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What Is an Industrial Scale?

Industrial scales are measuring instruments used to weigh things in the production and development of products, whether in agriculture, forestry, fisheries, or industry.

There are various types of industrial scales, ranging from electronic balances used for precise weighing in laboratories, such as chemical analysis, to floor scales that are embedded in the floor and used to weigh large trucks. Furthermore, there are various types depending on the intended use and measurement environment, such as:

• Dust-proof specifications for weighing powders.
• Waterproof specifications for weighing light liquids.
• Explosion-proof specifications for weighing in hazardous locations such as where explosive gases are generated.

Industrial Scale Applications

Industrial scales are used in a variety of industries to determine weights. Specifically, they are used in laboratory laboratories in the chemical field for research and development and analysis, in the agriculture, forestry, and fishery industries, in production plants for industrial products, and in warehouses in the logistics industry.

In the production and logistics industry, they are used to determine the quantity of products. For example, to count the number of small screws, the weight of about 100 pieces can be stored in advance on an industrial scale, and the number of products can be determined simply by placing them on the scale.

Industrial scales are also incorporated in a series of automated manufacturing processes, such as the automatic filling of liquids and powders, filling volume inspection, weighing for batch processing, blending, and dispensing. Industrial scales are used in a variety of fields, including the pharmaceutical, cosmetic, chemical, and food industries.

Principle of Industrial Scales

General scales include spring scales based on Hooke’s law and balances based on the principle of leverage, but industrial scales mainly use electromagnetic, load cell, and tuning fork measuring principles.

1. Electromagnetic Industrial Scales

The internal structure of an electromagnetic industrial scale is similar to that of a balance. A sample is placed on one side of the rod, and an electromagnetic coil is placed on the opposite side of the rod across the fulcrum.

The electromagnetic force required to maintain equilibrium for the weight of the sample is measured, and the electromagnetic force is converted to weight. The electromagnetic method enables measurement with high accuracy and is suitable for analytical balances and other scales that measure minute samples.

2. Load Cell Type Industrial Scale

This type of industrial scale is composed of a strain gauge that detects the distortion of the load cell and a body that is distorted by the weight of the body. One side of the body is fixed, and a sample is placed on the other side.

The strain generated by the weight of the sample is extracted by the strain gauge as a resistance value and converted to weight. The structure is relatively simple and inexpensive. This method is suitable for measuring heavy objects when high precision isn’t required.

3. Tuning Fork Industrial Scale

Tuning fork industrial scales measure the frequency of oscillation of a sample when a load is applied to a transducer consisting of two connected tuning forks, and convert the frequency to weight. This is a relatively new measuring principle, and its measurement accuracy is somewhere between that of the electromagnetic and load cell types.

Other Information on Industrial Scales

1. Platform Scale

Platform scale is the general term for a scale that measures the weight of a stationary object by placing it on a platform. The platform is designed to sink due to the weight of the object placed on it, and the extent to which it sinks is measured as the weight of the object.

There are a variety of products for a wide range of purposes and capacities. Examples include household scales, kitchen scales, store scales, scales for measuring the volume of propane gas, and truck scales, which have a structure with a weighing platform on the floor and can carry a large vehicle by itself.

In addition to the spring-loaded analog type, there are also a wide variety of products with various uses, weighing capacity, and price ranges. Examples include scales with load cells, electromagnetic sensors, digital types with digital numeric displays, and waterproof and explosion-proof builds.

2. Weighing Table

This is the name of the weighing pan or platform on which the object to be measured is placed in a weighing instrument. Depending on the manufacturer, it is sometimes called a weighing platform as a product name for a platform weigher. 

3. Electronic Balance

An electronic balance is mainly for measuring mass. Some models have a built-in balance structure, while others have a one-block structure without a balance structure. The measurement methods of electronic balances include the electromagnetic force balancing method, load cell method, and tuning fork vibration method.

The electromagnetic force-balancing method was the most common type of electronic balance in the early days, but the strain gauge load cell type is now widely available. In general, the measurement accuracy of the electromagnetic force balancing method is higher than that of the load cell method.

What Is an Industrial Endoscope?

An industrial endoscope is an instrument that allows observation of areas that cannot be seen with the naked eye, such as narrow spaces and winding pipes.

A camera is attached to the end of a long, thin probe. The camera is positioned on the part to be observed, and the inside of the part can be observed through the eyepiece, or images can be projected on a main monitor or PC for real-time observation of the inside of the part.

