What is the difference between cold pressing and hot pressing? What is the difference between a hot

First, the nature is different.

The essence of cold pressing is to use the characteristics of plastic deformation of metal to make the microscopic convex peak on the surface of the workpiece continuously flattened. The metal under the convex peak is not only pressed down, but also extruded from the valley on both sides of the convex peak, which reduces the microscopic unevenness and thus obtains a small surface roughness.

When hot-pressed, the fibers are in close contact with each other, and the lignin and hemicellulose that are otherwise in a bound state are made.

The interdiffusion movement of the macromolecular chain segments and the macromolecule itself gradually strengthens until the intermolecular gravitational force and hydrogen bonding interact, so that the interface disappears and the gluing process is completed.

Second, the definitions are different.

Cold pressing: It is the wire head and terminal when wiring.

Crimping (with tools such as crimping pliers) is used instead of soldering, and no heat treatment is required.

Hot pressing is to heat the slab after pavement molding and press it at the same time to make a fiber board with certain mechanical strength and water resistance.

process. Whether it is a wet process for the production of rigid or semi-rigid boards, or a dry process for the production of rigid or MDF boards.

It has to be hot-pressed before it can be made into a plate.

Third, the principle is different.

The cold pressing operation requires a special cold pressing press with a fixture, as shown in Figure 18-1. Using this (typical) working method, the workpiece (cavity blank) is fixed in a precisely shaped retaining ring. This helps to control the flow of metals and guarantee a favorable particle structure.

In contrast to the so-called free cold pressing, which is used only once in a while, the tightness of the body in the ferrule contributes to the precision of the cold pressing.

In the production of rigid boards by hot pressing wet method, no adhesive is generally added, and mainly relies on moisture and the intercellular layer material of wood cells and the composition of the cell wall.

The adhesive action of the filler between the fine fibers completes the bond between the fibers.

The difference between the two: cold pressing is carried out at room temperature, and hot pressing is carried out above 100.

Cold pressing is a loose powder composed of particles at room temperature under a certain pressure and under an instrument to make a green body with a certain shape, size, strength and density. Generally, the cold pressing process is used in powder metallurgy, ceramic industry, and tablet production. There are two types of force loading: one-way and two-way.

The hot pressing pressure, hot pressing temperature and hot pressing time are called the three elements of the hot pressing process. The actual hot pressing process is the result of the combined effect of the state of the slab (wood raw materials, adhesives, moisture content, etc.) and the hot pressing elements.

Summary. A thermoelectric cooler is an electrical appliance that does not use refrigerants and has no moving parts. Its thermopile acts as an ordinary refrigeration compressor, the cold end and its heat exchanger are equivalent to the evaporator of an ordinary refrigeration unit, and the hot end and its heat exchanger are equivalent to the condenser.

When energized, free electrons and holes move from the cold end of the thermopile to the hot end under the action of an external electric field, which is equivalent to the compression process of refrigerant in a refrigeration compressor. At the cold end of the thermopile, heat is absorbed through a heat exchanger while electron-hole pairs are generated, which is equivalent to endothermy and evaporation in the evaporator of the refrigerant. At the hot end of the thermopile.

The recombination of electron-hole pairs occurs, and at the same time heat is dissipated through the heat exchanger, which is equivalent to the heat release and condensation of the refrigerant in the condenser.

A thermoelectric cooler is an electrical appliance that does not use refrigerants and has no moving parts. Its thermopile acts as an ordinary refrigeration compressor, the cold end and its heat exchanger are equivalent to the evaporator of an ordinary refrigeration unit, and the hot end and its heat exchanger are equivalent to the condenser. When energized, free electrons and holes move from the cold end of the thermopile to the hot end under the action of an external electric field, which is equivalent to the compression of the refrigerant in the refrigeration compressor.

At the cold end of the thermopile, heat is absorbed through a heat exchanger while electron-hole pairs are generated, which is equivalent to endothermy and evaporation in the evaporator of the refrigerant. At the hot end of the thermopile. The recombination of the electron group and the recombination of the hole-hole pairs occurs, and the heat is dissipated through the heat exchanger at the same time, which is equivalent to the heat release and condensation of the refrigerant in the condenser.

Do you have any more questions?

【Heat Press】

A hot press is a device that heats two pre-applied tinned parts with flux to a temperature sufficient to melt and flow the solder, and after curing, forms a permanent electrical and mechanical connection between the parts and the solder. Depending on the product, the heating rate can be selected. The titanium alloy indenter ensures uniform temperature, fast heating and long service life.

