MACHINING PROCESS

Machining is any of various processes in which a piece of raw material is cut into desired final shape and size by a controlled material-removal process.Machining is a part of the manufacture of many metal products, but it can also be used on materials such as wood, plastic, ceramic and composites.Two types of machining processes:- 1.Conventional or traditional machining process 2.Non-traditional machining process

CONVENTIONAL MACHININGConventional machining can be defined as a process using mechanical (motion) energy.Conventional machining usually involves changing the shape of a work piece using an implement made of a harder material. Using conventional methods to machine hard metals and alloys means increased demand of time and energy and therefore increases in costs; in some cases conventional machining may not be feasible. Conventional machining also costs in terms of tool wear and in loss of quality in the product owing to induced residual stresses during manufacture.

NON-TRADITIONAL MACHININGNon-traditional manufacturing processes is defined as a group of processes that remove excess material by various techniques involving mechanical, thermal, electrical or chemical energy or combinations of these energies.But do not use a sharp cutting tools as it needs to be used for traditional manufacturing processes.Non traditional machining processes, also called advanced manufacturing processes, are employed where traditional machining processes are not feasible, satisfactory or economical.

Why Nontraditional Processes are Important ?Need to machine newly developed metals and non‑metals with special properties that make them difficult or impossible to machine by conventional methodsNeed for unusual and/or complex part geometries that cannot easily be accomplished by conventional machining Need to avoid surface damage that often accompanies conventional machining

Classification of Nontraditional Processes:-1. Mechanical ‑ erosion of work material by a

high velocity stream of abrasives or fluid (or both) is the typical form of mechanical action

2. Electrical ‑ electrochemical energy to remove material (reverse of electroplating)

3. Thermal – thermal energy usually applied to small portion of work surface, causing that portion to be removed by fusion and/or vaporization

4. Chemical – chemical etchants selectively remove material from portions of work-part, while other portions are protected by a mask

Non- traditional machining processes:-1)Mechanical Processes :- ⎯ Abrasive Jet Machining (AJM) ⎯ Ultrasonic Machining (USM) ⎯ Water Jet Machining (WJM) ⎯ Abrasive Water Jet Machining (AWJM) 2)Electrochemical Processes:- ⎯ Electrochemical Machining (ECM) ⎯ Electro Chemical Grinding (ECG) ⎯ Electro Jet Drilling (EJD) 3)Electro-Thermal Processes:- ⎯ Electro-discharge machining (EDM) ⎯ Laser Jet Machining (LJM) ⎯ Electron Beam Machining (EBM) 4)Chemical Processes:- ⎯ Chemical Milling (CHM) ⎯ Photochemical Milling (PCM)

1) Abrasive Jet Machining (AJM)

In Abrasive Jet Machining (AJM), abrasive particles are made to impinge on the work material at a high velocity.Almost any type of material ranging from hard brittle materials such as ceramics, metals and glass to extremely soft materials such as foam and rubbers can be cut by abrasive water jet cutting.Metallic, non-metallic and advanced composite materials of various thicknesses can be cut by this process.

Advantages:-i. No cutter induced distortion.ii. Low cutting forces on work-pieces.iii. Limited tooling requirements.iv. Little to no cutting burr.v. No heat affected zonevi. Eliminates thermal distortion.vii. No slag or cutting dross.Limitations:-viii. Cannot drill flat bottom.ix. Cannot cut materials that degrades quickly

with moisture.x. High capital cost and high noise levels during

operation.xi. The used abrasive powder can not reused.