It is necessary to select an appropriate endoscope depending on the observation target, application, and operating environment, such as resolution, depth of focus, length of the probe and main unit, flexibility of the probe, number of light sources, and operable temperature range. There is also a function that allows video images to be recorded, which is useful for later confirmation and data management.

Furthermore, recent models of industrial endoscopes are equipped with a high-performance camera and LED light, which can provide clearer images.

Uses of Industrial Endoscopes

Industrial endoscopes are widely used in industrial fields, such as automobiles, aircraft, power plants, and infrastructure, such as gas and water supply.

1. Automotive, Aircraft, Railroad, and Marine Fields

Internal inspection of engines, hydraulic parts, injection nozzles, turbines, etc.

2. Electric Power Industry

Maintenance and inspection of condensers, piping, turbines, etc. in nuclear and thermal power plants

Civil engineering and construction

Maintenance of bridges, diagnosis of steel frames, observation of under floors and ceilings, etc.

Infrastructure

Inspection of rust, corrosion, blockage, etc. of piping in water and gas facilities

Principle of Industrial Endoscopes

An endoscope consists of three components: an illumination mechanism, a camera, and an image processing function. At the tip of the endoscope, a mirror surface or optical lens is placed, which transmits the image to the camera. An optical fiber cable protected by a rigid tube or flexible sheath is used to transmit light.

Endoscopes are used for nondestructive testing to evaluate the condition of internal components and structures, and images can be displayed in real time during the inspection.

They are extremely difficult to operate and must be operated by technicians with specialized training.

Types of Industrial Endoscopes

An industrial endoscope consists of a main body and a probe, some of which have a monitor, some of which can be connected to a PC, and some of which look through an eyepiece.

Industrial endoscope types include videoscopes, fiberscopes, and rigid endoscopes.

1. Videoscopes

A small dedicated camera is mounted on the tip of the videoscope’s probe, which enables real-time viewing on a dedicated display, smartphone, or other device. At the same time, still images can be taken, and some can measure the length of the object.

In addition to being waterproof, they can also be used to examine the inside of underwater equipment and piping.

2. Fiberscope

Fiberscopes are mainly used for nondestructive inspection and repair. They are characterized by the use of probes made from thousands to tens of thousands of flexible fibers.

Each fiberglass fiber collects light and provides an image through an eyepiece on the opposite side. Since each glass fiber acts as a camera, the resulting image reflects the shadow of the glass fiber’s honeycomb structure.

3. Rigid Mirror

The image obtained by the objective lens is transmitted by a relay lens. The probe part of the relay lens is a metal tube and cannot be bent. It is characterized by its simple structure and easy operation.

Rigid mirror endoscopes consist of a light source, optical fiber, lens, and camera, and are used in the medical field for surgery, treatment, and observation of lesion sites.

Features of Industrial Endoscopes

1. Many Functions

An industrial endoscope is equipped with a variety of useful functions. Some products allow zooming on the monitor, or have a temperature sensor and alarm function at the end of the camera cable.

Others have a hands-free microphone for saving audio and video, an ultra-bright white LED on the tip to set the brightness of the subject as desired, and a flash function using LEDs, making them useful devices for a wide range of applications. This is a convenient device that allows you to choose the functions that best suit your needs.

In addition, many products can output data to a PC or TV monitor, making it possible to share images with multiple people. 

2. High Heat Resistance

Some industrial endoscope products have high heat resistance, which makes them suitable for observing the inside of pipes and machinery. For example, the temperature of automobile engine oil can sometimes greatly exceed 100°C, and it is desirable to use endoscopes with heat resistance of up to 200°C.

What Is a Liquid Level Indicator?

A Liquid Level Indicator is an instrument that measures the height of the liquid level inside a container or tank.

In some cases, it can also measure the amount of powder remaining. It is also sometimes called a Level Meter.

Various measurement methods have been developed, including float, tube, and ultrasonic types, depending on the object to be measured and the conditions of use. Accuracy and reliability are important for Liquid Level Indicators.

Since incorrect liquid level measurements can affect the production process, Liquid Level Indicators must be maintained and calibrated on a regular basis. With proper care, accurate liquid level measurements can be obtained over the long term.

Applications of Liquid Level Indicators

Liquid Level Indicators are used in a wide variety of industries and applications:

1. The Petroleum Industry

The petroleum industry uses Liquid Level Indicators to manage fuel inventories and schedule deliveries. They are also used as sensors to detect fuel leaks. 

2. Food Industry

In the food industry, Liquid Level Indicators are used in the production of milk, cheese, and other products. They are used to control product quality and determine the fullness of containers, thereby contributing to the improvement of the efficiency of the entire production line.

