PROJECT ON

CNC MACHINE

Presented by

Amit Kumar Gupta

INDEX

DEVELOPMENT OF CNC MACHINES

CNC SYSTEM

PROGRAMMABLE LOGIC CONTROLER

SERVO DRIVES

CNC RETROFITTING

MAINTENANCE MANAGEMENT

DEVELOPMENT OF CNC MACHINES

EVOLUTION OF THE CNC MACHINES

CNC MACHINES DEVELOPMENTS

BENEFITS OF CNC MACHINES

MAJOR FACTORS FOR ENHANCING THE UTILISATION

CELLULAR MANUFACTURING SYSTEM

FLEXIBLE MANUFACTURING SYSTEM

EVOLUTION OF THE CNC MACHINES

The first CNC Machine was built in 1949 at MIT ,USA for manufacturing of the Air Craft components having intricate profiles using electron tubes & core memory.

The technology advancement from the Tube technology to the open architecture system has enabled to revolutionize the manufacturing processes.

CNC MACHINES DEVELOPMENTS

VERTICAL MACHINING CENTRE (VMC)

TURRET MACHINING CENTRE (TMC)

HORIZONTAL MACHINING CENTRE (HMC)

UNIVERSAL MACHINING CENTRE (UMC)

CNC TURRET PUNCH PRESS

CNC BENDING MACHINE

CNC UNIVERSAL GRINDING MACHINE

CNC GEAR CUTTING MACHINE

BENEFITS OF CNC MACHINES

INCREASED FLEXIBILITY.

IMPROVED QUALITY.

REDUCED LEAD-TIME.

HIGHER PRODUCTIVITY.

ECONOMICAL BATCH PRODUCTION.

REDUCED CYCLE-TIME.

REDUCED SCRAP GENERATION.

MAJOR FACTORS FOR ENHANCING THE UTILISATION

* REDUCTION IN IDLE-TIME.

* INCREASE IN (CUTTING) MATERIAL REMOVAL TIME.

* EFFECTIVE PROGRAMMING, OPERATION AND MAINTENANCE.

CELLULAR MANUFACTURING SYSTEM(GROUPING OF MACHINES)

REDUCED MATERIAL HANDLING.

SET-UP TIME.

W I P INVENTORY.

FLEXIBLE MANUFACTURING SYSTEM (F.M.S.)

LEAD-TIME REDUCTION.

INCREASED MACHINE UTILISATION.

RECUCED W I P.

REDUCED PRODUCTION COST.

100% INSPECTION.

QUICKER RESPONSE TO BUSINESS ENVIRONMENT.

REDUCED OVERHEAD COST.

MAIN CONSTITUENTS OF FMS

M ACHINING CENT REST URNING CENT RESG RINDING CENT RESG EAR CUT T ING M /C ET C.

C NC M A C HINE S

RAIL G UIDED VEHICLEAUT OM AT IC G UIDED VEHICLEROBOT

M A T E RIA L HA ND L ING S YS T E M

PALLET ST ORELOAD/UNLOAD ST AT IONT OOL ST ORE/PRESET ERM EASURING EQUIPM ENT

A UX IL IA RY E Q UIPM E NT

SCHEDULING SOFT W ARESIM ULAT ION SOFT W AREDNC SOFT W ARE

C E NT RA L C O M PUT E R

FM S

FLEXIBLE MANUFACTURING SYSTEM (FMS)

INPUTS

OUTPUTS

FMC 1 FMC 2

FMC 3

FMC 4FMC 5

AGV

ASRS

TOOL MONITORING ON CNC MACHINES

TOOL LIFE MANAGEMENT

MINITORING BY MEASUREMENT OF ELECTRIC CURRENT

MONITORING BY FORCE MEASUREMENTS

MONITORING VIA GEOMETRIC MEASUREMENTS.

