23-11-2012, 05:08 PM
INDUSTRIAL TRAINING REPORT ON COMPUTER NUMERICAL CONTROL MACHINE
[attachment=40890]
INTRODUCTION
This unit of Jhansi was established around 14 km from the city on the Jhansi-Lalitpur road. It is BHEL second generation plant, and was set up with an estimated cost of 16.22crore which in-cludes 2.1 core for the township. The president of India, the late Mrs.Indira Gandhi, laid down its foundation and the commercial production of unit began in1976-1977 with an output of Rs 53 lacks. This plant of BHEL is equipped with the most modern manufacturing, processing and-testing facilities for the manufacturing of power, special and instrument transformer, diesel shunting locomotives and AC/DC locomotives. The layout of the plant is wellstreamlined to en-able smooth flow of the material from the raw material stage to the finished goods. All the feeder bays have been laid perpendicular to the main assembly bay and each feeder bay raw materials smoothly gets converted to sub-assemblies, whichafter inspection are sent to the main assembly bay. The raw materials that are produced for manufacturing are used only after a throughmaterial testing in the testing lab with strict quality checks at various stages of production. This unit of BHEL is basically engaged in the production of various types of transformers and capacities with the growing competition in the transformer section. In1985-86 the re-powering of BHEL took place, but it took a complete year for manufacturing to commence again. In 1987-88 BHEL had progressed a step further in undertaking the production of ac locomotives also.
CURRENT TRANSFORMER
• It is step down transformer. High current is not directly measured but by the current transformer is step down to lower measurable values, which is generally low.
• Body
• The main body is a bushing, it also act as insulator in which winding is placed.
• The CT has a bottom and top chamber.
• The top chamber is the cylindrical tank of mild steel. It hasterminals for connection of HV coils. It has a glass window toindicate the oil level.
• Below the top chamber there is bushing made of porcelain. It has several folds and “rain sheds” to provide a specificelectrical field distribution and long leakage path. Some bushings are of cylindrical while modern one is conical asamount of oil porce-lain used is reduced without any undesirable effect.
• Bottom chamber house the secondary winding. There isalso connection box to which the connection low voltage(LV) is made.
WINDINGS
The primary winding consists of hollow copper/aluminium pipe bentfrom of ‘U’ aluminium, used for low rating. For higher rating a set of wire is passed through the pipe. For still higher rating, copper pipe isused and for highest rating copper pipe with copper wire passing through it is used. This arrangement depends on the current carryingcapacity. The bent portion of primary as in the bottom chamber where as the free end is the top chamber. The straight portion lies inside the bushing.The primary is wound with crepe paper insulation goes in increasing as we go downwards in the bottom chamber. The free ends areprovides with ‘ferrules’, which are small hollow cylinder through which wires can pass connection to the madprimary are made through these ferrules. The secondary is divided in a number of coils for different set of tapings. Connections are different taping are made inconnection box. Each coil has an annular core of CRGO (silicon steel).
ESP TRANSFORMER
The Electro static precipitator rectifier transformer is used for environmental application. It is used to filter the suspended charged in the waste uses of an industry. They are of particular use in thermal power station and cementindustry.The ESP is a single ø phase transformer. It has primary and secondary windings. The core is laminated and ismade up of CRGO sheet. It is a step up transformer. An Acre actor is connected in series with primary coil. The output of the transformer must be DC which is obtained by rectifying Accusing a bridge rectifier (bridge rectifier is a combination of several hundred diodes). A radio frequency chock (RF chock) disconnected in series with the DC output for the protection of secondary circuit and filter circuit. The output chosen the negative because the particles of carbon are positively charged. The dc output from the secondary is given to a set of plate arrange one after the oth-ers. Impurity particles being positively charged stick to these plates, which can be jerked off by hammer. For this a network of plant has to be set up all across the plants .This is very costly process in comparison with the transformer cost. A relevant is also provided to prevent the transformer from bursting it higher pressure develops, inside it. It is the weakest point in the transformer body. An oil temperature indicator and the secondary supply spark detector are also provided. One side of the transformer output is taken and the other side has a “mar-shalling box” which is the control box of the transformer.
POWER TRANSFORMER:
Power transformer find their wide use in electrical power system. Actually these are the transformer, which have made A.C.transmission very easy. These are step up or down transformer. The primary and secondary voltage of power trans-former comprises material for magnetic circuit terminals, tanning switches, tank oil as well as cooling devices.
