Production technology of Chinese fir blockboard (2)

Drying, finishing and preservation of veneers

(1) Inner veneer (liner 1220mm): Rotary cut veneer with fir or poplar, which can be used to set up a small rotary cutting machine to make a fir veneer, or to buy poplar veneer. Whether it is fir veneer or poplar veneer, it must be tested according to the national standard of plywood. The moisture content should be less than 14%. If the moisture content is too high, it must be dried.

(2) Surface veneer (backsheet 2440mm): The surface backsheet is generally purchased in order to reduce the investment in large-format veneer manufacturing equipment. After the purchased veneer veneer or other tree species has arrived at the factory, it should be inspected according to the national standard of plywood. The moisture content is less than 14%. If the moisture content is too high, it must be dried.

(3) Drying and finishing of veneers: After the purchased vulture or poplar veneer is sent to the factory, it should be dried in time to prevent mildew. The moisture content of the dried veneer must be less than 12%, the thickness of the veneer must be uniform, and the thickness tolerance is ±0.1 mm. After drying, the veneers are cut by the shearing machine, then repaired by seams, and finally stacked neatly.

Slab preheating

(1) Gluing: At present, the production of blockboard is usually made of hot-pressed low-toxic urea-formaldehyde resin (UF) or melamine-modified urea-formaldehyde resin (MUF). The gluing equipment is a double-roll or four-roll gluing machine (with groove). glue roll).

(2) Billet and pre-compression: the billet is composed of the carpentry core board, the inner layer veneer and the front and back board according to the principle of symmetry, odd-numbered layer and texture vertical; the pre-compression is to stack the slab A certain period of cold pressing on the cold press first, after the initial gluing is flat, then enter the hot press hot press. In the production of 5-layer structure of Chinese fir blockboard, there are mainly three types of blanking and pre-pressing: one is the traditional process, that is, the double-layered inner veneer (2nd and 4th layers) and uncoated The rubber joinery core board (3rd layer) and the front and back board (1st and 5th layers) are combined together, one time with one plate and one preload; the second type is a new process, due to the thickness of the currently used back sheet Thinner, inner veneer (especially poplar) has large warping deformation or unevenness. It is often used to carry out a single-sided veneer inner veneer and uncoated table or backing plate. The board is pre- and hot-pressed, and then repaired, and then the inner layer of the veneer (liner) is glued, and the second board is pre-pressed with the joiner core board; the third type is also a new process. First, a single-sided glued inner veneer and an uncoated jigsaw core core board are firstly plated and pre-heated, then repaired, and then the inner veneer (liner) The side is glued on one side and the second plate and preload are carried out with the watch plate or with the back plate. The above three schemes, the first and the third are more commonly used, but the quality of the third scheme is most guaranteed.

(3) Hot pressing: The slab of the blockboard pre-pressed by the pre-pressing machine shall be hot pressed by a hot press. In the case of hot pressing, only one plate can be pressed at a time in each lamination interval, so a multi-layer hot press is generally used. The hot pressing process conditions when using urea-formaldehyde resin glue are: temperature 100-110 ° C, pressure 0 8-1.2 MPa, hot pressing time 8-12 min.

Trimming and sanding

(1) Saw edge and sanding: After hot pressing, the slab is longitudinally and horizontally sawed by a trimming machine, and then the surface of the blockboard is ground by a wide belt sander to ensure the surface of the blockboard. Smooth, uniform thickness, neat edge and format. (2) Inspection and grading and repair: The blockboard after sanding shall be inspected, graded and repaired, and then packed into the warehouse according to the grade.

Production equipment

Blockboard production equipment includes main processing equipment and auxiliary production equipment. The main processing equipment includes: band saw machine, drying kiln, cross-cut saw, double-sided planer, multi-blade saw, jigsaw machine, veneer dryer, shearing machine, glue applicator, pre-press, hot press, vertical and horizontal Saw edge machine, wide belt sander, etc. Auxiliary production equipment includes: rubber mixing equipment, sawing machine, grinding saw, sharpening machine, lifting platform, rail car, forklift, dust removal equipment system, boiler, etc. At present, there are many manufacturers of blockboard production equipment. This project can be based on domestic equipment manufacturers and purchase equipment according to the principle of “advanced performance, reliable quality, convenient use and reasonable price”.

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