CNC SYSTEM

INTRODUCTION CNC SYSTEM CLOSE LOOP SYSTEM OPEN LOOP SYSTEM CNC CONTROLLER CNC SYSTEM BLOCK DIAGRAM MODES OF CNC M/C OPERATION CNC MACHINES COORDINATES ZERO OFFSET CNC CONTROLLER OPEARTING AREAS BENEFITS OF CNC MACHINES

INTRODUCTION

CNC controllers are the heart of a machine or process. They provide control information used to produce parts. CNC controllers range in capability from simple point-to-point linear control to highly complex lagorithms that involve multiple axes control.  CNC controllers can be used to control various types of machine shop equipment.  These include horizontal mills, vertical mills, lathes and turning centers, grinders, electro discharge machines (EDM), welding machines, Flame Cutting machines ,Press machines and inspection machines.  The number of axes controlled by CNC controllers can range anywhere from one to five, with some CNC controllers configured to control greater than six axes.  Mounting types for CNC controllers include board, stand alone, desktop, pendant, pedestal, and rack mount.  Some units may have integral displays, touch screen displays, and keypads for control and programming.  

Industrial communications options for CNC controllers include ARCNet, CANBus, ControlNET, Data Highway Plus, DeviceNet, Ethernet 10/100 Base-T, parallel, PROFIBUS, SERCOS, Universal Serial Bus (USB), serial (RS232, RS422, RS485), and web-enabled.  Communications language choices include bitmap, conversational, DXF file, G/M codes, Hewlett Packard graphics language, and ladder logic.  A bit map (often spelled "bitmap") defines a display space and the color for each pixel or "bit" in the display space.  Conversational language is a higher level, easy to learn programming tool. It performs the same functions as the standard G-code commands.  Drawing eXchange Format (DXF) file that was created as a standard to freely exchange 2 and 3 dimensional drawings between different CAD programs.  It basically represents a shape as a wire frame mesh of x, y, z coordinates.  G-code is the programming language for the Computer Numerically Controlled (CNC) machine tools that can be downloaded to the controller to operate the machine.  M-code is the standard machine tool codes that are normally used to switch on the spindle, coolant or auxiliary devices.

CNC SYSTEM

CNC stands for Computer Numerical Control and has been around since the early 1970's. Prior to this, it was called NC, for Numerical Control .CNC controller are able to execute binary coded commands. The control code for a machine contains positioning as well as switching information. Positioning information is intended to position the workpiece or else the tool .Switching information controls the machines servo components. The coded instructions are entered manually at the control as well as DNC (Distributed Network Controller).Measuring system record when the position of the workpiece or tool indicated on the part program has been reached. Function such as lubrication , coolant on/ off and workpiece clamping are activated using PLC (Programmable Logic Controller ) through relays & contactor at electrical panel.

CNC controllers have several choices for operation.  These include polar coordinate command, cutter compensation, linear and circular interpolation, stored pitch error, helical interpolation, canned cycles, rigid tapping, and auto-scaling.  Polar coordinate command is a numerical control system in which all the coordinates are referred to a certain pole. The position is defined by the polar radius and polar angle.  Cutter compensation is the distance you want the CNC control to offset for the tool radius away from the programmed path.  Linear and circular interpolation is the programmed path of the machine, which appears to be straight or curved, but is actually a series of very small steps along that path.  Machine precision can be remarkably improved through such features as stored pitch error compensation, which corrects for lead screw pitch error and other mechanical positioning errors.  Helical interpolation is a technique used to make large diameter holes in workpieces. It allows for high metal removal rates with a minimum of tool wear.  There are machine routines like drilling, deep drilling, reaming, tapping, boring, etc. that involve a series of machine operations but are specified by a single G-code with appropriate parameters.  Rigid tapping is a CNC tapping feature where the tap is fed into the work piece at the precise rate needed for a perfect tapped hole. It also needs to retract at the same precise rate otherwise it will shave the hole and create an out of spec tapped hole.  Auto scaling translates the parameters of the CNC program to fit the work piece.

CNC MACHINE TOOL (CLOSE LOOP SYSTEM)

SERVODRIVE

SERVOMOTOR

SPINDLE

TABLE

D N C LINKTAPE READER

OTHER DEVICES

MACHINE ELEMENTSDISPLAY UNITINPUT/OUTPUT

KEYBOARDFLOPPY DISC / CD

BALLSCREW

ENCODER

JOB

TACHO / POSITIONSENSOR

VELOCITYFEEDBACK

POSITIONAL FEEDBACK

PLC NC

CNC

I / P

O /P

CNC MACHINE TOOL (OPEN LOOP SYSTEM)

SERVODRIVE

SERVOMOTOR

SPINDLE

TABLE

D N C LINKTAPE READER

OTHER DEVICES

MACHINE ELEMENTSDISPLAY UNITINPUT/OUTPUT

KEYBOARDFLOPPY DISC / CD

BALLSCREW

JOB

TACHO / POSITIONSENSOR

VELOCITYFEEDBACK

PLC NC

CNC

I / P

O /P

CNC CONTROLLER

Electrically, a CNC Machine consists of a multi-axis servo drive, spindle (cutting) drive, one or more controllers, power supplies, and safety circuits. On larger systems, a programmable logic controller (PLC) may be used to handle auxiliary functions such as water cooling and lubrication functions ATC (Automatic Tool Changer) system, APC (Automatic Pallet Changer) system.

