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unit5newppt-180520142423.pptx
- 3. UNIT – 5 CNCMACHINES & ITS COMPONENTS
- 4. NC -Numerical Control CNC - Computer Numerical Control MCU - Machine Control Unit HMC - Horizontal Machining Centre VMC - Vertical Machining Centre UMC - Universal Machining Centre
- 5. CMM - CoordinateMeasuring Machine LMB - Linear Motion Bearing ATC - Automatic Tool Changer CBN - Cubic Boron Nitride PCD - Poly Crystalline Diamond MDI - Manual Data Input
- 7. Numerical Control (NC) •NC is machine various defined slide functions by means as Control of movements & of Letters, Numbers and Symbols • Letters, Numbers and Symbols forming some sequence is called Part Program
- 9. 1.Starting and stoppingof machine tool spindle. 2.Controlling the spindle speed. 3.Positioning the tool tip 4.Guiding the tool in desired paths 5.Controlling the feed rate. 6.Changing of tool in the spindle
- 17. It isa Numerical Control system, which uses a Computer to perform all or some of the basic numerical control functions In CNC, the program is entered once and they stored in the computer memory
- 22. A CNC systemconsist of the following 1.Machine Control Unit (MCU) 2.Operator Control Panel 3.Servo Control Unit & Drives 4.Feedback Devices
- 23. In CNC systemsthe part program is fed into the computer. Then the instructions are read by the controller to convert it into signals that activate the machine tool. The signals are sent to the machine tool for performing different operations.
- 25. Input Device Display Unit Drive System Machine Control Unit Feed back devices Part Program MotionData Miscellaneous Function Position Feedback Velocity Feedback
- 26. Software of systemhas 3 major programs 1. Part Program: It has Part Dimensions, Spindle Speed, Feed rate 2. Service Program: Used to check , edit, correct the part program 3. Control Program: Accept the Part program as a Input data to produce signals to drive the axes of motion
- 32. Machine Control Unit(MCU) Consists of PLC, Processor, Memory Devices PLC control the Spindle ON/OFF, Coolant ON/OFF, Tool path, Speed, Feed, Tool Changes Convert the Program Commands into Signal
- 33. Operator Control Panel Providethe interaction between User & CNC system Consists of Monitor, Feather touch keyboard, machine control panel
- 35. Servo Control Unit& Drives PLC gives command signal to servo drives , this command signal values are converted into actual movement on the machine by servo drives
- 36. Feedback Devices PLCreceives feedback signal about actual movement of the machine tool through feedback devices Feedback Devices are Transducers & Encoders This feedback signals are compared with the Input signals and error correction is done
- 38. Storage ofmore than one part program Various forms of Data Input Program Editing Graphical Display of Cutter path & shape of the finished job before actually running the program is possible Sub program facility for repetitive machining sequence also possible
- 40. • Increased Productivity •High Accuracy • Reduced Time • Reduced man power • Simulation of program is available • Increased Safety operations • Lesser Floor place
- 42. NC CNC NC -Numerical Control CNC - Computer Numerical Control Machine is not controlled by Computer Machine is Controlled by Computer Input is given by punched tape Input is directly given through computer Reliability is less Reliability is more Program editing is not possible Program editing is possible
- 43. Simulation of partSimulation of part program is not possible program is possible Storing the part program is difficult Storing the part program is easy Less flexible High flexible Less Capability High Capability NC programmers are skilled persons Programmer not necessarily a skilled person
- 45. • CNC Turningcentre is a machine tool capable of performing various Turning & related operation in one setup under CNC system • CNC turning centers are designed mainly for machining shaft-type work pieces which are supported by a chuck
- 46. CNC turningcentre Tool Turret have Capacity of 8 to 12 tools Two axis control: Z axis - Parallel to Spindle axis X axis - Perpendicular to Spindle axis Types of CNC turning Centre: • Horizontal Spindle Turning Centre • Vertical Spindle Turning Centre
- 47.
- 48. Main Parts ofCNC Turning Centre: • Bed • Head Stock • Turrets • Machine Control Unit (MCU) • Servo Mechanism
- 51.
- 52. Vertical Spindle TurningCentre
- 53. • Vertical used formachine CNC lathes widely heavy components. • Some of these machines can also be used for milling operations. Such machines are sometimes known as turn - mill centers.
- 58. • A machiningcentre consists of machine tools, usually numerically controlled, automatically capable of drilling, reaming, tapping, milling and boring the multiple faces of a part with tool magazine, Automatic tool changer, automatic pallet changer.
