World War I era.

HOW AUTOMATE COMES…,

When World War II ended, the digital computer was poised to develop from a colossal laboratory curiosity into a practical technology that could begin to disseminate into business and industry

ABOUT CNC TURRET LATHES

Today, most CNC lathes have turrets, and so could logically be called turret lathes, but the terminology is usually not used that way.

Horizontal CNC lathes, with or without turrets, are generally called CNC lathes or CNC turning centers or turning centers

HISTORY OF CNC MACHINES

The first NC machines were built in the 1940s and 50s, based on existing tools that were modified with motors that moved the controls to follow points fed into the system on paper tape.

Late-19th through mid-20th centuries: key to mass production

From the late-19th through mid-20th centuries, turret lathes, both manual and automatic (i.e., screw machines and chuckers), were one of the most important classes of machine tools for mass production.

Mid-20th century to present: transition to small runs and second operations With the development and dissemination of

CNC lathes manual turret lathes began to lose their

position as the key to mass production of turned parts.

However, they did not become obsolete; the focus of their use simply shifted from the main turning operations of mass production

to small runs and second operations

STATUS OF AUTOMATED MACHINES Similarly, cam-operated screw machines and

chuckers did not disappear; they simply shifted to a different niche.

They still often compete with CNC machines in terms of unit cost per part produced, depending on the difference in overhead.

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