CNC Controller consist of various electronic cards such as Memory Board, NC-PLC communication Board, Input-Output Board, Video Board, PLC-CPU board, MCP(Machine control Panel), OCP (Operator Control Panel), Display unit etc.

In CNC System Part program is feed through manual or through program transfer device like digitek instrument & DNC (Distributed Network Controller) system. This part program stored in RAM memory of CNC controller. When machine is work in automatic mode the part program is called. Part program commands are executed by NC controller and give signal to Servo-drives, PLC etc.

In above CNC system block diagram commands are generated by CNC controller fed to Servo drive for axis movement. Servo drive generate the electrical power to move the servo motor for axes movements. In Servo loop the Tacho-generator which is coupled with servo motor give the velocity feedback signal to Servo drive .This system is known as velocity feedback system. For positioning of axis the encoder or Linear Scale-Transducer give positional feedback system to CNC controller. Apart from the positional command spindle CW/CCW, coolant ON/OFF, Tool change, Feed , G codes are executed by CNC controller & give signal to PLCs.

TYPE OF CNC CONTROLLER

Siemens Sinumerik controller 8T, 810GA3,

840C, 840D, 802D, 810D

HMT Hinumerik Controller, 3100M,2000V2

Heidenhain TNC135, TNC415

Fanuc Controller Fanuc 6M, 16M,18M, Fanuc0, Fanuc0I

CNC SYSTEM BLOCK DIAGRAM

MAINPROCESSOR

MEMORY

SYSTEMSOFTWARE

PROGRAM

MACHINEINTERFACE

P L C

DRIVE

MACHINE INPUTS

~ M D I~ PAPER TAPE~ MAGNETIC TAPE~ REMOTE LINK~ D N C LINK~ FLOPPY DISC / CD

OUTPUTS

~ DISPLAY UNIT~ REMOTE LINK~ D N C LINK~ FLOPPY DISC / CD

MODES OF CNC M/C OPERATION

CNC machine operates in different mode like JOG,MDI, AUTO, Increment mode 1, 10, 100, 1000, 10000 micron, REF, Data input / output mode, Repositioning mode .These all mode are to be selected from Machine Control Panel

JOG Mode: In this mode machine is operated in manually. In JOG mode machine moves in respective direction of axis when key is pressed. This mode is normally use for machine setting. when switch is not pressed machine can not move. Axis feed can be change by feed override switch.REF Mode: In this mode machine is referenced before operating the CNC machine in Automatic mode (programming mode), machine needed to be referenced. Reference means machine zero position. It is very necessary to reference M/c because during power off CNC system loose its positional value. AUTO Mode: In automatic mode, individual NC traversing programs are processed. The axes cannot be traversed by means of the direction keys. In this mode machine works in part programs .Part program is program of particular job. part program contains various codes like that the numeric value of axis position ,tool command, spindle rotation , spindle speed, coolant on/off, G-codes, M-codes, T-codes etc.

INCR 1,10,100,1000,10000 Mode: In this mode machine move in 1, 10, 100 , 1000, 10000 microns when switch is pressed with respect to direction of axis. This mode is normally is used for fine setting of jobs.

MDI Mode: This mode in known as manual data input mode .In MDI mode machine execute the program block.MDI mode normally is for small program.like Tool change Pallet change ,Spindle ON /OFF etc.

CNC MACHINES COORDINATES

Coordinate systems: Right–handed, rectangular coordinate systems are used for machine tools. Such systems describe the movements on the machine as a relative motion between tool and work piece.

Machine Coordinate System( MCS) :The orientation of the coordinate system on the machine tool depends on the particular machine type. It can be turned to various positions. The origin of the coordinate system is the machine zero. All axes are in zero position at this point. This point is merely a reference point determined by the machine manufacturer. It need not to be approachable.