BUS DUCT
Bus duct is used as connection between generators and transformer. Bus duct are used in power connection over 150 M V.The question now arise that why are bus duct preferred over normal conductors. In high power application, insulations are the majorproblems and frequent insulation breakdown occurs. If this does happens then possibility of shorting of conductor’s and hence seriousdamage may occur to both transformer and generators. Bus duct are hollow pipes made of aluminium the cross section of these ducts depends on requirements of the customer and is done bythe design department.The cross section may have different shapes, circular, square hexagon, octagon. The casing is also made of aluminium sheets. Although aluminium is not a good conductor as copper still is preferred over it because it is lighter than copper. Moreover, it is cheaper thancopper.Bus duct are of two types:
Segregated Bus Duct(SBD)b.
PRINCIPLES OF CNC MACHINE
Electronic industries association defines numerical control as a system in which actions are controlled by direct insertion of numeric data. The system must automatically interpret at least some portion of data. It means control by numbers. The main function into control the displacement and positioning of slides, spindles, speed feed rates, selection of tools and many other auxiliary functions. CNC directs the machine tool to achieve all these function in a very controlled and synchronized manner. The main element that comprise CNC machine tools are:
Control system CNC
The machine tool
Feedback devices
Operator’s control
Electrical cabinet A CNC production facility needs three pieces of equipment:
A computer: The computer is used to draw the design. However, the design is only picture and thence machine cannot use this to manufacture the product. The computer software must also convert the drawing into numbers (coordinates) that the CNC machine can use when it starts to cut and shape the material.
An interface: A computer cannot be directly connected to a CNC machine. The computer is connected to an interface. This converts the signal from the computer to a form that CNC machine understands. The signal are in the form of digital signals when they are sent to the CNCmachine.
FUNCTIONS OF CNC:
1. Machine tools control: it is prime function of the CNC system to control the machine tool. This involves conversion of the part program instruction into machine tool motion through the computer interface and servo system.
2. in process compensation: it is closely related function to machine tool control. This evolves the dynamic correction of the machine tool motions for changes of errors, which oc-curs during the processing. The main operations are as follows:
Adjustment for errors sensed by in-process inspection probes and gauges
Computation of an axis position when an inspection probe is used to locate datum reference on a work part.
Offset adjustment for tool radius and length
.Adaptive control adjustment to speed and feed.
3.Computation of predicted tool life and selection of alternative tooling when indicated. im-proved programming and operating features the soft wired control has permittedthe introduc-tion of many continent programming and operating features. The main features are as follows:
Editing of part programs at the machine.
Graphic display of the tool path to verify the shape.
Provision of various types of interpolation, circular, parabolic, exponential etc.
Support of old customary units and new metric units.
Use specially written subroutines.
Manual data input.
Local storage of more than single part program.
4. Diagnostics: presently CNC machine are equipped with a diagnostics capabilities to assist in maintaining and repairing the system.
ADVANTAGES OF CNC MACHINES:
Some of the most significant advantages of CNC machine are:1.High accuracy.2.High re-peatability.3.Reduced inspection.4.Ease of assembly and interchange ability.5.Less scrap and rework.6.Reduced floor space.7.Reduced work handling.8.Reduced lead-time.9.Flexibility for design changes.10.Reduced tooling.11.Design freedom.12.Ownership of skill.13.Better machine utilization.14.Reduced paper work.
CODES USED IN CNC PROGRAMS:
G-code is a common name for the programming language driving NC and CNC machine tool. It was developed by EIA in the early 1960s a final revision was approved in February 1980 as RS274D.G-code is also the name of any word in a CNC program that begins with the letter G and generally is a code telling the machine tool what action to perform, such as1.Rapid move2.Controlled feed move in straight line or arc3.Series of controlled feed moves that would result in a hole being bored, a work piece cut to a specific dimension, or a decorative profile shape added to the edge of a workpiece.4.Change a pallet5.Set tool information such as offset.
CONCLUSION:
To conclude numeric control is the most sophisticated form of automatic control of machine tool. It has high degree of precision, accuracy and reliability. The control system has undergone several stages of development. With the above qualities of CNC machines there are numerous advantages like:
1. High accuracy.
2. High repeatability.
3. Less scrap and network.
4. Better machine utilization.Some of the special features offered by CNC machine manufacture are
5. Thermal stabilization
6. Axis calibration.
7. Lost motion compensation.
The program written to CNC machine is easy to write and understand. This program usecode (G codes and M codes) that runs the program. The codes are simple to understand.
