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What should pay attention to when designing pulp molding products

Process of making paper pulp molding products

Paper pulp molding products have developed rapidly in recent years, becoming a new type of packaging material and a substitute for traditional wood packaging. The production process of the paper pulp molding products is raw material pulping, batching, molding, drying and shaping. After the paper pulp molding product is molded, there will be a lot of moisture, about 55%, and about 12% of the moisture in the process of making paper molding products. If you want to achieve this level, a lot of water needs to be removed during the drying process, and the heat absorbed becomes water vapor to be removed. Pulp mold products are processed into high energy consumption products.

Working forms of paper pulp molding machines

At present, there are two main working forms of paper pulp molding machines. One type of pulp molding machine uses an adsorption transfer network to enter the pulp tank, and then vacuumizes the pulp through a vacuum tube to suck up the filaments. The edge of this shaped product has trimming and is not smooth. Therefore, after the hot press molding of this type of paper pulp molding machine, a trimming design is required for trimming. Another form of the paper pulp molding machine is to use a quantitative bucket to supply the pulp, which uses the method of sucking filaments downward from the slurry tank. Such a pulp molding machine has controlled the burr problem, but this kind of burr problem still exists, and for customers with higher appearance requirements, trimming is also required.

According to the functional characteristics of the fundamental structural elements of paper plastic, paper tray, and environmental protection paper tray, the structure of the paper tray needs to be planned. The main points of the planning are as follows. Next, follow the Anyang General International Co., Ltd. to take a look at the design. What should you pay attention to when designing pulp molding products?

Fixed supporting surface. This is a fundamental point in the paper support structure planning. The fixed support surface can be confirmed according to the requirements of the packaged product, the external dimensions and the internal dimensions of the outer packaging. For example, if you want to plan a paper tray package for electrical products, you can confirm the length, width and corresponding structure of the paper tray according to the outer dimensions of the package and the internal dimensions of the outer packaging, and confirm the fixed support surface of the paper tray. 

paper molds

The focus of packaging is strength or cushioning. The packaging of some heavy and high-strength products focuses on strength, but it is necessary to maintain the cushioning function as a cushioning package, while the packaging of some valuable products focuses on cushioning. On the other hand, its packaging must also have a certain strength. In the planning, the two should be properly combined, and the appropriate base points should be selected according to the shape and structure of the packaged product, the center of gravity and the strength, and then the fixed support surface should be confirmed by these base points.

Mould cavity and stiffener. The cushioning effect of the paper tray is mainly realized by offsetting the external force from the elastic deformation of the paper wall when it is impacted. The elasticity of the paper support material itself is not high, mainly depends on the product’s stiffener plan and the buffer cavity formed. The cavity and stiffener plan play a crucial effect on the elastic deformation of the paper support. And the fundamental basis of the cavity and rib planning is the shape and purpose of the product itself.

Confirm the relevant parameters according to the requirements of the packaged product and the characteristics of the paper support product structure plan.

  • Scale and wall thickness. The fundamental requirement of the structure planning of paper molding products is to ensure close contact with the packaged objects and prevent the packaged objects from causing cross-motion during the circulation process. On this basis, buffering and shock-proof issues should be considered. Therefore, the size of the structure planning must be certain to be compact, the compactness of the scale is solved by the inductive cooperation of the fixed support surface, the cavity and the reinforcement ribs. In the structural planning, the wall thickness of the paper tray should be confirmed according to the operating conditions of the paper tray and the selected paper fiber type. Wall thickness is an important factor affecting the strength of the paper support. The addition of wall thickness not only adds raw material consumption, but also reduces production during adsorption molding. The addition of wall thickness also increases the energy consumption of the wet paper mold drying process, and makes paper quality defects such as dents, shrinkage holes and sandwiches are generated in the tray. Under the premise of meeting the strength of the paper support, the wall thickness should be reduced as much as possible. The wall thickness is between 0.5-6mm when the vacuum adsorption molding process is selected, and the wall thickness is between 3–20mm when the compression molding process is selected.
  • Demoulding slope. In the paper mold forming process, the wet paper mold is tightly attached to the mesh mold and the paper fibers will be embedded in the mesh. In order to facilitate the transfer of the wet paper mold, the surface of the paper support parallel to the demolding direction should be proper.  The larger the slope, the more convenient it is to demold. If the slope is too small, it will be difficult to demold, and it will also cause scratches or cracks on the surface of the paper support. Too large a slope will reduce the scale accuracy of the paper tray, and also affect the load-bearing ability and elastic recovery force of the paper tray. Generally, the draft angle is 3°-6°.

Specifications of pulper

Pulper modelsPulper volumeCorresponding egg tray machine modelsOutput (p/h)
ZDS44m³DT5×8; DT4×84000-5000
ZDS22m³DT4×4; DT3×82500-3000
ZDS11m³DT3×4; DTF4×1; DTF3×11000-2000
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