ACKNOWLEDGEMENTS

Report on

One & Half Months Industrial Training

At BHEL, Hardwar.

A Training Report submitted in partial fulfillment

Of the requirement for the award of degree of

Bachelor of Technology in

ELECTRONICS & COMMUNICATION ENGINEERING

Of Uttar Pradesh Technical University,Lucknow.

Submitted by:

SACHIN KUMAR(Roll No. 0712731087)

(Batch 2007-2011)

Submitted to:

Mr. PRAVEEN TIWARIH.O.D.

Department of

ELECTRONICS & COMMUNICATION ENGINEERING

IIMT ENGINEERING COLLEGE,MEERUT CERTIFICATE

This is to certify that Mr. Sachin Kumar here undergone One & half month training here in our organization Bharat Heavy Electrical Limited, Hardwar (UK). His discipline and performance during the training period was excellent. We wish his very prosperous and bright career in future.

(VISHAL VERMA)

(V.K. JOSHI)

DY.Mgr.

Mtr. TECH

(WEX-TELECOM)

(WEX-TELECOM)

ACKNOWLEDGEMENTS

First and foremost, I would like to thank my respected parents, who always encouraged me and taught me to think and workout innovatively what so ever be the field of life. My sincere thanks go to Mr. Vishal Verma (Dy.Mgr.) Telecom for his prodigious guidance, persuasion, and painstaking attitude, reformative and prudential suggestion throughout my summer training schedules.

Special thanks go to Mr.V.K.Joshi (Mtr.Technician) Telecom. Who helped me a lot in giving minute details of Telecom? Department and enlightened me with the knowledge of Exchange equipments and their working.

Last but not the least, my sincere thanks to all the staff members and friends for instilling in me a sense of self-confidence.

BRANCH: (ELECTRONICS & COMM. ENGG.)

Academic Year: 2007 to 2011

Institute: IIMT,Engineering colleage ,MeerutTELECOMMUNICATION SYSTEM IN BHEL, HARDWAR.

VOCATION TRAINING REPORT: 2010 CONTENTS

1. Introduction.

2. The Organization.

3. Telecommunications.

4. Electronic Exchange(s).

5. Telephone Lines.

6. Connection Types.

7. General faults occurring in an Exchange.

8. Special User Features of Various Exchanges.

9. Optical Fiber System.

10. Maintenance.

1. INTRODUCTION.

In past few years the field of communication has been developing with no leaps or bounds. It has become a necessity of each human being to be connected with each other. Telephone is rapidly becoming a tool to quench this thirst.

In Automatic Telephony, operators are not required to establish connections manually between the different calling and the called subscribers as are required in the case of manual telephone systems. In these system subscribers those selves establish required connections by operating the different switches placed at the central place known as the EXCHANGE from their telephones at remote place from it. The automatic telephone systems are rapidly replacing manual ones due to their outstanding merits over the latter types, some of which are enumerated below:

* In Automatic Telephony higher level of secrecy is maintained due to absence of

Operators who can overhear the conversation if they like in the manual telephone

Systems.

The working of an Automatic Telephone system does not depend for its efficiency

On the personal efficiencies of the operators.

* There is no possibility of the calls being missed or wrong metering being done due to faults of operators or due to phonetic errors between the subscribers and the operators.

As no operator is required, the running cost of the exchange is reduced.

COMMUNICATION Dia.I

2. THE ORGANIZATION.

BHEL was primarily set up to meet the needs of the power sector in the country. The first plant was established nearly 35 years ago at Bhopal, which heralded the genesis of the heavy electrical equipment in India. BHEL is today the largest engineering enterprise in India, with excellent track record of performance, making profits continuously since 1971-72. It achieved a sales turnover of Rs. 3154 carores with a pretax Profit of Rs.201 carores, in 1990-91.

The areas of BHEL operations broadly cover conversion, transmission, utilization and conservation of energy in core sectors of the economy like Power, Industry and Transportation, etc., and fulfill vital infrastructure needs of the country.

Today, BHEL has 13 manufacturing divisions, 8 service centers and 4 Power Sector Regional Centers, in addition to over 150 project sites spread all over India and even abroad to provide prompt and effective service to customers.

BHEL Hardwar is one of the premier organizations which is honored by I.S.O.-9002 specifications.

3. TELECOMMUNICATION.

BHEL manufactures EPABX and MAX systems based on C-Dot technology and has plans to make other ranges of telecommunication equipment also.

These are basically used for connecting links between various modules like peripherals, exchange and its equipments. It is necessary to run a number of internal cables of suitable conductors between the following stages and frames:-

1. Handset to exchange's cable chamber

2. Cable chamber to M.D.F.

3. M.D.F. to I.D.F.

4. I.D.F. to Number Block

5. Number Block to Exchange Equipment

6. Between two exchanges

7. Between two cities

8. Between two countries

Prior to advent of Electronic Exchanges inter-connection of various circuits are made by mechanical contacts that are operated by mechanical movements produced by the attraction of an iron armature of an electromagnet or by the operation of an electric motor. There are some disadvantages of such systems for using mechanical contacts, due to following reasons: Contacts are subjected to wear and tear.

Require adjustments time to time.

Maintenance is highly precise.

Prone to corrosion. Etc...

But now-a-days Electronic Exchanges are used. In Electronic exchange electronic devices effect the inter-connection between different transmission circuits and Electro-mechanical relays and switches are dispensed with. Such electronic devices remove difficulties associated with mechanical contacts. The greatest advantage of using electronic devices in place of electromechanical devices is that no time is loosed in making a connection and a very high speed of operation is possible.

4. ELECTRONIC EXCHANGES.

Electronic Exchanges are of two types:

1. Tone type

2. Pulse type

1. Tone type:In this type of exchange sine waves are used. There speed of dialing for a given number is more than that of Pulse type.

2. Pulse type:In this type of exchange square wave is used due to which the dialing speed is lesser. The telephone apparatus used for both types are different in construction. But now days both types of apparatus are integrated in a single machine in which switch-over can be made via a selector switch.