The indenter is specially designed to be horizontally adjustable to ensure that the components are evenly pressurized. Numerical control of temperature, clear and precise. A digital pressure gauge is available to preset the pressure range.

Areas of use:1Mobile phone manufacturers 2Touch screen manufacturer 3Computer 4Printer 5membrane switches, etc.

Cold press] Cold press, that is, refrigeration dryer compressor. The amount of water vapor in the compressed air is determined by the temperature of the compressed air: Lowering the temperature of the compressed air reduces the amount of water vapor in the compressed air while keeping the compressed air pressure basically constant, and the excess water vapor condenses into a liquid.

The refrigeration dryer (refrigeration dryer) uses this principle to dry compressed air using refrigeration technology.

Field of use: used in furniture production, speakers, wood, decoration, plastics, flat plywood, plywood, particleboard, veneer and other wood glued press parts processing and production. High production efficiency, suitable for the production of wood products components in various furniture production units and other industries.

Reference].

Cold press, no heating device;

The hot press heats the material to be processed and processes it!

The main difference between a hot press and a cold press is their working principle and application field.

A heat press is a machine that uses high temperature and pressure to process materials into the desired shape. It is commonly used to process materials such as metals, plastics, ceramics, etc., and can make a variety of parts and products. The working principle of the heat press machine is to heat the material to a certain temperature and then apply high pressure to make it form the desired shape in the mold.

The advantage of the heat press machine is that it can manufacture high-precision, high-strength products, but it requires high energy consumption and cost.

A cold press is a machine that uses low temperature and high pressure to process materials into the desired shape. It is commonly used to process materials such as wood, paper, rubber, etc., and can make a variety of parts and products. The working principle of the cold press machine is to put the material into the mold and then apply high pressure to make it form the desired shape in the mold.

The advantage of the cold press machine is that it is able to manufacture a large number of products, but the precision and strength are low.

Therefore, the choice of hot press and cold press machine depends on the requirements of the material, shape, precision and strength of the desired product.

The difference between pre-pressing and hot pressing Details:

Pre-pressing is the process of using a special roller to pre-press the glue clearing, rain flushing glue or wash the curd of the bucket water glue to partially dehydrate it to increase strength and hardness.

In the construction of the project (mostly referring to bridge construction), the Bailey bracket and the driven steel pipe pile are used as the load-bearing piles, which may produce settlement in the concrete pouring process, which will affect the overall force of the support. In order to avoid the occurrence of uneven settlement phenomenon in the pouring process, accurately know the inelastic and elastic deformation of the support under the load, test the strength, stiffness and stability of the support, and determine the adjustment value of the bottom elevation of the formwork, the engineering activity is called preloading. 、

Hot pressing refers to the uniaxial pressing of a powder or blank at high temperatures, which activates diffusion and creep phenomena. In addition, the gravity difference between the indoor and outdoor air columns or inside and outside the pipe caused by the temperature difference.

Hot pressing triad:

1. Hot pressing temperature.

The effect of temperature provides the energy required for the curing of the adhesive, increases the plasticity of the wood, and reduces the hot pressing pressure.

2. Time temperature curve.

The hot pressing temperature refers to the surface temperature of the hot pressing plate, and the actual heat transfer process of the slab is more complex.

3. The core temperature curve is divided into 5 sections:

In the T1 section, the surface layer of the slab heats up rapidly, and the temperature of the core layer does not change.

In the T2 section, the temperature of the core layer rises rapidly until the water begins to evaporate.

In the T3 section, the core temperature rises to 100;

In the T4 section, the core layer is kept at 100, and the moisture becomes steam and is discharged from the edge of the plate;

In the T5 section, the core temperature begins to exceed 100 and gradually rises close to the thermoplaten temperature.

Principles for determining temperature:

Factors such as the type of adhesive, the variety of wood-based panels, the production capacity of the equipment, the moisture content of the slab and the thickness of the plate should be considered when selecting the hot pressing temperature.

Typical hot pressing temperature:

For urea-formaldehyde resin glue, the hot pressing temperature of plywood is 105 120, particleboard 140 205, MDF 150 180. For phenolic resin glue, plywood 130 150 , particleboard with MDF 170 195

Didn't make it clear. If it is sealed, the pre-pressing is just connected and prepared, and the hot pressing has the strength and sealing.