30079_33a.pdf

CHAPTER 33

PRODUCTION PROCESSES

AND EQUIPMENT

Magd E. Zohdi

Industrial Engineering Department

Louisiana State University

Baton Rouge, Louisiana

William £. Biles

Industrial Engineering Department

University of Louisville

Louisville, Kentucky

Dennis B. Webster

Industrial Engineering Department

Louisiana State University

Baton Rouge, Louisiana

33.1 METAL-CUTTING

PRINCIPLES

33.9 GEAR MANUFACTURING 10 63

33.9.1 Machining Methods 10 63

33.9.2 Gear Finishing 10 67

10 36

33.2 MACHINING POWER AND

CUTTING FORCES

10 39

33.10 THREAD CUTTING AND

FORMING 1067

33.10.1 Internal Threads 1067

33.10.2 Thread Rolling 1068

33.3 TOOL LIFE

10 41

33.4 METAL-CUTTING

ECONOMICS

10 43

33.11 BROACHING

1068

33.4.1 Cutting Speed for

Minimum Cost (Vmin) 10 43

33.4.2 Tool Life Minimum Cost

OTJ

33.12 SHAPING, PLANING, AND

SLOTTING

1070

10 43

33.4.3 Cutting Speed for

Maximum Production

(Vmax) 10 44

33.4.4 Tool Life for Maximum

Production (rmax) 10 46

33.13 SAWING, SHEARING, AND

CUTTING OFF

1073

33.14 MACHINING PLASTICS 1074

33.15 GRINDING, ABRASIVE

MACHINING, AND

FINISHING 1074

33.15.1 Abrasives 1074

33.15.2 Temperature 1078

33.5 CUTTING-TOOL MATERIALS 1046

33.5.1 Cutting-Tool Geometry 1046

33.5.2 Cutting Fluids 10 47

33.5.3 Machinability 10 48

33.5.4 Cutting Speeds and Feeds 1048

33.16 NONTRADITIONAL

MACHINING

1079

33.6 TURNING MACHINES 10 48

33.6.1 Lathe Size

10 51

33.16.1 Abrasive Flow

Machining 1079

33.16.2 Abrasive Jet

Machining 1079

33.16.3 Hydrodynamic

Machining 1079

33.6.2 Break-Even (BE)

Conditions

10 51

33.7 DRILLING MACHINES 10 51

33.7.1 Accuracy of Drills 10 57

33.8 MILLING PROCESSES 10 60

Mechanical Engineers' Handbook, 2nd ed., Edited by Myer Kutz.

33.16.4 Low-Stress

Grinding

33.16.19 Shaped-Tube

Electrolytic Machining 1091

33. 1 6.20 Electron-Beam

Machining

1079

33.16.5 Thermally Assisted

Machining

1084

1092

33.16.6 Electromechanical

Machining 1084

33.16.7 Total Form Machining 1085

33.16.8 Ultrasonic Machining 1086

33.16.9 Water-Jet Machining 1086

33.16.10 Electrochemical

Deburring

33.16.21 Electrical Discharge

Grinding

1093

33.16.22 Electrical Discharge

Machining

1093

33. 16.23 Electrical Discharge

Sawing

1094

1087

33.16.24 Electrical Discharge

Wire Cutting

(Traveling Wire) 1094

33.16.25 Laser-Beam Machining 1095

33.16.26 Laser-Beam Torch 1096

33.16.27 Plasma-Beam

Machining

33. 1 6. 1 1 Electrochemical

Discharge Grinding 1088

33. 16. 12 Electrochemical

Grinding

1088

33.16.13 Electrochemical

Honing

1089

1096

33.16. 14 Electrochemical

Machining

33.16.28 Chemical Machining:

Chemical Milling,

Chemical Blanking 1096

33.16.29 Electropolishing

1089

33.16.15 Electrochemical

Polishing

1090

1098

33.16.16 Electrochemical

Sharpening

33. 16.30 Photochemical

Machining

1090

1098

33. 16. 17 Electrochemical

Turning

33 . 1 6.3 1 Thermochemical

Machining

1091

1099

33.16.18 Electro-Stream

1091

33.1 METAL-CUTTING PRINCIPLES

Material removal by chipping process began as early as 4000 BC, when the Egyptians used a rotating

bowstring device to drill holes in stones. Scientific work developed starting about the mid-19th

century. The basic chip-type machining operations are shown in Fig. 33.1.

Figure 33.2 shows a two-dimensional type of cutting in which the cutting edge is perpendicular

to the cut. This is known as orthogonal cutting, as contrasted with the three-dimensional oblique

cutting shown in Fig. 33.3. The main three cutting velocities are shown in Fig. 33.4. The metal-

cutting factors are defined as follows:

a rake angle

j8 friction angle

y strain

A chip compression ratio, t2/tl

JLI coefficient of friction

i/f tool angle

T shear stress

<f> shear angle

H relief angle

A0 cross section, wt1

em machine efficiency factor

/ feed rate ipr (in./revolution), ips (in./stroke), mm/rev (mm/revolution), or mm/stroke

/, feed rate (in./tooth, mm/tooth) for milling and broaching

F feed rate, in./min (mm/sec)

Fc cutting force

Ff friction force

Fn normal force on shear plane

Fs shear force

Ft thrust force

HPC cutting horsepower

Hpg gross horsepower

Work rotates

Tool feeds

Turning

Boring

Wheel

rotates

Cutter

rotates

Work feeds

Grinding

Milling

Reciprocating

tool

Tool feeds

laterally

Work feeds

laterally

Work

reciprocates

Shaping

Planing

Tool feeds

into work

Drill feeds

and revolves

-Work

stationary

• Work stationary

Drilling

Broaching

Sawing Reaming

Fig. 33.1 Conventional machining processes.

Hp^ unit horsepower

N revolutions per minute

Q rate of metal removal, in.3/min

R resultant force

T tool life in minutes

11 depth of cut

Fig. 33.2 Mechanics of metal-cutting process.

Fig. 33.3 Oblique cutting.

Fig. 33.4 Cutting velocities.

t^ chip thickness

V cutting speed, ft/min

Vc chip velocity

Vs shear velocity

The shear angle c/> controls the thickness of the chip and is given by

cos a

tan $ = :

(33.1)

A - sin a

The strain y that the material undergoes in shearing is given by

y = cot <f) + tan(</> -a)

The coefficient of friction /x on the face of the tool is

Ft + Fc tan a

* = Fe-F,tana

(33'2)

The friction force Ft along the tool is given by

Ft = Ft cos a + Fc sin a

Cutting forces are usually measured with dynamometers and/or wattmeters. The shear stress Tin the

shear plane is

Fc sin cf> cos <j> — Ft sin2 <f>

The speed relationships are

Vc sin (/>

V cos(0 — a)

Vc = V/X

(33.3)

33.2 MACHINING POWER AND CUTTING FORCES

Estimating the power required is useful when planning machining operations, optimizing existing

ones, and specifying new machines. The power consumed in cutting is given by

power = FCV

(33.4)

HP<= 53%

(33-5>

= Q HP^

(33.6)

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