CNC Machining Handbook About the Author Alan Overby received a B.S. in Electrical Engineering from Arizona State University. He has always had a hobbyist interest in CNC technology, and has owned, programmed, and operated several CNC routers and engraving machines on a professional level within the signage industry. Mr. Overby was co-owner of Custom CNC, Inc., a company that provided new and replacement controller systems to both individuals and original equipment manufacturers. CNC Machining Handbook Building, Programming, and Implementation Alan Overby Copyright © 2011 by The McGraw-Hill Companies, Inc. All rights reserved. Printed in the United States of America. Except as permitted under the United States Copyright Act of 1976, no part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written permission of the publisher. 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Contents Preface Part I The Physical Architecture 1 CNC Machines Common CNC Applications 2 Guide Systems Round Rail Profile Rail V-Style Roller Hybrid Roller Guides 3 Transmission Systems Screw and Nut Lead Screw and Nut Ball Screws Rotating Nut Rack and Pinion Reducers Timing Belt and Pulleys Constructing a Pulley-Reduction Unit 4 Motors Stepper Motors Servo Motors Stepper versus Servo: Pros and Cons Encoders Part II The CNC Controller 5 Controller Hardware Enclosure Breakout Board Drives Power Supply Adjunct Devices for Controller Hardware Pendant Wiring 6 Control Software Mach3 Control Software Enhanced Machine Controller, Version 2 (EMC2) A Foreword on Computer Operating Systems and Applications G-Code Editors G Code Part III Application Software 7 The Cartesian Coordinate System The Table or Mill Topology Lathe/Rotary Topology 8 CAD and Graphics Raster to Vector Conversion Utilities Difference between 2D and 3D Listing of CAD Vendors Graphics Programs 9 CAM Software Understanding and Using CAM Generalized Milling Options CAD and CAM Combination Software Part IV Building or Buying a CNC Machine 10 Choosing a Ready-Made CNC System Router/Plasma Table Mills and Lathes Do-It-Yourself (DIY) Vendor Listing 11 Building Your Own CNC Plasma Table Part V Appendices A Project Implementation and Examples Examples of Items that Can Be Produced on a CNC Router Unlimited Possibilities Programming Examples B Programming Examples in G Code Example 1 Example 2 C Engineering Process of Selecting a Ball Screw D NEMA Motor Mounting Templates Index Preface Using CNC, whether on a professional or hobbyist level, is not only an exciting process to be involved in but is also the direction manufacturing is heading. There are a great many facets and stages involved in the end-to-end process of understanding and implementing CNC, and, although there have been several books published on specific aspects or topics (such as G-code programming, building a CNC machine, etc.), there have been no books written that guide the reader through the overall process, that is, until now. It is not the intent of this book to replace any previously written information on this topic nor to delve into any particular area. However, by the time readers finish reading this book, they will have a solid understanding of the entire CNC process from a top-down end-to-end perspective. More specifically, this book is intended for the following audiences: • Academic: This book will provide the instructor and students a very informative introduction into applied CNC, the various machines, and their uses, along with the necessary tools used in the process. • Business owner: The aspect of moving a small-to medium-sized business, or even a startup company, from a manually concentric manufacturing process into the accuracy and repeatability of what CNC has to offer, can be a daunting task. This book guides business owners in the proper direction to help them understand and decide the ins and outs of automating their manufacturing process. Furthermore, also discussed will be what to look forward to when growing future CNC- based operations. • Hobbyist: There are a great number of individuals interested in the understanding and technical aspects of CNC, but are not exactly sure where to begin—what is absolutely required for the application at hand from both a hardware and software perspective and what is not. There are many free and low-cost software options to choose from that are listed for the reader to appropriately determine what is needed for their particular application. • Readers looking for an industry guide: This book is also intended to be