[attachment=40890]
INTRODUCTION
This unit of Jhansi was established around 14 km from the city on the Jhansi-Lalitpur road. It is BHEL second generation plant, and was set up with an estimated cost of 16.22crore which in-cludes 2.1 core for the township. The president of India, the late Mrs.Indira Gandhi, laid down its foundation and the commercial production of unit began in1976-1977 with an output of Rs 53 lacks. This plant of BHEL is equipped with the most modern manufacturing, processing and-testing facilities for the manufacturing of power, special and instrument transformer, diesel shunting locomotives and AC/DC locomotives. The layout of the plant is wellstreamlined to en-able smooth flow of the material from the raw material stage to the finished goods. All the feeder bays have been laid perpendicular to the main assembly bay and each feeder bay raw materials smoothly gets converted to sub-assemblies, whichafter inspection are sent to the main assembly bay. The raw materials that are produced for manufacturing are used only after a throughmaterial testing in the testing lab with strict quality checks at various stages of production. This unit of BHEL is basically engaged in the production of various types of transformers and capacities with the growing competition in the transformer section. In1985-86 the re-powering of BHEL took place, but it took a complete year for manufacturing to commence again. In 1987-88 BHEL had progressed a step further in undertaking the production of ac locomotives also.
CURRENT TRANSFORMER
• It is step down transformer. High current is not directly measured but by the current transformer is step down to lower measurable values, which is generally low.
• Body
• The main body is a bushing, it also act as insulator in which winding is placed.
• The CT has a bottom and top chamber.
• The top chamber is the cylindrical tank of mild steel. It hasterminals for connection of HV coils. It has a glass window toindicate the oil level.
• Below the top chamber there is bushing made of porcelain. It has several folds and “rain sheds” to provide a specificelectrical field distribution and long leakage path. Some bushings are of cylindrical while modern one is conical asamount of oil porce-lain used is reduced without any undesirable effect.
• Bottom chamber house the secondary winding. There isalso connection box to which the connection low voltage(LV) is made.
WINDINGS
The primary winding consists of hollow copper/aluminium pipe bentfrom of ‘U’ aluminium, used for low rating. For higher rating a set of wire is passed through the pipe. For still higher rating, copper pipe isused and for highest rating copper pipe with copper wire passing through it is used. This arrangement depends on the current carryingcapacity. The bent portion of primary as in the bottom chamber where as the free end is the top chamber. The straight portion lies inside the bushing.The primary is wound with crepe paper insulation goes in increasing as we go downwards in the bottom chamber. The free ends areprovides with ‘ferrules’, which are small hollow cylinder through which wires can pass connection to the madprimary are made through these ferrules. The secondary is divided in a number of coils for different set of tapings. Connections are different taping are made inconnection box. Each coil has an annular core of CRGO (silicon steel).
ESP TRANSFORMER
The Electro static precipitator rectifier transformer is used for environmental application. It is used to filter the suspended charged in the waste uses of an industry. They are of particular use in thermal power station and cementindustry.The ESP is a single ø phase transformer. It has primary and secondary windings. The core is laminated and ismade up of CRGO sheet. It is a step up transformer. An Acre actor is connected in series with primary coil. The output of the transformer must be DC which is obtained by rectifying Accusing a bridge rectifier (bridge rectifier is a combination of several hundred diodes). A radio frequency chock (RF chock) disconnected in series with the DC output for the protection of secondary circuit and filter circuit. The output chosen the negative because the particles of carbon are positively charged. The dc output from the secondary is given to a set of plate arrange one after the oth-ers. Impurity particles being positively charged stick to these plates, which can be jerked off by hammer. For this a network of plant has to be set up all across the plants .This is very costly process in comparison with the transformer cost. A relevant is also provided to prevent the transformer from bursting it higher pressure develops, inside it. It is the weakest point in the transformer body. An oil temperature indicator and the secondary supply spark detector are also provided. One side of the transformer output is taken and the other side has a “mar-shalling box” which is the control box of the transformer.
POWER TRANSFORMER:
Power transformer find their wide use in electrical power system. Actually these are the transformer, which have made A.C.transmission very easy. These are step up or down transformer. The primary and secondary voltage of power trans-former comprises material for magnetic circuit terminals, tanning switches, tank oil as well as cooling devices.
