 Hello everyone, I am Nawal Emul working as assistant professor in mechanical engineering department Walsh and Institute of Technology, in this video we are going to see the classification of CNC machine. Learning outcome, at the end of this session students will be able to identify CNC machine and its classification. Content, Introduction to CNC, Classifications of CNC and References First introduction to CNC. CNC stands for Computer Numerical Control Machining is the process through which computers control machine based process in manufacturing. The kinds of machine controlled includes lates, mills and grinders all used for manufacturing of metal and plastic products. Computer Numerical Control that is CNC system can be defined as NC system for a single machine tool that uses a dedicated computer control by stored instructions in the memory to implement some or all basic NC functions. Classification of CNC. So the classification are based on the motion type. There are two types of motion type. First is point to point system and second is continuing system or it is also called as continuous path system. Secondly, the classification is based on the control loops. There are two types. One is open loop system and second is closed loop system. And thirdly, the classification is based on the number of axis. First, there are two and three axis CNC machines and second is higher axis machines. The classification is based on power supply. It can be electrical, it can be hydraulic or pneumatic. So think will give a few seconds to lease down few numerical control machines, you know. Okay, let's start with the classification of motion type. That is first point to point system in point to point system is used in CNC machines such as for drilling, boring and tapping machines or etc. And control equipment for use with them are known as point to point control equipment. In point to point system feedback rates are need not to be programmed. For example, in the figure shown in second figure shows that a work piece is loaded on the CNC machine and if there is only a drilling or boring which is done on the work piece, we can use point to point system as shown in the figure. The tool is located at a certain position. This point to point system is also called as positioning system. It goes to a certain point and then it drills or bows according to the condition. Second type in the motion type is contouring system or is also called as continuous path system. In continuous path system is used mainly for milling machines or when milling operations is performed. These machines required simultaneous control of access. Contouring machines can also be used as point to point machine but it will be uneconomical to use them unless the work piece also requires having a contouring operation to be performed on it. As shown in the figure 3, the contour drilling the part is loaded on the CNC machine and the tool is used as a milling where the surface is removed completely not as a drilling or boring as we have seen in the previous picture. Next type in classification will look at control loops. In control we will see open loop system. As the name itself indicates it is an open loop. We do not have any feedback supplied to the program. In open loop system programmed instructions are fed into the controller through an input device. These instructions are then converted to electrical pulses that is also called as signals by the controller and send to the servo amplifier to energize the servo motors. The primary drawback of the open loop system is that there is no feedback system to check whether the program position and velocity has been achieved. So here we can see the open loop system. Here CNC control sends the instructions or signals to the work piece and to the tool and it performs a certain operations. But in open loop system it does not get the feedback from the work piece or the tool and to the CNC controller. In the next figure the layout of open loop system we can get a clear picture like there is a control unit and control unit sends a signal to the stepping motor and from stepping motor the machine tools are in progress. While machine tool is in progress there is a cutting operation done but there is no feedback given from the machine tool to the MCU and so it is called as open loop system. In closed loop system as a feedback subsystem to monitor the actual output and correct any discrepancy from the programmed input. This system uses position and velocity feedback. The feedback system would be either analog or digital. In this figure number 6 closed loop system the CNC control sends the signals to the spindle as well as work piece. In fact it gets a feedback from them. It shows the correct position and it shows the correct velocity and it shows the operations performed correctly to the CNC. If there is any wrong step taken then the corrective measures are taken and then the feedback is again sent back to the CNC controller. This can be clearly understood with the layout of the closed loop system. Here MCU it is similar to the open loop system but the feedback system it is given from the machine tool back to the MCU again. So in the figure we can see the signals are sent to the hydraulic motor or you can use any type of motor. From there the power is supplied to the machine tool and then the cutting tool and the spindle are used to do the operations. Then if the position of the velocity position and the velocity of the tool position of the tool is taken feedback and then sent to the MCU. So this works as a closed loop system. And the next type of classification is number of axis. Two and three axis CNC machine. CNC lathe machines will be coming under two axis machines. There will be two axis along which motion takes place. The saddle will move longitudinally on the bed that is z axis and cross slide moves transversely on the saddle along x axis. In three axis machine there will be one more axis that is perpendicular to the above two axis. By the simultaneous control of all three axis complex surfaces can be machined. So this figure number eight shows a two and three axis CNC machine where x axis, y axis and z axis all three axis work piece is rotated. In figure nine A and B shows the three axis and the six axis CNC machines respectively. In figure A the work piece is rotated in x axis and y axis and z axis. So it is three axis system but in figure B the work piece is rotated in all three direction as well as in x y direction and y z direction and z x direction. So it has six axis CNC machine. These are advanced CNC machines. So this is again higher axis machining which reduces cycle time and it is used in complex components machining the complex components. In addition it saves lots of time and it is improved with a lot of accuracy and the errors are eliminated almost eliminated. So in the figure ten it shows the higher axis where the axis is more than ten or twelve axis. So lastly we will see the power supply. In power supply mechanical power unit refers to the device which transforms some form of energy to the mechanical power which may be used for driving slides, saddles or gantries forming a part of machine tool. The input power may be electric, hydraulic or pneumatic. So the figure shows the AC servo motor for CNC machine tool. So these were the classifications of CNC. In the next video we are going to see the advantages and disadvantages of the CNC. These are the references I have used. Thank you.