Cnc machining nm09/2

CNC Machining 1

NM09/2 2

Table of contents 3

Introduction 4

Section 1: Industrial applications of CNC machines 7

Objectives 8

1.1 Numerical control 10

1.2 CNC operation 14

1.3 Computer numerical control (CNC) applications 16

1.4 Economics of numerical control 22

1.5 Numerical control (NC) advantages 23

1.6 Numerical control (NC) disadvantages 24

1.7 Features of numerical control machines 25

1.8 CNC machine features 28

1.9 Types of machine control units (MCU) 37

1.10 Machine control unit (MCU) development 42

1.11 Computer numerical control machine axes 56

1.12 CNC lathes 64

Review questions — section 1 66

Section 2: Basic operation of CNC machines 69

2.1 Machine positioning system 72

2.2 Motion control systems 79

2.3 Stored stroke limit 89

2.4 Buffer storage 90

2.5 Work handling 92

2.6 Tool changers 93

2.7 Work holding 95

2.8 Flexible manufacturing systems 97

2.9 Types of manufacturing systems 102

2.10 Special manufacturing systems 103

2.11 Manufacturing cells 105

2.12 Flexible manufacturing systems 106

2.13 Components of a CIM system 108

Review questions — section 2 122

Section 3: Job planning 124

3.1 The NC procedure 127

Review questions — section 3 146

Section 4: Write and edit basic CNC programs 150

4.1 Cartesian coordinate system 153

4.2 Program zero points 157

4.3 Absolute and incremental co-ordinate programming 159

4.4 Machine home and work zero 162

4.5 CNC calculations — Basic trigonometry 164

Review questions — Section 4 179

Practical exercises — section 4 181

4.6 Preparing NC programs 190

4.7 Program validation 195

4.8 The computer 211

4.9 Review of computer terms 217

4.10 Computer hardware 218

4.11 Punched tape 223

4.12 Computer software 228

4.13 CAD/CAM software 229

4.14 Writing simple programs 236

4.15 Program formats 237

4.16 Modal codes 245

4.17 Contour machining using circular interpolation 260

4.18 Programming examples 270

4.19 Writing a program for a machining centre 274

4.20 CNC Machining centre program format 280

4.21 Writing a program for the 0kuma LB15 CNC lathe 293

4.22 OKUMA LBt5 CNC lathe program format 300

4.23 Points on CNC lathe programming 309

4.24 Tool nose radius compensation 325

4.25 How to call up and use tool nose radius compensation 334

Exercise 9 — section 4 — lathe programming 337

4.26 Quality control 341

4.27 Canned cycles 343

Review questions — section 4 345

Section 5: Transfer programs to CNC machines 346

5.1 Setting up a CNC Milling Machine 349

5.2 Program entering and checking 350

5.3 Safety 351

Exercise 10 — section 5 — program transfer 352

Section 6: CNC machine preparation 354

6.1 Work holding devices 358

6.2 Mounting tools in the tool changer 361

6.3 Offsets 362

6.4 Tool change position 363

6.5 Workpiece datum 364

6.6 Workpiece and machine checks before and after machining 365

6.7 Dry running program 370

Practical exercise 11 — section 6 371

Section 7: CNC machine operation 374

7.1 Quality Assurance 378

7.2 Machine operations 381

7.3 Control Panel 382

7.4 Machining 384

7.5 Proving 385

7.6 Editing 386

7.7 Machining 387

Practical exercise 12 — section 7 389

Answers to questions 392

Review questions — section 4 409

Answers to exercises — section 4 — exercise 1 415

Answers to exercises — section 4 — exercise 2 416

Answers to exercises — section 4 — exercise 3 417

Answers to exercises — section 4 — exercise 4 418

Answers to exercises — section 4 — exercise 5 420

Answers to exercises — section 4 — exercise 6 421

Answers to exercises — section 4 — exercise 7 422