月: 2023年2月

What Is an Epoxy Paint?

Epoxy paint is a type of coating derived from epoxy resin, a form of plastic. Epoxy resin paint stands out for its superior adhesion compared to other resins used in coatings, such as melamine resin and acrylic resin. Its exceptional corrosion resistance and adhesive properties make it ideal for areas susceptible to rust.

Uses of Epoxy Paints

Epoxy paints are notable for their excellent corrosion resistance, attributed to their impermeability to moisture and oxygen. They are commonly used in marine environments, such as on ships and fishing rods, to prevent rusting. These paints are also employed on exterior walls, roofs, and other surfaces of residential buildings that are prone to corrosion.

Additionally, the solvent resistance of epoxy paints makes them suitable for coating the interiors of tanks holding chemicals like concentrated hydrochloric acid and concentrated sulfuric acid.

Types of Epoxy Paints

Epoxy paints are primarily divided into two categories: room temperature curing type and heat (baking) curing type. The distinction is based on the curing process and the type of resin used.

The room temperature curing type is often a two-component paint, combining a main agent with bisphenol A epoxy resin and a curing agent (such as epichlorohydrin), which is mixed just before application and cures without heating. This variety is prevalent as a primer, particularly in settings requiring corrosion and chemical resistance, like on ships.

The heat (baking) curing type, a one-component paint, requires heating to form a durable coating film. It’s mainly used as a powder coating, applied as a dry powder, and then baked to cure. This method enhances the hardness and adhesion of the coating film and is typically used for the inner and outer surfaces of pipes, electrical and electronic components, and other applications.

What Is a Resistance Welding Service?

Resistance welding is a technique that utilizes the heat generated by electrical resistance when current is passed through metal. This process involves applying an electric current to the metals to be joined under moderate pressure. The heat generated melts the metal, which then cools and solidifies, forming a strong joint.

Distinct from arc and laser welding, resistance welding relies on internally generated heat rather than an external heat source. This method directly melts the base metals, creating a strong bond without the need for solder or other welding aids, thus reducing costs. Moreover, weld marks are typically less noticeable, providing a more aesthetically pleasing finish.

Uses of Resistance Welding Services

Resistance welding is known for its efficiency, often completing processes faster than other welding methods due to the rapid melting of metal under current. This ease of automation, often implemented with robotics, makes it a popular choice in mass-production settings such as home appliances and automotive manufacturing. Its ability to achieve a visually appealing finish also makes it suitable for exterior parts of automobiles and railcars.

However, resistance welding is not suitable for all materials. It requires materials that conduct electricity, are not overly thick, and have suitable properties for resistance welding. Materials like nickel and stainless steel are commonly used in resistance welding services.

Principle of Resistance Welding Services

Figure 1. Principle of resistance welding

Resistance welding operates on the principle of using heat generated by electrical resistance when current is applied to metal. This process is a reversal of conventional electricity use, where resistance and the resulting heat are typically minimized. In resistance welding, however, this conductive loss is harnessed to melt and join metals.

The process is governed by four key factors, often referred to as the “four major conditions of resistance welding”: applied pressure, welding current, energizing time, and electrode shape. These factors are crucial in determining the quality of the welding.

1. Applied Pressure

Applied pressure refers to the force exerted by the electrode on the metal, facilitating the flow of electric current and affecting the stability of the weld.

2. Welding Current

The welding current influences the rate at which heat is generated and the speed of metal melting, impacting the overall strength of the weld.

3. Energizing Time

Energizing time, the duration for which the current is applied, directly affects welding efficiency.

4. Electrode Shape

The shape of the electrode impacts the distribution of the current and the area of metal melted, affecting the strength and quality of the weld.

Types of Resistance Welding Services

Resistance welding can be primarily categorized into two types: spot welding and seam welding.

1. Spot Welding

Figure 2. Spot welding

Spot welding involves welding at specific points using two electrodes. This method is effective for joining two metal rods with minimal heat distortion. However, care must be taken to avoid shunting in areas near existing welds.

2. Seam Welding

Figure 3. Seam Welding

Seam welding uses roller-shaped electrodes to create continuous, linear welds. While this method is efficient and strong, it can lead to heat distortion in the processed product.

What Is Laser Welding?

Laser welding is a technique that joins materials, typically metals, by melting and fusing them with a concentrated laser beam. This technology utilizes a special material to generate laser light, amplified and directed to the workpiece through optical fibers or mirrors. Concentrating the laser into a tiny spot allows for minimal thermal distortion and rapid welding speeds, making it an efficient process for precision work.

