Author: pesapa

Reaming is the process of making regular and precise holes. Electrification may be done by hand, machine tools, or drills. The holes created by the drill do not have a certain tolerance, nor are they smooth and polished, so it is necessary to perform a new operation that can obtain the necessary specifications. The saw can be called a rotating cutting tool. Because this tool has one or more cutting edges that can be used to make the holes to the actual size. The electrodes are usually made of tool steel or high-speed steel, the edges of the electrodes are plated with different types, then the winning edge is sharpened with a stone machine.

Types of electricity:

1. A) Manual electric: 1. Simple electric 2. Spiral electric 3. Conical electric 4. Variable electric (abdominal-knife)
2. B) Machine electrodes: In terms of fixed and variable form, they are the same as manual electrodes.

Manual spiral electrode: To electrify holes that have grooves or grooves, helical electrodes with a twist angle of about 25 degrees are used.

Cone screws: for electroplating holes where the cone pins are inserted.

For conical holes greater than 1:10, we use a triple cone electrode (rough, pre-electro), polished electro.

To machine the dead-end holes, use machine electrodes that have a rectangular end.

Never turn the switch clockwise, even when pulling the switch out of the hole.

Use coolant in electrical work.

Avoid shrinking the pleats for any reason.

To electrify uneven holes, first use a preheater.

Cutting speed in electroplating is cutting speed in drilling hole.

The speed of progress in electro work is faster than the speed of progress in drilling.

In general, electrodes consist of two main parts, which are: the main body of the electrode and the tail, which may be a conical or cylindrical tail. To guide the electrode into the head hole, it is tapered. The length of the conical head, called the lead, varies in the brackets. There are some things to keep in mind when using an electric grinder to make sure the holes are properly seated.

In general, the types of electricity are:

• Diamond power supply
• Open the switch
• Adjustable switch
• Hollow power supply
• Electric barrier
• Cucumber electricity
• Manual switch
• Trailing lightning
• Electrical opener
• Machine power
• Open machine electric
• Cucumber machine electrician
• Heavy machine power
• Petal machine electrifier
• Cone
• Morse Cone Screwdriver

 History of machines ‌ Numerical control

After World War II, the need for devices capable of making sophisticated and precise parts for the aerospace industry was felt before 1949; In 1949, Parsons signed its first contract with the US Air Force to build the first NC numerically controlled device. In 1951 the project was awarded to the Massachusetts Institute of Technology (MIT).

In 1952, the Massachusetts Institute of Technology’s Serum Mechanism Laboratory began its research efforts, and the first NC milling machine made great efforts to develop more advanced control devices. With the advent of computers in NC systems, another change in NC technology took place. Today, CNC machines with a greater number of axes, more control, and better accuracy and speed can be seen at very high levels of automation in DNC, CAD / CAM and CIMS systems.

Numerical control (NC)

Numerical control is the use of encrypted codes of numbers, letters, and symbols that are intelligible to the control unit and, after decoding, are converted into electrical pulses, current, and these pulses are used to turn the machine on and off. It becomes. The philosophy behind NC machines is not only the need for the ability to make complex parts, but also the creation of automation and automation.

Humans have always strived to mechanize production because automation can improve the quality and quantity of productivity of human activities and also allows a small number of professionals to achieve the results that they can achieve. The past required the participation of a large number of experienced people. Automated systems, on the other hand, make it possible to do things that go beyond human capabilities.

Computer numerical control

Computer Numerical Control (CNC) is an NC system based on the use of a computer as a control unit. In these “controls”, the speed of data processing is very high due to the use of computers, and unlike NC machines, which read programs line by line, it is able to read and check all program lines and then execute its high speed and flexibility with CNC machines and it gives them the courage to try what they have in mind as soon as possible and to think about improving their product and to meet the needs of their customers quickly and to adapt to the needs of the market as soon as possible.

Main components of CNC machines

Machine program (input unit)

The program contains a set of numbers, letters, and symbols that tell the machine what to do. The set of numbers, letters and symbols, which are encrypted in code, are interpreted by the Machine Control Unit (CNU). In addition to workpiece path information, the program includes information on technology (speed and progress values) and auxiliary information (such as turning on and off three systems, switching on and off the cooling fluid flow. The program can, in addition to typing directly through the device keyboard) MDI) is sent to the machine via perforated tape, magnetic tape, magnetic disk and computer (DNC).

