月: 2023年1月

What Is a Live Center?

A live center is a type of center that is a component of a machine tool, such as a lathe. It is sometimes called a turning center.

The center is attached to the headstock of a lathe or other machine tool and is used for centering during cutting operations and for maintaining the center of rotation of the workpiece.

There are two types of centers: fixed centers and live centers. The live center is a center with a built-in bearing and has the feature of reducing friction at high speed rotation compared to the fixed center.

Uses of Live Centers

Live centers are used to support rotating workpieces on a variety of machine tools, such as ordinary lathes, NC lathes, grinding machines, gear grinding machines, hobbing machines, and polishing machines.

While fixed centers that do not incorporate bearings have limited rotational speed due to friction caused by rotation, live centers can perform high-speed rotational machining because friction is reduced by bearings.

On the other hand, live centers are not suitable for high-precision machining because bearing rotation affects machining accuracy.

Characteristics of Live Centers

Live centers have a built-in bearing in its body and can hold a workpiece in conjunction with the spindle of a machine tool such as a lathe. The live center holds even long workpieces stably and prevents the workpiece from swinging even when machining at high speeds. Because bearings reduce friction, live centers also have the advantage of a long service life.

Live centers have a thicker header due to the built-in bearing. Therefore, depending on the shape and diameter of the workpiece, the tool (byte) and the center may interfere with each other and machining may not be possible, so interference between fixtures must be checked before machining.

The live center has a built-in bearing in the header, which makes the fulcrum distance longer, and a load moment proportional to the distance is applied to the tip of the center. A longer fulcrum distance will create greater deflection during processing. Therefore, live centers have the disadvantage of being inferior to fixed centers in terms of rigidity and accuracy.

What Is a Logarithmic Amplifier?

A logarithmic amplifier is an amplifier that outputs a logarithmic conversion of an input signal. As it compresses the input signal and then outputs it, logarithmic amplifiers find application in situations where handling signals with a broad input range is necessary. Since the frequency and temperature characteristics vary depending on the configuration of the logarithmic amplifier, it is necessary to select the appropriate configuration for the application. An amplifier that restores the signal compressed by a logarithmic amplifier is called an anti-log amplifier (inverse logarithmic amplifier).

Uses of Logarithmic Amplifiers

Logarithmic amplifiers can be used, for example, to compress an analog signal with a wide dynamic range that varies by digits to fit the input range of the ADC when the analog signal is converted to a digital signal by an A/D converter (ADC). For example, logarithmic amplifiers are used to adapt a signal whose amplitude variation exceeds 100dB to a standard operational amplifier or ADC with a dynamic range of 60dB to 100dB. Logarithmic amplifiers are used in many systems, including communication systems, measurement systems, and acoustic systems.

Principle of Logarithmic Amplifiers

Logarithmic amplifiers are configured to provide high gain for low-level signals and progressively lower gain for higher-level signals. There are two main types of logarithmic amplifier configurations. These are the multi-stage logarithmic amplifiers and the DC logarithmic amplifiers.

In a multistage log amplifier, several stages of linear amplifiers are connected in series, and the outputs of each stage are added together. Low-level signals are amplified sequentially by several stages of linear amplifiers to achieve high gain. As the signal becomes higher level, a logarithmic output characteristic can be obtained by controlling how many stages of linear amplifiers are added up to the output of the linear amplifiers.

DC logarithmic amplifiers are achieved by using a diode in the feedback of the inverting amplifier circuit of an operational amplifier. Instead of a diode, a diode-connected transistor can be used. By using the logarithmic portion of the voltage and current characteristics of the diode or transistor, a logarithmic output can be obtained.

What Is Zinc?

Zinc is a transition metal element whose elemental symbol is Zn.

Zinc is widely distributed on the earth, but it does not exist by itself. It is produced as ores such as sphalerite and rhozinc ore, and must be smelted in order to extract zinc alone.

Zinc has a long history, with evidence of the use of brass, an alloy of copper and zinc, as early as 4000 BC.

However, it was not until the 1600s that zinc was extracted as a stand-alone metal, and smelting methods were developed in India and China.

Uses of Zinc

Zinc is used in a wide variety of applications.

It is often used as a metal in plating materials, conductive films, battery electrodes, and steel sheets.

However, zinc is rarely used alone, but rather as an alloy with various other metals.

For example, it is alloyed with copper to make anode plates for batteries, and with aluminum to make galvalume steel sheets for roofing.

Zinc is also one of the building blocks of the body, and a daily intake standard of 7 to 10 mg has been established. It is also sold as a dietary supplement in drugstores.

