月: 2023年1月

What Is Stainless Steel?

Stainless steel is an alloy steel that contains more than 50% iron (Fe), less than 1.2% carbon (C), and more than 10.5% chromium (Cr) as its main constituent.

It is well known for its excellent corrosion resistance and rust resistance. It also has excellent properties in terms of heat resistance, workability, and strength. The name “stainless steel” derives from “stain” (rust) and “less”.

Stainless steel is rust-resistant due to the formation of a thin film, known as a passive film, on its surface. Generally, when iron combines with oxygen, it becomes iron oxide and rust occurs. Chromium, however, binds to oxygen more easily than iron, and when chromium oxidizes before iron does, it forms a passive film that covers the steel surface and inhibits rust formation.

This property of chromium makes stainless steel resistant to rust. Adding nickel to stainless steel further increases its corrosion resistance, making it possible to obtain a stainless steel that is even more resistant to rust. However, even stainless steel can rust. Specifically, this is the case where the metal has been in contact with rusted metal for a long period of time or has been scratched.

The type of stainless steel is indicated by “SUS + number” as in “SUS304” or “SUS430.” SUS is an acronym for “steel use stainless,” and the number following it is the grade of stainless steel. SUS304″ is a stainless steel used worldwide.

Uses of Stainless Steel

Stainless steel is used in a wide variety of fields, taking advantage of its excellent corrosion resistance. In precision equipment, home appliances, and industrial equipment, it is often used as exterior covers and mechanical parts.

The reasons include the fact that a clean appearance can be obtained without surface treatment, and because plating or painting is not required for dual rust-preventive purposes. Also, the lead time for parts is short, and under certain conditions, the use of stainless steel may be less expensive than the use of ordinary steel.

Another advantage is its excellent heat resistance and heat retention properties due to its low thermal conductivity. At home, stainless steel is used for spoons, forks, and kitchen sinks. In addition, due to its high strength and hardness, stainless steel is sometimes used as a roofing material for large facilities such as dome stadiums, and for parts that play an important role, such as turbine blades and brake discs used in jet aircraft.

Characteristics of Stainless Steel

It has very high corrosion resistance and can be classified into five types according to alloy ratios and other factors, each with different characteristics.

Types of Stainless Steel

1. Martensitic Type

Martensitic stainless steel is composed mainly of chromium and carbon and does not contain nickel. It has high hardness due to the formation of a hard metallic structure called martensite by heat treatment. However, it is more susceptible to rust and has the lowest corrosion resistance in harsh environments compared to other types of stainless steel.

Like ordinary steel, it is characterized by its magnetic properties (magnets stick to it). The main applications of martensitic stainless steel include blades, nozzles, turbine blades, and disc brakes.

2. Ferritic Stainless Steel

Ferritic stainless steel is mainly composed of chromium and does not contain nickel. After austenitic stainless steel, ferritic stainless steel has excellent corrosion resistance and is suitable for press work because it remains soft with little hardening after heat treatment.

Its main applications include building interior materials and gas and electric appliance parts. Another characteristic of ferritic stainless steel, such as SUS430, is its magnetic properties.

3. Austenitic Stainless Steel

Austenitic stainless steel is composed mainly of chromium and nickel and forms a metallic structure called austenite at room temperature. It has excellent corrosion resistance, heat resistance, and weldability, and is used in various fields, including household items such as spoons and forks, automotive parts, and construction supplies.

4. Precipitation Hardening Type

Precipitation hardening type stainless steel is composed mainly of chromium and nickel, to which elements such as aluminum and copper are added. They are then subjected to a precipitation hardening treatment, a heat treatment similar to quenching and tempering, to improve hardness by utilizing precipitation of intermetallic compounds of these elements. Although not as resistant to corrosion as austenitic stainless steel, it is superior to ferritic stainless steel.

SUS630 is a precipitation hardening stainless steel.

5. Duplex Stainless Steel

Duplex stainless steel is a mixture of austenitic and ferritic stainless steel. A typical example is SUS329J1.

What Is a Wrench?

A wrench is a tool used to tighten or loosen a hexagonal bolt or nut. The wrench is inserted into the two parallel hexagonal surfaces of the bolt or nut and force is applied by hand to transmit torque. A wrench is also known as tools for tightening and loosening hexagonal bolts and nuts. “Spanner” is the British English word and “Wrench” is the American English word. There is no difference in their original meanings, and the difference between a wrench and a spanner is not clearly defined. 