3. Chemical Industry

Liquid Level Indicators can be used to measure the liquid level of containers for liquid chemicals. It is used for process control and quality control.

Principle of Liquid Level Indicator

Liquid Level Indicators measure liquid levels by utilizing buoyancy, pressure, and electrical phase differences. More accurate Liquid Level Indicators have been developed by combining these principles and adding innovations.

1. Buoyancy Type

Buoyancy-type liquid level gauges measure the liquid level by using a floating body. 

2. Phase Difference Type

In the phase difference type, a high-frequency electrical signal is sent into the liquid, and the phase difference between the signal reflected at the boundary between the liquid and gas is measured to determine the liquid level.

3. Pressure Type

The pressure type measures the liquid level by measuring the pressure generated by the weight of the liquid.

Types of Liquid Level Indicators

There are various types of Liquid Level Indicators, depending on the measurement method. The following are examples of Liquid Level Indicator types:

1. Float Type Liquid Level Indicator

Liquid Level Indicator measures the liquid level using a float called a float. The float, which contains a magnet, floats on the liquid surface and outputs a signal. The measuring principle is similar to that of a ball tap used for flushing toilets, etc., and often has an electrical contact output for use in control.

Float Level Indicators can be broadly classified into two types: wind-up and non-wind-up. Retractable types include spring-balanced and counterweighted types, while nonretractable types include arm float and ball float types.

2. Tube Liquid Level Indicator

Liquid Level Indicator is a tube attached to the outside of the container that is linked to the height of the liquid surface. If the tube is made of glass, the liquid level can be visually confirmed from the outside. The installation of Liquid Level Indicators should be considered when designing tanks and containers.

Liquid Level Indicators are used in a wide range of applications, such as for measuring the liquid level in boilers and water tanks. 

3. Ultrasonic Liquid Level Indicator

This is a method of measuring the liquid level by transmitting ultrasonic waves toward the liquid surface and measuring the time taken for the waves to reflect back. This method is characterized by the fact that the Liquid Level Indicator does not come into contact with the liquid to be measured and by the fact that it can be easily installed.

Since the ultrasonic type requires the signal to be converted to liquid level, it is common for such a system to be equipped with a control board for calculation. Continuous measurement is possible and often has an analog output signal. 

4. Differential Pressure Type Liquid Level Indicator

Liquid Level Indicator converts the pressure difference between the bottom and top of the tank to be measured into the liquid level. It cannot be easily retrofitted because the liquid density must be known and a measurement outlet is required at the bottom of the tank.

However, since it can be used for sealed tanks, it is widely used for pressure tanks such as boilers. 

5. Capacitance Type Liquid Level Indicator

An electrode is inserted into the tank, and changes in the electrostatic capacitance on the electrode are detected and converted to liquid level. It is characterized by its ability to be used in harsh environments such as high temperatures and high pressures.

How to Select a Liquid Level Indicator

It is important to select a Liquid Level Indicator that is appropriate for the type and characteristics of the liquid. If the liquid is corrosive or at high temperatures and pressures, a pressure Liquid Level Indicator with high durability and high accuracy is suitable. On the other hand, if the liquid is volatile, a Buoyancy Liquid Level Indicator or a Phase Difference Liquid Level Indicator is suitable.

Measurement accuracy is another important factor. The required measurement accuracy varies depending on the nature and temperature of the liquid to be measured. When selecting a Liquid Level Indicator, it is important to select the appropriate measurement accuracy.

The type of Liquid Level Indicator should also be selected according to the installation location. A small Liquid Level Indicator is suitable for installation in a small space. There are also Liquid Level Indicators with special shapes to fit the complex shapes of tanks.

The functional aspects of Liquid Level Indicators should also be considered. Selecting a Liquid Level Indicator with remote control and data logging capabilities will allow for efficient operation and monitoring.

What Is an Optical Cable?

Optical cables are hollow cables made of glass or plastic ; they are also called fiber-optic cables.

They provide a path for light to travel, which is how they transmit information.

Optical communication using optical fiber is less susceptible to noise than telecommunications using metal cables and thus has the advantage of providing stable, high-quality communication.

The drawback of using light for communication is attenuation, but efforts are being made to solve this problem through the structure of optical cables and amplification at relay points.

Uses of Optical Cables

Optical cables are used for high-speed communication on fixed lines of the internet.Different optical cables are used for such optical communication depending on the communication distance and speed.

Optical cables connecting a fixed line from a base station to a home require high-speed communication over long distances, so cables with a small inner diameter are used to communicate at a single wavelength, called single mode.

