Computer Integrated Manufacturing

Outline 1. Introduction to CNC machine 2. Component and Function of CNC 3. Coordinate System

1.Introduction to CNC machine CNC = Computerized Numerical Control

History and Development of Technology Conventional M/C NC M/C (1948 US Air force, MIT 21 months ) 1997  1st commercial NC m/c “CINCINNATIC HYDROTEL VERTICAL-SPINDLE MACHINE “ CNC M/C

History and Development of Technology

Conventional vs. CNC machine Machine Structure The CNC machine tools are basically built in the same way as conventional machine tools. The difference lies in the fact that the machine components relevant for turning and milling processes are controlled by computers.

Conventional vs. CNC machine Function

Conventional vs. CNC machine

Conventional vs. CNC machine Conventional machine  eyes, hands, brain, skill CNC machine Program Control unit Motor Motion Measuring & Reflection Unit No skill is required for operating CNC m/c .

Conventional machine CNC machine

Difference between Conventional M/C & CNC M/C Item Conventional machine CNC machine 1. Movement Acme screw Ball screw 2. Feed manual motor 3.measurement Linear scale

Advantages of CNC Flexible, high accuracy Short production time Complex shapes Short setting time No skill requirement Short inspection time/ high quality product Low cost

Disadvantages of CNC High machine cost Complicated maintenance Skill & training are required for programming and maintenance. Parts are imported from aboard. High tooling cost Temperature, humidity & dust must be controlled.

Why CNC? HUMAN  LIMITATION

2. Component and Function of CNC Feed drive Measuring system  Direct / Indirect Work spindle  hydraulic Cooling system  reduce heat Tool turret

Feed drive

Measuring System

Tool change facilities

3. Coordinate System 3.1 CNC Axes

Axes on a CNC lathe

Axes on a CNC milling machine

Zero and reference points on CNC

Zero Point of machine on a CNC lathe

Machine Zero Point and Work part zero point on CNC milling machine

3.2 Two types of dimensioning in NC programming Absolute dimensioning (G90)-พิกัดสัมบูรณ์ Incremental dimensioning(G91)-พิกัดต่อเนื่อง

Exercise 1

หาพิกัดของงาน X Y P0 X0 Y0 P0-P1 X-20 Y-20 P0-P2 X12 P1-P2 X32 P0-P3 G90 Absolute X Y G91 Increment P0 X0 Y0 P0-P1 X-20 Y-20 P0-P2 X12 P1-P2 X32 P0-P3 X20 Y-12 P2-P3 X8 Y8 P0-P4 Y14 P3-P4 Y26 P0-P5 Y20 P4-P5 X-8 Y6 P0-P6 P5-P6 X-32

Exercise 2

Basics of coordinate point calculations

Exercise 3

Exercise 4 กำหนดจุดศูนย์ของชิ้นงานอยู่ที่กึ่งกลางงาน

การบ้าน หาพิกัดแบบสัมบูรณ์และแบบต่อเนื่องของรูปใน Exercise2 ตอบคำถามจากข้อสอบย่อย Quiz1 หมายเหตุ ทุกข้อให้เขียนหรือคัดลอกแบบงานมาด้วย แต่ให้เขียนตอบด้วยลายมือตนเอง (ห้ามพิมพ์) สัปดาห์หน้า เตรียมสอบการอ่านค่าจากเวอร์เนียร์