The control system is the brain of Computer Numerical Control (CNC) machines. It directly influences the performance of CNC machines involved in the production processes such as milling, turning, polishing, grinding, and even monitoring physical parts. Since the first industrial revolution, the control system has undergone rapid transformation making it highly automated and complex. The control system encompasses both the motion control factors of machines, such as position and speed, and process control factors, such as temperature.
Today's conventional control system is dependent on various technologies operating within CNC machines, including detection sensors, information processing, servo drive, automatic control, and system software. The detection sensor identifies physical factors of the machines, including temperature, flow, displacement, and force. The performance of a CNC machine depends on the correctness of the detection effectiveness of a sensor. In a mechatronic system, computers and physical equipment are integrated to facilitate information processing and increase its computing speed. The accuracy and speed of information processing influence the reliability of a CNC machine. Servo drive of a control system features an automatic control system, which monitors the position and speed of the parts having actuating mechanism. The performance of the servo drive affects the precision of movement, efficiency, and reliability of a machine. The effectiveness of the control system of CNC machines also depends on embedded automatic control devices used for functions such as positioning control, self-adaptive control, and speed control. Automatic control is the process of using control devices to make the precision machines function automatically in a predetermined way without human intervention. Software is an important part of the control system and directs the mechanical parts of machines to perform their respective functions. Modern CNC machines are controlled by computer-aided manufacturing (CAM) software programs. CAM software enables machines to produce parts in large quantities with less or no human intervention. CAM software also helps embedded lasers of machines detect even minute flaws in the machined parts and alerts the operator of machines on the issue instantly. Computer-aided design (CAD) software helps design equipment parts in 2D and 3D models, which the CAM software program finally manufacture. Besides, Computer-aided engineering (CAE) software allows engineers to analyze, simulate, plan, diagnose, and conduct maintenance of machining works.
Broadly, the CNC control systems can be grouped under motion-type CNC control, loop-control CNC systems, and axis-type CNC control. As the name suggests, motion-type CNC control regulates the feed rate and the degree of motion of the mechanical parts. It functions through a contouring system and a point-to-point control system. The contouring machine follows the external contour of a part being produced in a continuous line. It includes machines such as milling, lathe, and routing. It may also function as a point-to-point system. On the other hand, the point-to-point system operates when the cutting tool is correctly positioned on a work piece and stops when it completes the work. Some of the machines that fall under this system include drilling, boring, and tapping.
In the loop-control CNC system, the control function depends on the looping mechanism and based on the mechanism the system may be categorized under open-loop system and closed-loop system. In an open-loop CNC system, programmed instructions are sent to the controller through an input device, which get converted into electrical signals and finally drives the servo motors. Since the open-loop system lacks a feedback mechanism, it is usually used in operations where the accuracy is not critical. In contrast, a closed-loop CNC system is equipped with a feedback system to monitor any operational variations in the output and rectify any deviations and faults from the programmed instructions in real-time. Thus, a closed-loop system is more reliable and precise than an open-loop system.
Today, common axis-type CNC control system ranges from two-axis type to five-axis. The reference to axes is used for denoting CNC machines' multi-axis operations. The numbers of axes indicate the kind of work a CNC machine can perform, the detail it can cut on a work piece, and the degree by which it can manipulate the position of a work piece. Three-axis machines are used to cut mechanical parts of equipment and are appropriate for works like milling and drilling. Four-axis machines are suitable for jobs such as intermittent cutting, continuous cutting, and engraving. Five-axis machines are mainly used in high-technology industries like automotive and aerospace, which require complex parts. Newer versions of CNC machines are equipped with higher axes such as seven, nine, and twelve. However, more axes do not necessarily mean better results. Choosing the appropriate number of axes is sensible to level cost and finish in machining.
With the advent of Industry 4.0, CNC machines are being upgraded to an intelligent level. The Internet of Things and cyber-physical systems facilitate the development of smart machines. In this regard, it is beneficial to equip these machines with a greater level of intelligence to learn skills autonomously and adapt in real-time to changing instructions and uncertain operational conditions. These non-conventional intelligent CNC machines deliver high processing accuracy and efficiency and can self-diagnose and rectify faults. These machines are armed with an intelligent control system capable of using information from process sensors and neural networks to autonomously adjust process functions, including cutting speed and depth. These intelligent machines allow vibration and thermal compensation, voice indication, and remote maintenance activities. Machines with intelligent control systems behave and act like humans in real-life manufacturing sites and can easily communicate with operators through self-learning and evolutionary procedures.
Lambda Function's Intelligent Control System (ICS) inspects process parameters of the machine, contextual parameters, and engineering data to generate performance evaluation reports, conduct process impact analysis, and assist machinists in effective decision making.
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