The medium density fiberboard manufacturing process graph

The medium density fiberboard manufacturing process graph is as follows:

↗ sewage treatment

The slices → hot-grinded→ dry → laid out → hot-pressed → saw edges→ sanded → plate embryo sorting → packed out of the warehouse

-Apply glue

In order to enable employees to better understand the production of medium fiber plate, here is a detailed introduction to the above-mentioned process manufacturing:

First, 1,chipping: it is the entire plate production of raw materials manufacturing workshop, mainly the pine wood into the production specifications of wood chips, in case of heat for fiber separation to provide better conditions.

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2, Keywords: mdf raw material types, wood specifications, pine wood ratio.

(1) Raw material type: medium fiber plate production of raw materials plant fiber, its cellulose content is generally more than 30%,the Company is used by wood fiber, it mainly includes logging residues (e.g. trail material, sheet, firewood), material residue (cut-off), plus residues (skins, wood cores, broken sheets and other foot material), as well as recycled waste wood, etc., can also be directly used in forest areas or wood processing enterprises to produce wood chips.

(2) Wood chip specifications: wood chip size qualified, uniform, flat, wood chip specifications are generally: 16-  30mm long, 15-25mm wide, 3-5mm thick.The type of chipper we use is a drum chipper to make the wood chips suitable for production in order to prevent feeding.

Spiral blocking, high power consumption, on the one hand, to adjust the gap between the flying knife and the bottom knife, The adjusted clearance is 0.8-  1.0mm. On the other hand, we should strengthen the timely control of the moisture content of raw materials, as far as possible to ensure that not less than 40%,so that the wood sheet neat and uniform, high rate of fit, less debris, but also improve tool life.

(3) Pine wood ratio: Because the strength of the medium fiber plate depends on the interwoven performance of the fiber and the process conditions at the time of binding, about the fiber form, in this brief introduction as follows:

A: fiber: It is generally divided into fibroblasts (commonly known as fiber) and heterocytes, the content of more and less heterocytes determines the good and poor fiber quality, generally speaking, Conifer heterocyte content is the lowest, and broad-leaved material, in addition to the content of the impact on quality, fiber form, chemical composition and raw materials, such as mechanical processing performance, relative to consider the strength of the plate should pay attention to the following points (1) length, length and width ratio of large fibers have better binding properties, (2) cell wall thinner, smaller than the wall cavity fibers in Fiber separation and thermal pressure process easy to flatten, become ribbon, softness is better, with a larger contact area, (3) length, coarse fiber qualified combination can fill the gap between fibers, increase contact surface, improve product density and binding strength, about chemical composition and raw materials mechanical processing performance here without much, the following table needles and broad leaves.

The averagelength and widthfibers is greatercell wall cavities
Conifer  (general)  3.57280.8
Broadleaf  (general)13755

In summary, the reasonable combination of conifer and  broadleaf can improve and stabilize the mechanics of wood. In addition to the above points, in the raw materials to strengthen the bark content and iron and other aspects of management, because the bark content of the board affects the static strength, water absorption rate, and iron will damage the equipment, reduce the operating rate.

B: hot grinding, the cutting workshop cut out of the wood chips by preheated cooking, mechanical separation of the fiber.

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Keywords: Preheat the cooking fiber separation for mdf board

1, preheated cooking: improve the plasticity of fiber raw materials, reduce power consumption, shorten the time to dissolve fiber, improve the quality of separation fiber, and we use the preheated cooking method is pressurized cooking process, and the most critical cooking pressure is the cooking temperature.

A Cooking temperature and time Cooking temperature (C)   Plastic (10-4s).
Uncooked wood chips (water content60%)1400
135 3660
155 4523
175 5501

As seen from the table above, the cooking temperature increases by about 50% from 135 to 175 degrees C, and the corresponding mechanical damage to the fiber is reduced when the fiber is de-fibreed, so the strength of the plate is increased. On the other hand, the cooking temperature can not be increased blindly, because the fiber raw material in poor toughness and reduced yield.

2, fiber separation, at present, the fiber board industry is divided into mechanical method and blasting method Mechanical method is divided into heating machinery method, chemical machinery method and pure machinery method, we use heating machinery method.

A   Heating machinery method, this method has two important factors are the elastic plasticity of raw materials and the frequency of external forces, in addition, the unit after force and wood wafer moisture content, etc. , will also affect the strength of fiber.