Car control unit

CNC is a type of control used on machines and software for automation, and each control system has three main components: input unit, processor unit, and output unit.

The most complex control system is man, in which the five senses function as the input unit, the human brain, as the processor, and the human muscles and speech as the output unit.

In CNC, the three main components of the cut letter and the title of the input unit, the processor unit and the output unit. The components of the control unit are: tape reader, CPU microprocessor, RAM, ROM, Buffers, PHC, amplifier, control panel Operations that are very simple for humans, such as reading size, distinguishing between numbers, letters, and symbols, are very difficult for electronic, computer, and computer equipment, so the information entering the machine must be encrypted for quick and easy recognition.

Information signals have one of the following four states.

1-Analog or continuous signal:

Human verbal signals, thermometers, pressure gauges are such signals and it is very difficult to work with these signals.

2-Discrete or discrete signal:

Is a signal whose values ​​have constant values ​​over a period of time equal to these values. These values ​​have no relation to each other. The best example for the signals above is a statistical example.

3-Digital signal or step: ‌

It is a discrete or discrete type of signal, except that its values ​​change by a certain ratio. Telecommunication systems work with digital signals.

4-Binary signal or two-sided:

It is a kind of digital signal, except that its values ​​change only between the two zeros and ones. Like a switch, it has two open-state states, which are considered zero in the open state and one in the closed state. The signals most commonly used in engineering are digital signals, most of which are considered to be part of these signals. Binary signals are very valuable in presenting information because in control they can be easily displayed, as well as mathematical operations can be easily done with them. Numbers of letters and symbols can be easily encoded with these signals. In Boolean algebra, which uses only two numbers zero and one, unlike general algebra, which uses numbers from the spectrum and range, the logical operations Not, AND, NOR, and NAND can be written in mathematical language and used in control technology. A computer is an electrical device that works with voltage. If a computer is built based on decimal numbers (analog), it needs tens of different voltages to identify the numbers 9…, 2, 1, and 0, which is very expensive and difficult to do. We need a voltage unit, which can have two modes of voltage presence (one) and no voltage. Numbers in binary chain systems are from zero to one, which are standardized in two types of ISO and EIA.

Machinery

The third main part of a CNC system is the machine tool, which performs the main work of the process, i.e., chipping. This part actually includes the workpiece, tool, fixture and other mechanical and electrical components in the CNC machine. The machine tools are also divided into several groups.

1-Machines in which the workpiece has rotational motion and the tool has linear motion, such as CNC lathe.

2-Machines in which the workpiece has a linear motion and a rotary motion tool such as a CNC milling machine.

3-Machines in which chipping is done by electric discharge method.

4-Machines that use abrasive chips, such as CNC stone.

Mechanical and electrical components, CNC machines

car body:

It is a part of a machine on which other surface components are mounted, so it must be very strong and resistant to vibration and heat to withstand high accelerations and speeds, mainly made of gray cast iron, hardened, and in some cases made of ceramic or graphite.

Sliders:

The plates are smooth and hard, with the tool holder or table sliding on the roller and lubrication system to reduce friction, the sliders being coated, or the surface of a thin layer of oil or cushion moving through the air.

Main axis:

The main motor rotates the workpiece in the lathe and the tool in the milling machine. In both cases, the motor must provide the power needed to cut the workpiece. The main motor can be of DC type for cars and small robots, or of three-phase AC type for higher power. In the latter type, we need the help of a special drive to create different speeds.

Types of motors, actuators, axles

CNC machines use electric, hydraulic, and pneumatic actuators to move and advance the axes. Numerically controlled actuators are used, each of which is described in detail. He named electricity consumption, maintenance.

Electrical stimuli

Electrical actuators include AC, DC, or stepper motors.

1. A) DC motors (DC)

In this type of motor, the rotor is driven by magnetic field, stator or electric current. The rotational speeds of these motors can be well controlled by changing the voltage as well as the torque of the motor with the amount of input current. Fast, relative to changes, speed, and… are most used in CNC machines. These motors are not used in open circuits, but they are widely used in closed circuits. These motors are mostly used for the main cycle of three systems.

1. B) AC motors

In this type of motor, the rotational speed is alternated by changing the input frequency, and the only advantage of these motors is that they do not need a rectifier and because of their large volume, they are less used in CNC machines than DC motors. Axes are used.