CNC MACHINES COORDINATES

WORKPEICE COORDINATE SYSTEM (WCS): The workpiece coordinate system described is also used to describe the geometry of a workpiece in the workpiece program. The workpiece zero can be freely selected by the programmer. The programmer need not know the real movement conditions on the machine, i.e. whether the workpiece or the tool moves; this can be different in the individual axes. The definition of the directions is based on the assumption that the workpiece does not move and the tool moves.

ZERO OFFSET

ZERO OFFSET: The actual values are referred to the machine zero after a reference point approach. The machining program of the workpiece refers to the workpiece zero. Machine zero and workpiece zero need not be identical. Depending on the type of workpiece and the way it is clamped, the distance between the machine zero and workpiece zero can vary. In part program processing this is compensated for by the zero offset.

P - Tool setting pointW- Workpiece zeroF - Slide reference pointXMR, ZMR Reference point

coordinatesXMW, ZMW Zero offsetM- Machine zeroR - Machine reference pointWR- Workpiece reference point

TYPE OF ZERO OFFSET

SETTABLE ZERO OFFSET: Settable zero offset in the program e called with G54 to G57 and other G functions Basic zero offset (Basic frame): displayed like a settable ZO.

PROGRAMMABLE ZERO OFFSET: programmable zero offset program an additional zero offset for geometry and special axes in the part program called. The values of the programmed zero offsets are deleted with end of program or reset..

EXTERNAL ZERO OFFSET : In addition to all the offsets which define the position of the workpiece zero, an external zero offset can be overlaid by means of the handwheel (DRF offset) or from the PLC.

DRF OFFSET: Differential Resolver Function: NC function that works in conjunction with an electronic handwheel to generate an incremental zero offset in Automatic mode.

FRAME: Frame is the conventional term for a geometrical expression that describes an arithmetic rule, such as translation or rotation. Frames are used to describe the position of a destination coordinate system by specifying coordinates or angles starting from the current workpiece coordinate system. Possible framesBasic frame (basic offset)Settable frames (G54...G599)Programmable frames

CNC CONTROLLER OPEARTING AREAS

CNC system have different type of operating areas for various functions. These windows are

Machine

Parameter,

Program

Services

Diagnosis

Startup,

Cycles

CNC CONTROLLER OPERATING AREA (MACHINE)

Machine: This operating area is used for Execution of part programs, Manual control operation of machines. In this operating area we can see the different area of mode Operating areas, Channel status, Program status, Channel name, Alarm and message line, Operating mode, Program name of selected program, Channel operational messages, Channel status display, Additional explanatory text (Help) can be called, Working windows, NC displays The working windows (program editor) and NC displays (feedrate,tool) available in the selected operating area are displayed here, Dialog line with Operator prompts , Recall function, ETC. function, Horizontal softkeys, Vertical softkeys,. When press the "Area switchover" key, operating areas are displayed on the horizontal softkey bar and operating modes are displayed on the vertical softkey bar. By this key to go to the area menu bar from any location in the menu hierarchy if you wish to select another operating mode or a different operating area.

CNC CONTROLLER OPERATING AREA (PARAMETER)

CNC system have many type of parameters which control the different function of machine.

Too Data, Tool Compensation, tool Management, Setting parameters, Zero Offsets,R-parameter

Machine parameter,Working Area Limitation

Setting Parameter: Setting parameter contains various setting data, Jog data, Spindle data, Dry run feed rate, Starting angle thread cutting,Zero Offsets, Setting bits, etc. Setting data are related with jog feed, dry run feed, Spindle max & min. speed, axes negative & positive limitation etc.

R-Parameter: This is programming parameter. R-parameter mainly used for arithmetic function in in part program .

Machine Parameter: Machine parameter is heart of CNC system. Without this parameter machine never work. M/c parameter contains various data like machine configuration data, Servo drive configuration data, Individual Axis data, Display data, Channel data,

Configuration data decide the no. of axes in CNC machine, which type of drive used in machine, rating of servo drives. Drive configuration data indicate the power of servo motor & drives, Its current capacity , torque, acceleration, Gain etc. Axis parameter contains the each individual axis parameter like axis traverse limit in both direction, type of measuring system, encoder pulse,

CNC CONTROLLER OPERATING AREA (PROGRAM)

Program: In program operating area the following are contain.

