Design and development of an open architecture CNC controller for milling machine retrofitting

Most computer numerical control (CNC) machines used in Thai industry are imported. With regular maintenance, these CNC machines could last up to 10 years. After that, the owners would either purchase a new machine or upgrade the old model; the later process is widely known as ldquoretrofitting.rdquo However, purchasing a new CNC machine is a big financial burden for small-to-medium enterprises (SMEs) whereas retrofitting usually do not cost much less because most CNC machines are developed based on closed technology. In addition, many models are discontinued after 10 years of service making retrofitting even more costly or nearly impossible. Such problem also permeates educational institutes such as Thai Vocational Technical Colleges, which usually own 5-10 CNC milling and turning machines per institute; that amounts to 400 machines in total that need retrofitting after 10 years of usage. Most of these machines require new industrial motion control cards which had been long discontinued. Hence, an industrial grade CNC motion control prototype system based on open architecture and modular technologies has been developed as a pioneer research project for retrofitting old milling machines for Vocational Technical Colleges.