Non-Traditional Machining

Question 1

What are the four categories of non-traditional machining?

Answer 1

Mechanical
Electrical
Thermal
Chemical

Question 2

Briefly describe mechanical non-traditional machining?

Answer 2

Mechanical energy in some for mother than the action of a conventional cutting tool is used in these non-traditional processes. Erosion of the work material by a high velocity stream of abrasives or fluid (or both)is a typical form of mechanical action in these processes.

Question 3

Briefly describe electical non-traditional machining?

Answer 3

These non-traditional processes use electrochemical energy to remove material; the mechanism is the reverse of electroplating.

Question 4

Briefly describe thermal non-traditional machining?

Answer 4

These processes use thermal energy to cut or shape the workpart. The thermal energy is generally applied to a very small portion of the work surface, causing that portion to be removed by fusion and/or vaporization. The thermal energy is generated by the conversion of electrical energy.

Question 5

Briefly describe chemical non-traditional machining?

Answer 5

Most materials (metals particularly) are susceptible to chemical attack by certain acids or other etchants. In chemical machining, chemicals selectively remove material from portions of the workpart, whereas other portions of the surface are protected by a mask.

Question 6

What is ultrasonic machining?

Answer 6

Ultrasonic machining (USM) is a non-traditional machining process in which abrasives contained in a slurry are driven at high velocity against the work by a tool vibrating at low amplitude and high frequency.

Question 7

What is typical amplitude and frequency of USM

Answer 7

The amplitudes are around 0.075 mm, and the frequencies are approximately 20,000 Hz.

Question 8

Describe the slurry used in USM

Answer 8

The slurry in USM consists of a mixture of water and abrasive particles. Concentration of abrasives in water ranges from 20% to 60%.

Question 9

What is water jet cutting?

Answer 9

Water jet cutting (WJC) uses a fine, high-pressure, high-velocity stream of water directed at the work surface to cause cutting of the work

Question 10

Give an overview of the data involved with the high pressure water jet

Answer 10

To obtain the fine stream of water a small nozzle opening of diameter 0.1 to 0.4 mm is used. To provide the stream with sufficient energy for cutting, pressures up to 400MPa are used, and the jet reaches velocities up to 900 m/s.

Question 11

In WJC what are the components made of.

Answer 11

The nozzle unit consists of a holder made of stainless steel, and a jewel nozzle made of sapphire, ruby, or diamond.

Question 12

What are some advantages of WJC

Answer 12

(1) no crushing or burning of the work surface typical in other mechanical or thermal processes
(2) minimum material loss because of the narrow cut slit
(3) no environmental pollution
(4) ease of automating the process

Question 13

What is a limitation of WJC?

Answer 13

A limitation of WJC is that the process is not suitable for cutting brittle materials (e.g., glass) because of their tendency to crack during cutting.

Question 14

What is abrasive water jet cutting?

Answer 14

For cutting metal abrasive particles may be added to the water jet.

Question 15

What are typical abrasives used in AWJC?

Answer 15

Aluminum oxide, silicon dioxide, and garnet (a silicate mineral).

Question 16

What is abrasive jet machining?

Answer 16

A material removal process caused by the action of a high-velocity stream of gas containing small abrasive particles

Question 17

What gases are used in AJM

Answer 17

Gases include dry air, nitrogen, carbon dioxide, and helium.

Question 18

What is a common limitation of thermal energy processes

Answer 18

Poor surface finish

Question 19

What are the five main thermal energy processes?

Answer 19

(1) electric discharge machining and electric discharge wire cutting
(2) electron beam machining
(3) laser beam machining
(4) arc cutting processes
(5) oxyfuel cutting processes.

Question 20

What is electric discharge machining (EDM)?

Answer 20

An electrode tool in the desired shape cause a spark to occur across a small gap in the presence of a dielectric fluid. The discharges are generated by a pulsating direct current power supply. The discharge occurs at the closest surfaces and a tiny chip is removed. This occurs thousands of times per second causing the gradual erosion of the entire surface area.

Question 21

What is overcut in EDM?

Answer 21

Overcut in EDM is the distance by which the machined cavity in the workpart exceeds the size of the tool on each side of the tool. It is produced because the electrical discharges occur at the sides of the tool as well as its frontal area.

Question 22

What is electric discharge wire cutting?

Answer 22

A special form of electric discharge machining that uses a small diameter wire as the electrode to cut a narrow kerf in the work. It must take place in the presence of dielectric.

Question 23

What materials may be used for the wire in EDWC

Answer 23

Brass, copper, tungsten, and molybdenum

Question 24

Describe arc-cutting processes?

Answer 24

The intense heat from an electric arc can be used to melt virtually any metal for the purpose of welding or cutting. Most arc-cutting processes use the heat generated by an arc between an electrode and a metallic workpart.

Question 25

What are the two most common types of arc cutting?

Answer 25

Plasma arc cutting

Air carbon arc cutting

Question 26

What is plasma?

Answer 26

A plasma is defined as a superheated, electrically ionized gas.

Question 27

What is plasma arc cutting (PAC)

Answer 27

Plasma arc cutting (PAC) uses a plasma stream operating at temperatures in the range 10,000◦C to 14,000◦C to cut metal by melting