Program Type: Workpiece, Part Program,Subroutine, Cycles

Storing programs

Program Basic display

Editing programs

User-defined contour programming

Program simulation

Program management

Memory info

Part Program: A part program consists of a sequence of instructions to the NC control. In its entirety, this sequence effects the production of a specific workpiece or a particular machining process on a given blank.

Subroutine: A subprogram is a sequence of instructions in a part program which can be called repeatedly with different defining parameters. Cycles area type of subprogram.

Workpiece: A workpiece is a part to be produced/machined by the machine tool or a directory in which programs and other data are stored.

Cycles: Cycles are subprograms for the execution of a recurring machining process on the workpiece.

CNC CONTROLLER OPERATING AREA (SERVICES)

Services The Operating Area "Services" provides the following functions:

Function: Read data in/out, Manage data, Series start-up

Directory structure: All files are organized in a directory structure.

NC active data :The NC memory contains data (e.g. R parameters, tool offsets, machine data …) that are not stored in the form of files. However, to allow the operator to access these data and store them as files on the hard disk, the file tree contains a directory named "NC-active data". This directory contains an overview of data that can be copied from the NC memory.

The following directories contain special files:

1. Clipboard: Files and directories of any type may be created/stored in the clipboard. The clipboard is a directory on the hard disk, where files, which cannot be included in the copy target directory, are stored. This may be the case, for example, if their file type is unknown, or is not permitted in the copy target directory.

2. Archive: For save several files, store them in an archive file (.ARC). Archive files are generated in a special format: a. Punched tape format b. PC format The source path of files stored in an archive file is also saved in the archive. allowing the packed file to be transferred back to the same directory from which it was copied when the archive file is unpacked again. Series start-up archives are also stored in this directory.

Data are to be import & Export by V24 interface .V24 interface parameter are to be set for data transmit devices such like parity, baud rate, stop bit, X ON/OFF, Device type etc.

CNC CONTROLLER OPERATING AREA (DIAGNOSIS)

Diagnosis basic display: A display headed “Alarms, message, alarm log, PLC status” appears when selected operating area Diagnosis

Explanation of display: Number The alarm number is output under "Number". The alarms are output in chronological order. Date The date and time at which the alarm occurred is displayed with the date, in hours, min, sec, 1/100 sec (MMC 100.2 only). Clear criterion The symbol denoting the alarm abort key is displayed for every alarm. Text The alarm text is displayed under "Text".

• Information on the current status of the PLC memory locations.

BENEFITS OF CNC SYSTEM

INCREASED FLEXIBILITY.

IMPROVED QUALITY.

REDUCED LEAD-TIME.

HIGHER PRODUCTIVITY.

ECONOMICAL BATCH PRODUCTION.

REDUCED CYCLE-TIME.

REDUCED SCRAP GENERATION.

PROGRAMMABLE LOGIC CONTROLLER

WHAT IS PLC ?

BASIC ELEMET OF PLC CONTROLLER

PLC PROGRAMMING

PLC LANGUAGES

PLC HARDWARE

BENEFITS OF PLC

WHAT IS PLC ?

A programmable logic controller, PLC, or programmable controller is a small computer used for automation of real-world processes, such as control of machinery on factory assembly lines CNC machines . The PLC usually uses a microprocessor. The program is usually created by an engineers at an industrial site, rather than a professional computer programmer. The program is stored in battery-backed memory.

PLC is actually an industrial microcontroller system (in more recent times we meet processors instead of microcontrollers) where you have hardware and software specifically adapted to industrial environment. Block schema with typical components which PLC consists of is found in the following picture. Special attention needs to be given to input and output, because in these blocks you find protection needed in isolating a CPU blocks from damaging influences that industrial environment can bring to a CPU via input lines. Program unit is usually a computer used for writing a program (often in ladder diagram).

The main difference from other computers are the special input/output arrangements. These connect the PLC to a process's sensors and actuators. PLCs read limit switches, dual-level devices, temperature indicators and the positions of complex positioning systems. Some even use machine vision. On the actuator side, PLCs drive any kind of electric motor, pneumatic or hydraulic cylinders or diaphragms, magnetic relays or solenoids. The input/output arrangements may be built into a simple PLC, or the PLC may have external I/O modules attached to a proprietary computer network that plugs into the PLC.