Uses of Wrenches

Wrenches are used to fasten or loosen hexagonal bolts, nuts, and other screws with two parallel sides. They are indispensable fastening tools for machinery and equipment, precision instruments, vehicles, engines, construction, furniture, DIY, and all other situations. They are highly versatile and their range of use is very wide. One method of preventing nuts from loosening is the double nut method, in which two nuts are stacked on top of each other, but wrenches are always required for double nut fastening. In most cases, two wrenches are used for fastening.

Characteristics of Wrenches

Wrenches are not suitable for turning a bolt or nut 360°, because it requires a large space to do so. Therefore, they are often tightened first by hand or with other tools, such as a screwdriver, to the point of temporary tightening, and then finally tightened with a wrench. Since wrenches tighten on two sides, applying excessive force can deform the bolt/nut or damage the tool. When tightening with a large torque, spectacle wrenches (which receive force at the six apex points) should be used. For parts that require a wrench with a large amount of force, a striking wrench is used. This wrench can apply large force instantaneously by striking the tip of the handle with a hammer or the like. It can be used when retightening is necessary or for nuts that are rusted and cannot be loosened.

The nominal dimensions and sizes of wrenches are expressed in terms of the dimension of the 2-sided width (the dimension of the open part). Therefore, even if it is not a bolt or nut, the wrenches can be used by matching its dimensions. With a round shaft, the wrenches can be used by taking out two sides, and with a small torque, the wrenches can be used by only taking out one side (so-called “D cut”).

What Is a Center Drill?

A center drill is a type of cutting tool used in machine tools.

Although center drills are used for positioning before drilling a pre-drilled hole, they are often used for purposes other than positioning due to their versatility.

A locating hole is a hole used to support a workpiece when machining a cylindrical workpiece (shafts) on a lathe or cylindrical grinder. Since the locating hole is the base of the pre-drilling process, it must be highly accurate and free from bends and distortions. Therefore, the center drill is more rigid than an ordinary drill and is less prone to misalignment during drilling.

Uses of Center Drills

Center drills are used to drill a center hole in the end face of a cylindrical workpiece (shaft). In addition to drilling center holes, center drills are used in the following situations:

1. Positioning Hole Drilling

A center drill is used to drill a hole precisely when drilling. When starting drilling, the tip of the drill may be shaky, and in such cases, a center drill can be used to prevent shaking. 

2. Hole Chamfering

Center drills are available with 60°, 75°, 90°, and R-shaped edges, which can be used for chamfering.

3. Drilling Holes in Plates

Through-holes can be drilled into thin plates. This eliminates the need for a pre-drilling process and allows chamfering after drilling in one step, thus shortening the work time.

Types of Center Drills

Center drills have a short overall length, a thick shank, and high rigidity. When machining with an ordinary drill, the tip of the blade shakes when the blade bites into the workpiece, affecting the accuracy of the drilling position. Center drills with high rigidity have very little blade shake. Types of center drills are as follows:

1. Type A

The short, small-diameter portion of the cutting edge is followed by a 60° taper portion. The tapered part is also available in 75° and 90° versions.

2. Type B

A short, small-diameter section of the cutting edge is followed by a 60° taper section, which is followed by a large chamfer cutting edge as the third step. This serves to protect the center hole during machining and setup.

3. Type C

The short, small-diameter portion of the cutting edge is followed by a 60° tapered portion, and then a blade is attached to the third step in the form of a counterbored edge. The counterbored portion serves to protect the center hole in the same way as the chamfer of Type B.

4. Type R

The taper portion next to the short small-diameter portion of the cutting edge has an R. Because of the R, the contact with the center is a linear contact. Even when the angle of the taper does not match or the shaft center is off-center, linear contact can be used to support the workpiece. It is often used for precision machining of small workpieces.

How to Use a Center Drill

It is important to pay attention to the depth of the center drill when using a center drill for positioning.

If the center drill depth is too shallow, the accuracy of the pre-drilled hole will be reduced and chamfering will have to be performed again after the pre-drilled hole is drilled, which is not efficient.

On the other hand, if the center drill is too deep, the load on the center drill will increase, and in the worst case, the center drill may break if it is drilled too deep beyond the taper section, so be sure to complete drilling in the middle of the taper section.