Uses of Laser Welding

Laser welding’s compatibility with automated systems, including robotic arms and CAD/CAM software, makes it highly adaptable for both small-scale and large-scale applications. It’s particularly beneficial in the automotive industry for frame and body welding, offering the flexibility to access hard-to-reach areas without the need for direct contact between electrodes and the base metal.

Principle of Laser Welding

The process begins with inducing emission to amplify light energy. Atoms excited by external light energy emit photons, initiating a chain reaction that amplifies the light in a focused beam. This beam, when directed at the target material, generates sufficient heat to melt and fuse the metal, facilitating the welding process.

Types of Laser Welding

Laser welding technologies vary, mainly classified by the state of the laser-generating material:

1. CO₂ Laser

A gaseous laser type using carbon dioxide to produce the laser beam, noted for its high efficiency and capability for continuous high-power output.

2. YAG Laser

A solid-state laser using a crystal medium made of yttrium, aluminum, and garnet, offering a higher energy absorption rate due to its shorter wavelength.

3. Disk Laser

Characterized by a thin disk-shaped crystal, disk lasers combine the properties of solid-state lasers with unique geometry for versatile applications beyond welding, including cutting.

4. Fiber Laser

Optical fibers doped with rare earth elements serve as the laser medium in fiber lasers, simplifying the oscillator structure for a more compact setup increasingly popular in modern applications.

Other Information on Laser Welding

Pros of Laser Welding

Laser welding offers precise control over the weld area with minimal impact on surrounding materials, making it ideal for tasks requiring localized welding. Its high energy density allows for the welding of materials with varying melting points, producing narrow weld seams.

Cons of Laser Welding

The process demands precise control over positioning and alignment due to its focused nature and lacks a pressurization step. Safety precautions are essential to prevent burns from reflected light and retinal damage from direct laser exposure.

What Is Surface Grinding?

Surface grinding is the final step in the metal and wood processing process (cutting, grinding, and polishing). In addition to finishing to improve the aesthetics of the workpiece, surface polishing is used to remove minute irregularities and fine precision adjustment to prevent rust and dirt from adhering to the workpiece. It is also used for paint removal, rust removal, and base finishing prior to painting.

Surface grinding includes abrasive grinding using a grinding stone with embedded abrasive grains, polishing with abrasives, and electropolishing, in which processing is performed in an electrolytic solution.

Uses of Surface Grinding

Surface grinding is widely used for DIY projects, removing scratches from car and motorcycle bodies, manufacturing industrial products, and in construction and building sites. Typical applications are as follows:

• DIY: Used for woodworking surface finishing, plastic processing, etc.
• Automobiles: Used to remove rust and scratches, and to produce a mirror-finish on the body after painting.
• Industrial Products: Used for finishing of furniture, bearings, bearings, aircraft propellers, ship screws, metal pipes, granite, etc.
• Construction and Architecture: In addition to paint removal from bridges and surface preparation prior to painting, it is also used for surface treatment of concrete, asphalt, and stone.

Types of Surface Grinding

Surface grinding processes include grinding wheel polishing, lapping, buffing, barrel polishing, electrolytic polishing, and chemical polishing. The features of each are described below.

• Abrasive Wheel Polishing: Abrasive wheel polishing is a process in which a grinding wheel with embedded abrasive grains is rotated and polished.
• Lapping: Lapping is a process in which the workpiece is placed on a flat surface called a lap and force is applied from above to rub the abrasive grains against the workpiece. There are two types of lapping methods: wet lapping using a liquid abrasive and dry lapping using a lap with embedded abrasive grains.
• Buffing: Buffing is a process in which a cloth buff is coated with an abrasive and rotated to polish the surface grinding of the workpiece.
• Barrel Polishing: Barrel polishing is a process in which the workpiece, abrasive stones, abrasive, and water are simultaneously fed into a large machine, which rotates or vibrates to mix them together.
• Electropolishing: Electropolishing is a surface grinding process in which the workpiece is immersed in an electrolytic solution and an electric current is passed between the anode and a suitable cathode.
• Chemical Polishing: Chemical polishing is a process in which the object is immersed in a chemical polishing solution (acidic liquid) to dissolve and polish fine surface irregularities.

What Is Lapping?

Lapping is a precision polishing method often employed for workpieces requiring high accuracy. This process involves rubbing abrasive grains (lapping agent) between a flat base (lap) and the workpiece. This action eliminates surface irregularities through abrasion, achieving a highly smooth finish.