Characteristics of Zinc

Zinc is characterized by its greater ionization tendency than other metallic elements.

The greater ionization tendency means that it releases electrons and becomes a cation more easily, and is more likely to bond with oxygen. When it bonds with oxygen, it corrodes faster.

For this reason, zinc plating on other metals, such as iron, is used to prevent corrosion of the steel by corroding the zinc first.

In batteries, zinc, which ionizes easily, is used as the anode, and a metal that is more difficult to ionize than zinc is used as the cathode, thereby creating a flow of electricity.

In the body, zinc is involved in the synthesis of proteins and DNA.

Therefore, a deficiency of zinc can cause a variety of adverse effects, including growth impediment, impaired reproductive function, anemia, and cognitive dysfunction.

Taste disorder is a well-known and particularly noticeable symptom in which the inability to sense taste is impaired.

However, excessive intake of zinc can also cause health problems. For example, daily intake of more than 10 mg of zinc is known to increase the risk of prostate cancer.

What Is a Safety Control?

A safety control is a device that controls machine startup based on signals from safety input devices. When it detects behaviors such as malfunction or unintended human operation, it independently assesses the anomaly and subsequently deactivates the safety output. By doing so, the startup of the machine is stopped.

A safety control input includes safety plugs, laser sensors, and emergency stop switches.

Uses of Safety Controls

Safety controls are mainly used to construct systems that protect the safety of workers.

There are two types of safety controls: safety PLCs, which are capable of complex programming, and safety relay units, which are not programmable. Safety relay units are available with one set of inputs and one set of outputs, or with multiple inputs and outputs to build simple safety control circuits.

A safety PLC is suitable when you want to determine the operation limit by taking various conditions into account, while a safety relay unit is suitable when you want to determine the operation limit simply and immediately. In this way, it is important to use both according to the system you want to realize.

Principle of Safety Controls

Safety controls are electrically connected to safety plugs, laser sensors, and non-emergency stop switches on the input side. It is also electrically connected to the output devices in the same way.

The safety controls constantly monitor the electrical connections of the equipment on the input side. For example, an operation panel installed on a production line is equipped with an emergency stop switch. If a worker presses the emergency stop switch for any reason, it disrupts the electrical connection between the emergency stop switch and the safety controls. The safety controls then identify this interruption and promptly interrupt the electrical connection of the equipment on the output side (if a safety relay unit is employed). In this way, the output devices can be deactivated almost as soon as the emergency stop switch is pressed.

On the other hand, if a safety PLC is used, the output side operation is restricted according to the programmed process. Programming is highly flexible, and a variety of operations can be realized. However, in the case of applications where human casualties are to be prevented, the speed of the process is related to the magnitude of the damage, so the system must be carefully considered.

What Is a Safety Sensor?

A safety sensor is a sensor used to prevent accidents, fires, and other disasters in various locations. They are used in homes, factories, offices, and transportation equipment.

A familiar example is a safety sensor that detects a fire resulting from spilled gas on a gas range and subsequently shuts off the gas supply.

Various types of safety sensors are available, including those that detect temperature, shaking, speed, the concentration of certain gases, and overweight items.

Uses of Safety Sensors

Examples of safety sensor uses include:

1. Safety Light Curtains
   For example, on a factory production line, if a worker enters an area where an industrial robot is operating, the robot’s power is automatically turned off.
   This is because safety sensors called “safety light curtains” (area sensors) are used to monitor whether people or objects have passed through the designated space constantly.

2. Safety Limit Switches
   These switches are often installed to check the opening and closing of equipment doors and inspection windows of safety fences.
   When a worker opens the inspection window to check the equipment, the power of the equipment is turned off.

Features of Safety Sensors

Safety sensors come in many types and applications, and their features vary widely.
The following is a description of typical safety sensor features.

1. Safety Light Curtains
   Light curtains detect when a person or object blocks a specific space and send this information to the facility.
   Light curtains are usually divided into a light-emitting side and a light-receiving side sensor. Multiple rays of light are constantly emitted from the light-emitting side to the light-receiving side sensor at regular intervals.
   Therefore, if the light emission interval is too wide, the light curtain should be selected in consideration of the size of the object to be detected, since the object may slip through.
2. Flame Detectors
   Flame detectors are safety sensors designed to identify the absence of a flame in gas burners and other devices used in industrial furnaces. Some types detect ultraviolet and infrared radiation emitted by flames, while others assess the light and conductivity of flames.
   In ultraviolet flame detectors, a UV tube is built into the sensor, which detects the slight ultraviolet light emitted by the flame.
   When the UV light hits the UV tube and the light-receiving surface of the sensor, the photoelectric effect sends an appliance signal.