- 59. Five axis control: X axis, Y axis, Z axis - Linear Movement A axis - Spindle Tilt B axis - Table rotation Types of CNC Machining Centre: • Horizontal Spindle Machining Centre (HMC) • Vertical Spindle Machining Centre (VMC)
- 60. Main Parts ofCNC Machining Centre: • Bed • Column • Spindle • Table • Servo Mechanism • Tool Magazine • Automatic Tool Changer (ATC) • Automatic Pallet Changer (APC)
- 62.
- 68. • HMC hasits Spindle on Horizontal Axis • Used for heavier work piece with large metal removal • X axis - Table Longitudinal movement • Y axis - Spindle Up & down movement • Z axis - Table movements towards spindle • HMC have Rotary table with axis parallel to Y axis & is called B axis
- 69. • Tool magazinehave tools upto 60 – 120 • Generally these are Single spindle machines with ATC & APC
- 70.
- 72. • VMC hasits Spindle on Vertical Axis • Used for heavier work piece with large metal removal • X axis - Table Longitudinal movement • Y axis - Table cross wise movement • Z axis - Spindle Up & down movement • VMC have Rotary table with axis parallel to X axis & is called A axis
- 74. •Tool magazine haveupto 60 tools •Generally these are Single spindle with ATC Multi spindle with Turret Head
- 79. • In CNCmachine tool, each of the axis of motion is controlled by axis feed drive mechanism • Primary axis of motion are referred as X, Y and Z axis • Rotary axis : A, B, C identifies the rotary motion about X, Y and Z axis
- 80.
- 82. • A CNCturning centre has two axis X & Z • Z Axis: Tool Movement parallel to the Spindle axis Z + (Positive) : Tool movement away from spindle Z - (Negative) : Tool movement towards the spindle
- 83. X Axis: ToolMovement perpendicular to the Spindle axis X + (Positive) : Tool movement away from work piece zero point X - (Negative) : Tool movement towards work piece zero point
- 84.
- 88. • A CNCMachining centre has three axis X , Y & Z • Z Axis: Up & Down movement of Spindle & tool Z + (Positive) : Tool movement away from Workpiece Z - (Negative) : Tool movement towards the Workpiece
- 89. •X Axis: Tablelongitudinal movement X + (Positive) : Table movements towards right X- (Negative) : Table movements towards left
- 90. • Y Axis: movement Y + Table Crosswise (Positive) movements away : Table from the machine column Y - (Negative) : Table movements towards the machine column
- 91.
- 92. • CMM isan Electro mechanical system designed to determine the location, orientation, dimensions and geometry of a object • CMM is used to measure various features of work piece by using Probes
- 93.
- 95. • CMM hasfollowing major elements Stationary Granite measuring table Length measuring system Air bearings Control unit Probe head Software
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- 110. Benefits of CMM •Flexibility •IncreasedProductivity •Unmanned Operations •Greater accuracy •Reduced operator error
- 111.
- 112. CNC MACHINE COMPONENETS Slideways Friction & Anti friction Slide ways Linear motion bearings Recirculation ball screw Automatic Tool Changer (ATC) Tool Magazine Feedback Devices Transducers Encoders Tool inserts Inprocess Probing
- 114. Slide ways Precise positioningand Repeatability of tool slides are the major requirements of CNC machine functional machines. The inaccuracies that caused are mainly due to the stick slip motion when plain slide ways (metal to metal contact) are used. Slide ways are used for movement between tool members of machine tool such as carriage & bed in a lathe
- 115. Requirement of GoodSlide ways: • Low wear • Negligible stick-slip • Low price • Low co-efficient of friction properties • Good surface finish on slideway surface • High Stiffness
- 116. Types of Slidewa ys Friction Slidewa ys V -Slideways Flat Slideways Round Slideways Antifrictio n Slidewa ys Linear Motion Bearings
- 117. Friction Slideways 1. V- Slideways
- 118. Friction Slideways 2. FlatSlideways
- 119. Friction Slideways 3. RoundSlideways
- 120. Friction Slideways 4. DovetailSlideways
- 123. Antifriction Slideways It involvesintermediate rolling member(Balls or Rollers) between the sliding members, thus reducing the friction Low friction, No stick slip, high load capacity
- 124.
- 127. Recirculation Ball Screw Balls rotate between the screw & nut and convert the sliding Friction into Rolling friction
- 133.
