computer numerical control programming basics - Industrial Press

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CNC Foreword As the National Technical Committee Chairman for the Precision Machining Technology portion of the Skills USA-VICA championships I get to see students of varying levels of competence compete each year. Each year my Industry committee works very hard to design a competition that is challenging but fair. Since both Secondary and Post-Secondary students compete at the Nationals, the level of difficulty is always a topic of discussion. Of major concern are the low scores in the CNC programming sections of this national competition. Only basic CNC programming skills are required to complete these portions of the competition. However, the scores indicate that too many competitors do not have these basic skills. Because the committee feels a responsibility to help educators provide this basic knowledge to students interested in manufacturing technology, the committee suggested that this booklet be furnished to all Skills USA-VICA State Directors and all instructors with a machining curriculum in that state. This book can be photocopied with the written permission from Kelmar Associates so that as many students as possible can be exposed to this basic information; It is not for resale. The information should also be furnished to all local and state precision machining technical committees so they can incorporate CNC Programming in their competitions. The information is also available on the Skills USA-VICA Precision Machining Technology web site. The 1999 National competition had two CNC programming stations as part of the overall Precision Machining Technology portion of the Skills USA Championships. Each of these CNC Programming sections was worth 100 points. CNC programming represents 28% of the National competition. Contestants sent to the nationals without this basic skill have no chance of winning a medal and would have difficulty receiving a passing grade. CNC TURNING: The average score of the secondary contestants was 32.4 with the highest score being 100 and the lowest being six contestants with zeros. The post-secondary scores were higher, but still not where they should be. The average was 52.9, with the highest score being 99 and the lowest being two contestants with zeros. 1
CNC MILLING: The Milling programming scores were even lower. Secondary average was 25.8 with a high of 100 and five contestants with zeros. Post-secondary average was 25.7 with a high of 58 and four contestants with zero. These scores indicate a definite lack of fundamental CNC programming skills! All contestants were given a guide to the Fanuc software that would be used. The Fanuc software guide, that is used in over 80% of the CNC applications throughout the world, included all the codes needed for the competition. Contestants were given time to familiarize themselves with and ask questions about the computers and the software they would be using. Technical committee members were shocked to find several contestants that did not even have the basic computer skills to open the software program. It is our recommendation that any school with a Precision Machining curriculum should be utilizing manual machines to provide a basic understanding of and to develop basic skills related to the fundamental machining processes. The focus of this phase should be work-holding techniques, how metal is removed, tooling terminology, proper speeds, feed and depth of cut for different materials and obtaining geometric and size tolerances. After this basic introduction to machining processes (utilizing manual machines) instruction should quickly transition to CNC programming utilizing and applying all the fundamental machining skills learned in the manual-machining phase. We are not suggesting that every school with a metalworking program invest in costly full-sized CNC machines; just the opposite is true. Inexpensive text books, trade literature, video tapes, machine simulators (this is how the small bench-top CNC teaching machines should be looked upon), and computer software is available today. We also feel that the NIMS (National Institute for Metalworking Skills) Machining, level I and II skill standards should be incorporated into every school’s machining program. 2
Page 1 and 2: COMPUTER NUMERICAL CONTROL PROGRAMM
Page 3 and 4: Computer Numerical Control Programm
Page 5: CONTENTS SECTION PAGE Foreword 1 Pr
Page 9 and 10: Why CNC (Computer Numerical Control
Page 11 and 12: We must all do our part; State Dire
Page 13 and 14: terms from any other point along th
Page 15 and 16: Machine Types Lathe The engine lath
Page 17 and 18: Fig. 6 A workpiece dimensioned in t
Page 19 and 20: Point-to-Point or Positioning CNC P
Page 21 and 22: merge individual axis points into a
Page 23 and 24: format that the machine control uni
Page 25 and 26: Group Code Function 01 G00 Rapid po
Page 27 and 28: Code Function M00 Program stop M02
Page 29 and 30: Fig. 18 The first step in producing
Page 31 and 32: ABSOLUTE ZERO SHIFT - The absolute
Page 33 and 34: length is recorded on the tool list
Page 35 and 36: CNC Bench-Top Milling and Turning C
Page 37 and 38: CNC Programming Hints - MILLING Mac
Page 39 and 40: Milling and Drilling Programming Pr
Page 41 and 42: N70 G01 Z-.250 F10 tool feeds .250
Page 43 and 44: CNC Programming Hints - TURNING Ind
Page 45 and 46: Turning Programming Programming Seq
Page 47 and 48: N85 Z-2.050 Z-2.050 the .925 diamet
Page 49: QUICK & EASY WAYS TO CONTACT INDUST

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