Molded tray
The full name is a plant fiber molded flat industrial tray. The raw materials used for the pallet are wood shavings, plant straws, etc., which is an integral structure, and the panel and 9 supporting feet are molded at one time. The surface of the pallet is flat and smooth, which can meet the transportation of various goods, and the lower surface is provided with reinforcing ribs. The horizontal and vertical force of the board is balanced, and the distribution of nine feet can meet the four-way insertion of the forklift. It belongs to a single-sided pallet with a four-way fork.
Causes of molded tray
The pallet is a carrier for stacking goods, and it is a tool for mechanized loading, unloading and handling. The pallet aggregates the scattered small goods and containers in a certain amount, and is transported in the form of a unit together with a forklift to form a transportation system for the container unit. Therefore, the pallet has become an indispensable and important tool of the modern logistics system and is widely used by countries around the world. With the development of the national economy, especially China's accession to the WTO, the transportation of goods is increasing, and the demand for pallets is also increasing. In the past, most of the pallets used solid wood as the raw material to meet the needs of the pallet market. However, with the decrease of forest resources, the full use of small-diameter grade wood, wood processing residues and wood fiber materials has been paid more and more attention. Germany and the United States have successively researched and developed wooden molded wood shaving trays to improve wood and wood fiber materials. Utilization rate.
In 1971, Werzalit Company invented the patented technology of adding new molded tray 1210 double layer and aviation tray mixed with thermosetting resin wood fiber material and wood shavings to manufacture particle board. Litco used the technology in 1979 to establish the first molded wood pallet plant (Presswood Pallet Plant).
Molded industrial pallets are an important category of wood chip molded products. They are mainly used for transportation and storage of goods in docks, freight yards, warehouses, workshops, shopping malls, etc. It forms a mobile unit or handling unit with the goods, and forklifts, pallet trucks, cranes And other coordination. The general specifications of industrial pallets are 400 mm ~ 600 mm, 600mm ~ 800mm, 800mm ~ 1000mm, 1000mm ~ 1200mm, 1100mm ~ 1100mm. The dynamic load-carrying capacity is from 250kg to 1500kg, the pallet's own weight is 10kg to 20kg, the curved edge of the pallet, channel beam and ingenious perfect rib design make the load factor up to 80 (dynamic load). The shaving moulded industrial pallet is shaped and has a thin shell with equal strength. It has light weight and high strength. Its load-to-weight ratio (load capacity) is as high as 60 ~ 80 (dynamic load) and 200 ~ 300 (static load).
The technological principle of pallet production
The finely divided wood chips are first steam dried from high temperature to low temperature from 148 ° C to 138 ° C, heat treatment time is 30min, and then mixed with thermosetting resin, placed under 220 ° C for compression molding, and the pressure is 1400psi or 98kg / cm3. During this process, the internal temperature of the tray reaches 105 ° C, and the time to keep the internal temperature of the tray above 56 ° C for more than 30 minutes, and the final moisture content of the product does not exceed 9%.
The entire production process is carried out under high temperature and high pressure, which kills any insects and fungi remaining in the wood. At the same time, due to the high density of the wood products produced, it can prevent any other insects from re-propagating and re-invading. This molded product is the latest "artificial wooden packaging material" instead of the traditional "solid wood packaging material", its products no longer need to be treated with insects, and there are no live insects in the products, which conforms to ISPM15 (Insternational Standard for Phytosanitary Measures 15 ) The demand for wood packaging products for export, and after various cycle life fatigue tests, without any special treatment, can be shipped to other countries with the goods.
Production process of molded tray
Preparation of raw materials and shavings: using light wood (the density of large pallets increases in weight), the shape of shavings is generally 50mm long, 10-20mm wide, and about 0.5mm thick. The small-diameter wood, twig wood or wood processing residues should be cleaned of dust, and the bark content should be strictly controlled, not exceeding 5% to ensure good shavings. The shavings thickness is 0.3 ~ 0.5mm as the top grade. After the wood chips are magnetically separated, they are sent to a double drum flake machine for processing into shavings, and then sent to a dryer. The moisture content of the shavings after drying should be controlled in the range of 2 to 3%. Small shavings and unqualified oversized shavings need to be sorted and removed.