On the other hand, optical cables with a large inner diameter are used for short-distance ethernet through media converters for multimode communication using multiple wavelengths.

In addition to these information and communication technologies, optical cables are also used for lighting by drawing light from a light source.

Principle of Optical Cable

Light has the property of traveling in a straight line, but it is gradually attenuated by scattering.Therefore, optical cables are designed to minimize light scattering.

Transmission of light using optical cables is performed by repeated total reflection of light inside the fiber.Total reflection means that, when light enters a medium with a large refractive index into a medium with a small refractive index, if the angle of incidence is larger than the refractive angle, all the light is reflected and none is transmitted through the medium.

Optical cables have a double structure called a cladding and a core, and light comes through the core.

The core is designed to have a higher refractive index than the cladding, so the incident light is repeatedly reflected and travels through the core in a confined manner.

However, if the cable is bent in the middle, the angle of incidence increases, resulting in light loss.Therefore, as the distance increases, the risk of such light loss increases.Optical amplifiers are used to amplify the attenuated light again to improve this situation.

Types of Optical Cables

There are two types of optical cables: single-mode fiber (SMF) and multimode fiber (MMF).

1. Single-Mode Fiber

Single-mode fiber cables are characterized by a narrowly designed range over which light can pass, resulting in a single mode of light transmission and reduced attenuation. Therefore, transmission over long distances and at high speeds is possible. Although it has high performance, it is expensive, so it is generally used for communication between facilities. 

2. Multimode Fiber

Multimode fiber cables are designed to have a large range of light transmission, and since light is transmitted in multiple modes, data loss is likely to occur due to the dispersion of light among each other. Therefore, it is suitable for short-distance communications and is used for laying lines within a facility. This makes them inexpensive.

Optical cables are divided into LC connectors, SC connectors, FC connectors, etc., depending on the shape of the connector. SC connectors are the most common type of connector. FC connectors use a screw-tightening method for connection and are characterized by their high cable fixing force.

What Is an X-ray Inspection System?

X-ray inspection equipment are devices that can accurately  identify elements and hazardous substances in areas invisible to the eye without destroying the object.

Based on the transmitted image obtained by irradiating X-rays to the inspected item, the invisible internal conditions are inspected and evaluated.

Since it can see through the inside of a product, which cannot be photographed by a visible light camera, this equipment is indispensable for maintaining high quality in manufacturing, including measures to prevent contamination by foreign matter and hazardous substances.

 

Applications of X-ray Inspection Systems

Today, X-ray inspection systems are used not only in the manufacturing and processing of medical, food, and electronic parts, but also in the construction and aviation industries.

Examples include X-ray imaging at hospitals and baggage checks at airports.

In the medical industry, they are used for endoscopes, CT scanner systems, digital ray systems, and in research fields such as animal research.

Principle of X-ray Inspection Systems

X-rays are a form of radiation consisting of photons that have high energy and propagate in flux, and “electromagnetic rays” with short wavelengths. X-rays are a type of radiation.

There are five types of ionizing radiation, including X-rays: alpha rays, beta rays, gamma rays, X-rays, and neutron rays.

Among these, X-rays, along with gamma rays, are electromagnetic waves with very short wavelengths, making them highly penetrating through matter by passing between atoms that make up matter.

However, they can be blocked by thick plates of lead or iron.

When X-rays collide with electrons orbiting the nucleus of a material, various interactions such as the photoelectric effect and inelastic scattering occur.

X-rays that do not undergo these phenomena penetrate the material and become transmitted X-rays, and the more transmission there is, the darker the image appears.

Conversely, areas that are attenuated appear bright and white. In fact, images taken using X-rays are black and white, where the shade is determined by the amount of transmitted X-rays.

In general, it is known that the intensity of transmitted X-rays is determined by factors such as the atomic number, density, and thickness of the object material.

Miniaturization of X-ray Inspection Equipment

X-rays, discovered by Roentgen in 1895, are electromagnetic waves with wavelengths of approximately 1 pm – 10 nm.
They are also a form of radiation, and are used in X-ray photography for medical examinations and nondestructive testing, as well as in the analysis of crystal structures using the diffraction phenomenon.
Most people’s conception of X-ray inspection equipment is that it is a large-scale device that takes pictures of the entire body.
However, today, a wide variety of portable X-ray inspection systems are available, and they are mainly used for nondestructive testing at factories and construction sites.