TONES USED IN MODERN TELEPHONY

Dial Tone:When handset is picked up from the cradle, then Dial tone is heard if a free line is available. This means that the instrument is ready to send the signals to the exchange. When the subscriber takes up the receiver then signals are sent M.D.F. then to I.D.F., line Number block and to Peripherals where in various line-cards are mounted in a shelf. When corresponding number on the line-card is free then the Ringer section of that Peripheral generates a signal called tone. This tone is a continuous burble sound of 400 Hz. modulated by 25Hz. and is sent to the calling subscriber as soon as his line seizes the free line. The subscriber must not dial before receiving this tone; otherwise he is liable to get wrong connection. If he does not get this tone, he should try after some time.Busy Tone: When the called subscriber is engaged with other call, this tone is heard. It consists of a sound of 400 Hz. which is regularly interrupted at equal intervals. It is generally on for 0.75 sec. and off for also 0.75 sec. Ringing Tone: When a number is dialed then telephone of the called subscriber starts ringing. Calling subscriber should get this information and this is indicated by sending ringing tone of interrupted 400 Hz. supplies modulated by 25 Hz. and its durations are generally equal to the duration of ringing current, which rings the bell. It may be 0.4 sec. on, 0.2 sec. off , 0.4 sec. on and 2 sec. off and so on or it may be 0.75 sec. on and 0.75 sec. Off and so on. When this ringing tone is received, the calling subscriber knows that the connection is completed and that the bell of the called subscriber is ringingNumber Unobtainable Tone: This tone is sent when the number dialed cannot be obtained. If any subscriber dials which is not actually connected to the exchange, this indication is send. This is also a tone of 400 Hz. with interruption of 200 msec. every 3 sec.

Now-a-days push button type telephone apparatus are used. This apparatus can be exploded into following sections:

1. Ringer section

2. Speech section (Transmitter and Receiver section) 3. Voltage limiter sectionFrom telephone exchange two wires or connectors run for each number, in which one is neutral and the other is main or positive. For the telephone circuit to work the necessary supply is provided by the exchange. Like other circuits telephone also operates when a circuit is established between calling and called subscriber. When one dials a number then the corresponding relays at the exchange established a circuit automatically. The telephone exchange supplies 40-60 volt D.C. and 110/20 Hz. to operate this circuit. This is required because of voltage drop that may creep in long transmission wires. As soon as the handset is picked-up this 48-volt D.C. supply is available at voltage limiter section, dialing pulse generator and speech section.

In telephone dialing two types of frequencies are used which are:

* High band tone (1216 Hz. to 1645 Hz.)

* Low band tone (701 Hz. to 936 Hz.)

Frequencies used in Telephony

The numbers from 1 to 5 falls in low band and 6 to 9, 0 falls in high band. Till the handset is on-hook, the ringing section of the apparatus is on through telephone line but on lifting the handset the ringing section becomes off, also the dialing and speech section becomes ready. On lifting the handset first the dial tone is received which is amplified by the amplifier of speech section.

When a number is pressed on the keyboard, the dialing pulses are made on and off according to the number dialed. For example if 5 is pressed then dialing pulses are made on and off 5 times. This process can be heard on the receiver. There is a gap of 1 sec. between consecutively pressed numbers.

When the handset is placed on or is lifted from the instrument a switch is operated called the hook-switch. The main function of this switch is to toggle between telephone-line and ringer, dialing & speech sections of the telephone. When the handset is on the telephone then ringer section of the telephone is on while on lifting it ringer section is disconnected and dialing section is connected.

How the telephone call is made:

Telephone call is characterized into two sections:

1. Outgoing calls: Generally a voltage of 48V-60V D.C. always remains on the telephone line but as the handset is picked-up the voltage limiter drops this voltage to 9-12V. On hearing the dial tone it is confirmed that the apparatus is ready to work and after dialing the number a ringing pulse is send to the called party. When the calling party picks-up the handset the billing meter of the exchange becomes activated. There is a counter in the exchange, which counts the pulse and converts them into calls.

2. Incoming calls: These are just opposite of outgoing calls. In the incoming calls the telephone detects the ringing signal from the exchange and provides the ring. At the instance of ringing signal, there remains a voltage of 75-110V./20 Hz. on the telephone. A high voltage (A.C.) is sent from the ringer section of the exchange to start the ringer circuit of the telephone. When the ringing signal is received it should be properly isolated as it may give a shock. This ringing circuit is on until the handset is not picked-up at the called party. The duration of this tone, if unattended, is 1 minute after which an engage tone is heard. After lifting the handset a circuit is established and a call is made.

Electronic Exchange Dig.II

There are various powers providing circuits available in the exchange to run the circuitry. These are broadly categorized in two categories:

* Outside the exchange

* Inside the exchange

Outside the Exchange:

Since the voltage supplied in Indian Subcontinent is 220-volts/50 Hz. A.C. but for the normal working of the exchange 48(46-53) volts of D.C. is required.

Hence a Rectifier circuit, backed with battery array for power-failures, is used. This rectifier block not only rectifies the input supply but also works as a battery charger. It is known as Float rectifier cum charger.

Battery backup is utilized for smooth operation of the exchange during power failures. For battery back-up lead acid battery array is used in parallel to the supply from the rectifier block, so that during power failures the exchange supplies are not terminated.

Inside the Exchange:

Inside the telephone exchange various types of power supplies are used for powering various modules (for example: - Line-cards, Ringer). Some of them are: -

# -5 V. 12 A

# +5 V. 12 A

# +12 V. 6A.

From M.D.F. a number of cables, based upon the requirement of a place, are connected to cabinets. On the cabinets these cables are divided into cables of 20 pairs. Now every 20 pair cable goes to the distribution box (D.B.). At the D.B. this 20 pair cable is further divided into two parts of 10 pairs each. These pairs are then connected to the subscriber ports via jumpers. The line from these ports then goes to the subscribers through single pair cables which are usually of P.V.C. type. These wires are connected to the instrument via Rosette-Box.M.D.F.: -

This frame serves the following purposes: -

It is place where both external and internal cables are terminated. The external individuals cable carry conductors from subscribers who are necessarily from the same locality and as such their numbers cannot be in numerical order. On the other hand, the internal cable conductors come from apparatus side in numerical order. This cross-section between the two cables is done on the M.D.F. through jumper wires.

It carries all the protectors used in the exchange. The different protectors that are used are (a) Fuses, (b) Heat coils, and (c) lightning protectors.

This M.D.F. is an ideal place for testing purpose. Both the internal and the external cables are available at this frame and, therefore, both external and internal wiring and lines can be tested for this purpose.

I.D.F.: -

These frames like M.D.F. consists of a large number of verticals with horizontal cross-arms fitted with tag blocks at both the ends. The cable from M.D.F. is terminated on the multiple sides from where connections are extended to metering and from the exchange side cables are run to the respected line-cards. The two tag blocks are joined by means of jumper wires as in the M.D.F., so that any subscriber can be given connection to any uniselector on the line-card. The subscriber and, therefore, their uniselector are divided into different groups and it is necessary for these groups to originate more or less the same amount of traffic for smooth distribution among different trunks.

NEW MDF Dig.III

OLD MDF Dig.IV

5. TELEPHONE LINES.

In BHEL-Hardwar three types of telephone lines are used. They are: -

MAX Lines

EPABX Lines

C-DOT Lines

MAX Lines:

Before MAX Ex. Lines are used only Internal Exchange. But New (CORAL) MAX lines are used for both internal (Intercom) and external communication links BHEL.