BUS DUCT
Bus duct is used as connection between generators and transformer. Bus duct are used in power connection over 150 M V.The question now arise that why are bus duct preferred over normal conductors. In high power application, insulations are the majorproblems and frequent insulation breakdown occurs. If this does happens then possibility of shorting of conductor’s and hence seriousdamage may occur to both transformer and generators. Bus duct are hollow pipes made of aluminium the cross section of these ducts depends on requirements of the customer and is done bythe design department.The cross section may have different shapes, circular, square hexagon, octagon. The casing is also made of aluminium sheets. Although aluminium is not a good conductor as copper still is preferred over it because it is lighter than copper. Moreover, it is cheaper thancopper.Bus duct are of two types:
Segregated Bus Duct(SBD)b.
PRINCIPLES OF CNC MACHINE
Electronic industries association defines numerical control as a system in which actions are controlled by direct insertion of numeric data. The system must automatically interpret at least some portion of data. It means control by numbers. The main function into control the displacement and positioning of slides, spindles, speed feed rates, selection of tools and many other auxiliary functions. CNC directs the machine tool to achieve all these function in a very controlled and synchronized manner. The main element that comprise CNC machine tools are:
Control system CNC
The machine tool
Feedback devices
Operator’s control
Electrical cabinet A CNC production facility needs three pieces of equipment:
A computer: The computer is used to draw the design. However, the design is only picture and thence machine cannot use this to manufacture the product. The computer software must also convert the drawing into numbers (coordinates) that the CNC machine can use when it starts to cut and shape the material.
An interface: A computer cannot be directly connected to a CNC machine. The computer is connected to an interface. This converts the signal from the computer to a form that CNC machine understands. The signal are in the form of digital signals when they are sent to the CNCmachine.
FUNCTIONS OF CNC:
1. Machine tools control: it is prime function of the CNC system to control the machine tool. This involves conversion of the part program instruction into machine tool motion through the computer interface and servo system.
2. in process compensation: it is closely related function to machine tool control. This evolves the dynamic correction of the machine tool motions for changes of errors, which oc-curs during the processing. The main operations are as follows:
Adjustment for errors sensed by in-process inspection probes and gauges
Computation of an axis position when an inspection probe is used to locate datum reference on a work part.
Offset adjustment for tool radius and length
.Adaptive control adjustment to speed and feed.
3.Computation of predicted tool life and selection of alternative tooling when indicated. im-proved programming and operating features the soft wired control has permittedthe introduc-tion of many continent programming and operating features. The main features are as follows:
Editing of part programs at the machine.
Graphic display of the tool path to verify the shape.
Provision of various types of interpolation, circular, parabolic, exponential etc.
Support of old customary units and new metric units.
Use specially written subroutines.
Manual data input.
Local storage of more than single part program.
4. Diagnostics: presently CNC machine are equipped with a diagnostics capabilities to assist in maintaining and repairing the system.
ADVANTAGES OF CNC MACHINES:
Some of the most significant advantages of CNC machine are:1.High accuracy.2.High re-peatability.3.Reduced inspection.4.Ease of assembly and interchange ability.5.Less scrap and rework.6.Reduced floor space.7.Reduced work handling.8.Reduced lead-time.9.Flexibility for design changes.10.Reduced tooling.11.Design freedom.12.Ownership of skill.13.Better machine utilization.14.Reduced paper work.
CODES USED IN CNC PROGRAMS:
G-code is a common name for the programming language driving NC and CNC machine tool. It was developed by EIA in the early 1960s a final revision was approved in February 1980 as RS274D.G-code is also the name of any word in a CNC program that begins with the letter G and generally is a code telling the machine tool what action to perform, such as1.Rapid move2.Controlled feed move in straight line or arc3.Series of controlled feed moves that would result in a hole being bored, a work piece cut to a specific dimension, or a decorative profile shape added to the edge of a workpiece.4.Change a pallet5.Set tool information such as offset.
CONCLUSION:
To conclude numeric control is the most sophisticated form of automatic control of machine tool. It has high degree of precision, accuracy and reliability. The control system has undergone several stages of development. With the above qualities of CNC machines there are numerous advantages like:
1. High accuracy.
2. High repeatability.
3. Less scrap and network.
4. Better machine utilization.Some of the special features offered by CNC machine manufacture are
5. Thermal stabilization
6. Axis calibration.
7. Lost motion compensation.
The program written to CNC machine is easy to write and understand. This program usecode (G codes and M codes) that runs the program. The codes are simple to understand.