Their features are often referred to as portable nondestructive testing equipment that can be easily used at any time and place.
It is a device that inspects all kinds of objects with X-ray images by combining a polarized X-ray and a high-precision digital detector.
Without destroying the object to be inspected, it is possible to check for cracks, fissures, corrosion, and other abnormalities, as well as the finish of welded parts.
X-ray inspection systems are highly mobile and ideal for completion and periodic inspections at factories and construction sites. However, since they are a source of ionizing radiation, they should be handled with care.

What Is an Evaluation Board?

An evaluation board is an electronic board that contains ICs, circuits with specific functions, and input/output terminals.

They are also called reference boards. There are CPU evaluation boards by semiconductor manufacturers and microcontroller development boards (target boards) by microcontroller manufacturers.

Usage of Evaluation Boards

Evaluation boards are used to check the performance of mounted ICs, circuit compatibility, hardware and software development, and other purposes. It is necessary to select an evaluation board equipped with ICs and electronic components suitable for the intended use.

Examples of evaluation board uses are as follows:

• Equipment manufacturer (evaluation)
  To evaluate the performance of mounted ICs and circuits and to check compatibility.
• Equipment manufacturer (development)
  To develop new products and software in a short time and at a low cost.
• Educational institutions, students, and the public
  For learning about electronics, electric circuits, programming, etc.

A wide variety of evaluation boards are available from various semiconductor manufacturers. Typical evaluation targets are as follows:

• Automotive systems.
• Video cameras.
• Industrial robots.
• Terrestrial/satellite communications.
• Mobile communication terminals.
• Aerospace.

Our evaluation boards are used for a wide range of products, from those close to familiar home appliances to those related to robots and satellites.

Principle of Evaluation Boards

The principle of operation is that when power is supplied, the microcontroller operates according to the program written in the memory of the microcontroller. The program can be rewritten arbitrarily, and the source code of the program created on a PC is written into the memory area of the microcontroller using software called a writer.

The hardware used to support the debugging process is an emulator. The emulator is connected to the Evaluation Board.

Evaluation Board Configuration

In most cases, an evaluation board consists of IC chips, communication devices, sensors, input/output terminals, etc., on a single printed circuit board. There are various types of evaluation boards depending on the components mounted on them, but microcontroller evaluation boards sold by microcontroller manufacturers are widely used in general.

Microcontroller evaluation boards are used to evaluate and experiment with the functions and circuit characteristics of the microcontrollers on which they are mounted.

1. Microcontroller

A microcontroller is an LSI that writes programs and combines circuits to perform arbitrary operations. It consists of a CPU that performs various processes and flash memory or SRAM for writing programs. 

2. Power Supply IC

An IC that generates the voltage required for a microcontroller to operate from a power supply voltage of 100 VAC. 

3. Clock

An oscillator with a specific frequency that operates the microcontroller. It is sometimes built into the microcontroller. 

4. Communication Device

A USB terminal or LAN for communication with an external PC for programming. 

5. Input/Output Terminals

USB pins for communication/power supply and input/output (I/O) pins for sending data to external interfaces.

Debugging functions include LEDs and a reset button for visual confirmation of the microcontroller status, a switch for switching operations, a sensor for measuring external information, and a 7-segment display for displaying collected data.

Other Information on the Evaluation Board

1. ICE (In-Circuit Emulator)

It can take on the functions of a CPU and can be attached to a board under development in place of a CPU to enable verification of program operation. Since there is no microcontroller on the target board, the ICE itself has an emulation chip and memory, and the target board is responsible for the operation of peripheral circuits. Advanced debugging functions such as real-time trace can be used.

Generally, a sample program for operating a microcontroller Evaluation Board is included.

2. How to Use an Evaluation Board

Evaluation boards are often used by connecting them to a PC for evaluation. The interface is typically USB, RS232C, or other terminals that the PC is equipped with.

The power supply for the board may come with an AC adapter that can be plugged into an ordinary household 100 V outlet. Or, it may be a cable that connects to a power supply unit such as a regulated power supply instead of an AC adapter.

The environment on the PC for evaluation is typically provided by the manufacturer of the evaluation board, using a software package specific to that evaluation board. However, the manufacturer or other party that receives the delivery may prepare its own software for evaluation.

In addition, since waveform measurement is frequently performed using measurement devices such as oscilloscopes and logistic analyzers, some evaluation boards may have terminals for connecting such devices in advance.

The Price of Evaluation Boards

Prices vary widely depending on the semiconductor manufacturer and the purpose of the board.

Note that when a manufacturer orders a full custom-made board for the development of its own products, the cost will depend on the quotation from the semiconductor manufacturer.