1. C) stepper motors

In these motors, by giving each input control pulse, the motors rotate to a specific angle called the step angle, and rotate according to the angle of the rotating ball, which causes the linear motion of the nut to rotate at the desired speed. It is and by increasing the number of poles can increase their accuracy. Characteristics of these motors are low volume, precise control of axles and their cheapness, and their disadvantage is their low power. These types of motors are used in open circuit systems. Tool Changer is used in small numerical control machines.

Hydraulic actuators

In hydraulic actuators, cylinders and pistons are used for short lengths, and hydraulic motors are used for long lengths. They have low weight and volume and can be used in hazardous environments. Also, hydraulic actuators have a uniform motion and are not stepped.

Pneumatic actuators

The performance of these actuators is similar to that of hydraulic actuators, and they are less accurate than their advantages.

BALL SCREW

A ball screw is commonly used to ensure the movement of the shafts (table or tool holder). In this way, between the bolt and the nut, the error occurs, not slipping, and despite the precise bullets, the direction of motion is minimized when reversed, resulting in very smooth and precise movement, so that the machine can be moved easily. It gave 0.001 mm and everyone expected accurate movement.

Axis position measurement systems (ENCODER)

Encoder is used to control the position of the axes. In this mechanism, a glass disk with dark and light lines designed along it is placed along the axis, one light source on one side of the screen and one or more light sensors on the other side. They always move with the axis. During the rotation of the axis, the path of light is cut and connected by dark lines on the disk, and the optical cell transmits the output voltage based on the intensity of the light, and as a result the photocell sends a sinusoidal wave that transforms this source into one. And the output pulses are counted, from which the displacement of the axes is calculated. In this type of measurement system, the glass plate is usually circular, called angular encoders, and mounts on the axis of the ball screw and rotates with it. These encoders are smaller and easier to maintain. In addition, the linear encoder is also used.

This type of welding is a solid-state welding process that is performed as a result of the collision of one of the components at a very high speed due to the use of explosives.

The most common use of this process is typically for coating or cladding carbon steel with a thin layer of corrosion-resistant material (such as stainless steel, nickel alloy, titanium or zirconium). Due to the nature of the process, the shape of the parts is very important and they should be simple in general. Commonly produced shapes are sheets, tubes and tube sheets.

Unlike other welding methods such as arc welding, which developed in the late 19th century, blast welding is a relatively new method and was developed in the decades after World War II. Of course, it dates back to World War I, when bullet debris was seen sticking to the armor plates of weapons (when in fact they were welded to the metal). Since heat played no role in this case, it was concluded that this phenomenon was due to the force of the explosion on the shattered particles or fragments. These results were later repeated in the laboratory and after sometime this process was recorded and used.

In 1962, Dupont patented the blast welding method, which was approved in January 1964 under U.S. Patent No. 3,137,937, identified by the Detailed trademark. In July 1996, Dynamic Materials Corporation acquired ownership of Detailed Processes for $ 5321,850. In Iran, Vetra Engineering Group has been working on explosive welding and other solid-state welding processes for nearly 10 years and has been able to provide valuable services in this field, one of the highlights of this series of welding simulations before Explosive operations and accurate calculation of the composition and number of explosives.

Benefits of Explosive Welding:

1-Explosive welding can be used to connect and weld most metals and alloys that cannot be welded by conventional welding methods (Vetra Company has welded most of the alloys used in the country’s industry in various projects in this way).)

2-Explosive welding method does not melt the metals, instead it introduces the surfaces of both metals into the plasticization area, which causes sufficient initial contact to create welding. As a result, no melting defects will occur in the alloys (such as welding aluminum and copper). The principles of this method are similar to other non-melting welding methods such as friction welding.

3-Large surfaces in explosive welding can be connected to each other very quickly and the weld itself is very clean because the surface wastes in both metals are removed from the contact area with great intensity during the reaction.

One of the most important advantages of blast welding is their application in the bonding of heterogeneous metals. Coating large plates to make composite plates for use in the construction of pressure vessels, creating cylindrical joints such as pipe-to-pipe welding and tubing in a defective heat exchanger, pipe-to-pipe connection in all directions and double-walled, thin-sheet edge welding and the manufacture of reinforced wire composites are among other applications of blast welding. The mechanical and metallurgical properties of explosive welds are important. Determining the strength and quality of the bond between a thin coating layer and a thicker plate is difficult for any method, and explosive welding is no exception. In general, the metallurgical problems of this type of welding are not as severe as fusion welding.