 Hello, students. This is Mr. Nagesh Arthambake, Assistant Professor, Department of Mechanical Engineering, Valchan Institute of Technology, Sholapur. Today, we will discuss on classification of CNC machine tools. Learning outcome. At the end of this session, students will be able to explain classification of CNC machine tools. In this particular session, we are going to discuss introduction, classification of CNC machine tools based on the motion type, based on the control loops, based on the number of axis, based on the power supply. First of all, I will ask the question to you, what is a CNC machining? Please think on it and try to get the answer. CNC machining is a process used in the manufacturing sector that involves the use of computers to control machine tools like lathes, mills and grinders. Classification based on the motion type, first one is point to point system. It is used in some CNC machines such as drilling, boring and tapping machines, where the spindle is always vertical or sometimes horizontal to the component or sometimes angle is also given. The control equipment for use with them are known as point to point control equipment. Field rates need not to be programmed. In these machine tools, each axis is driven separately because once the drill boot is inserted into the object, then it is lifted up and again separately it is going to another position. Likewise, different holes can be prepared with the help of this point to point system. Next one is contouring system that is also called as continuous path system. As shown in the figure, it is used in CNC machine tools such as milling machines. These machines require simultaneous control of axis. Contouring machines can also be used as point to point machines, but it will be uneconomical to use them unless the workpiece also requires having a contouring operation to be performed on it. Now next one is classification based on the control loops, open loop system. Programmed instructions are fed into the controller through the input device. These instructions are then converted to the electrical pulses, signals by the controller and sent to the servo amplifier to energize the servo motor. 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. The open loop system is generally used in point to point systems where accuracy requirements are not critical. Very few continuous path systems utilize open loops control classification based on the control loop in that closed loop system. The closed loop system has a feedback subsystem to monitor the actual output and correct any discrepancy from the program input. These systems use position and velocity feedback. This feedback system could be either along or digital. The analog systems measure the variation of physical variables such as position and velocity in terms of voltage levels. Digital systems monitor output variations by means of electrical pulses. Closed loop systems are very powerful and accurate because they are capable of monitoring operating conditions through feedback subsystems and automatically compensating for any variations in real time. Next one that is classification based on the number of access. Two and three access CNC machines. CNC lets will be coming under two access machines. There will be two access along which motion takes place either X or Y. The saddle will be moving longitudinally on the bed Z axis and the cross slide moves transversely on the saddle along X axis. In three access machines there will be one more access perpendicular to the above two access. By the simultaneous control of all three access complex surfaces can be machined. Here in this figure the right hand thumb rule is shown. Here the middle finger shows the Z axis. The first finger shows the Y axis and the thumb shows the X axis. And also the thumb is showing the direction of axis and all the fingers are showing the direction of rotation of the tool. Now importance, now classification based on number of access again in that importance of higher access machining that we will discuss over here. Reduce the cycle time by machining complex components using a single setup. In addition to time saving, improved accuracy can also be achieved as positioning errors between setups and setups are eliminated. Improved surfaces finish and tool life by tilting the tool to maintain optimum tool to part, contract, contact all the times. Here you can see whatever the spindle is there, we can move in any angle so that we will get the holes to be drilled, the contours to be made in any angle. Improved access to undercuts and deep pockets by tilting the tool. The tool can be made normal to the work surface and the errors may be reduced as the major components of cutting force will be along the tool axis. Higher access machining has been widely used for machining, sculptures, surfaces in aerospace and automobile industry. So likewise if we use number of access to then the spindle is moving in two axis and if we are using three axis then definitely job and spindle together they are synchronizing and we are getting the machining at all surfaces. Now classification based on the power supply. Mechanical power unit refers to a device which transmits some form of energy to mechanical power which may be used for driving slides, saddles or gantries forming a part of machine tool. The input power may be electrical, hydraulic or pneumatic. Sometimes electrical power is directly used in the CNC machine and sometimes if we require more torque, if we require more force that time hydraulic and pneumatic systems may be used. Therefore in this figure you can see the servo motor for CNC machine tool. These servo motors are used to drive a tools at the required positions in the CNC machines. Therefore these are the references you can refer the Hazra Choudhury book that is elements of workshop technology volume to media promoters and second book that I will recommend that is Ian Rao manufacturing technology metal cutting and machine tools that is published by Tata McGraw-Hill and another third book I will recommend that book is nothing but the Raghu Omsi that is also the manufacturing technology. That is a simple one and some of the contents are given in that book therefore you can refer that book for more information. Thank you. Thank you.