PLCs were invented as less-expensive replacements for older automated systems that would use hundreds or thousands of relays and cam timers. Often, a single PLC can be programmed to replace thousands of relays. Programmable controllers were initially adopted by the automotive manufacturing industry, where software revision replaced the re-wiring of hard-wired control panels.

BASIS ELEMENT OF PLC CONTROLLER

PLC PROGRAMMING

PLCs programs are generally written in a special application on a personal computer then downloaded over a custom cable to the PLC. The program is typically stored in the PLC either in battery-backed-up RAM or some other non-volatile memory (flash).

PLC's were programmed in "ladder logic", which strongly resembles a schematic of relay logic. Modern PLCs can be programmed in a variety of ways, from ladder logic to more traditional programming languages such as BASIC and C. Another method is State Logic, a Very High Level Programming Language designed to program PLCs based on State Transition Diagrams.

Recently, the International standard IEC 61131-3 has become popular. IEC 61131-3 currently defines 5 programming languages for programmable control systems: FBD (Function Block Diagram), LD (Ladder Diagram), ST (Structured Text, Pascal type language), IL (Instruction List) and SFC (Sequential Function Chart). These techniques emphasize logical organization of operations.

Ladder logic is widely used to program industrial Programmable logic controllers, where sequential control of a process or manufacturing operation is required. Ladder logic is useful for simple but critical control systems, or for reworking old hardwired relay circuits. As programmable logic controllers became more sophisticated it has also been used in very complex automation systems

PLC LANGUAGES

The following is a list of programming languages specified by this standard:

Ladder diagram (LD) Sequential Function Charts (SFC) Function Block Diagram (FBD) Structured Text (ST) Instruction List (IL)

Ladder Logic: Ladder logic is the main programming method used for PLC's. As mentioned before, ladder logic has been developed to mimic relay logic. The decision to use the relay logic diagrams was a strategic one. By selecting ladder logic as the main programming method, the amount of retraining needed for engineers and trades people was greatly reduced.

Mnemonic Instruction: There are other methods to program PLCs. One of the earliest techniques involved mnemonic instructions. These instructions can be derived directly from the ladder logic diagrams and entered into the PLC through a simple programming terminal.

Sequential Function Charts (SFC) : SFC have been developed to accommodate the programming of more advanced systems. These are similar to flowcharts, but much more powerful. This method is much different from flowcharts because it does not have to follow a single path through the flowchart.

Structured Text (ST) : Programming has been developed as a more modern programming language. It is quite similar to languages such as BASIC and Pascal.

Function Block Diagram (FBD): FBD is another graphical programming language. The main concept is the data flow that start from inputs and passes in block(s) and generate the output

PLC HARDWARE

PLC controller consist of CPU (Central processorunit) ,PLC Input board, PLC Output board and Power Supply board.

Power supply is used in bringing electrical energy to central processing unit. Most PLCcontrollers work either at 24 VDC or 220 VAC.

Main function of CPU is to process the PLCprogram .In CPU board the PLC program is storedin RAM. This program is backup by Battery. CPUboard contain microprocessor .

The main function of PLC Input board is to give theinput signal to CPU from sensor like limit switch, proximity switch ,pressure switch, float switch, Optical sensor etc.

The main function of PLC output board is to actuate the actuator like relays, solenoid valves, contactor etc. CPU generate the output signal according to PLC program and this signal is outputted at output board.

The PLC program is written in Ladder logic ,STL and CFB (control Function Block) language.

BENEFITS OF PLC

Flexibility: One single Programmable Logic Controller can easily run many machines.

Correcting Errors: In old days, with wired relay-type panels, any program alterations required time for rewiring of panels and devices. With PLC control any change in circuit design or sequence is as simple as retyping the logic. Correcting errors in PLC is extremely short and cost effective.

Space Efficient: Today's Programmable Logic Control memory is getting bigger and bigger this means that we can generate more and more contacts, coils, timers, sequencers, counters and so on. We can have thousands of contact timers and counters in a single PLC. Imagine what it would be like to have so many things in one panel.

Low Cost: Prices of Programmable Logic Controlers vary from few hundreds to few thousands. This is nothing compared to the prices of the contact and coils and timers that you would pay to match the same things. Add to that the installation cost, the shipping cost and so on.