While less efficient than grinding, lapping excels in delivering extremely smooth surfaces with high dimensional accuracy, making it ideal for the final finishing of workpieces.

Typically performed with specialized lapping machines, lapping can also be done by hand for intricate adjustments of shapes and dimensions not easily achieved with machines. Hand lapping, however, demands significant skill.

Uses of Lapping

Lapping is crucial in the finishing stages of products and parts where precise machining accuracy is paramount.

Effective in achieving high dimensional precision and mirror-smooth finishes, lapping reduces frictional resistance, enhancing the performance of mating and sliding parts. Consequently, it finds extensive use in precision components such as optical parts, gauges, and bearings. It is also integral in manufacturing semiconductor wafers, where smooth, parallel surfaces are essential.

Principles of Lapping

In hand lapping, for instance, a workpiece is pressed against a moving flat base (lap) with abrasive grains (lapping agent) in between. This movement causes the abrasive grains to grind away the workpiece surface gradually, resulting in a uniformly smooth and undistorted surface.

Machine lapping varies in its configuration, with changes in the shape and number of laps, driving methods, and types of lapping agents, depending on the workpiece’s material, shape, and processing requirements.

Lapping is categorized into wet and dry processes, based on the lapping agent used. Wet lapping employs a slurry of abrasive grains in a fluid, leading to a large-scale, non-directional finish. Dry lapping, in contrast, semi-fixes the abrasive grains on the lap, creating a sliding, scratching action that produces a more mirror-like finish with less work involved.

What Is Surface Grinding?

Surface grinding is a grinding technique where a high-speed rotating grinding wheel is used to create a flat surface on the work material. This process involves using a surface grinding machine and a rotary grinding stone.

Disc grinding, a related but distinct method, differs in purpose and technique from surface grinding. While disc grinding primarily focuses on smoothing surfaces and offers higher precision, surface grinding is aimed at enhancing the flatness and parallelism of the workpiece.

Uses of Surface Grinding

Surface grinding is commonly used for adjusting material thickness and improving flatness and parallelism. It’s particularly valuable in the finishing stages of manufacturing due to its ability to achieve micron-level precision and high surface finish accuracy. This method is extensively used in the fabrication of machine parts requiring strict parallelism and in semiconductor wafer processing.

Surface grinders, available in various configurations, are crucial in these applications.

Types of Surface Grinding

Surface grinders are categorized into vertical-axis or horizontal-axis types, based on the orientation of the grinding wheel’s spindle relative to the table. Additionally, they are differentiated by the shape of their tables, which can be either square or round. The combination of spindle orientation and table shape defines the specific type of grinder. The methods and features of each type are as follows:

• With a left-and-right moving table and the grinding wheel’s sides for grinding, this type excels in processing long workpieces, covering a wide area at once.
• Featuring a rotating table and using the sides of the grinding wheel, this type is efficient for mass-producing small parts.
• The most common is the method where the table moves left and right, and the outer surface of the grinding wheel performs the grinding.
• For mass production of small parts, grinders with a rotating table that uses the outer surface of the grinding wheel are preferred.

What Is Gun Drilling?

Gun drilling is a precision machining process used to create narrow, deep holes in a workpiece. Originally developed for drilling barrel holes in firearms, this technique employs a long, specialized drill bit.

This method is notable for its ability to create small-diameter holes with high precision and linearity. It is effective on hard materials such as chrome molybdenum steel, carbon steel for machine structural use, and chrome steel.

Uses of Gun Drilling

Gun drilling is widely used in various industries to produce components with deep holes. Its applications include manufacturing parts for electrical equipment, railroad cars, aircraft, ships, automobiles, machinery (like spindles, shafts, and cylinders), injection machine nozzles, hydraulic equipment, semiconductor heat plates, LCD production equipment, construction machinery, and more.

Principles of Gun Drilling

The gun drilling process involves:

• A carbide cutting edge (drill blade)
• A shank (handle of the drill)
• A driver (part holding the shank and connecting to the machine)

The gun drill has a lubricant passage, with an outlet at the tip for injecting lubricant. Grooves along the carbide cutting edge and shank enable the ejection of machining debris. By rotating at high speed and injecting lubricant through the tip, the drill shaves material while expelling debris through the grooves.

This mechanism allows efficient debris removal during machining, offering greater efficiency than other deep-hole drilling methods. Additionally, the lubricant helps control temperature and reduce tool wear.

Gun drilling is particularly suited for small holes, typically ranging from 1 mm to about 30 mm in diameter, and is less effective for drilling larger deep holes.