Software Based Computer Numerical Controller for ...

Copyright 6th IFAC Symposium on Cost Oriented Automation Berlin, Germany, 2001

SOFTWARE BASED COMPUTER NUMERICAL CONTROLLER FOR LOW COST AUTOMATIONS AT SMALL AND MEDIUM METAL-WORKING COMPANIES FOR DEVELOPING COUNTRIES

M.Se. Miguel de J. Ramirez Cadena Ph. D. Arturo Molina Gutierrez

Centro de Sistemas Integrados de Manufactura (CSIM). Instituto Tecnol6gico y de Estudios Superiores de Monterrey (ITESM). 2501 Garza Sada Av.• Monterrey. Nuevo Leon. Mexico. 68410.

Abstract: The objective of this project is to provide an alternative Computer Numerical Controlled (CNC) Machine Tool technology to Small and Medium Metal-working industry in order to face the requirements of new global markets where quality, time and cost are key to become competitive. This alternative CNC technology has been developed at prototype level using an European reference Model called OSACA. An opportunity has been identified to use this technology in companies who want to automate their manual machine tools or improve their updated CNC machine tools at less cost of the most competitive CNC technology of the market. Copyright © 2001 IFAC Keywords: CNC, Automation, Object Oriented programming.

controls. But in this enterprise environment dominate by proprietary and inflexible systems come a new age of numerical control whose tendency is to move the technology platform toward the PC based and open architecture controls. In this scenario there is an huge opportunity to develop the next generation CNC technology using low cost PCs, object oriented programming technologies and software based open system architectures.

INTRODUCTION Machine tools have a key position within the industrial sector as a whole. In turn, the functionality, attractiveness and acceptance of machine tools are determined by the efficiency of their control systems. On the basis of the typical control task which machine tools are required to carry out, a traditional division into numerical controller, programmable controller, drives and cell or master computer has become established. But it is in the area of numerical control systems in particular that automation and control systems manufacturers (Mitsubishi, AlIan Bradley, GE Fanuc, Siemmens) incurred into a increase effort for developing new concepts which permit to provide flexible control functions with a broad scope of freedom to adapt the functions to the specific requirements of the application concerned, to increase the use of standardized components, to provide standardized user interface and to permit the integration of different manufacturer numerical control into the same shop floor environment (Pfeiffer, et al., 1994).

The rationale of the Universal Numerical Control (CNU) project is related to the fact that in countries like Mexico, small and medium metal-working industry rarely have access to computer numerical control machine tools and then they work with conventional machine tools. On the other hand, only well established companies have access to automated machine tools due to its cost. Also the research group has pointed out that Mexican small and medium metal-working industry has been facing major problems in international markets due to lack CNC technology which is the basis for competition in this sector (Phillips et al., 1997). Therefore an area of opportunity has been identified to develop national technology in the area of CNC. According with the research group investigations, a CNC machining cost around 20,000 to 60,000 USD and taking into account that small and medium metal-working industry count in their majority with conventional machine tools, the research group has

Computer numerical control (CNC) systems have been and even today are mainly offered as closed manufacturer-specific solutions since there is a great number of vendor which each one propose properties solutions. Additionally some machine tool manufacturers are developing their own

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been developing a laboratory prototype of a CNC under 7,000 USD which can be used to retrofit outdated machine tools (Ramirez, 1996). Another opportunity is the development of low cost CNC educational technology for technical schools in Mexico that can not afford the costs of this technology.

like a "Black Box". The customer can choose the specific sofware modules to do his own CNC controller.

