Knowledge points about plywood, series two.

  1. Briefly describe the conditions of adhesives in wood-based plywood sheet production.
    (1) The adhesive should have enough fluidity to wet the solid surface well. Good wettability, to form a firm combination, this is the first condition.
    (2) the characteristics of various adhesives are not the same when they are used, and they should have different performance according to the requirements of use. The performance of the main viscosity, concentration, activity period, curing conditions, curing speed, etc.
    (3) the adhesive can form a firm adhesive layer after curing, with chemical stability, and the products have enough durability.
    (4) The internal strain of the adhesive joint formed by the adhesive should be small when its volume shrinks, and it should have the ability to gradually disappear.
  2. What are the chemical additives in wood-based panel marine plywood production? The function of curing agent and filler in plywood production was briefly introduced. Additives include water-proofing agent, flame retardant, curing agent, preservative and so on. Curing agent is a kind of acidic material, adding it to the resin, can reduce the pH value of the resin, and promote the resin curing material.
    The function of filler is to save the consumption of resin and reduce the cost of glue; Increase the solid content, viscosity and initial viscosity of the glue liquid, avoid the glue defects caused by excessive penetration of the glue liquid, can prolong the application period of the glue liquid, improve the operation; Prevent and reduce the internal stress caused by the shrinkage of the adhesive layer in the curing process, improve the aging resistance of the adhesive layer; It can also reduce the release of free aldehyde and reduce public hazards.
  3. Briefly describe the method of veneer manufacturing. Thin wood manufacturing methods generally have a method of cutting, planing, semicircular cutting method, such as a few categories.
    Planing method production needs to first planing logs into wood square, cooking, softening and then planing and cutting into thin wood on the planing machine. Planer cut thin wood grain li straight, suitable for all kinds of patterns.
    Rotary cutting is a precision rotary cutting machine to cut thin wood. The veneer obtained by rotary cutting is banded without splicing, which is easy to realize continuous chemical production.
  4. What is the basic unit of wood-based panel and basic unit processing? From large or coarse wood or non-wood raw materials through some reasonable processing, into a certain pattern and shape of the relatively small raw materials, that is, the basic unit. The basic unit of manufacturing is called basic unit processing.
  5. Purpose and method of plywood section softening.
    Objective :(1) to reduce the hardness of raw materials, increase plasticity, reduce stress for rotary cutting; (2) reduce the joint hardness, not easy to damage the tool; (3) to prevent the veneer from cracking and crushing too much; (4) Part of the sapwood resin and cell SAP come out after hydrothermal exchange, which is conducive to veneer drying, gluing and painting. Softening method: spray water; Boiling treatment method; Water and air simultaneously heating treatment method; Steam heat treatment; Pressure cooking; Cold alkali Method; Lye cooking method; Neutral sulfite method, etc. Request a Quote
  1. Briefly describe the concept, purpose and essence of wooden section centering. Concept: The operation that completes the coincidence of the center line of the segment rotation with the center line of the largest internalized cylinder is called fixed center.
    Objective: (1) The wood section has sharp cutting and bending, so it is inevitable to appear broken veneer and narrow long veneer in the rotary cutting, only after spinning into a cylinder, continuous strip veneer, only the correct centering, can make broken veneer, narrow long veneer reduction. (2) The increase of narrow and long veneer will cause the burden of post-processing, increase the cost and energy consumption, such as shearing, splicing, drying.
    The essence of the center of the wood segment: is to accurately determine the rotary center position of the wood segment in the rotary cutting machine, so that the maximum cylinder.
  2. What is rotary cutting, rotary cutting curve, nominal thickness of veneer, type I knife bed, type II knife bed?
    Rotary cutting: wood for fixed axis rotation movement, rotary knife for linear feed movement, rotary knife blade is basically parallel to the wood fiber, and vertical wood fiber length direction upward cutting, known as rotary cutting. Cutting curve: the track that the cutting edge of the rotary knife passes on the cross section of the wood. Nominal thickness of veneer: the feed quantity of tool rest when the wooden section rotates once.
    The first type of knife bed: the rotary knife does not move relative to the knife bed (does not turn), and only moves in a straight line with the knife bed. The second type of knife bed: rotary knife horizontal movement, and automatically around the horizontal plane through the card axis and the extension of the front of the rotary knife phase horizontal line for fixed axis rotary movement.
  3. What is the change of the back Angle required by the spin cutting process? Why is that?
    (1) The back Angle must be reduced as the diameter of the wood segment becomes smaller. Generally, the change of the back Angle in the process of rotary cutting is small at 1-3 degrees, and the wood segment is straight
    When the diameter is large, the rear Angle is 3-4 degrees, when the diameter is small, it is 1 degree or negative value;
    (2) too large, the reverse bending deformation of the veneer is large, easy to produce cracks, the tool rest is easy to vibrate, and the veneer becomes corrugated plate;
    (3) if it is too small, the contact area between the back of the rotary knife and the surface of the wood section increases, resulting in large pressure, resulting in the splitting and bending of the wood section, and the thickness of the single plate changes.
  4. Briefly describe the role of pressing teeth.
    (1) Can prevent the splitting phenomenon caused by the rotary knife force
    (2) The veneer is compressed, and its transverse tensile strength is increased, which is beneficial to reduce the cracks on the back of the veneer
    (3) A part of water is pressed out of the veneer to shorten the drying time of the veneer.
  5. How to evaluate the quality of ply boards?
    (1) Veneer thickness deviation, reasons: body density, back Angle, wood internal stress, pressure ruler stress, tree species, diameter class. After fruit: sizing quantity, plate thickness uneven.
    (2) Cracks on the back of the veneer, the reason: tensile stress is generated during rotary cutting. Consequence: Infiltrate into the veneer and affect the bonding quality.
    (3) Veneer back finish, reason: soft wood, easy to fuzz. Consequence: the roughness of the back is large, and the amount of sizing and sanding is increased.
    (4) Tensile strength of transverse grain of veneer

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