Unconventional machining process

INTRODUCTION

1 INTRODUCTION

Unconventional 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.

Extremely hard and brittle materials are difficult to machine by traditional machining processes such as turning, drilling, shaping and milling. Nontraditional machining processes, also called advanced manufacturing processes, are employed where traditional machining processes are not feasible, satisfactory or economical due to special reasons as outlined below.

•                     Very hard fragile materials difficult to clamp for traditional machining

•                     When the work piece is too flexible or slender

•                     When the shape of the part is too complex

Several types of non-traditional machining processes have been developed to meet extra required machining conditions. When these processes are employed properly, they offer many advantages over non-traditional machining processes. The common non- traditional machining processes are described in this section.

Manufacturing processes can be broadly divided into two groups)

a) Primary manufacturing processes: Provide basic shape and size

b) Secondary manufacturing processes: Provide final shape and size with tighter control on dimension, surface characteristics

Material Removal Processes Once Again Can Be Divided Into     Two Groups

1. Conventional Machining Processes

2. Non-Traditional Manufacturing Processes or Unconventional Machining processes

Conventional Machining Processes mostly remove material in the form of chips by applying forces on the work material with a wedge shaped cutting tool that is harder than the work material under machining condition.

THE MAJOR CHARACTERISTICS OF CONVENTIONAL MACHINING ARE:

• Generally macroscopic chip formation by shear deformation

• Material removal takes place due to application of cutting forces – energy domain can be Classified as mechanical

• Cutting tool is harder than work piece at room temperature as well as under machining Conditions

Non-conventional 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. Material removal may occur with chip formation or even no chip formation may take place. For example in AJM, chips are of microscopic size and in case of Electrochemical machining material removal occurs due to electrochemical dissolution at atomic level.

2 NEED FOR UNCONVENTIONAL MACHINING PROCESSES

•  Extremely hard and brittle materials or Difficult to machine material are difficult to Machine by traditional machining processes.

• When the work piece is too flexible or slender to support the cutting or grinding Forces when the shape of the part is too complex.

3 CLASSIFICATION OF UCM PROCESSES:

1. Mechanical Processes

•                     Abrasive Jet Machining (AJM)

•                     Abrasive Water Jet Machining (AWJM)

•                     Water Jet Machining (WJM)

•                     Ultrasonic Machining (USM)

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)

4 BRIEF OVERVIEW

1  ULTRA SONIC MACHINING

USM is a mechanical material removal process in which the material is removed by repetitive impact of abrasive particles carried in liquid medium on to the work surface, by a shaped tool, vibrating at ultrasonic frequency.

2 ABRASIVE JET MACHINING

It is the material removal process where the material is removed or machined by the impact erosion of the high velocity stream of air or gas and abrasive mixture, which is focused on to the work piece.

3. LASER BEAM MACHINING

Laser-beam machining is a thermal material-removal process that utilizes a high- Energy, Coherent light beam to melt and vaporize particles on the surface of metallic and non- Metallic work pieces. Lasers can be used to cut, drill, weld and mark. LBM is particularly suitable for making accurately placed holes

4. ELECTRON EAM MACHINING

It is the thermo-electrical material removal process on which the material is removed by the high velocity electron beam emitted from the tungsten filament made to impinge on the work surface, where kinetic energy of the beam is transferred to the work piece material, producing intense heat, which makes the material to melt or vaporize it locally.

5. ELECTRO CHEMICAL MACHINING

It is the controlled removal of metals by the anodic dissolution in an electrolytic medium, where the work piece (anode) and the tool (cathode) are connected to the electrolytic circuit, which is kept, immersed in the electrolytic medium

6. ELECTO CHEMICAL GRINDING

ECG is the material removal process in which the material is removed by the combination of Electro- Chemical decomposition as in ECM process and abrasive due to grinding.

7. PLASMA ARC MACHINING

Plasma is defined as the gas, which has been heated to a sufficiently high temperature to Become ionized.

8. WATER JET MACHINING

Water jet cutting can reduce the costs and speed up the processes by eliminating or reducing expensive secondary machining process. Since no heat is applied on the materials, cut edges are clean with minimal burr. Problems such as cracked edge defects, crystallization, hardening, reduced wealdability and machinability are reduced in this process.

9. ELECTRICAL DISCHARGE MACHINING

EDM is the controlled erosion of electrically conductive materials by the Initiation of rapid and repetitive spark discharge between the electrode tool to the cathode and work to anode separated by a small gap kept in the path of dielectric medium. This Process also called spark erosion.