What Is a Safety Glass?

Safety glass refers to glasses that prevent dust, dirt, metal powder, and chemicals from entering the eyes.

They are often called “safety glasses” or “laboratory glasses.” They are used in a wide variety of locations, including laboratories and workrooms at universities and manufacturers, as well as outdoor workplaces where power tools and laser equipment are used.

Unlike ordinary eyeglasses, the type, construction, and materials used in safety goggles are strictly regulated by certain standards. There is also a type of safety eyewear known as protective goggles, which offers a higher level of protection compared to standard safety glasses.

Uses of Safety Glasses

Safety glasses are used in workplaces where people handle items that could be dangerous if they get into their eyes, and the standards stipulate the conditions for their use. In some cases, the use of safety goggles is required by each business site even in places where it is not required by law.

The method of use is the same as for ordinary eyeglasses, with the arms being placed over the ears to complete the wearing process. Currently, safety glasses designed to be worn over regular eyeglasses are also available in the market. To ensure the protection of one’s eyes, it is necessary to conduct a thorough inspection for any scratches or deformities before use.

Types of Safety Glasses

Safety glasses are used in a wide variety of workplaces, and there are many different types of safety glasses. Examples are as follows:

1. Overglass Type

Generally, safety glasses do not come in a lens-type version. For this reason, they are designed to be worn over eyeglasses for people who normally use glasses to correct their vision. The lenses are wider than those of ordinary safety glasses, and can fully cover the eyeglasses.

2. Heat-Resistant Type

In biological research fields, it is sometimes necessary to work in a sterilized environment. In such cases, all instruments used must be sterilized at high temperatures by autoclave or other means. General safety glasses cannot withstand sterilization at high temperatures (approx. 120°C) and become deformed. If you choose a heat-resistant type, you can sterilize them without any problem.

3. Anti-Scratch Type

Safety glasses are used not only in chemical and biological fields but also in grinding and cutting fields. Safety glasses with anti-scratch coating are used to ensure safety when working with metal fragments that may fly out. Other types of safety glasses are also available, such as small-sized ones for women and ones with anti-fog coating.

Structure of Safety Glasses

The difference between the construction of safety glasses and ordinary glasses is the shape of the lens portion. Ordinary spectacles have a gap around the lens, whereas safety glasses have a surrounding area around the eyes.

In situations where safety glasses are used, even a foreign object entering through a gap in the lens can cause a serious accident, so the structure is more protective.

Other Information on Safety Glasses

1. Standards for Safety Glasses

Safety glasses are more impact-resistant, abrasion-resistant, heat-resistant, and fog-resistant than ordinary glasses. They are constructed to withstand harsh environments, such as a laboratory surrounded by chemicals, or an outdoor work site where the environment is hot and subject to strong vibrations and impacts.

The standard for impact resistance is that the lens must not crack or split when an iron ball weighing 44g is dropped from a height of approximately 1.3m. The standard for heat resistance is that there must be no deformation at 55°C.

2. Material of Safety Glasses

Safety glasses are made of hard, impact-resistant plastic resin such as polycarbonate or acrylic resin for the lens portion. The frames are made of soft and easy-to-process materials such as polypropylene and soft polyvinyl chloride.

It is said that the lens portion can be used for 3 years and the frame portion for 5 years. Check daily for loose screws or hinges and for scratches or cracks on the lenses. Replace them with new ones as soon you notice any defects or you feel any discomfort.

What Are Safety Shoes?

Safety shoes are designed to protect workers’ feet in hazardous environments such as construction sites and factories.

They are equipped with metal cores in the toe area to guard against heavy objects falling and impacting the feet. Compliance with standards ensures their safety effectiveness.

Depending on their application, safety shoes may also offer additional protective features, such as static electricity dissipation for environments with organic solvents, or puncture resistance for construction sites.

Usage of Safety Shoes

Safety shoes are essential in various industrial settings, allowing selection based on specific needs.

The short shoe type is the most common, favored for its toe protection, cushioning, and waterproofing, making it ideal for extended wear.

Specialized safety shoes cater to unique demands, such as anti-slip properties for kitchen and food factory workers or static electricity prevention for those working at gas stations.

Features of Safety Shoes

The protective efficacy of safety shoes is anchored by internal cores. The toe core, made from steel or resin, provides a protective space to safeguard the foot under pressure or impact.

 The outer sole typically consists of leather or rubber, with rubber or urethane used for the sole for its slip-resistant and insulating properties.

Structure of Safety Shoes

Safety shoes vary in design, ranging from short shoes to protective sneakers, with Velcro or lace closures.