What Is a DC Servo Motor?

A DC Servomotor is a servomotor that operates on DC.

DC Servomotors are used in precision equipment, etc. Since DC Servomotors are controlled by detecting the motor’s speed and position, they are generally integrated with a motor and a sensor that detects speed and position, such as an encoder or resolver. The motor is controlled by a sensor that detects the speed and position of the motor.

To rotate a DC motor, current supplied to the motor must be passed to the rotating shaft by a component called a brush, which wears out due to wear and tear on the brush, requiring periodic maintenance.

Uses of DC Servo Motors

Figure 1. Uses of DC servo motors

DC servo motors are widely used in industrial robots that require precise control. Compared to general-purpose motors, DC servo motors respond more quickly to signals from robot controllers of industrial robots to output rotation speed and torque, and function as actuators for precise movement of robot arms and other parts.

DC servo motors are also used for the steering angle drive of radio-controlled vehicles, XYZ axis drive of machine tools, positioning drive of precision equipment, etc. It is important to select a DC servo motor appropriately according to the level of output and torque capacity, accuracy, and response speed required by the equipment to be used.

Principle of DC Servo Motor

Figure 2. Principle of DC servo motors

A DC servo motor consists of a “motor,” an “encoder,” and a “controller.” It is composed of a permanent magnet, an iron core (rotor) divided into two or more parts, coils wound around each iron core, electrodes, and brushes that pass current through the coils.

The principle of operation of a DC servo motor is explained separately for the motor and other functions.

1. Motor

The motor is made to rotate by the Lorentz force generated from two sources: the current flowing in the coil and the magnetic field from the permanent magnet, which causes the iron core to rotate. When applying current to the coils, direct current from the outside is passed through brushes to the iron core and then transmitted to the coils. Since the current is passed directly to the coil, the Lorentz force can be quickly controlled and the response speed is fast.

2. Other Functions

DC servo motors use command signals transmitted from an external controller to rotate the motor to achieve a commanded target value. The encoder attached to the motor sends speed and position information to the controller, which performs feedback control based on the position and speed information from the encoder in response to commands sent from the controller so that the motor’s rotation speed and rotation position approach the target values.

Control of DC Servo Motor

Figure 3. Control of DC servo motors

DC servo motors can be controlled in the following three ways

1. Position Control

DC servo motors are equipped with an encoder, a sensor that detects rotation angle and position and feeds back the detected rotation speed and position to the controller. If a position deviation from the command position is detected, a position correction command is issued by applying a gain to the amount of deviation to enable highly accurate control that moves the motor to the desired position and then stops the motor.

2. Speed Control

The simplest way to control the speed of a DC motor is to vary the voltage applied to the motor. In the case of a DC servo motor, a variable resistor is used to control the speed of the motor.

For DC servo motors, instead of a variable resistor, the voltage applied to the motor is controlled via an H-bridge composed of power semiconductors such as IGBTs and FETs that are incorporated in the servo amplifier.

On the other hand, the speed control of AC motors requires changing not only the voltage applied to the motor but also the drive frequency, whereas DC motors are widely used in small motors for speed control because they only change the voltage.

3. Torque Control

Torque control of the DC Servomotor is based on the proportional relationship between current and torque. Therefore, the current is controlled to maintain the torque at a constant value by detecting the current from the voltage value of the current sensor or current shunt resistor and feeding back the current command.

Other Information on DC Servomotor

Types of Servo Motors

Servomotors are constructed to be more durable than ordinary motors to operate repeatedly even in harsh environments and can be broadly classified into two types: DC Servomotors and AC Servomotors.

1. DC Servo Motor
DC Servomotor is a servomotor driven by a DC power supply. DC Servomotor is used in a wide variety of applications because it is easier to control rotation and more efficient than AC Servomotor, and its simple mechanical structure makes it inexpensive. However, the disadvantage of DC servomotors is that they have mechanical wear parts called “brushes” that require periodic replacement and maintenance.

2. AC Servo Motor
AC Servomotors are servo motors driven by an AC power source. Compared to DC motors, AC Servomotors are more complicated to control, but they are used in equipment in almost all industrial fields due to their high practicality, such as the progress in control technology and the trend toward smaller and lighter robots.

There are two types of AC motors: synchronous (SM) motors that use permanent magnets and induction (IM) motors that do not use permanent magnets, but currently synchronous motors are mainly used.

What Is a Limit Switch?