BODY The concept of Universal Numerical Control aims to tackle two important issues: to provide the Mexican industry with CNC technology at low cost and to explore the new concepts behind the development of open CNC architectures. The Universal Numerical Control has been developed under two concepts: Open systems architectures and PC-based controllers. An open system is defined as one which enables applications to operate from variety of platforms from multiple vendors and are able to inter-operate with other system applications. The main goals for an open system architecture are interoperability, portability, scalability and interchangeability. Interoperability will only be guaranteed by using standardized data semantics and be ha vi oral models, communication and interaction mechanisms. Portability allows to operate the system components to operate on different platforms. Scalability is a feature which enables the customer to increase or decrease the functionality of a system by upgrading or downgrading specific components. Interchangeability allows the interchanging of one component with one another due to its capabilities, reliability or performance. Also open system architecture concept is related to internal openness and external openness. The first one refers to an openness concerning the internal control functions and the second cover all external interfaces of the CNU. With the open system concept the CNU will integrate in transparent way all functions that user want to utilize in the manufacturer process. On the other hand users cheer the movement to PC based hardware as an effective way to address the issue of open architecture. PC-based CNC's, by virtue of PC potential to be modernized, will have a greater resistance to technical obsolescence. Moreover, as PC hardware is readily available and under constant development, CNC controllers benefit from the technological advances in the personal computer industry (Ramirez et al.,1998). The figure I show the concept reached by CNU in order to do retrofits in diferents machine-tools, this concept get a library of software modules which can integrate to CNU reference architecture that is see

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Fig. I. The CNU application concept The CNU concept will offer a system software layers which will serve as link between applications software and hardware. It will offer an exactly specified application interface which will provide standard services in the fields of communication, data storage, graphics, dialogue management, configuration and operating system. The CNU architecture is based on OSACA architecture an European research effort in the development of new CNC systems. In figure 2 is showed the information flow for a CNC program, the flow begin when the user introduce a CNC program in the man-machine interface. The CNC code is driven by movement control module to get the basic lengh unit table. The axis control module process the basic lengh unit table to get the signals table for each axis. The auxiliary process module drive the information relate with M codes. The sensors and actuators module convert this information in electrical signals and receive the retrofeed signal of the sensors in the machine-tool. The system software layer hide the specific characteristics of processors, operating systems or communication media which are used within the platform, so that the user always finds the same application interface. Without new coding efforts, the CNU itself is able to convey its software on different platforms by simply transferring, compiling and connecting the source programs. This is possible by using object-oriented design and programming (Ramirez, et al., 1997). The CNU

project is a study case for Ph.D. thesis of Guillenno Jimenez in the area of open software systems.

project, the donation consist in the follow items: microkernel of the system, Watcom C++ compilator, Photom rnicroGUI development kit; with a value of 4,200 USD.

REFERENCES Pfeiffer, W. Eversheim, W. Konig and M. Week, Manufacturing Excellence: The competitive edge, Chapman & Hall, 1994. Phillips L., Valero Gil J.N., Tijerina Guajardo lA. , Bienes de produccion criticos en la industria manufacturera del estado de Nuevo Leon: el caso de los tornos de control numerico, Journal Entorno Econ6mico, Vol. XXXV, pages 13-16, June 1997 .

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Fig. 2. CNU Reference Architecture

CONCLUSION

Ramirez, C. M. de J., Desarrollo de tecnologia nacional de CNC para la modernizacion de la industria manufacturera Mexicana, Transferencia magazine, no. 36, vol. 9, pages 17 -19, October '96. Ramirez, C. M. de J., Pifia Ortiz 1., Molina Gutierrez A., Disefio conceptual del Control Numerico Universal basado en un sistema de arquitectura abierta y computadoras personales,

Memories of XXVII Research and extension congress of ITESM system, Vol. I , pages 207216, Monterrey, Mexico, January 1997.

The research group considers the CNU concept an excellent software based technology, by its low cost projected and high technical flexibility, which will impact the growing of the small and medium national metal-working industry. With the CNU, the user can be reach a capitalization and know-how about CNC technology so that posteriory, will buy great commercials CNC machine-tools.

Ramirez, C. M. de J. , Piiia Ortiz 1., Molina Gutierrez A., Control Numerico Universal para el control de maquinas-herramienta basado en una arquitectura abierta y tecnologia de Memories of computadoras personales,

Simposium of IEEE. chapter Monterrey (SIEEEM'96) , Vol. 11, pages. 60-67, Monterrey, Mexico, October 1998.

The project has been accepted by the QNX Educational Programm of QNX Software Systems LTD, and therefore the QNX operating system has been given as a grant to our research group that consist in development software for the CNU