Knowledge points about plywood, series three.
- Briefly describe the measures to improve the output rate of single boards okoume plywood.
(1) Reduce the diameter of wood core. (Can use double card head with pressure roller rotary cutting machine; The power roller and ruler are used to reduce the rotary resistance moment of wood section, which is beneficial to reduce the diameter of wood core. To reduce the deformation of thick veneer after drying, can be used with tooth pressure ruler on the front of the veneer to eliminate the imbalance caused by the cracks on the back, this treatment is called veneer softening.
(2) is to determine the center and wood, that is, to improve the wood section in the rotary cutting machine installation benchmark.
(3) the wooden section is sawed and then rotated on the small rotary cutting machine, which can be put together as a whole veneer.
(4) Reasonable selection of broken veneer and narrow length veneer.
(5) Wet board edge sealing. (Especially when the thin veneer is rotated, the adhesive tape is used to stick on both ends of the veneer to prevent the veneer from being torn in the later processing and causing losses. It is rolled into a volume and stored for 1h and then dried, so that the adhesive tape can be tightly glued on the veneer.)
- Briefly describe the nature and three stages of wood unit drying greenply marine plywood.
Essence: Under the action of dry medium, through the heat and mass transfer process, the evaporation of free water and suction water in the wood unit, so that it meets the requirements of the production process.
(1) In the preheating stage, the drying medium is in direct contact with the drying unit, and the temperature of the material rises rapidly, generally without water evaporation;
(2) In the constant drying stage, the evaporation of free water is mainly, and the evaporation rate remains unchanged, which can be increased as much as possible;
(3) In the deceleration and drying stage, A evaporates the remaining free water and absorbing water in the second stage, and B evaporates the remaining part of absorbing water. The drying rate decreases gradually and the temperature of drying unit rises.
- What are the methods for determining the moisture content of veneer? Compare their characteristics of marine plywood manufacturer .
(1) Quantitative method. Disadvantages: Due to the long time required for specimen drying to absolute drying, it cannot immediately reflect the change of moisture content of veneer in the drying process.
(2) Resistance measurement method, disadvantages: wood damage, long operation time.
(3) Microwave measurement method, disadvantages: the veneer thickness change, wood structure uniformity and moisture distribution uniformity is more sensitive, can not get a repeatable result, the reading always fluctuates within a certain range.
(4) medium constant wet method, disadvantages: after long-term use, the reading is easy to drift, can only show the trend of moisture content increase or decrease, the measurement range is limited
- Briefly describe the drying characteristics of veneer and the main factors affecting its drying speed. Features: surface evaporation and internal diffusion of water.
(1) The higher the temperature of dry medium is, the faster the water movement rate is;
(2) The lower the relative humidity of drying medium, the faster the drying speed;
(3) With the increase of wind speed and airflow velocity, the critical layer thickness can be reduced and the drying speed can be increased;
(4) Veneer conditions: the higher the initial water content of a tree, the longer the drying time; B The thicker the board is, the slower the drying speed is.
- Briefly describe the advantages and disadvantages of veneer plywood mesh belt dryer and roller dryer.
Mesh belt dryer:
Advantages: the upper and lower mesh belt can provide proper compression force during the drying process of veneer to prevent the deformation of veneer
Disadvantages: belt length adjustment has an impact on transmission, will produce belt correction.
Excellent: it has the function of pressing and heat transfer. After drying, the flatness of the veneer is better than the mesh belt dryer for drying the backboard and core board. Roller dryer is mainly used for core plate drying.
- Briefly describe the measures to prevent dry shrinkage deformation and cracking of veneer.
(1) When the single sheet is dried, the edge overlaps 1~2mm when entering the board, reduces the evaporation speed of the edge, and removes deformation and cracking;
(2) When the strip veneer is dry, spray water on the width of 6mm on both sides of the veneer to delay the evaporation of water at the edge and reduce wavy deformation and cracking;
(3) During continuous drying, attach reinforcing tape to both ends of the wet board to improve the strength of the board in the transverse direction and prevent the end cracking of the bs1088 marine ply board.
- Briefly describe the two processes of veneer shearing.
(1) first cut and then dry process
The wet boards are cut directly after being rotated. That is, the board shears wet boards. Generally used in roller dryers. Due to the drying treatment after shearing, and the process will also appear processing defects, so the defects close to the edge can not be treated temporarily.
Transverse feed mesh belt air dryer
(2) dry after cutting process
The dry board is cut. Dry veneer shear can not consider the dry shrinkage allowance, cut out of the strip veneer in glue spell do not have to be aligned. Dry veneer shear classification is the veneer storage and group of billet judgment basis.
- What are the ways of splicing boards marine plywood colours? What equipment are used?
Veneer lengthwise, veneer binding
(1) longitudinal belt glue machine, longitudinal belt glue machine, commonly used to splice backplane suitable for various thickness of veneer splicing;
(2) Horizontal and horizontal belt gluing machine, mainly used to splice the whole core board, can also be used to splice the backplane, horizontal belt gluing machine,
It is suitable for gluing the veneer strips into continuous veneer strips and then cutting them into whole veneer strips.
- What is “three-board balance”? How to achieve “three board balance”?
(1) “Balance of three boards” : in plywood production, maintain a certain proportion between the number of panels, backboards and core boards to avoid misalignment.
(1) log sawing, as far as possible to concentrate the material defects to the core board wood section, cut off both ends of the large diameter crack, ring crack and end crack, and strive to more high quality board wood section.
(2) Veneer rotary cutting, special attention should be paid to improve the accuracy of the centering of the wood section, as much as possible to the whole veneer, to correctly install the rotary knife and pressure ruler, improve the quality of veneer, but also pay attention to control, use the middle cutter to less core plate.
(3) Veneer cutting, according to the material under the knife, reasonable sawing, strict control of processing allowance, avoid wasting panel and backplane materials, use good material tree production veneer.
(4) promote thick core structure.
- Why is the adhesive modulated?
(1) The wood-based panel prepared by sizing has higher bond strength, water resistance and aging resistance;
(2) Achieve fast curing speed in the bonding process, improve production efficiency;
(3) the glue has a certain activity period. Request a Quote