Limit Switches are switches that are activated by the movement of machine parts or the presence of objects. As part of a control system, they are used to detect safety interlocks or objects passing through a specific position to automatically start or stop a machine, limit the range of motion of a machine, or detect its position.

Limit Switches are microswitches built into a metal or plastic case with an enclosed case to protect them from external forces, water, oil, gases, and dust in the operating environment. The contact is turned on and off by the movement of an actuator (mechanical sensing part).

Actuators include plunger type (direct-acting type), rotary lever, fork-lock lever, flexible rod, etc., and are available in a variety of shapes according to the application and operating environment.

Limit Switch Applications

Limit Switches are used to turn on or off an electric circuit based on the result of detecting the position of an object.

In automation systems for automatic control of factory production lines and the like, Limit Switches are used to detect the movement and position of machines. For example, Limit Switches are installed in the detection position and turn on at the abnormal operation position to alarm and stop the machine operation.

Another familiar example is an elevator cage (a conveyor that carries people and luggage up and down). When the cage reaches a certain position on the floor where it stops, the limit switch activates to stop the motor and the cage comes to a stop.
Limit switches are thus used in a variety of applications in automatic control systems.

Principle of Limit Switches

A basic Limit Switch consists of a body, head, microswitch, plunger, rotating shaft (rotating lever and fork lock bar only), and actuator.

The principle of Limit Switch is explained below for a rotary lever-type actuator.

1) The object to be detected moves, and toward the detection position.

2) The actuator is pushed by the object to be detected and rotates.

3) The rotary shaft fixed to the actuator rotates.

4) The cam on the rotary shaft pushes the plunger.

5) The movable contact attached to the end of the plunger moves.

6) The movable contact touches the stationary contact, and the electrical circuit is turned on.

How to Select a Limit Switch

There are many types and specifications of Limit Switches, and the following is a basic guide to selecting the right one:

1) Selection by operating environment

• General type
  This type is for indoor or outdoor use in a general environment. The ambient temperature range is from -10 to 80°C.
• Environment-resistant type
  This type is for use in the following special environments:
  High or low temperatures in the environment where the switch is used.
  Limit Switches are exposed to chemicals, oil, water droplets, or dust.
• Spatter-resistant type
  Exposure to welding spatter.
• Long life type
  Usage requires high durability.
• Explosion-proof type
  Need to use explosion-proof type in hazardous area where it is used

2) Selection by actuator type

Select an actuator type that is suitable for the intended use. The following are typical examples, though several other types of actuators are available.

• Plunger type (direct-acting type)
• Rotating lever
• Fork lock lever
• Flexible rod

3) Selection by characteristics

• Movement to operation (PT).
  The “movement” here indicates the angle or distance until the contact turns on or off.

For rotary levers and fork lock levers, the mounting position of the Limit Switch and the angle of the actuator must be set so that the angle at which the detected object rotates the actuator is greater than the movement (angle) to the operation.

In the case of plunger type and flexible rod type, the limit switch mounting position and actuator position must be set so that the distance that the detected object pushes the actuator is greater than the movement (distance) to the operation.

Note that the movement of the detected object must be kept within the actuator’s motion limit position (TTP).

• Ratings
  Limit Switch ratings are specified for each model and are listed in the catalog and instruction manual. It is necessary to select a Limit Switch with a rating that is appropriate for the power supply used in the electrical circuit.

Limit Switch Failures and Countermeasures

Limit Switch failures may be caused by age-related deterioration due to mechanical life or wear, but the majority of failures are said to be caused by the way the switch is used. These include poor positioning of the dog or actuator and poor sealing.

Poor installation of Limit Switches is another cause of failure. If a switch installed to limit the range of motion of a machine is actuated multiple times, the position of the switch will gradually shift, and the switch may stop operating due to insufficient push-in. As a countermeasure, some switches come with a setting position indicator attached to the switch itself. If the switch is programmed to be pushed in to a preset position in advance, it will operate normally even if the switch is slightly out of position.

Care must also be taken in the design of the detectable object used to actuate the Limit Switch. The cut angle of the object to be detected should be 45 degrees or less; if it exceeds 45 degrees, the force applied to the lever shaft will be excessive depending on the moving speed of the object to be detected, which may cause a malfunction. If the moving speed is high, it is also effective to make the lever parallel to the cut surface of the object to be detected.

Also, if there is a steep step in the dog, a strong shock may be applied when the switch returns to the reference position. The ON/OFF switching of the switch should be designed to be as smooth as possible.

There are two types of plunger type switches: one seals the plunger part with an O-ring or rubber diaphragm and the other covers it with a rubber cap.

