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2008 | Book

Theory and Design of CNC Systems

Authors: Suk-Hwan Suh, Seong Kyoon Kang, Dae-Hyuk Chung, Ian Stroud

Publisher: Springer London

Book Series : Springer Series in Advanced Manufacturing

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About this book

Computer Numerical Control (CNC) controllers are high value-added products counting for over 30% of the price of machine tools. The development of CNC technology depends on the integration of technologies from many different industries, and requires strategic long-term support. “Theory and Design of CNC Systems” covers the elements of control, the design of control systems, and modern open-architecture control systems. Topics covered include Numerical Control Kernel (NCK) design of CNC, Programmable Logic Control (PLC), and the Man-Machine Interface (MMI), as well as the major modules for the development of conversational programming methods. The concepts and primary elements of STEP-NC are also introduced. A collaboration of several authors with considerable experience in CNC development, education, and research, this highly focused textbook on the principles and development technologies of CNC controllers can also be used as a guide for those working on CNC development in industry.

Table of Contents

Frontmatter

Principles and NCK Design of CNC Systems

Frontmatter
1. Introduction to NC Systems
Abstract
NC machines, being typical mechatronics products, comprise machine tools that have a mechanical component and a numerical control system that is an electrical component. In this chapter, the history, the constituent units, the functions, and future directions of NC systems, being the intelligence of NC machines, will be addressed. Through studying this chapter, you will obtain a comprehensive understanding and fundamental knowledge about NC systems.
2. Interpreter
Abstract
The Numerical Control Kernel (NCK) unit is the key component of a CNC system and consists of a variety of modules that are sequentially executed in a synchronized schedule. In this chapter the code interpreter will be addressed. This is responsible for converting the part program and machine instructions into internal commands for NC. In order to understand the code interpreter the first thing is to understand the part program that is the input to the interpreter. After this, the structure and the functions of the code interpreter will be addressed in detail.
3. Interpolator
Abstract
The interpolator plays the role of generator of axis movement data from the block data generated by the interpreter and is one of the key components of CNC, reflecting its accuracy. In this chapter, the various software interpolators will be introduced and their strengths and weaknesses will be described. In addition, a NURBS interpolator, which is an advanced interpolationmethod, will be described and the implementation algorithm will be introduced.
4. Acceleration and Deceleration
Abstract
In order to smooth the movement of a machine, the acceleration and deceleration for the movement of the machine axes should be controlled. For CNC systems, two kinds of Acceleration and Deceleration (Acc/Dec) control methods have been developed; Acc/Dec Control Before Interpolation (ADCBI) and Acc/Dec Control After Interpolation (ADCAI). These are classified based on the order in which the Acc/Dec control is executed. In this chapter, first we will introduce the Acc/Dec control after interpolation that was originally used for NC systems. Following this, we will introduce the Acc/Dec control before interpolation which is suitable for high-speed and highaccuracy machining. In addition, a Look Ahead Algorithm will be addressed that is used with the Acc/Dec control before interpolation for Die and Mold machining.
5. PID Control System
Abstract
The information of a program block for moving the axis of a machine tool passes sequentially through the interpreter, the interpolator, and the Acc/Dec controller before being finally transmitted to the position controller. The position controller has the displacement at each interpolation interval from the interpolator as input and performs feedback control to minimize the position error. In this chapter, the Proportional Integral Derivative (PID) controller, which is widely used in industry, will be introduced and gain tuning for PID control will be addressed. In addition, the feedforward controller for high-speed applications will be introduced.
6. Numerical Control Kernel
Abstract
In this chapter, an NCK system is built by integrating the modules that were addressed in the previous chapters. Two kinds of NCK enabling the execution of Acceleration/Deceleration-After-Interpolation (ADCAI) and Acceleration/ Deceleration- Before-Interpolation (ADCBI) will be designed. The reader will acquire practical knowledge related to the implementation of the servo control system through investigation of the source code.

Open-architectural Soft CNC Systems

Frontmatter
7. Programmable Logic Control
Abstract
The Programmable Logic Control, PLC, is the automation component for controlling the execution sequence of machines or production processes. In the CNC system, the PLC has the task of controlling the mechanical behavior of the machine with the exception of axis control. In this chapter, the general architecture, function, and behavior of a PLC will be addressed and the role and characteristics of PLCs in the CNC system will be described. Also, IEC-1311-3, the international standard PLC programming language, will be introduced and Soft-PLC will be introduced. Finally, with respect to the design of a PLC system, the architecture and execution conditions will be described and an executor of a PLC program will be implemented.
8. Man–Machine Interface
Abstract
The Man–Machine Interface (MMI) provides the interface that enables a user to operate a machine tool, edit a part program, perform the part program, set the parameters, and transmit data. In this chapter, the function and components of the MMI will be addressed, and programming methods such as CAPS (Conversational Automatic Programming System) will be described. In addition, for designing CAPS, the main functions and components of CAPS will be described.
9. CNC Architecture Design
Abstract
It is necessary to design the architecture of hardware and software modules in order to implement a CNC system consisting of a variety of modules such as NCK, MMI, and PLC. System programming for operating these modules in real time is also required. In this chapter, the main functionalities and commands of real time operating systems (OS) for real-time programming systems will be described. Through investigation of multi-processing hardware architecture, the user will learn the basic approach for designing the architecture of a CNC system that requires the guarantee of real-time operation.
10. Design of PC-NC and Open CNC
Abstract
Recently, industrial controllers based on PC hardware seem to have replaced conventional controllers based on a closed hardware structure. We will discuss the design issue of PC-NC running the NC functions described in other chapters on a personal computer (PC). The hardware architecture, software model, and communication mechanism for building PC-NC will be addressed. In particular, Soft-NC, where a single processor is used and all functions of PC-NC are implemented as software tasks, will be described. In addition, an open CNC architecture supporting openness of H/W and S/W of CNC systems will be discussed.
11. STEP-NC System
Abstract
With the rapid advancement of information technology associated with NC technology, the manufacturing environment has changed significantly since the last decade. However, the low-level standard, G&M codes, have for over 50 years been used as the interface between CAM and CNC, and are now considered as an obstacle for global, collaborative and intelligent manufacturing. A new model of data transfer between CAD/CAM systems and CNC machines, known as STEP-NC, is being developed worldwide to replace G&M codes. In this chapter, we will give an overview of STEP-NC and its related technology, including data models for STEP-NC, CNC systems based on STEP-NC, namely STEP-compliant CNC systems, together with worldwide research status and future prospects.
Backmatter
Metadata
Title
Theory and Design of CNC Systems
Authors
Suk-Hwan Suh
Seong Kyoon Kang
Dae-Hyuk Chung
Ian Stroud
Copyright Year
2008
Publisher
Springer London
Electronic ISBN
978-1-84800-336-1
Print ISBN
978-1-84800-335-4
DOI
https://doi.org/10.1007/978-1-84800-336-1

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