EPABX Lines:

EPABX lines are used for both internal and external communication links in BHEL. If the user wants to dial outside the periphery of BHEL, he can use these lines. There are about 500 lines available here. These lines are distributed in 17 line-cards with 24 line numbers in each. Its I.D.F. section has 40 tag blocks. 96 numbers available here are connected via digital lines in which a host of facilities are provided that can be accessed using code 69.

C-DOT Lines:

These lines are the direct telephone lines from C-DOT The facility they provide is called DID (Direct Inward Dialing). It has 24 lines and any BHEL number starting with digit 5 can be accessed using code 48.

6. CONNECTION TYPES.

Types of Connections:

* With wires i.e. Cables

* Wireless Microwave Links through Satellite

Cables: Two types of Cables are used. They are:

1) Underground cables: These types of cables run under the earth and are basically used to connect the exchange to the subscriber's Distribution Box (D.B.). They are further of two types based upon their construction and the insulating material used.

a. Paper core A.T.C. (Armored Tin Cable)

b. Jelly filled A.T.C. (Armored Tin Cable)

2) Overhead cables: These types of cables are used to connect the equipments inside the exchange and to connect the peripheral devices to the subscriber's Distribution Box

(DB) They are generally of P.V.C. type.

In an exchange, based upon the number of conductor pairs, following types of cables are used:

* Single Pair cable

* 2 Pairs cable

* 5 Pairs cable

* 10 Pairs cable

* 20 Pairs cable

* 50 Pairs cable

* 100 Pairs cable

Color-coding:

TYPE OF CABLECOLOR OF WIRES

Single pair Blue-White

2 Pair cable Blue-White/Orange-White5 Pair cable Blue-White/Orange-White/Green-White/Brown-White/Grey-White10 Pair cableBlue-White/Orange-White/Green-White/Brown-White/

Grey-White/Blue-Red/Orange-Red/Green-Red/Brown-Red/Grey-Red20 Pair cable

Blue-White/Orange-White/Green-White/Brown-White/Gray-White/Blue-

White-Blue/Orange-White-Blue/Green-White-Blue/Brown-White-Blue/

Gray-White-Blue/Blue-White-Orange/Orange-White-Orange/Green-White

-Orange/Brown-White-Orange/Gray-White-Orange/Blue-White-Green/

Orange-White-Green/ Green-White-Green/Brown-White-Green/

Gray-White-Green.For 100 pairs cable the color-coding is same as that of the above 20 pairs cable except

That the mate color is changed after each bunch of 20 pairs.

PAIRMATE COLOR1st 20 pairs White2nd 20 pairsYellow3rd 20 pairsBlack4th 20 pairsViolet5th 20 pairs Red

7. General faults occurring in an Exchange.There are mainly two types of faults that often occur in the Exchange. These are basically

* Faults that occur from Line

* Faults that occur due to Instrument

A. Faults that occur from Line:

Due to line three types of faults may occur. They are categorized as under:

1. Break fault: They are also called as Disconnection faults. They can occur in the connectors at home, in line or in exchange. In common they are broadly called as "Telephone is dead".

2. Loop fault: They are also called as Line-Shorting faults. In this fault connectors are shorted prior the instrument forming a local loop. If unattended for a long time they may cause severe damage to the Exchange.

3. Earth fault: This fault may occur due to:

* wetting of connectors

* Water in Rosette-Box

* Weak insulation or

* Oxidation of copper wire

Connectors can either touch from earth, with other connector or with any conductor (such as metallic table, frame etc.) Problems that can occur due to line faults:

1. Subscriber can not dial a number.

2. Ring Trip i.e. connection from the exchange breaks after one ring.

3. False Ring

4. Low speech

5. One sided speech

Faults that occur due to instrument:

These may be:

* The number is not being dialed

* One way speech

Receiver coil is faulty

Faults that occur due to instrument: contd

* Plunger or Push switch faulty. Dial tone breaks after two or three rings.

From second subscriber bell is heard to be going but at first subscriber only dial tone

Is heard.* Instrument circuitry faulty.

When loop or earth fault is received than exchange can be affected so it is wedged as soon as possible because if not wedge for longer it can damage line-card too.

To sense these faults first line-side is checked and then exchange side is checked at exchange. If however exchange side is correct then line faults after detection are handed over to the concerned lineman for further checking.

Testing Procedure Dig.V

Testing Procedure Dig.VI

Testing Procedure Dig.VII

Testing Procedure Dig.VIII

Testing Procedure Dig.IX

Testing Procedure Dig.XTesting Procedure Dig.XI

Testing Procedure Dig.XII

8. LIST OF SPECIAL USER FEATURES ON VARIOUS EXCHANGES.

A) MAX (CORAL INDIA PVT.LTD.NOIDA) Manufacturer: - JEUMONT SCHINEDIER, FRANCE

Capacity: - 2700 lines

CALL PICK UP: 89-xxxx to pick up a call ringing at another location xxxx.

CALL TRANSFER: 2 Parties conversing, any party can dial 3rd party, then

Conversation among them Hang-up. The party on line now

Talks to 3rd party.

PARTY CONFERENCE: While speaking with a party:

(From Pulse Instrument: -- If CALLER requires dialing 3rd party

During conversation and maintaining talks, then dial 4.

(From Tone Instrument: -- If CALLER requires dialing 3rd party

During conversation and maintaining talks, then flash, and dial 4.

MALICIOUS CALL TRACE: Dial 29 during conversation, to trace a malicious call From a MAX Extension. Then enquire from 4999 or 4424.

APPOINTMENT REMINDER: Dial 80-xx-yy {xx=hr, yy=min}.

To Cancel: Dial 27.

LIST OF SPECIAL USER FEATURES ON VARIOUS EXCHANGES Contd

B) EPABX=ALCATEL 4400

Manufacturer: - ALCATEL, FRANCE

Capacity: - 500 lines (96 DIGITAL, 404 ANALOG)

Technology used: - P.C.M. - T.D.M.

1. TONE MODE DIAL: Dial # before no.{If instrument is not tone enabled )

2. CALL TRANSFER: Hook FLASH: Do Hook Flash -

On hearing prompt "Please dial." Dial the no., wait for party to respond, then

Disconnect.

3. ENQUIRY CALL: FLASH (from Tone mode instrument.) or 2 (from Pulse mode)

During converses, to put the party on HOLD. Then, dial a 3rd party and speak.

4. BROKER CALL: (After ENQUIRY CALL): Dial 1

To go BACK & FORTH, between two parties (one party in conversation & other

On HOLD)

5. CONFERENCE-3 PARTY: While talking to 1st party, first make ENQUIRY CALL

(Put on hold){FLASH from Tone; or 2 from Pulse}.