1. Short Shoes

These ankle-length shoes combine ease of use with mobility and professional appearance, suitable for general work.

2. Medium-Length Upper Shoes

Extending over the ankles, these shoes offer added protection against water, sand, and sparks, ideal for metalworking and welding tasks.

3. Long-Knit Upper Shoes

Boot-like in design, they cover up to the shin, offering enhanced fit and protection, suitable for demolition or elevated work.

4. Half Boots

Rubber-constructed for shin-high protection, these boots are designed for quick donning and removal, perfect for civil engineering and demolition work.

5. Protective Sneakers

Lightweight and designed like sneakers, these are meant for light-duty work.

6. Velcro Type

Velcro closures allow for quick and easy adjustment, even with gloves on.

7. Shoelace Type

Laces provide a snug fit and versatility for everyday wear, though caution is advised in environments where they may pose a hazard.

How to Select Safety Shoes

Selection should be based on the specific functions required:

1. Heat Resistance

Choose shoes with high heat resistance for work in high-temperature environments.

2. Fire Resistance

For welding or furnace work, opt for shoes with high fire resistance.

3. Breathability

Mesh materials are preferable for hot settings, reducing moisture and odor.

4. Slip Resistance

Essential for slippery floors or inclined surfaces.

5. Water Resistance

Look for shoes that withstand water and oil for cleaning tasks or outdoor work.

What Is a Safety Guard?

A safety guard is a piece of safety equipment that restricts entry into a dangerous area. It is a fence that prevents workers from entering the vicinity of processing machines, assembly machines, and rotating equipment that can cause serious accidents if contacted.

In addition to preventing entry into hazardous areas, a safety guard can also serve to contain the dispersion of dust produced during the process and manage the noise generated throughout the processing.

In many cases, safety guards consist of a fence and a door for entry and exit. The base is made of aluminum or iron, and the surrounding area is covered with a mesh or transparent resin such as polycarbonate so that the inside can be seen.

Uses of Safety Guards

Safety guards are used to ensure safety from factory automation (FA) equipment. In the case of specialized machines that greatly improve production efficiency, safety devices are often built into the equipment, and safety guards are not often used. However, in the case of industrial robots, which have been on the increase recently, safety guards are often installed in accordance with the actual environment in which the robot is used and the robot’s movements.

Even in FA systems using cooperative robots, where safety guards are not required, there are cases where safety guards are used to ensure safety because of the danger of end effectors (also called hands) and workpieces coming into contact with people.

Principle of Safety Guards

Safety guards consist of a fence, a door through which people enter and exit, and a safety sensor that checks whether the door is open or closed. Similar to safety guards, there are also sensors called area sensors, which are used to prevent people from entering dangerous areas. Area sensors include area curtains and laser scanners. When a person or object enters a set area, the sensor detects it and activates the safety device.

One aspect that differentiates the use of safety guards and area sensors is visibility. Area sensors rely on infrared light, making it challenging to visually confirm the sensing area. In contrast, a safety guard can prevent accidental entry because the fence itself is visible and the boundary with the danger area can be visually confirmed.

Area sensors have the advantage of being easy to install and inexpensive, but they also have the disadvantage of increasing the risk of unintentional equipment shutdown. Safety guards are used when unexpected equipment stoppage is to be avoided as much as possible.

What Is Stress Analysis Software?

Stress analysis software is software that simulates the stress on an object.

Stress is the force per unit area applied to the interior of an object (internal force per unit area). When an object undergoes deformation, stress is applied to the object in order to deform or rupture it. However, it is impossible to visually verify the stress applied to the object’s interior during this process.

Therefore, stress analysis software is used to analyze the stress in an object using a computer and to verify whether the object can withstand the stress.

Uses of Stress Analysis Software

Stress analysis software primarily serves to assess and confirm the structural strength. For instance, when designing a machine, it is used to ascertain the forces acting on the structure in order to evaluate its resilience. The structure and materials of the machine are reviewed and redesigned for higher strength.

In the days when stress analysis software was not available, the designed machine was actually manufactured and stress analysis was performed by experiment. However, the time and cost of conducting experiments each time was too much. The stress analysis software has reduced the time and cost of such experiments.

Principle of Stress Analysis Software

The basic principle of stress analysis software consists of the finite element method (FEM). The finite element method is “a mathematical method for solving differential equations in an approximate manner.”

When analyzing an object on a computer, it is necessary to represent (model) the properties of the object with mathematical equations, as computers can only process mathematical equations. The method to model the structure and properties of an object in an approximate manner is called the finite element method. In the finite element method, an object with a complex structure and properties is divided into a finite number of elements.