In the former type, the sealing rubber is not exposed to the outside, so it is resistant to hot foreign materials such as machine tool chips. However, it has a weak point that fine particles such as sand, chips, and dust can get caught in the sliding plunger surface.

The latter type has superior sealing performance because sand, chips, and other particles and dust do not become entrapped. However, hot foreign objects such as machine tool chips may melt or tear the rubber cap, making it necessary to select the right type depending on cost, application, and location.

When Limit Switches are operated, air is compressed and sucked by the piston motion of the plunger. Therefore, if the plunger is kept pushed in for a long time, the internal pressure in the Limit Switch becomes the same as atmospheric pressure, and the plunger may return slowly due to resistance from the atmospheric pressure when the plunger returns.

In addition, the accumulation of oil or dust on the plunger or on the sealing portion of the rotary shaft can also impede the operation of the Limit Switch, resulting in poor operation of the Limit Switch.

What Is a Press Unit?

Press units, specifically servo presses, utilize a servo motor for numerical control to precisely manage the presser’s movement. This technology enables detailed control over the presser’s speed and frequency, offering significant improvements over traditional mechanical presses powered by hydraulic or pneumatic systems.

Uses of Press Units

Servo presses are versatile, supporting a range of applications such as press fitting, caulking, distortion correction, punching, forming, heat welding, and powder forming. They are particularly beneficial in automotive manufacturing for producing complex and lightweight components like doors and hoods.

Principle of Press Units

Servo press units employ servo motors for applying pressure, facilitating precise and complex slide movements. This system constantly monitors and adjusts its performance (e.g., speed, torque) to match predefined parameters. Unlike conventional presses, servo presses can vary their speed, allowing for nuanced operations like slow pressurization when contacting materials, thereby enhancing efficiency and accuracy. Additionally, their CNC capability enables easy integration with external systems and complex programming for advanced tasks.

Other Information on Press Units

Advantages of Press Units

Press units offer several benefits compared to mechanical presses:

• Improved Formability: They enable the forming of materials previously challenging to press, such as high-tensile steel, stainless steel, and aluminum alloys, by optimizing slide motion to minimize wrinkles and cracks.
• Controlled Springback: The ability to adjust press actions helps suppress springback in high-tensile steel plates.
• Higher Precision: By constantly monitoring and adjusting the bottom dead center, servo presses maintain part accuracy despite thermal expansion or environmental temperature changes.
• Extended Die Life: The precise control over pressing speed extends the life of dies by reducing wear.
• Prevention of Lubricant Loss: Adding vibratory motion to the slide helps maintain lubrication effectiveness by enhancing lubricant penetration into material-die gaps.
• Process Reduction: Complex parts requiring multiple conventional press operations can now be formed in fewer steps, reducing equipment and maintenance costs while improving precision.

What Is a Leaf Switch?

Leaf switches are switches that conduct electricity by physically bringing two or three thin copper plates into contact with each other.

Like other types of switches, they have an ON-OFF or ON-ON function.

Some leaf switches have exposed contacts, while others are fitted with plastic covers. Both are simple in construction and have few parts, so if contact failure occurs, they can be restored with simple maintenance such as polishing the contacts and applying a contact revival agent.

Uses of Leaf Switches

Leaf switches are generally used to detect the position of the pickup body or motor of a CD player. Leaf switches with increased dust resistance and longer life are also used in pushbutton switches for elevators and other equipment.

When the pickup body moves to the end, it contacts the leaf switch and the contact turns ON. This controls the pickup body from moving any further when electricity flows through it. If the leaf switch has poor contact, it cannot detect that the pickup body has moved to the end, so it tries to move forcibly, which may cause a failure.

Principle of Leaf Switches

Leaf switches consist of two or three thin copper plates fixed to the base in a long protruding position. At the end of the copper plates is a contact point and on the other side is a terminal. The thin copper plates bend easily even with light force, and when the contact points come into contact with each other, electricity flows. By detecting this current on the circuit side, it is possible to detect the position of the desired object.

In the case of a leaf switch with two copper plates, the switch is OFF when they are far apart and ON when they are in contact with each other; in the case of a leaf switch with three plates, the central copper plate is originally in contact with one side, allowing the switch to flip where electricity flows.

Leaf switches have a simple construction in which electricity is conducted by the copper plates making contact, but over time the contacts can become worn and corroded. If the contacts remain corroded, electricity will not flow even if they are in contact, resulting in poor contact. As a countermeasure, gold, which is more corrosion-resistant than copper, is used in leaf switches that are used under severe conditions.