Then - Dial 3rd party - Flash-- Dial 3.

6. AUTO CALLBACK: Dial 5 to book auto-callback when a busy PABX hangs up.

( To cancel auto-callback request: Dial 67 or/and 848)7. PASSWORD MODIFICATION: 847-0000-xxxx (0000=old password; xxxx = new

Password). This facility is available on STD enabled extensions only.

8. LAST CALLER CALLBACK: 851 {to ring the last unattended PABX Caller}

9. APPOINTMENT REMINDER: 852 then dial the time as {xx (hr) xx (min)}

To cancel: 85310. LAST NO. REDIAL: 854 User can use this if instrument. Doesnt have a Redial

Button.

11. CALL PICKUP: 72 - XXXX to pickup a call ringing at another extension.

12. CALL-PARK / RETRIEVE: It is used during an incoming or outgoing call, to speak

From a different set.

(To park from own (speaking) set: FLASH-855- dial own extension number. Then

"Hang-up". The call is now parked, and the other party is kept on hold.

(To pick up from a different set: 855- dial own extension number)

(To pick up from own set (later, if not taken elsewhere) 855)

9. OPTICAL FIBER SYSTEM.

Fiber optical transmission medium is fast emerging as an alternative and strong competitor to coaxial cables in telecommunication networks.

Long distance data transmission in electrical cables suffers from ground loop problems. The merits of the optical fiber stem from the fact tat the basic material used in their construction is nonmetallic and electrically non conductive.

In contrast, the nonmetallic and totally dielectric fiber optical cable are immune to radio frequency an other electromagnetic interferences. Ground loop and common mode voltage problem do not exist and data can be transmitted between points of vastly different potential. In optical cables the information is transmitted by packets of photons which have no charge. There is no possibility of sparks or short circuit when a fiber is cut. The bandwidth high compared to that of the electrical cables. The standard RG-58 coaxial cable has bandwidth distance product of a typical optical fiber is about 100 MHz-Km.

Fiber cables are about the thickness of a human hair any dirt obstructing the optical port causes poor transmission. The thin dimension results in a low weight for given length when compared to electrical cables. However, being thin and somewhat brittle in nature, fiber tend to break easily if bent beyond a certain limit a direct viewing into the optical point can be harmful to the eyes. 10. MAINTENANCE.

The subject of maintenance of Automatic Telephone Exchange can be broadly divided under two categories: -

1. Prevention of Service Failures.

2. Location of Faults and their removal.

Prevention of Service Failures can be done in following ways: -

1. Suitable design and adoption of suitable adjustment standards of the equipment parts of the exchange can minimize failures in service.

2. Some preventive measures may also reduce service failures viz. keeping the rooms dust free, maintaining temperature and humidity under tolerable limits using air-conditioners etc...

3. Routine inspection, routine tests and routine adjustments also help in preventing service failures.

When faults occur in some parts of the exchange, they should be detected and removed as quickly as possible.

Various tools are also used to check the faults in the telephone lines.

For checking fault inside the exchange

INTRODUCTION

Development of computer numerically controlled (CNC) machines is an outstanding contribution to the manufacturing industries. It has made possible the automation of the machining process with flexibility to handle small to medium batch of quantities in part production.Initially, the CNC technology was applied on basic metal cutting machine like lathes, milling machines, etc. Later, to increase the flexibility of the machines in handling a variety of components and to finish them in a single setup on the same machine, CNC machines capable of performing multiple operations were developed. To start with, this concept was applied to develop a CNC machining center for machining prismatic components combining operations like milling, drilling, boring and taping. Further, the concept of multi-operations was also extended for machining cylindrical components, which led to the development of turning centers.

ADVANTAGE OF CNC MACHINES

Higher flexibility Increased productivity Consistent quality Reduced scrap rate Reliable operation Reduced non productive time Reduced manpower Shorter cycle time High accuracy Reduced lead time Just in time (JIT) manufacture Automatic material handling Lesser floor space Increased operation safety Machining of advanced materialCNC SYSTEMS

INTRODUCTION

Numerical control (NC) is a method employed for controlling the motions of a machine tool slide and its auxiliary functions with input in the form of numerical data. A computer numerical control (CNC) is a microprocessor-based system to store and process the data for the control of slide motions and auxiliary functions of the machine tools. The CNC system is the heart and brain of a CNC machine which enables the operation of various machine members such as slides, spindles, etc. as per the sequence programmed into it, depending on the machining operations. The main advantage of a CNC system lies in the fact that the skills of the operator hitherto required in the operation of a conventional machine is removed and the part production is made automatic. The CNC systems are constructed with a NC unit integrated with a programmable logic controller (PLC) and some times with an additional external PLC (non-integrated). The NC controls the spindle movement and the speeds and feeds in machining. It calculates the traversing path of the axes as defined by the inputs. The PLC controls the peripheral actuating elements of the machine such as solenoids, relay coils, etc. Working together, the NC and PLC enable the machine tool to operate automatically. Positioning and part accuracy depend on the CNC system's computer control algorithms, the system resolution and the basic mechanical machine accuracy. Control algorithm may cause errors while computing, which will reflect during contouring, but they are very negligible. Though this does not cause point to point positioning error, but when mechanical machine inaccuracy are present, it will result in poorer part accuracy.

This chapter gives an overview of the configuration of the CNC system, interfacing and introduction to PLC programming.CONFIGURATION OF THE CNC SYSTEM

Fig.1 shows a schematic diagram of the working principle of a NC axis of a CNC machine and the interface of a CNC control.

CNC system

Fig.1 Schematic diagram of a CNC machine toolA CNC system basically consists of the following:

Central processing unit (CPU)

Servo-control unit

Operator control panel

Machine control panel

Other peripheral device

Programmable logic controller (PLC)

Fig.2 gives the typical numerical control configuration of Hinumerik 3100 CNC system

Central Processing Unit (CPU)

The CPU is the heart and brain of a CNC system. It accepts the information stored in the memory as part program. This data is decoded and transformed into specific position control and velocity control signals. It also oversees the movement of the control axis or spindle whenever this does not match the programmed values, a corrective action is taken.

All the compensations required for machine accuracy (like lead screw pitch error, tool wear out, backlash, etc.) are calculated by the CPU depending upon the corresponding inputs made available to the system. The same will be taken care of during the generation of control signals for the axis movement. Also, some safety checks are built into the system through this unit and the CPU unit will provide continuous necessary corrective actions. Whenever the situation goes beyond control of the CPU, it takes the final action of shutting down the system in turn the machine.