- 134. •The device usedto pick up a tool from Tool magazine and replace it with the tool in the spindle with in 3 to 7 seconds is called ATC •Reducing idle time during tool changing operations
- 140. 1. ATC armRotates through 90º from the Rest position 2. One end grips tool in the magazine & another end grips tool in the spindle 3. Both tools are pulled out 4. ATC arm rotates through 180º 5. It inserts new tool to the spindle & old tool to the magazine 6. ATC arm Rotates through 90º & goes to the Rest position
- 141. Tool Magazine AT C 1. Arm comesfrom the rest position & Grips both Tools
- 142. 2. Arm pullthe tools from the Mounting
- 143. 3. Arm rotatesthrough 180º
- 144. 4. Carrier Insertstools
- 145. 5. Arm rotates& go to rest position AT C Spindl e Tool Magazine
- 147. • The systemof arrangement which holds large number of tools is called Tool Magazine • It is specified by Storage Capacity & Shape • Storage capacity ranges from 12 - 200 • Used in CNC turning centre & CNC machining centre
- 148.
- 149. Tool Turret Itis the Simplest form of tool magazine It consists of tool storage without tool changer Turret is indexed in required position for desired operation Tool can be easily identified Tool change time is more
- 153. Disc or DrumType Tool Magazine It is the Rotates to get the desired tool in position with tool change arm It carries 12 - 50 tools If diameter of the disc is large more number of tools can be hold It have pockets where the tools can be inserted
- 157. Chain type magazine Itis the Capable of storing more number of tools Used in machining centre Tools are inserted into their pockets which are attached to the chain Chain moving on sprocket & sprockets are driven by motors
- 166. Rack Tool Magazine Itis the Cost efficient alternative to usual tool magazine system It carries up to 400 tools It consists of high tool storage without tool changer
- 169. Egg box typeMagazine
- 171.
- 175. • The electronicdevices such as Transducer & Encoders used for giving the position & velocity of the machine elements are called Feedback devices • Based on feedback control the systems are classified as 1. Open loop control system 2. Closed loop control system
- 176. Open loop controlsystem: Machin e Contr ol Unit Drive Moto r Machine tool slide The machine tool control system in which there is No feed back devices to compare the actual position of the cutting tool or work piece with the input signals are called open loop control systems
- 178. Closed loop controlsystem: Machin e Contr ol Unit Drive Moto r Machine tool slide The machine tool control system in which there are feed back devices to compare the actual position of the cutting tool or work piece with the input signals are called open loop control systems Velocity feed back Positionfeed
- 181. • Transducers areelectronic devices used for converting the physical quantities like Speed, velocity, Displacement Feed, into Electronic signals that give feed back • Two types of transducers 1.Linear transducer 2.Rotary Transducer
- 182. Linear Transducer • Itis used to measure the Displacement of machine slide
- 184. Rotary Transducer (Angular Positionmeasuring Transducer) • It is used to measure the Angular Rotation of the Lead Screw
- 190. • Encoders aredevices used to measure the linear movement of the Machine table • Any devices that is used to give positioning feedback to the control it applies a code or changes information into coded form
- 191. • Two typesof encoders 1. Linear encoders 2. Rotary encoders
- 192. Rotary encoders A rotaryencoder is a type of sensor that when mounted to the shaft of the motor can detect its angular position Its is made from light source, optical sensor, disc with small slits cut into it like spokes
- 195. Linear encoders Its ismade from light source, optical sensor, glass scale
- 198. • It isthe process of performing the inspection procedure during manufacturing operation. • In this process manufacturing as well as inspection are done simultaneously • The process of inspection is called & device used for is called Inspection probing inspection Probe
- 199. Method of Probing: •ContactProbe system •Non-Contact Probe system
- 200. Advantages of Probing •100%inspection is achieved •High quality is ensured •Inspection time is reduced •Inspection cost is reduced
- 202. High speedsteel (HSS) Cemented Carbide Coated Carbide Ceramics High Carbon tool steel Cast Alloy Cubic Boron Nitride (CBN) Poly Crystalline Diamond (PCD)
- 204. •Tool inserts carbide pieces aresmall having cutting edges which comes in various shapes & size geometries & clamped in the Insert holder
- 205. Commonly used shapes •Round (R) • Square (S) • Triangular (T) • Rhomboidal 80º (C) • Rhomboidal 35º (V) • Rhomboidal 55º (D) • Parallelogram 55º (K)