A Web based remote control of CNC machines

Due to the large variety of products in small batch sizes, a modern machining shop floor requires an advanced real-time control system able to both monitor all the features and adapt the manufacturing system to the rapid changes of production capability and functionality. This is especially true when the shop floors are combined with the e-Manufacturing concept. e-Manufacturing is a transformation system which enables the manufacturing operations to achieve a predictive near-zero-downtime performance as well as to synchronize with the management systems through the use of infotronics technologies (i.e., wireless connections, web applications, networking systems, etc.). In recent years, the impact of web-oriented technologies has added “velocity” to the design, manufacturing, and aftermarket service of a product. Today’s competition in manufacturing industry depends not only on lean manufacturing but also on the ability to provide customers with total solution and life-cycle costs for sustainable value. Companies are always under a high pressure to improve their efficiency in terms of product development, operations, and resource utilization with a transparent visibility of production and quality control. However, a highly efficient infrastructure, able to integrate all the parts of an automated equipment together and to link them to the e-Manufacturing, is still not available. The objective of this research is to develop an appropriate methodology with open architecture for real-time monitoring and remote control of some networked CNC machines. A new enabling technology is therefore urgently required in order to bring traditional CNC machine tools on-line with combined monitoring and control capability. Without it, the advanced factory automation will hardly have the possibility to become practical in the next generation distributed manufacturing shop floor environments. Thanks to the availability of low cost and Open Source CNC systems, it is currently possible to use CNC technology even in very simple and small production environment. The milestone of this research is EMC2, a Linux CNC-executable control program, freely downloadable on the Internet, able to control servo-motors, stepper motors, robots and other automated devices. It allows CNC machine users to manage a numerical control machine from the parallel port of an even low-performing PC. It provides motion planning with cutter radius compensation, tool length offsets, and constant velocity control. It also have support for non-Cartesian motion systems. This includes hexapods (Stewart platforms and similar concepts) and systems with rotary joints to provide motion. In order to remotely manage a EMC2 based CNC machine, a computer remote control of a milling station has been realised in two different configurations: thanks to a webcam pointed on the working table, the remote computer shows the milling machine movements. The first configuration uses an SSH client and server - indeed it is possible to install them not only on a great number of such UNIX versions as Linux and Mac OS X, but also on Windows. The second one uses a remote text shell (like telnet) and three different methods to broadcast images. The structure is based on a server running Linux (Ubuntu 8.04) on which EMC2 is installed. Thanks to a TCP/IP network, the server connects many CNC machines; moreover users are able to connect their computer to the server and to control CNC machines by using a wireless LAN. Some tests have been performed by using different computers (also a brand new netbook) in order to verify the real efficiency of the structure. The remote programs can be seen on separated windows: this way users are able to open multiple windows at the same time, one with EMC2 and the other with the webcam image visualisation program. In this aim, a suitable software which is able to send images to a server by an ordinary Internet browser has been selected. This has proven to be a more than satisfactory solution as far as image quality and fluency are concerned. Moreover, it gives the users an opportunity to visualise webcam images on different computers at the same time, if they are in network. EMC2 remote control could result to be an interesting tool, as an example in all those case when, for safety reasons, the operator cannot closely follow either the operations or the manufacturing; such an idea is made realer when we think about the chance to command robots by EMC2. It can also be applied to rapid fabrication, offsite NC machining training, and distant trouble-shooting, in addition to remote real-time monitoring and control. This network has demonstrated its efficiency not only in the production, but also in the educational field, where it is very important to train students by practical sessions as long as possible. Due to the high costs of CNC equipment, there’s a need to share it among the students. Since the training sessions of the courses are limited to a few hours per week, it is crucial to share every resource and make them available as long as possible. A very important target of this project is to put engineering students in a position to access and use CNC machines from remote places. As a matter of fact, students can connect their computer (usually a laptop with a wireless broadband connection) to the server, transfer their NC file, simulate it within a virtual test environment and schedule a machining session using the real CNC machine. Thanks to the developed environment, it is possible to remotely control the machine and visualize the machining session via an ordinary webcam.