Speed Control Unit

This unit acts in unison with the CPU for the movement of the machine axes. The CPU sends the control signals generated for the movement of the axis to the servo control unit and the servo control unit convert these signals into the suitable digital or analog signal to be fed to the machine tool axis movement. This also checks whether machine tool axis movement is at the same speed as directed by the CPU. In case any safety conditions related to the axis are overruled during movement or otherwise they are reported to the CPU for corrective action.

Servo-Control Unit

The decoded position and velocity control signals, generated by the CPU for the axis movement forms the input to the servo-control unit. This unit in turn generates suitable signals as command values. The servo-drive unit converts the command values, which are interfaced with the axis and the spindle motors (Fig.1).

The servo-control unit receives the position feedback signals for actual movement of the machine tool axes from the feedback devices (like linear scales, rotary encoders, resolves, etc.). The velocity feedback is generally obtained through tacho generators. The feedback signals are passed on to the CPU for further processing. Thus the servo-control unit performs the data communication between the machine tool and the CPU.

As explained earlier, the actual movements of the slides on the machine tool is achieved through servo drives. The amount of movement and the rate of movement are controlled by the CNC system depending upon the type of feedback system used, i.e. closed-loop or open-loop system (Fig.3).

Position Feedback

A closed-loop system, regardless of the type of feedback device, will constantly try to achieve and maintain a given position by self-correcting. As the slide of the machine tool moves, its movement is fed back to the CNC system for determining the position of the slide to decide how much is yet to be traveled and also to decide whether the movement is as per the commanded rate. If the actual rate is not as per the required rate, the system tries to correct it. In case this is not possible, the system declares fault and initiates action for disabling the drives and if necessary, switches off the machine.

Open-loop positioning control

Close-loop positioning control

Fig.3 Open-and Closed-loop positioning systemVelocity feedback

In case no time constraint is put on the system to reach the final programmed position, then the system may not produce the required path or the surface finish accuracy. Hence, velocity feedback must be present along with the position feedback whenever CNC system are used for contouring, in order to produce correct interpolation and also specified acceleration and deceleration velocities. The tacho generator used for velocity feedback is normally connected to the motor and it rotates whenever the motor rotates, thus giving an analog output proportional to the speed of motor. The analog voltage is taken as speed feedback by the servo-controller and swift action is taken by the controller to maintain the speed of the motor within the required limits.

Open-loop system

The open loop system lacks feedback. In this system, the CNC system send out signals for movement but does not check whether actual movement is taking place or not. Stepper motors are used for actual movement and the electronics of these stepper motors is run on digital pulses from the CNC system. Since system controllers have no access to any real time information about the system performance, they cannot counteract disturbances appearing during the operation. They can be utilized in point to point system, where loading torque on the axial motor is low and almost constant.

Servo-drives

As shown in Fig.1 the servo-drive receives signals from the CNC system and transforms it into actual movement on the machine. The actual rate of movement and direction depend upon the command signal from CNC system. There are various types of servo-drives, viz., dc drives, ac drives and stepper motor drives. A servo-drive consists of two parts, namely, the motor and the electronics for driving the motor.

Operator Control Panel

Fig.4 shows a typical Hinumerik 3100 CNC system's operator control panel. The operator control panel provides the user interface to facilitate a two-way communication between the user, CNC system and the machine tool. This consists of two parts:

Video Display Unit (VDU)

Keyboard

Video Display Unit (VDU)

The VDU displays the status of the various parameters of the CNC system and the machine tool. It displays all current information such as:

Complete information of the block currently being executed

Actual position value, set or actual difference, current feed rate, spindle speed

Active G functions

Main program number, subroutine number

Display of all entered data, user programs, user data, machine data, etc.

Alarm messages in plain text

Soft key designations

In addition to a CRT, a few LEDs are generally provided to indicate important operating modes and status.

Video display units may be of two types:

1. Monochrome or black and white displays

2. Color displays

Operator's and machine panel

Keyboard

A keyboard is provided for the following purposes:

Editing of part programs, tool data, and machine parameters.

Selection of different pages for viewing.

Selection of operating modes, e.g. manual data input.

Selection of feed rate override and spindles speed override.

Execution of part programs.

Execution of other toll functions.

Machine Control Panel (MCP)

It is the direct interface between operator and the NC system, enabling the operation of the machine through the CNC system. Fig.5 shows the MCP of Hinumerik 3100 system.

During program execution, the CNC controls the axis motion, spindle function or tool function on a machine tool, depending upon the part program stored in the memory. Prior to the starting of the machine process, machine should first be prepared with some specific tasks like,

Establishing a correct reference point

Loading the system memory with the required part program

Loading and checking of tool offsets, zero offsets, etc.

For these tasks, the system must be operated in specific operating mode so that these preparatory functions can be established.

Control elements of the machine control panel

Modes of operation

Generally, the CNC system can be operated in the following modes:

Manual mode

Manual data input (MDI) mode

Automatic mode

Reference mode

Input mode

Output mode, etc.

Manual mode: In this mode, movement of a machine slide can carried out manually by pressing the particular jog button (+ or -). The slide (axis) is selected through an axis selector switch or through individual switches (e.g., X+, X-, Y+, Y-, Z+, Z-, etc.). The feed rate of the slide movement is prefixed. CNC system allows the axis to be jogged at high feed rate also. The axis movement can also be achieved manually using a hand wheel interface instead of jog buttons. In this mode slides can be moved in two ways:

Continuous

Incremental

Continuous mode: In This mode, the slide will move as long as the jog button is pressed.

Incremental mode: Hence the slide will move through a fixed distance, which is selectable. Normally, system allows jogging of axes in 1, 10, 100, 1000, 10000, increments. Axis movement is at a prefixed feed rate. It is initiated by pressing the proper jog or jog- key and will be limited to the no of increments selected even if the jog button is continuously pressed. For subsequent movement the jog button has to be released and once again pressed.

Manual Data Input (MDI) Mode

In this mode the following operation can be performed:

Building a new part program

Editing or deleting of part program stored in the system memory

Entering or editing or deleting of:

------ Tool offsets (TO)

------ Zero offsets (ZO)

------ Test data, etc.

Teach-in

Some system allows direct manual input of a program block and execution of the same. The blocks thus executed can be checked for correctness of dimensions and consequently transferred into the program memory as part program.

Playback

In setting up modes like jog or incremental, the axis can be traversed either through the direction keys or via the hand wheel, and the end position can be transferred into the system memory as command values. But the required feed rates, switching functions and other auxiliary functions have to be added to the part program in program editing mode.

Thus, teach-in and playback operating method allows a program to created during the first component prove out.