Glue mixing: In order to prevent the shavings from breaking, it is not suitable to use a high-speed glue mixing machine. Generally, a roller glue mixing machine is used. Two spray systems can be provided to apply two types of glue that are not suitable for mixing together. Generally, isocyanate and urea-formaldehyde resin are mixed, or phenolic resin and melamine resin, the sizing amount is 2% -15%, generally 4% -10%. The metered shavings and the quantitative urea-formaldehyde resin are sent to the rubber mixing machine at the same time. The water content of the shaved shavings after mixing should be controlled within the range of 8-10%.
Paving and hot pressing: using special equipment, the paving is carried out in two steps, first paving the pallet feet and pre-pressing, and then paving the flat part of the pallet. Some shallow foot trays can also be paved at once. The punch is fixed on the upper movable beam of the hot press, and the concave die travels between the hot press and the paver. It is placed on the lower working table of the hot press and has a special demoulding device. Spread the glue-mixed wood shavings in the mold, and then pre-press and hot-press until the resin is completely cured, and then the mold can be lifted. Firstly, the shavings after sizing are quantitatively laid into a metal mold and cold-pressed for pre-forming. And then placed in a hot press to shape.
The whole edge: mainly for trimming, that is, removing the extra flash on the edge of the product.
The main technical characteristics of the product
(1) The moisture content is low, generally controlled between 6% and 8%, and the tray does not absorb moisture or deform during use.
(2) Stable size, light weight, no distortion and warpage.
(3) The dimensional accuracy of the molded products is high, and the specially designed ribs ensure the strength and precision of the products.
(4) The strength and rigidity can be kept constant, the natural defects of the wood itself are eliminated during the molding process, and the strength is higher than that of the products assembled by traditional wooden boards.
(5) The weight is 50% lighter than the pallet products made of hard hardwood wood.
(6) The rounded corners around prevent the product from being damaged during packaging and transportation. It can realize automatic binding operation and save operation time.
(7) Multiple trays can be stacked on top of each other. The height of 50 trays is about 7 feet. The static load is 10 times the dynamic load, and the pallet can be shoveled from four sides with a forklift.
(8) It can be transported to meet the import and export business without fumigation treatment.
(9) It can be manufactured using wood processing residues and waste materials and low-grade wood.
(10) The product is environmentally friendly and can be recycled, recycled, and reused, with low pollution and a recovery rate of up to 100%.
(11) The price is cheaper than traditional coniferous or broad-leaved timber.
(12) Using environmentally friendly urea-formaldehyde resin glue as an adhesive to directly mold wood shavings or wood fibers.
(13) Each standard container locker can hold about 1,000 pallets, which minimizes the user's transportation costs.
(14) The maximum carrying capacity can reach more than 2500KG.
(15) The same number of pallets saves 3/4 of space than ordinary wooden pallets. Forklifts can handle 60 pallets at a time, while ordinary wooden pallets can only carry 18-20 pallets at a time.
Current development of molded trays
Molded pallets now account for about 3% of the overall pallet market, and the market share after 2010 has increased by more than 150% compared to the previous market. The market share of solid wood pallets is declining at a rate of 30% per year. The remaining market is mainly occupied by molded pallets. Because molded pallets are a new type of environmentally friendly pallets, they have no pollution to the environment. The raw materials used are straws and branches. Recyclable resources, while also increasing farmers' income. Especially after the introduction of the "Twelfth Five-Year Plan", it fully complies with the content of the "Twelfth Five-Year Plan for National Economic and Social Development. The product has been recognized by the market and also received strong support from the country.
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