Testing: A Programmable Logic Control program can be tested and evaluated in a lab. The program can be tested, validated and corrected saving very valuable time.

Visual observation: When running a PLC program a visual operation can be seen on the screen. Hence troubleshooting a circuit is really quick, easy and simple.

SERVO SYSTEM

SERVOMECHANISM SERVO SYSTEM BLOCK DIAGRAM SERVO DRIVE THE CONCEPT OF A SERVO SYSTEM DRIVE TYPES SERVO MOTORS SERVO MOTOR BENIFITS

SERVO MECHANISM

Servomechanism, usually shortened to just servo, is a device used to provide mechanical control at a distance. The most common type of servo is that mentioned, which gives positional control. Servos are commonly electrical or partially electronic in nature, using an electric motor as the primary means of creating mechanical force, though other types that operate on hydraulic or magnetic principles are available. Usually, servos operate on the principle of negative feedback, where the control input is compared to the actual position of the mechanical system as measured by some sort of transducer (Tachogenerator or Encoder) at the output. Any difference between the actual and wanted values is amplified and used to drive the system in the direction necessary to reduce or eliminate the error. A whole science of this type of system has been developed, known as servo system .

Servos are found in many applications. Servos are used to operate the CNC machines , throttle of engines that use a cruise control. Fly-by-wire systems in aircraft use servos to actuate the control surfaces that control the aircraft.

  

SERVO SYSTEM BLOCK DIAGRAM

SERVO DRIVE

Servo can be described as follows. A command signal which is issued from the user's interface panel comes into the servo's "positioning controller". The positioning controller is the device which stores information about various jobs or tasks. It has been programmed to activate the motor/load, i.e. change speed/position. The signal then passes into the servo control or "amplifier" section. The servo control takes this low power level signal and increases, or amplifies, the power up to appropriate levels to actually result in movement of the servo motor/load.These low power level signals must be amplified: Higher voltage levels are needed to rotate the servo motor at appropriate higher speeds and higher current levels are required to provide torque to move heavier loads.This power is supplied to the servo control (amplifier) from the "power supply" which simply converts.AC power into the required DC level. It also supplies any low level voltage required for operation of integrated circuits.As power is applied onto the servo motor, the load begins to move desired speed and position changes.As the load moves, so does some other "device" move. This other "device" is either a tachometer,resolver or encoder (providing a signal which is "sent back" to the controller). This "feedback" signal is informing the positioning controller whether the motor is doing the proper job.

Feedback device are Analog Tachogenerator, Digital Tachogenerator, Absolute Encoder, Incremental Encoder , Resolvers.

THE CONCEPT OF A SERVO SYSTEM

DRIVE TYPES

SERVO MOTORS

Servomotors – A motor with a "feedback" device. Electronic packages control speed and position accuracy.Servo motors are normally used for linear motion & rotary motion in machine tools application & automation industries.

Servomotors are mainly two types as AC or DC motors. Servo motor basically works in velocity feedback system. In servomotor the feedback device is known as Tachogenerator or Encoder.

Early servomotors were generally DC motors because the only type of control for large currents was through SCRs . As transistors became capable of controlling larger currents and switching the large currents at higher frequencies, the AC servomotor became used more often. Early servomotors were specifically designed for servo amplifiers. Today a class of motors is designed for applications that may use a servo amplifier or a variable-frequency controller, which means that a motor may be used in a servo system in one application, and used in a variable-frequency drive in another application.

Type of servomotor

DC Servomotor: AC servomotor

SERVO MOTOR BENIFITS

High intermittent torque High torque to inertia ratio High speeds Work well for velocity control Available in all sizes High performance Small size Wide variety of components with specialized controls

CNC RETROFITTING

OBJECTIVE OF CNC RETROFITTING

FEATURE OF CNC RETROFITTING

ADVANTAGES OF RETROFITTING

WHAT IS CNC RETROFITTING ?

OBJECTIVES

COST- EFFECTIVE MODERNISATION.

LARGE SIZE & COSTLIER AGEING MACHINE TOOLS NEED

NOT BE DISCARDED.

RETROFITTING IS A STEPPING STONE TO A FULL FLEDGED

CNC TECHNOLOGY.

FACTORS FOR SELECTION

GEOMETRIC ACCURACY.