Automatic Mode (Auto and Single Block)

In this mode the system allows the execution of a part program continuously. The part program is executed block by block. While one block is being executed, the next block is read by the system, analyzed and kept ready for execution. Execution of the program can be one block after another automatically or the system will execute a block, stop the execution of the next block till it is initiated to do so (by pressing the start button). Selection of part program execution continuously (Auto) or one block at a time (Single Block) is done through the machine control panel.

Many systems allow blocks (single or multiple) to be retraced in the opposite direction. Block retrace is allowed only when a cycle stop state is established. Part program execution can resume and its execution begins with the retraced block. This is useful for tool inspection or in case of tool breakage. Program start can be affected at any block in the program, through the BLOCK SEARCH facility.

Reference Mode

Under this mode the machine can be referenced to its home position so that all the compensations (e.g., pitch error compensation) can be properly applied. Part programs are generally prepared in absolute mode with respect to machine zero. Many CNC systems make it compulsory to reference the slides of the machine to their home positions before a program is executed while others make it optional.

Input Mode and Output Mode (I/O Mode)

In this mode, the part programs, machine setup data, tool offsets, etc. can be loaded/unloaded into/from the memory of the system from external devices like programming units, magnetic cassettes or floppy discs, etc. During data input, some systems check for simple errors (like parity, tape format, block length, unknown characters, and program already present in the memory, etc.). Transfer of data is done through a RS232C or RS422C port.

Other Peripherals

These include sensor interface, provision for communication equipment, programming units, printer, tape reader/puncher interface, etc.

Fig.6 gives an overview of the system with few peripheral devices.

Programmable Logic Controller (PLC)

A PLC matches the NC to the machine. PLCs were basically introduced as replacement for hard wired relay control panels. They were developed to be reprogrammed without hardware changes when requirements were altered and thus are reusable. PLCs are now available with increased functions, more memory and large input/output capabilities. Fig.7 gives the generalized PLC block diagram.

In the CPU, all the decisions are made relative to controlling a machine or a process. The CPU receives input data, performs logical decisions based upon stored programs and drives the outputs. Connections to a computer for hierarchical control are done via the CPU.

The I/O structure of the PLCs is one of their major strengths. The inputs can be push buttons, limit switches, relay contacts, analog sensor, selector switches, proximity switches, float switches, etc. The outputs can be motor starters, solenoid valves, position valves, relay coils, indicator lights, LED displays, etc.

The field devices are typically selected, supplied and installed by the machine tool builder or the end user. The voltage level of the field devices thus normally determines the type of I/O. So, power to actuate these devices must also be supplied external to the PLC. The PLC power supply is designated and rated only to operate the

Internal portions of the I/O structures, and not the field devices. A wide variety of voltages, current capacities and types of I/O modules are available.

Fig.6 System with peripheral devices

Fig.7 Generalized PLC block diagram

INTERFACING

Interconnecting the individual elements of both the machine and the CNC system using cables and connectors is called interfacing.

Extreme care should be taken during interfacing. Proper grounding in electrical installation is most essential. This reduces the effects of interference and guards against electronic shock to personnel. It is also essential to properly protect the electronic equipment.

Cable wires of sufficiently large cross-sectional area must be used. Even though proper grounding reduces the effect of electrical interference, signal cable requires additional protection. This is generally achieved by using shielded cables. All the cable shields must be grounded at control only, leaving other end free. Other noise reduction techniques include using suppression devices, proper cable separation, ferrous metal wire ways, etc. Electrical enclosures should be designed to provide proper ambient conditions for the controller.

MONITORING

In addition to the care taken by the machine tool builder during design and interfacing, basic control also includes constantly active monitoring functions. This is in order to identify faults in the NC, the interface control and the machine at an large stage to prevent damages occurring to the work piece, tool or machine. If a fault occurs, first the machining sequence is interrupted, the drives are stopped, the cause of the fault is stored and then displayed as an alarm. At the same time, the PLC is informed that an NC alarm exits. In Hinumerik CNC system, for example, the following can be monitored:

Read-in

Format

Measuring circuit cables

Position encoders and drives

Contour

Spindle speed

Enable signals

Voltage

Temperature

Microprocessors

Data transfer between operator control panel and logic unit

Transfer between NC and PLC

Change of status of buffer battery

System program memory

User program memory

Serial interfaces

DIAGNOSTICS

The control will generally be provided with test assistance for service purposes in order to display some status on the CRT such as:

Interface signals between NC and PLC as well as between PLC and machine

Flags of the PLC

Timers of the PLC

Counters of the PLC

Input/output of the PLC

For the output signals, it is also possible to set and generate signal combinations for test purposes in order to observe how the machine react to a changed signal. This simplifies trouble shooting considerably.

MACHINE DATA

Generally, a CNC system is designed as a general-purpose control unit, which has to be matched with the particular machine to which the system is interfaced. The CNC is interfaced to the machine by means of data, which is machine specific. The NC and PLC machine data can be entered and changed by means of external equipment or manually by the keyboard. These data are fixed and entered during commissioning of the machine and generally left unaltered during machine operations.

Machine data entered is usually relevant to the axis travel limits, feed rates, rapid traverse speeds and spindle speeds, position control multiplication factor, Kv factor, acceleration, drift compensation, adjustment of reference point, backlash compensation, pitch error compensation, etc. Also the optional features of the control system are made available to the machine tool builder by enabling some of the bits of machine data.

COMPENSATIONS FOR MACHINE ACCURACY

Machine accuracy is the accuracy of the movement of the carriage, and is influenced by:

(a) Geometric accuracy in the alignment of the slide ways

(b) Deflection of the bed due to load

(c) Temperature gradients on the machine

(d) Accuracy of the screw thread of any drive screw and the amount of backlash (lost motion)

(e) Amount of twist (wind up) of the shaft which will influence the measurement of rotary transducers

The CNC systems offer compensation for the various machines' accuracy. These are detailed below:

Lead Screw Pitch Error Compensation

To compensate for movements of the machine slide due to in accuracy of the pitch along the length of the ball screw, pitch error compensation is required. To begin with, the pitch error curve for the entire length of the screw is built up by physical measurement with the aid of an external device (like laser). Then the required compensation at predetermined points is fed in to the system. Whenever a slide is moved, these compensation are automatically added up by the CNC system (Fig.8)

Fig.8 Typical error curveBacklash Compensation

Whenever a slide is reversed, there is some lost motion due to backlash between nut and the screw; a compensation is provided by the CNC system for the motion lost due to reversal, i.e. extra movement is added into the actual movement whenever reversal takes place. This extra movement is equal to backlash between the screw and the nut. This has to be measured in advance and fed to the system. This value keeps on varying due to wear of the ball screws, hence the compensation value has to be updated regularly from time to time

Fig.9 Backlash compensation

Sag Compensation

Inaccuracy due to sag in the slide can be compensated by the system. Compensations required along the length of the slide have to be physically measured and fed to the system. The system automatically adds up the compensation to the movement of the slide.