The bullet plasticity of raw materials, that is, the time to restore the original after the deformation of raw materials, such as long recovery time, then the fiber is easy to be cut off, such as the board described below for pre-treatment is this purpose.

External force frequency: external force action frequency is cut off by the fiber two intervals short, then fiber separation yield and quality is better, in the actual production, can increase the grinding disc straight diameter, improve the speed of the grinding disc, change the grinding disc profile and so on.

Fiber separation unit pressure and moisture content should be appropriate according to the requirements of the equipment reason.

Glue: the fiber produced by thermal grinding into the glue, can greatly enhance the board’s various mechanics, we are using argon adhesive, due to the production of glue production and production relationship is lighter, we are mainly to control the uniform application of glue, improve the stability of the operation to improve the ratio of glue in the plate, and the actual production affects the glue quality

The amount is mainly affected by the following aspects:(1) the ratio of urea to formaldehyde (2) reaction media

the PH value of the mass.(3) the reaction temperature and reaction time endpoint control (4) the reaction fluid concentration and the quality of the original material.

In the production of medium fiber plate for glue requires low viscosity and large permeability, because fiber than particle board, single plate has a larger surface area, so adhesive must cover the surface of fiber, as the saying goes, the finer the fiber, the greater the amount of glue used.

Waterproof agent, paraffin is a hydrophobic meltable, soft substance, mainly used to reduce the adsorption of fiber surface, so as to avoid surface adsorption of water caused by plate size changes and deformation. As a popular saying, the essence of paraffin is to add water repellent substances to the fiber, its main role is as follows: (1) partially block the gap between fibers, cut off the water transfer channel, (2) increase the water and fiber.

Third, fiber drying: hot grinding out fiber coupled with glue so that fiber moisture content of up to 40% –  50%,if not dry treatment fiber difficult to adapt to the follow-up section, in this

The process segment mainly controls the drying temperature at around 165degrees C and does not cause resin precuring, thus affecting thestatic (MOR) and pulling  (IB)  of the plate, and other mechanics.

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Keywords: drying mode drying temperature  for mdf manufacture

A:Drying mode: (1) Drying is the evaporation of the moisture in the fiber from the liquid phase to the gas phase, the fiber runs in a normal pressure pipe, and the hot and high temperature medium is in short contact, before the moisture is not evaporated, the temperature of the fiber itself will not rise sharply, there will be no fiber overheating damage and glue shrinkage and early curing.     

Guide the fibers to dry, allowing them to get heat and vaporize the fibers in the pipes

because of the use of primary air flow drying, drying time is short, therefore, to always pay attention to the change of drying temperature, especially not ultra-high control.

B:Drying temperature, which is the determining factor in determining whether the fiber is drying well or not, and it depends on the drying medium, we use oil and gas to heat up, the heat sink group from the actual short time to heat the drying system required hot air.

IV. paving: it will be dry after the fiber silo storage for a period of time fiber, through the feed fan to the paver, the use of real air flow to achieve the coarse molding of fiber, and then through the sweep roller and pre-press to achieve the plate bad molding process.

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Keywords: true air flow molding, plate bad pre-press mdf board molding and sawing

(1) true air flow molding: fibers by feeding fan to the paving machine,”Z”type tube so that the fiber flow down, and ensure that the fiber drop even, because in the lower part of the paving mesh belt is negative swing swing force Under the guidance of the method, so that the fiber in the lateral direction can obtain a small difference in thickness, out of the molding box of the plate bad sweep roller and by the electronic weight measuring device to adjust the amount of broom, so that the plate bad laid out fiber to obtain a set density.

(2) We are using a level of formal air flow drying, heat through the blower slab pre-press molding, basic molding of slab by pre-press application of a certain pressureForce and sawing remove the air from the interior, allowing the slabs to be compressed into blocks for transportation and wire transportation.

Transmission and hot pressure provide conditions for good mating, we use a continuous belt-type pre-Pressure, mainly by the guide roller before and after pressurized roller, pressure roller composition, pre-press molding

The slab must be cut by a cross-sectional saw to obtain a complete cross-section, conforming to the slab entering the hot press long width.

V. Hot pressure: it is an important process of medium fiber plate manufacturing, product quality and output of the decisive role, it is in the combination of heat and pressure, water gasification in the slab, evaporation, density increase, adhesive, waterproof re-distribution, raw materials in the various components of a series of changes, so that the formation of a variety of binding forces between fibers. The process of making a product meet and meet quality requirements.

