Unit 16

Unconventional Machining Processes (Ⅱ

)

1. Laser Beam MachiningLaser beam machining (LBM)utilises the energy from the

coherent light beams called laser (light amplification by

stimulated emission [放射] of radiation [辐射] ).

One of the important properties of laser is

the coherency.

Typical power densities used for cutting are of order of

Fig.1 Schematic set up of a laser drilling operation

Laser beams are also used for the following:(1) Welding

(2)Small-scale and localized heat treating of metals and

ceramics to modify their surface mechanical and tribological

[摩擦学的] properties

(3)The marking of parts, such as letters, numbers, codes, ect

2. Electron-beam Machining

Fig.2 Schematic illustration of the electron-beam machining process

3. Water-jet Machining

A pressure level of about 400 MPa (60 ksi)is generally used for efficient operation, although pressures as high as 1,400 MPa (200 ksi)can be generated. Jet-nozzle [喷嘴] diameters range between 0.05 mm

and 1 mm (0.002 in. and 0.04 in.).

A variety of materials can be cut, including

plastics, fabrics, rubber, wood products, paper, leather,

insulating [绝缘的] materials, brick, and composite materials.

A water-jet cutting machine and its operation are shown in Fig.3.

Fig.3 Schematic illustration of water-jet machining

In abrasive water-jet machining

(AWJM),the water jet contains abrasive particles(such as silicon carbide or aluminum oxide), which increase the material-removal rate above that of water-jet machining.

silicon carbidealuminum oxide

5. Photochemical Machining (PCM)

Fig.4 Processing of substrates coated with negative-and positive-working photoresists

Electron-beam Machining

A machining process in which heat is produced by a focused electron beam at a sufficiently high temperature to volatilize

[挥发] and thereby remove metal in a desired manner; takes place in a vacuum. Abbreviated EBM.

Water-jet Cutter

A water jet cutter is a tool

capable of slicing into metal or

other materials using a jet of

water at high velocity [高速]

and pressure, or a mixture of

water and an abrasive

substance. The process is

essentially the same as water

erosion found in nature but

accelerated and concentrated by orders of magnitude.

Photochemical Machining

The process of using photochemical machining is ideal for thin metal parts fabrication, fine line etching [蚀刻] , and

engineering of micro machined parts. Many of these thin metal parts are then precisely formed into complex shapes. The advantages of photochemical machining are quite

diverse in what it can do for metal parts manufacturing. Large format panels, tight tolerances, and low cost of tooling are but a few of the advantages with PCM for producing burr free

intricate metal parts. Additionally the time from concept design engineering, to prototype [标准件] , to manufacturing the parts, is substantially reduced.

Notes句意：激光加工的基本原理是在一定条件下采用特定频率的光激发原子中的电子，使其发射特征与原光源完全相同的光。