For example, in the Tokyo Tower, a complex structure can be easily approximated by dividing each red bar. One finite element can be represented by a relatively simple mathematical formula. Each micro-region that is divided is represented by a mathematical formula, and by connecting them together, the properties of the entire object are approximated. In other words, a complex structure is divided into a finite number of small elements, and the stresses and displacements of each element are determined. Then the whole structure is joined together.

The finite element method (finite element analysis) is a method to analyze the displacement and stress of an object by modeling the structure and properties of each finite element and adding them together, considering a single complex object as a whole.

Additional Information on Stress Analysis Software

Forces can be broadly divided into external and internal forces. The internal force per unit area is called stress.

1. External Force, Internal Force, and Stress

External Force
External forces are forces acting outside of an object. For example, an external force is a force that pulls a member, such as a bar, from the outside by a surface in contact with it. Since external force is a force applied from outside the object, it is generated by the act of pulling by hand or compressing by a machine.

Internal force
Internal force is a force acting inside an object. When a member to which an external force is applied is hypothetically cut, an inner force is generated to balance the external force. While external force is a visible concept through actions such as pulling by hand, internal force is important in evaluating objects’ deformation and fracture.

Stress
Stress is the force per unit area applied to the interior of an object. As a result, the unit of measurement for stress is not the unit of force [N] but [Pa], which is the same as the unit for pressure. An object subject to an external force generates an internal force to counterbalance the external force. Therefore, the greater the external force applied, the greater the internal force it generates.

When considering the deformation or rupture of an object, attention is paid to the internal force. However, since the dimensions of the member cannot be taken into account only by the internal force, stress, which represents the force per unit area, is calculated by dividing the internal force by the area. By using stress, the load on an object can be verified regardless of the size of the object.

2. Types of Stress

Stress can be broadly divided into two types: tensile stress and shear stress.

Tensile stress is the stress produced when an object is pulled and is uniformly distributed across the hypothetical cut surface of the object. Shear stress is the stress that acts when an object is sheared. For example, when cutting cardboard with scissors, shear stress is generated in the scissors and cardboard because shear cuts the cardboard.

Combining tensile and shear stresses can address complex problems. For example, if you hold both ends of a carrot with both hands and make a bending motion, tensile and shear stresses are applied to the center, causing the carrot to break near the center.

If the same thing were to occur in a structure such as a bridge, it would cause a major accident. To avoid such a situation, stress analysis software should be used to verify what stresses are applied to the object.

What Is a Thermometer?

A thermometer is an instrument that can measure the temperature of an object. Commonly used thermometer includes glass thermometer, bimetallic thermometer, and radiation thermometer.

A glass thermometer is a thermometer with a glass tube filled with mercury or alcohol as a temperature-sensitive liquid. The accuracy varies depending on the glass used and the temperature-sensitive liquid. If you choose the right type for the object to be measured, you can perform measurements with a high degree of accuracy.

A bimetal thermometer is a type of contact thermometer that uses the expansion of metal. Although they are less accurate than glass thermometers, a bimetallic thermometer is more durable and can measure temperatures stably.

A radiation thermometer is a type of thermometer that can take measurements without directly touching an object and is becoming increasingly popular at manufacturing sites.

Uses of Thermometers

There are several types of thermometers with different specifications in terms of measurement methods and principles. Each type has its own characteristics and is often used, especially in industrial fields.

For example, thermometers can be used to detect heat generation in home appliances and electronic components. This can be used to detect abnormalities during product testing and inspections, making work more efficient than visual inspections.

Another typical application of thermometers is in factory production lines. By utilizing thermometers in food production lines to control temperatures during fermentation and roasting processes, quality can be easily maintained and improved.

Principle of Thermometers

The method of measuring temperature in thermometers varies from product to product. There are two main types of measurement methods: contact and non-contact, and the method differs depending on what is used as the standard for detecting the temperature of an object.

The contact method is a measurement method in which the measuring section of the thermometers is in direct contact with the solid, liquid, or gas (called the workpiece) to be measured. The temperature of the solid or liquid workpiece is measured by thermal conduction. The temperature of the gaseous workpiece is measured by convection. Most thermometers using this method are simple in construction and low in cost.

With the contact method, there is a possibility of loss of heat from the workpiece due to direct contact. This issue is solved by the non-contact method, which can measure temperatures without direct contact.

The non-contact method uses radiation from the solid or liquid workpiece to read the surface temperature, making it possible to perform measurements in a short time. However, since emissivity varies depending on the workpiece, emissivity must be set appropriately for accurate temperature measurement.