In addition, if you calculate the machining depth so that the chamfer portion remains in consideration of the diameter of the pre-drilled hole and then perform positioning drilling, the chamfering work after drilling can be eliminated, allowing for more efficient hole drilling.

Other Information on Center Drills

Center Drill Rotation Speed

The rotation speed of a center drill is generally 1,000 rpm.

For widely used steel materials such as S45C and SS400, a speed of around 1,000 rpm is fine, but when drilling very hard steel materials such as die steel, the rpm should be reduced to around 500 rpm and the feed rate should be slowed down. When the material is hard, a cemented carbide center drill may be used.

The material used for center drills is generally HSS (high-speed steel), but cemented carbide can also be used for machining hard steel materials such as die steel.

What Is a Die Set?

A die set is a critical tooling component in press machines, designed for metal and plastic forming processes. It comprises upper and lower parts that hold the die, connected by guide posts to ensure vertical movement accuracy. Made from materials like polyurethane, and nitrile rubber, and sometimes reinforced with fibers, die sets enable the precise shaping of various products by changing the installed dies.

Uses of Die Sets

Die sets are instrumental in forming various industrial and automotive parts, including gears and joints, through metal and plastic forming processes. This method is favored for its ability to produce high-strength products cost-effectively and efficiently.

Principle of Die Sets

Die sets integrate several components, such as the mounting section for press machine attachment, the pressure-receiving section for force transmission, and the forming section for shaping the product. They maintain accurate alignment through guide posts and bushings, ensuring the quality of the final product.

Types of Die Sets

• Back Post (B Type): Open on three sides, suitable for single operations with easy access for robotic machining.
• Center Post (C Type): Central load distribution, ideal for hole punching and bending tasks.
• Diagonal Post (D Type): Designed for smaller, progressive, or automated dies.
• Fore Post (F Type): Features guides at all four corners for progressive dies, ensuring mold accuracy but less convenient for single operations.

Choosing a Die Set

Selection is based on required precision, rigidity, and specific application needs, considering guide post positioning and guide types, such as plain, ball guide, or roller type for higher performance.

Advantages and Disadvantages

Die sets allow for versatile forming processes through die exchanges, enhancing production flexibility. However, ensuring eccentricity and concentricity accuracy is crucial to prevent quality issues.

Structure of Die Sets

Essential components include the guide post for alignment and the guide bush for smooth operation, ensuring the die set’s top and bottom halves remain accurately aligned during use.

What Is a Timing Belt?

A timing belt, or toothed belt, is an essential component in automobile engines, designed to synchronize the movement of the pistons and valves. Made from elastic materials like polyurethane or nitrile rubber, often reinforced with glass fiber or aramid fiber, timing belts ensure precise transmission of drive without slippage by engaging with the teeth of pulleys.

Uses of Timing Belts

• Synchronization of Pistons and Valves: By linking the crankshaft and camshaft, timing belts maintain the correct timing for air and fuel mixing and burning in the combustion chamber, preventing potential engine damage from piston and valve collisions.
• Driving the Water Pump: Timing belts also play a crucial role in engine cooling by driving the water pump, facilitating coolant circulation.

Principle of Timing Belts

• Crankshaft: Converts the pistons’ up-and-down motion into rotational force, driving the timing belt.
• Timing Belt: Connects to the camshaft and water pump, rotating them with a precise 2:1 crankshaft to camshaft rotation ratio.
• Camshaft: Uses cams to open and close the intake and exhaust valves in sync with the piston movements.
• Water Pump: Circulated engine coolant, driven by the timing belt’s rotation.

Other Information on Timing Belts

When to Replace the Timing Belt

For optimal engine performance and safety, timing belts should be replaced based on:

• Mileage: Generally recommended every 100,000 to 150,000 km, depending on the vehicle.
• Years of Use: Typically, every 5 to 7 years, due to material degradation over time.
• Conditions of Use: Environmental factors like temperature and humidity can accelerate wear and tear.

Regular maintenance and timely replacement of the timing belt are crucial to preventing engine damage and ensuring vehicle safety.

What Is a Direct Drive Motor?

Normally, AC servo motors use an intermediate mechanism (speed reducer, belt, chain, etc.) to extract a large amount of torque effectively.

In contrast, a direct drive motor is a motor that directly couples a motor and a load (driven object) to transmit power and motion.