Tool Nose Compensation

Tool nose compensation normally used on tool for turning centers. While machining chamfers, angles or turning curves, it is necessary to make allowance for the tool tip radius; this radius is known as radius compensation. As shown in Fig.10 (a), if the allowance is nit made, the edges of the tool tip radius would be positioned at the programmed X and Z coordinates, and the tool will follow the path AB and the taper produced will be incorrect. In order to obtain correct taper, tool position has to be adjusted.

It is essential that the radius at the tip of the tool is fed to the system to make an automatic adjustment on the position and movement of the tool to get the correct taper on the work. In Fig.10 (b) the distance Xc is the adjustment necessary at the start of the cut and distance Zc is the adjustment at the end of the cut.

Fig.10 Tool nose radius compensation

Cutter Diameter Compensation

The diameter of the used tool may be different from the actual value because of regrinding of the tool or due to non-availability of the assumed tool. It is possible to adjust the relative position of cutter size and this adjustment is known as cutter diameter compensation.

Fig.11 Tool offsets

Tool Offset

A part program is generated keeping in mind a tool of a particular length, shape and thickness as a reference tool. But during the actual mounting of tools on the machine, different tools of varying lengths, thickness and shapes may be available. A correction for dimension of the tools and movements of the work piece has to be incorporated to give the exact machining of the component. This is known as tool offset. This is the difference in the positions of the centre line of the tool holder for different tools and the reference tool. When a number of tools are used, it is necessary to determine the tool offset of each tool and store it in the memory of the control unit. Fig.11 explains the function of the tool offset.

Normally, it is found that the size of the work piece (diameter or length) is not within tolerance due to wear of the tool; it is the possible to edit the value of offsets to obtain the correct size. This is known as tool wear compensation.

PLC PROGRAMMING

The principle of operation of a PLC is determined essentially by the PLC program memory, processor, inputs and outputs.

The program that determines PLC operation is stored in the internal PLC program memory. The PLC operates cyclically, i.e. when a complete program has been scanned, it starts again at the beginning of the program. At the beginning of each cycle, the processor examines the signal status at all inputs as well as the external timers and counters and are stored in a process image input (PII). During subsequent program scanning, the processor the accesses this process image.

To execute the program, the processor fetches one statement after another from the programming memory and executes it. The results are constantly stored in the process image output (PIO) during the cycle. At the end of a scanning cycle, i.e. program completion, the processor transfers the contents of the process image output to the output modules and to the external timers and counters. The processor then begins a new program scan.

STEP 5 programming language is used for writing user programs for SIMATIC S5 programmable controllers. The program can be written and entered into the programmable controller as in:

Statement list (STL), Fig.12 (a)

Control system flowchart (CSF), Fig.12 (b)

Ladder diagram (LAD), Fig.12 (c)

(a)

Fig.12 Programmable controller

The statement list describes the automation task by means of mnemonic function designations.

The control system flowchart is a graphic representation of the automation task.

The ladder diagram uses relay ladder logic symbols to represent the automation task.

The statement is the smallest STEP 5 program component. It consists of the following:

Operation, i.e. what is to be done?

E.g.

A = AND operation (series connection)

O= OR operation (parallel connection)

S= SET operation (actuation)

Operand, i.e. what is to be done with?

E.g.

I 4.5, i.e. with the signal of input 4.5

The operand consists of:

Operand identifier (I = input, Q = output, F = flag, etc.)

Parameter, i.e. the number of operand identifiers addressed by the statement. For inputs, outputs and flags (internal relay equivalents), the parameter consists of the byte and bit addresses, and for timers and counter, byte address only.

The statement may include absolute operands, e.g. I 5.1, or symbolic operand, e.g. I LS1. Programming is considerably simplified in the later case as the actual plant designation is directly used to describe the device connected to the input or output.

Typically, a statement takes up one word (two bytes) in the program memory.

STRUCTURED PROGRAMMING

The user program can be made more manageable and straightforward if it is broken down into relative sections. Various software block types are available for constructing the user program.

Program blocks (PB) contain the user program broken down into technologically or functionally related sections (e.g. program block for transportation, monitoring, etc.). Further blocks, such as program blocks or function blocks can be called from a PB.

Organization blocks (OB) contain block calls determining the sequence in which the PBs are to be processed. It is therefore possible to call PBs conditionally (depending on certain conditions).

In addition, special OBs can be programmed by the user to react to interruptions during cyclic programming processing. Such an interrupt can be triggered by a monitoring function if one or several monitored events occur.

Function block (FB) is block with programs for recurrent and usually complex function. In addition to the basic operations, the user has a extended operation at his disposal for developing function blocks. The program in a function block is usually not written with absolute operands (e.g. I 1.5) but with symbolic operands. This enables a function block to be used several times over with different absolute operands.

For even more complex functions, standard function blocks are available from a program library. Such FBs are available, e.g. for individual controls, sequence controls, messages, arithmetic operations, two step control loops, operator communications, listing, etc. These standard FBs for complex functions can be linked it the user program just like user written FBs simply by means of a call along with the relevant parameters.

The Sequence block (SB) contain the step enabling conditions, monitoring times and conditions for the current step in sequence cascade. Sequence blocks are employed, for example, to organise the sequence cascade in communication with a standard FB.

The data blocks (DB) contain all fixed or variable data of the user program.

CYCLIC PROGRAM PROCESSING

The blocks of the user program are executed in the sequence in which they specified in the organisation block.

INTERRUPT DRIVEN PROGRAM PROCESSING

When certain input signal changes occur, cyclic processing is interrupted at the next block boundary and an OB assigned to this event is started. The user can formulate his response program to this interrupt in the OB. The cyclic program execution is the resumed from the point at which it was interrupted.

TIME CONTROLLED PROGRAM EXECUTION

Certain Obs are executed at the predetermined time intervals (e.g. every 100ms, 200ms, 500ms, 1s, 2s, and 5s). For this purpose, cyclic program execution is interrupted at the block boundary and resumed again at this point, once the relevant OB has been executed. Fig.13 gives the organisation and execution of a structured user program.

Fig.13 Organisation and execution of a structured user program

EXAMPLES OF PLC PROGRAM

Before attempting to write a PLC program, first go through the instruction set of the particular language used for the equipment, and understand the meaning of each instruction. Then study how to use these instructions in the program (through illustration examples given in the manual). Once the familiarization task is over, then start writing the program.

Follow the following steps to write a PLC program.

List down each individual element (field device) on the machine as Input/Output.

Indicate against each element the respective address as identifier during electrical interfacing of these elements with the PLC.