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Keywords: hot pressure anti-thermal pressure process of mdf sheet                     

(1) hot press, the current medium and high density fiberboard production, hot press type, the main to have two, one is intermittent multi-layer heat press, the other is continuous press, we use the former, in this brief introduction of multi-layer hot press main part

Subs: a  simultaneous closure device;  b thickness control device; c oil road system;  d Equipment such as press and unloader. Here is a brief introduction to both closed and thickness controls.

At the same time closed device: press closed and open, through it so that the slab in the contraction and exhaust can obtain the same displacement, pressed out of the slab thickness is uniform. Thickness control device: mainly by the rotary encoder placed on the press and thickness gauge composition, rotating encoder is mainly to change the displacement signal into an electrical signal into a PC,  and by the program to control the press press pressure, decompression operation, and thickness gauge, used to heat pressure plate in the closing limit, play a safety protection role, such as when the loading plate leakage, orAvoid bending and deformation when closing and pressurized to protect the hot press plate from damage.

(2) Hot pressure process: about the thermal pressure process is mainly to master the temperature, time and its pressure, the role of the three elements of hot pressure.

A hot pressure temperature: hot pressure temperature improves the plasticity of fibers, for the combination of various keys to create favorable conditions, heat so that the water gasification in the slab, thermoset resin in a short heating time, due to friction reduction, increased mobility, conducive to accelerated curing, generally speaking, hot pressure temperature refers to the heat plate temperature, and the actual role is the temperature in the slab, generally speaking, the appropriate increase in thermal pressure temperature, can ensure thermal pressure performance (shown below).            

Hot pressure temperature   P (g/cm  3)MORIBabsorbent expansion rate  

But on the other hand, the hot pressure temperature is too high, then the board will appear strength and water resistance, the phenomenon of decline. In general, the choice of hot pressure temperature to fully cure the glue, improve the mechanics performance is better.

(2) hot pressure pressure, hot pressure pressure mainly has the following aspects of the role: (1) to overcome the rebound force of the billet;

The pressurized section, the second section is divided into high-pressure and low-pressure segment, the high-pressure segment makes the slab structure

Tight and drained air, to meet the thickness requirements, while the low pressure segment is the evaporation of water gasification,

Adhesive curing, the formation of various binding forces between fibers, for the choice of high-pressure segment should also pay attention to moderate, because if the selection of excessive pressure, then the surface density is large, core density is small, compression quickly, the density difference between the layers is more obvious, then the mechanics performance will decline, and the low pressure segment can not be too low, too low thermal efficiency is low, thermal pressure time is extended.                                    

(3) hot pressure time, medium density fiber slabs in hot pressure, no matter how high temperature and pressure, must be a certain amount of time, in order to ensure the transmission of heat and pressure to obtain the curing of glue, the production of a predetermined density and ideal density distribution of the plate products. While ensuring the best quality, the hot press time should be short. Hot pressure time determination and glue type and performance, fiber quality, slab moisture content, hot pressure temperature, pressure heating mode and slab thickness and density and other factors, in general, the appropriate extension of thermal pressure time, to improve the physical and mechanics of the product are beneficial, hot pressure time is extended, glue can be fully cured.

Saw edge: saw edge is to ensure that the product is uniform specifications, saw blade section in particular, it is important to pay attention to the use of saw blades, saw blades to be replaced in time, otherwise make the edge pull affect the appearance of the plate quality.

Sand: hot-pressed plate products surface uneven, pre-curing layer, low density, affecting plate performance and plate surface quality, and to secondary processing difficulties, in order to get a solid, smooth surface, control the finished product in line with the thickness tolerance requirements, the surface of the board needs to be sanded.

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Keywords: sand provid good quality mdf board

(1) Pay attention to the matching of sand belt models, and pay attention to the feed speed;

(2) The sand belt should be parallel to the sander working surface to prevent vibration, so as not to cause ripples on the plate surface;

(3) The amount of sand light should be calculated accurately to ensure that after sand cutting, the thickness deviation of the plate density distribution is symmetrical and the thickness deviation meets the standard requirements.

Sewage treatment:

Dry production of fiber plate basically no large number of industrial wastewater, it is mainly some of the input spiral out of the cork water for this kind of wastewater we mainly use anaerobic treatment, process flow diagram as follows: process:

Workshop wastewater → pre-precipitation → catchment sedimentation pool → anaerobic pool → air sink →

SBR pool → clean pool → fiber transitioner drainage →.

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