Which production cost is lower, molded pulp products with trimming-free or margin trimming?
In fact, the trimming-free process consumes more energy than the margin trimming process.
The quality of the trimming-free molded pulp products is much less good than the margin trimming molded pulp products. Especially in the pulp molded tableware products industry, trimming-free molded pulp products edge fiber shedding , paper powder shedding, missing edge, yellow edge black edge phenomenon in the process of use affect the appearance effect and use performance of the products.
Due to many previous pulp molding equipment automation degree is low, can not achieve automatic margin trimming and automatic punching, are to manually cut edge, hand punching (side punching), so there are some trimming-free molded pulp products. More than 20 years of practice have proved that the trimming-free molded pulp products have poor quality, instability and low qualified rate, the cost of producing trimming-free molded pulp products is also very high.
In the past, because the pulp moulding equipment can not achieve automatic margin trimming , using artificial margin trimming is inefficient, so some factories consider using the free-trimming method. The free-trimming issue has been explored for over 20 years and was patented in 1998, but he effect has not been ideal. From the theoretical calculation and practical summary, making pulp molding products with using the trimming-free method. is more energy consuming than automatic margin trimming.
1. If pulp density is high, free-trimming production will have poor effect with serious burrs. So the pulp density is much lower than margin trimming process while producing trimming-free product. Generally, the pulp density of trimming product is 4-5% and of trimming-free product is 2-3%. At the same time, while producing 1t molded pulp products by vacuum suction filtration molding technology, the water discharge volume increases a lot, which is almost up to 2 times and even more. In that case, producing trimming-free product consumes a lot more vacuum than producing trimming product. Vacuum and heating are main energy-consuming links during molded pulp production process.
2. To achieve free-trimming processes, try to minimize burr at the edges of the molded pulp products during pulp molding. After the wet products ("wet blank") is transferred to the hot pressure mold, after the hot pressure mold is closed, no clamp force is applied to the mold, otherwise, the water steam generated by hot pressure will break the edge of the product, appear "cracked product edge" phenomenon or lead to more burrs on the edge of the molded pulp products. After the "wet products" are baked to a certain degree of drying, then the mold clamp force is applied to the mold to dry and solidify the wet products.
This baking process without mold force wastes a lot of heat, and another adverse consequence is the low density of the product. Resulting in the same amount of products stacked together, the stacking height of trimming-free products is much higher than that of margin trimming products, which greatly increases the cost of packaging and transportation. For example, the same 300piece 10-inch disc products are stacked together, and the stacking height of trimming-free products is 30-50CM higher than margin trimming products.
3. Regarding to free-trimming product row material problem, many manufacturers who have used the production technology give a feedback that 100% pure straw pulps such as bagasse pulp and rice straw pulp, etc., cannot achieve trimming-free effect. Thus, anfree-trimming d pulp should be mixed into them so as to achieve a certain effect.
4. Tree-trimming mold is high-priced.
5. The productivity of free-trimming product is lower than trimming product. As above several points show, ①trimming-free technology has large water discharge volume, long filtering time, which will reduce the production capacity; ②Long time virtual pressure process leads to low production capacity.
6. Large-small edge issue exists. While mold thermal expansion is inevitable, the filtering shaped molding does not expand according to thermal. Therefore, large-small edge issue is inevitable when the wet earth brick is shafted to hot pressing mold. The conversion will certainly occur especially for large plate (up to 1500mm) equipment. In conclusion, and verified by practical situation, production cost of trimming-free product is around 20% higher than trimming product.
Use trimming-free method to produce pulp molding tableware products manufacturers are: a A factory in Zoucheng City, Shandong Province, Guangdong Luzhou company , Qiaowang Company, some factories in Malaysia , but ultimately can not really realize the production of trimming-free molded pulp products. Later, these companies added margin trimming machines to cut the products. Guangdong Luzhou company simply removed the production trimming-free equipment no longer use.
These are all past experiences and lessons.
In the pulp molding products, there are a large number of molded fiber clamshell take-out containers. The clamshell consists of the tops cover and the box body. They feature a tab locking system that keeps the tops securely fastened. Small sizes have one tab lock and larger have two. So, the label locking system requires one or two narrow holes on the side of the bottom box of the clamshell.
margin trimming products
Fully automatic pulp molding and trimming machines can laterally punch out these narrow holes during product production, and the narrow long holes are neat and beautiful, with good sealing performance.
The method of making narrow long holes by free-trimming process is to form these narrow long holes when absorbing filter and forming wet billet. After hot pressure and drying, the product retains these narrow long holes. But suction molding is difficult to make narrow long holes on the side, because the narrow long holes easily turn into large width. Wide long holes seriously affect the sealing effect of the label locking system on the clamshell. The wide holes produced by free-trimming process are bonded by a lot of broken fibers that are easy to shed. It affects both use and hygiene. If used in food containers, it may attract complaints from users.