SOUND MECHANICAL CONDITION.

AVAILABILITY OF SPACE ON THE MACHINE.

UPGRADATION OF OBSOLETE CNC SYSTEM.

ADDITION OF FEATURE / FACILITIES

Complete reconditioning of the machine

State of the art CNC control system with PLC.

AC/DC Digital/Analog servo feed drives for individual axes and

Spindle.

Linear/ Rotary position feedback systems.

Backlash free re-circulating ball screws & nuts.

Complete new wiring/ panels cable drag chains.

Automatic Tool Turrets/Changers.

Hydraulic Power Packs ,Chucks & Tail-stock.

Automatic Centralised lubrication system & Coolant

Chip disposal systems & machine guard & Telescopic covers for

axes.

ADVANTAGES OF CNC RETROFITTING

A NEW LEASE OF LIFE TO THE MACHINE TOOLS THROUGH

COST EFFECTIVE MODERNISTION

CAPABILITY ENHANCEMENT

ADDITION OF FACILITIES

RESTORATION OF ACCURACIES

QUALITY IMPROVEMENT

BETTER ACCURACY

PRODUCTIVITY ENHANCEMENT BY 100-200% By

CYCLE TIME REDUCTION

REDUCTION IN REWORK / REJECTION

REDUCTION IN DOWN TIME

FLEXIBILITY OF OPERATION & PROGRAMING

CAPABILITY OF ON-LINE PROGRAMMING /MONITORING THROUGH LAN/

DNC

MAINTENANCE MANAGEMENT

MAINTENANCE is an important part of the life-cycle of Machine Tools & Plants, and must be considered from the design stage through the end-of-life stage of the system. Maintenance covers two aspects of systems - operation and performance. Maintenance is generally performed in anticipation of, or in reaction to, a failure. Maintenance is performed to ensure or restore system performance to specified levels. Improperly performed or timed maintenance can exacerbate problems because of faulty parts, maintainer error, or decreased profits. A systematic and structured approach to system maintenance, starting during the design process, is necessary to ensure proper and cost-effective maintenance.

Maintenance operations have been categorized based on their frequency and their motivating factors. Four of the most common designations are described Predictive, Preventative, Corrective and Fault-finding.

TYPE OF MAINTENANCE

PREDICTIVE MAINTENANCE

Predictive maintenance involves a series of steps prior to actually performing maintenance. It begins with sampling physical data over time, such as vibration or particulate matter in oil. Analysis is then performed on the collected data to create an appropriate maintenance schedule, and maintenance is performed according to the schedule. This type of maintenance analysis works well for mechanical systems because the failure modes are well understood. Additionally there is historical data useful for creating and validating performance and maintenance models for mechanical systems.

PREVENTATIVE MAINTENANCE

Preventative maintenance refers to maintenance performed when a system is functioning properly to prevent a later failure. Generally, it is performed on a regular basis and the maintenance will be performed regardless of whether functionality or performance is degraded. The frequency of the maintenance is generally constant, and is usually based on the expected life of the components being maintained, but there is not necessarily any monitoring occurring at the same time (as there would be in predictive maintenance).

TYPE OF MAINTENANCE

CORRECTIVE MAINTENANCE

Corrective maintenance refers to maintenance done to correct a problem when something has failed, or is failing. The need for corrective maintenance can be beneficial or detrimental depending on the product and the profit model used during the design phase of the product. On the most obvious level, corrective maintenance is detrimental to operation because it means that something failed, and the system is (probably) not available during the time needed to perform the maintenance. On the other hand, it may be that the economics and planned functionality of a system are such that using a cheaper, replaceable device for which failure is anticipated, makes sense.

FAILURE-FINDING MAINTENANCE

Failure-finding maintenance involves checking a (quiescent) part of a system to see if it is still working. This is most often performed on portions of a system dedicated to safety -- protective devices. This is an important type of maintenance check to perform because failures in safety systems can have more catastrophic effects, if other parts of the system fail.

TYPE OF MAINTENANCE

STRATEGIC PLANNING

Due to ageing of machines the component of machines get detoriated , The electronic spare of machines get absolute , the Mechanical accuracy of machines get decreases & due to non standardized spare it is very difficult to procure all spare of machines.

To resolve the these problem Strategic Planning to be needed.For the improve the mechanical accuracy machine to reconditioned completely.