The main advantages of a direct drive motor are as follows:

• Space Saving
  A direct drive motor does not require a reduction gearbox. Therefore, the entire drive system can be made smaller and more space-efficient.
• Maintenance-free
  The combination of AC servo motor and reduction gear requires disassembly, cleaning, assembly, and adjustment to remove metal powder, deteriorated grease, and other debris due to wear on the gear sliding parts of the reduction gear. In contrast, the direct drive motor has a simple configuration with no gear sliding parts themselves and basically requires no maintenance. In addition, since there is no deceleration mechanism, there is no risk of malfunction or damage, even if rapid acceleration or deceleration is performed.
• High Response
  The low-inertia rotating parts and increased rigidity of the drive system directly reflect the control characteristics of the servo, thus improving the machine’s performance.
• Realization of high-precision speed control
  Since the direct drive motor does not require a reduction gear, there is no backlash and the large number of motor poles minimizes output torque variation, resulting in high-speed stability.

Principle of Direct Drive Motors

The structure of direct drive motors consists of four major components: the stator, rotor, bearing, and rotary position sensor (encoder).

Crossed roller bearings are often used for the bearings, which can support radial, axial, and moment loads with a single bearing, enabling thinner and significantly more rigid bearings compared to double-row angular contact ball bearings. Furthermore, the adjustable bearing clearance structure allows preload to be applied, resulting in highly accurate rotation.

In combination with a high-resolution encoder, precision control is possible. While a typical AC servo motor has 8 to 12 poles, direct drive motors have more than 20 poles, and a large direct drive motor has more than 100 poles, resulting in low torque ripple and high torque.

Uses of Direct Drive Motors

Direct drive motors can be used as a drive source for various equipment that require higher performance and environmental friendliness.

They are mainly used in precision drives for various semiconductor manufacturing processes, high-speed transport drives for processing and inspecting minute electronic components, and endurance test drives for automobile transmissions, engines, etc.

They are also used for processing and transport drive of large flat panels, solar panels, ultra-low speed stable drive of astronomical observation equipment, fine grinding drive of optical lenses, and precision feed drive for high-performance film molding.

Major Industries and Equipment Where Direct Drive Motors Are Used

• Semiconductor and electronic component industries
  Wafer dicing equipment, mounters, test handlers, wafer transfer equipment, wafer chamfering equipment, grinder equipment, inspection equipment, etc.
• Automotive industry
  Torque testers, endurance testers, steering testers, parts processing machines, transfer equipment, etc.
• FPD industry
  Lamination equipment, scriber, inspection equipment, laser processing equipment, etc.
• Converting and printing machine industry
  Film forming equipment, stretching equipment, roll coaters, unwinding and winding mechanisms, laminating equipment, PE printing machines, screen printing machines, rotary printing machines, etc.
• Food equipment industry
  Cappers, food conveying equipment, filling machines, etc.

What Is Titanium?

Titanium, symbolized as Ti and with atomic number 22, is a silvery-white, lightweight, and strong metal known for its exceptional corrosion and heat resistance. Its biocompatibility makes it ideal for medical devices like artificial joints and dental implants. However, its toughness necessitates specialized processing techniques, especially since it forms an oxide film when exposed to oxygen, affecting welding and processing methods.

Uses of Titanium

• Aircraft: Used in frames, wings, landing gear, and engine parts.
• Automobiles: Found in engine parts, exhaust systems, suspensions, and wheels.
• Medical Devices: Utilized for artificial joints, dental implants, and surgical instruments.
• Electronics: Used in smartphone casings, electronic contacts, and circuit boards.
• Chemical Industry: Applied in piping, reaction vessels, and hardware for its resistance to chemicals.
• Sporting Goods: Common in bicycle frames, tennis rackets, and golf clubs for its strength and lightweight.
• Manufacturing and Energy Industries: Employed in tools, machine parts, and components for thermal and nuclear plants.

Properties of Titanium

• Lightweight and High Strength: About half the mass of iron with superior strength due to its hexagonal close-packed structure.
• Corrosion Resistance: Forms a protective oxide film that shields it from acids, alkalis, and seawater.
• Heat Resistance: Maintains physical properties at high temperatures, suitable for high-temperature environments.
• Wear Resistance: The oxide film provides high wear resistance, protecting the metal even when it wears down.

