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Taizhou Union Plastic Mould Co.,Ltd

ADD:No.26, MaoFeng Street, Beicheng Development Area, Huangyan Dist., Taizhou, Zhejiang, China

Post Code: 312080

Contact:Ms vicky






No Spraying Material For Injection Molding Process And Mold Requirements
Mar 09, 2019

Requirements on injection molding process and mold of spray-free material:

High-gloss and high-brightness, high-gloss steam mold and high-temperature and high-pressure injection molding parameters;

High addition amount of mineral/metal powder, wear resistant material for mold material;

For the single-gate mold, it is necessary to select the proper glue injection position and shape of glue mouth according to the product size.

For injection molding products with multiple plastic ports, the injection method shall be sequential injection.

Requirements of free spraying material for product structure design:

Little holes

Less rib

Avoid complex structure

Common paint-free resin, mainly ABS, PMMA/ABS, PC/ABS, high-gloss ABS, etc., these materials are suitable for products that need a better surface gloss, but not all product structures can be done with paint-free material, because, especially for the surface has obvious hollow structure; The back of the product has more screw column, buckle, reinforcement, etc. The product wall thickness is uneven, the middle position part is thinner and so on.

Three typical product structures that are prone to flow marks and fusion wiring, but not limited to the above three, are prone to these problems in complex product structures. And to improve these problems must be the product structure, mold structure, molding technology, materials at the same time to achieve the four aspects, so the application of non-spraying materials in actual products, the need for rich experience accumulation and systematic solutions to ensure the smooth progress of the project.

1. The product surface has obvious pore structure

To melt in the filling process, in the surrounding parts of the hole after shunt to meet again, and then create a weld line in the region of convergence problem, for normal dyeing material, weld line is only a fine line, for avoid spraying material, "visual" weld line on both sides of the color difference, so the weld line showed more obvious, therefore, apparent surface has obvious holes class product structure, generally avoid spraying material are not suitable for direct injection molding directly.

2. The back of the product has a lot of screw column, buckle, reinforcement bars and other product structure

In the process of injection molding, when filling the position of screw column, the melt adhesive will generate shunt, part of the melt adhesive will vertically fill the structure of screw column/buckle, and part of the melt adhesive will horizontally fill the appearance surface of the product, resulting in the reduction of the amount of glue flowing horizontally. Therefore, the flow mark problem will occur in this position due to the change of material flow state.

3. The structure of uneven wall thickness and thinning of the middle part of the product

In the filling process, compared with the thinning part in the middle, the flow velocity on both sides is significantly faster than that on the thinning part, and both sides form a coating towards the middle, so a binding line will be formed at the thinning end.


Although, free of spraying has a variety of benefits, but it is true that for these difficult to deal with the structure of the product, its application is relatively limited, product defects are more prominent. However, spray free products are still widely used in: refrigerator panel, air conditioning panel, decorative strip, speaker panel, base, LCD TV panel, small home appliance shell, cosmetics packaging and so on