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NC-introduction

This document provides an introduction to Numerical Control (NC) and Computer Numerical Control (CNC) systems in manufacturing, tracing their origins back to John Parsons' methods for shape recording in the 1950s. It outlines the fundamental aspects of NC programming, including the use of codes (G&M codes) and the structure of NC instructions. The importance of coordinate systems, absolute and incremental positioning, tool management, and common commands, such as dwell and arc interpolation, are also discussed. This overview serves as a valuable resource for engineers and technicians involved in computer-aided manufacturing.

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NC-introduction

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  1. NC-introduction • John Parsons devised a method for the manufacture of smooth shape-recording on punched cards to drive a cutter • In 1952, modified 3-axis Cincinnati hydrotel milling machine was demonstrated by MIT • NC is a system in which actions are controlled by direct insertion of numerical data at some point. The system must automatically interpret at least some portion of this data GSNU-CAM

  2. NC/CNC/DNC • NC-no facility to store program within the MCU • CNC-computer numerical control • DNC-direct numerical control GSNU-CAM

  3. NC Program의 종류 GSNU-CAM

  4. Manual NC Programming • NC code (G&M code) • Computer language which NC machine can understand • Text-based code (ASCII) Engineer NC Code Controller CAD Geometry NC Milling/Lathe/… GSNU-CAM

  5. Basic NC code • NC word GSNU-CAM

  6. NC Address GSNU-CAM

  7. Coordinate word(X,Y,Z,I,J,K,R) • 최소설정 단위(BLU: basic length unit) 입력방식 :BLU=0.001 • X50000 Y23457 • 소수점 입력 방식 • X50. Y23.47 GSNU-CAM

  8. Tool No., Cutting Condition(T, F, S) • Tn : Tool Slot No. • Ff : 이송속도 • Ss : Main spindle rpm GSNU-CAM

  9. Miscellaneous (M code) GSNU-CAM

  10. G Code • Preparatory: G GSNU-CAM

  11. 좌표값 입력 단위의 지정 • G20 : inch unit • G21 : mm unit • Note : G20 또는 G21은 좌표값을 쓰기전에 단독으로 정의 되어야 한다. GSNU-CAM

  12. 좌표값 입력 형태 지정 • G90 : 좌표값의 절대값 입력(absolute) • G91 : 좌표값의 증분 값 입력(incremental) • 예 • G90 X40. Y70. : 좌표값의 절대값 지정 • G91 X-60. Y40. : 좌표값의 증분값 지정 GSNU-CAM

  13. Coordinate Systems GSNU-CAM

  14. Machine Coordinate GSNU-CAM

  15. 공작물 좌표계 설정 및 공구 출발점 지정(G92) • 파트 프로그램에서 좌표값을 지정할 때는 항상 공작물 좌표계를 기준으로 삼는다. • 즉 공작물에 올라 앉아 있다고 가정하여 공구가 움직이는 것을 관측하는 상태 GSNU-CAM

  16. 절삭이동 : 원호보간(G02, G03) G17 : XY 평면 G02 : 시계방향 G03: 시계반대방향 Xx Yy : 다음 점의 좌표 Ii Jj : 현재점으로부터 원호 중심까지의 변위 Ff : 공구의 이동속도 GSNU-CAM

  17. 공구 일시 정지(dwell, G04) • 공구의 경로가 꺽이게 되면 직각코너 부분을 정확하게 따라가지 못한다. 이때 모서리에서 공구를 잠시 정지시키면 꺾인 경로를 따라가게 된다. GSNU-CAM

  18. Typical NC Program GSNU-CAM

  19. CATIA generated NC code-APT (Automatically Programmed Tool) GSNU-CAM

  20. H.W. • 연습문제 (P87, CAD/CAM시스템과 CNC 절삭가공) • 3.1 • 3.2 • 3.3 GSNU-CAM

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