Types of Titanium

• Titanium Dioxide: A white powder used in paints, food additives, and as a UV absorber.
• Titanium Carbide: Known for its hardness, and used in cutting tools and machining parts.
• Titanium Nitride: Offers wear and corrosion resistance, used in coatings and tools.
• Titanium Silicon Carbide: A compound with high-temperature strength, used in aerospace and nuclear applications.

Other Information on Titanium

• Low Thermal Conductivity: Its tightly packed atoms limit thermal energy conduction, making it a poor conductor of heat.
• Non-magnetic: Pure titanium and most alloys are nonmagnetic, with some exceptions.
• Oxidation Resistance: Forms a thin, adherent oxide film that protects it from further oxidation.
• Biocompatibility: The oxide layer’s stability and chemical inertness make titanium ideal for medical implants and devices.
• Softening Phenomenon: Prolonged exposure to high temperatures can lead to softening due to changes in its crystalline structure.

What Is a Chuck?

A chuck is a mechanical drive unit used in machining centers and automated assembly machines to grip the material (workpiece) to be processed or the processing tool.

For example, a chuck is an electric hand attached to a robot arm or a part that holds the cutting tool of a milling machine or drilling machine.

There are various types of chuck depending on the application, and there are multiple ways to install chuck.

Uses of Chucks

The use of chucks depends on what you want to achieve with it. Typical applications are shown below:

1. To grip the material (workpiece) to be processed
   Chucks are used as a hand for a robot arm, etc.
2. To fix a tool to process a workpiece
   For example, chucks are used to hold tools to process a workpiece on a milling machine or drilling machine.

When you want to clamp a workpiece without damaging it, you can control the clamping force by attaching silicone or other material to the end of the chucks. In this way, various innovations are made to suit the purpose.

Characteristics of Chucks

There are various types of chucks, each with its own characteristics. Typical chucks and their features are listed below:

1. Scroll Chuck
   It has a scroll-shaped cam inside. All the jaws are interlocked, and simply rotating the handle at one point drives all the jaws simultaneously. Since all the jaws are interlocked and move in the same motion, it is suitable, for example, for gripping cylindrical workpieces.
2. Independent Chuck
   In contrast to scroll chucks, independent chucks are chucks in which all jaws are driven independently of each other. Since each jaw is independent, the amount of movement can be set for each jaw. This type of chuck is used to grip workpieces with complex shapes.
3. Magnetic Chuck
   Magnetic chucks use electromagnets or permanent magnets to attract the workpiece by magnetic force to hold it in place.
4. Vacuum Chuck
   This chuck creates a vacuum and grips the workpiece with the force of the vacuum. It is used to grip small workpieces, or when there is a risk of damaging the workpiece with hard jaws.

What Is a Thumb Screw?

A thumb screw is a screw that is intended to be tightened or loosened by hand without using tools such as screwdrivers. Because thumb screws are tightened by hand, the head part is characterized by its large size and finger-friendly shape.

A thumb screw is ideal for locations where they are repeatedly taken on and off. Since they are tightened by hand each time, the screw-tightening force is not consistent. It is necessary to consider the type of person who will be installing and removing the screws, and whether there will be any impact if the screw is not tightened properly.

Uses of Thumb Screws

Thumb screws come in both male and female types. As mentioned above, they are used in various fields, including office equipment, household goods, furniture, industrial equipment, assembly, and processing jigs, due to their ease of use. At home, they are used as lids for replacing batteries in electrical appliances, for fixing cameras on tripods, and for smartphone stands. In industrial equipment, they are used to secure covers, guides, and other items that users remove when conveyance is jammed. They are also used for fixing parts in jigs at processing and assembly sites.

Principle of Thumb Screws

When a product is equipped with thumb screws, the user intuitively understands that it is a part that can be removed. It is characterized by the fact that it can be easily attached and detached and also has the effect of pointing to the part. Conversely, thumb screws are not used for a part that is not to be removed (or a part that should not be removed) because it is easy to assemble.

In most thumb screws, the threaded part is made of metal. The knob part can be made of either resin or metal, but in the case of resin, injection molding allows for a wider range of designs. Many of them are designed to be easier to grip. There are also simply circular thumb screws regardless of whether they are made of metal or resin. In such cases, they always have knurling around the periphery. This is to make it easier for fingers to catch on the knob.

When designing thumb screws, it is important to note the following: the thumb screws must be strong enough to handle the weight and vibration of the part, there must be enough space to turn it by hand, and there must be no problem if the thumb screws happen to fail.