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Common Issues about Paper Molding Products

When making paper molding products, there are always some questions which confuse customers, here are some common issues about paper molding products, hope will be helpful to our customers.

Why is the weight of the paper molding products inconsistent?

Firstly, the concentration of pulp is changing. When the prepared pulp with a certain concentration is released from the forming machine during the production process, the pulp concentration will begin to change, and it is generally controlled between 2.56% and 3.6%. Secondly, the vacuum is constantly changing. In the molding process, the negative pressure value of the negative pressure tank loaded by the air compressor is also variable as the production progresses. The superposition of the two variables causes the weight of the paper tray formed by the same suction time to vary between ±10%.

Why can’t you do the perfect color I need of the paper molding products?

The color of paper molding products, mostly are add dyes in the pulp proportioning process. One is that the change of the pulp concentration also leads to the change of the dye concentration as the production progresses, and the other is that most dyes are sensitive to temperature(during the drying process, the color changes with the temperature change, and the temperature of the mold during hot pressing is 150℃~250℃, and the dye will also change at different temperatures). In summary, products with higher color requirements should not be dyed.

How to make paper molding products smooth and tidy?

The paper molding products are completely wet after molding. After the drying process, it will be deformed, and then to restore the original design geometry by using hot pressing mould(temperature:150~250℃,pressure:3T~50T). Because the hot pressing mold is vertically stressed by the upper and lower molds, the plane position is strong, the paper holder appears smooth, and the inclined surface is not easy to receive force and appears slightly rough. According to the actual requirements of product design, the smaller the inclined surface, the more ribs, the smaller the plane, and the more spherical arcs, the more the smoothness decreases after shaping.

Why are there slight cracks on the surface of the paper molding products?

When the paper molding product is formed, the pulp fibers will naturally gather together layer by layer. The liquid pulp will not flow out in some grooves, which will cause the thickness of the different positions of the paper molding products to be different from the design standard thickness after drying. Then, when the paper molding product is squeezed by a strong external force during the high pressure forming process, the outermost fibers with uneven inner and outer thickness will break, and small cracks will appear from the surface. This phenomenon will not affect the strength of the paper molding products packaging, so it is acceptable in the industry.

Why are there uneven burrs around the flanging paper molding product?

Flanging structure paper molding products are formed with flat edges. When a vacuum is formed and the pulp is naturally absorbed, the edge of the mold is a stainless steel filter screen. The edges of the gathered pulp fibers after being absorbed will be irregular batt. This is an uncontrollable process. After forming and flanging, the burr will turn to the side, will not affect the packaging, and will not be used as a production control element in the industry. If customers have high requirements for this, they can use trimming and die-cutting to remove burrs.

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