Break down the complete machine auxiliary functions that are controlled by the PLC into individual, self contained functions.

Identify each individual function as separate block (PBxx/FBxx)

Once the PBs and FBs for each function are identified, take them one by one for writing the program.

List down the preconditions required for the particular function separately.

Note down the address of the listed elements.

Write down the flow chart for the function.

Translate the flow chart into PLC program using the instructions already familiarized.

Complete the program translation of all individual functions in similar lines.

Check the individual blocks independently and correct the program to get the required results.

Organize all the program blocks in the organization block depending upon the sequence in which they are supposed to be executed as per the main machine function flow chart.

Check the complete program with all the blocks incorporated in the final program.

Example 1: Spindle ON

PreconditionsFeedback elementsAddressFault indicationAddressRemark

Tool clamp

Pressure switchI 2.4

Lamp

Q 2.1

Job clamp

Proximity switchI 3.2

Lamp

Q 1.7

Door close

Limit switch

I 5.7

Lamp

Q 4.0

Lubrication ONPLC output bit

Q 1.0

Lamp

Q 7.7

Drive ready

Input signal from I 4.6

Lamp

Q 0.4

Drive unit

PB 12 written is the individual function module for spindle ON for all the preconditions checked and found satisfactory. This function is required to be executed only when the spindle rotation is requested by the NC in the form of a block in the part program.

Whenever NC decodes the part program block, it in turn informs the PLC through a fixed buffer location that spindle rotation is requested. Say Flag bit F 100.0 is identified for this information communication. With this data, spindle ON function module can be recalled in the organisation block OB1 as follows.

Now, spindle ON function module PB12 will be executed only when F 100.0 is set. Otherwise the function execution will be bypassed.

FLOW CHART

Spindle Head

Servo Motor

Servo Drive

Encoder

PLC

Command value

NC

Lead

Screw

Tacho

Generator

Work piece

Table

Velocity

Feedback

Position Feedback

Tape Reader

Tape Punch

Other Devices

Proximity switches

Limit switches

Relay coils

Pressure switches

Float switches

Inputs

Machine

Elements

Outputs

Table

Lead Screw

Servo Motor

Controller

Tape reader

Comparison

Circuit

Stop at

Zero

Command

Counter

Subtraction

Circuit

Position

Control

Amplifier

Error

Signal

Table

Active

Buffer

Storage

Transducer

Count

Comparator

Amplifier

Lead Screw

Servo Motor

Tape reader

Position feedback signal

Fig.4 Operator control panel of Hinumerik 3100 system

Change to actual value display

Change of display

Leaf forwards

Leaf backwards

Right-Left Cursor

LED-indicator

For assignment

Of keys

CRT

Basic display

Tool compensation

Zero offset

Test

Part program

Program in progress

Feed hold

Position not yet reached

(Machine in motion)

Alarm

Control elements and indicators of the operator's panel

Cycle

Emergency Stop

POWER ON

X+

Z+

X -

Z -

SIEMENS

SINUMERIK

SYSTEM 3

Reset changeover

Assignment of keys

Cancel word

Alter word

Enter word

Change over to customer display

Operator guidance Yes,No

Delete input

Start

Address Keys/Numerical keyboard

Rapid traverse activate

Direction keys

Federate/rapid traverse override

Spindle speed override

Mode selector Switch

X+

Z+

Z -

Feed

Hold/Start

X -

Cycle start

POWER ON

Cycle

Emergency Stop

Spindle

OFF ON

Block Delete

Dry Run

Single block

NC ON

Rapid Traverse

Override active

Manual encoder active in

X-and Z-axis resp.

Key operated switch for input inhibit

Block search

Fig.5 Machine control panel of Hinumerik 3100 system

Tape Puncher

Printers

Tape Reader

Programming Units

Programmer

Field Devices

Logic memory

Processor

Storage memory

Inputs

Outputs

Power Supply

Power

Supply

Pitch error (um)

To negative end limit

Positive end limit

Reference point

Negative backlash

Positive backlash (the usual case)

Table

Table

Backlash

Toothed wheel

Encoder

Backlash here

M

M

Encoder

Ballscrew

Actual movement of the table precedes the encoder measurement

Encoder actual value precedes the table movement

Z 0

X 0

Z 0

X 0

Tool

Datum Position

Datum Position

Minimum radius of taper

Xc

A

X 20,0

Z -25,0

Z -15,0

Zc

X 20,0

Z 0

X 30,0

B

Z -15,0

X 30,0

Z0

ZR

ZR=Setting distance for reference tool

X0

XR=Setting distance for reference tool

Reference tool

Tool no.1

ZR

XR

Tool no.2

X offset for tool no.2

Z offset for tool no.2

(b) Control system flow chart CSF

I 2.3

AND

Statement list STL

A I 2.3

A I 4.1

O I 3.2

= Q 1.6

I 4.1

O

R

Q 1.6

I 3.2

(c) Ladder diagram LAD

A I 2.3

I 2.3

I 4.1

Statement

Operation

Operand

A

I 2.3

Parameter

I

2.3

I 3.2

Operand identifier

Structured programming

FB2

PB1

OB1

FB3

PB2

Function block (PB)

Program block (PB)

Organisation block (OB)

Cycle execution

OB

PB

FB

FB

PB

Interrupt-driven execution

FB

PB

OB

Points at which interrupt-driven program can be inserted

Start and finish of interrupt-driven program execution

PB12

START

Comments

NO

AN I 2.4 Tool not clamped

= Q 2.1 Display fault lamp

INDICATE FAULT

TOOL CLAMP

YES

NO

AN I 3.2 Job not clamped

= Q 1.7 Display fault lamp

INDICATE FAULT

JOB CLAMP

YES

NO

AN I 5.7 Door not closed

= Q 4.0 Display fault lamp

INDICATE FAULT

DOOR CLOSED

YES

NO

AN Q 1.0 Lubrication not on

= Q 7.7 Display fault lamp

INDICATE FAULT

LUBRICATION ON

YES

NO

INDICATE FAULT

DRIVE READY

AN I 4.6 Drive not ready

= Q 0.4 Display fault lamp

YES

YES

ON I 2.4 Tool not clamped

ON I 3.2 Job not clamped

ON I 5.7 Door not closed

ON Q 1.0 Lubrication not on

ON I 4.6 Drive not ready

R Q 67.3 Reset spindle enable bit

BEC Block end conditionally

A I 2.4 Tool clamped

A I 3.2 Job clamped

A I 5.7 Door closed

A Q 1.0 Lubrication ON

A I 4.6 Drive ready

S Q 67.3 Set spindle enable bit

BE Block end

Exit

STOP SPINDLE

ANY FAULT

NO

DO SPINDLE ON

END

PAGE XLVI