Free spray material on the injection molding process and mold requirements:
High-gloss and high-brightness, the mold uses high-gloss steam mold, injection molding parameters using high temperature and high pressure;
Minerals/metal powders are added in high amounts, and mold materials are made of wear-resistant materials;
For a single gate mold, it is necessary to select the appropriate position and shape of the plastic inlet according to the size of the product;
For plastic injection molding products, the glue must be fed in order.
Spray-free material requirements for product structural design:
Less holes
Less ribs
Avoid complex structures
Common non-spraying resins, mainly ABS, PMMA/ABS, PC/ABS, high gloss ABS, etc. These materials are suitable for products that require a good surface gloss, but not all product structures can be used spray-free materials To do it, because, especially for the surface there are obvious hollow structure; the back of the product has more screw posts, snaps, ribs, etc.; uneven wall thickness of the product, the middle part of the thinner.
Three typical product structures that are prone to flow marks and weld lines, but not limited to the above three, are complex product structures that are prone to these problems. To improve these problems, the product structure, mold structure, molding technology, and materials must be combined to achieve the four aspects. Therefore, the application of spray-free materials in actual products requires extensive experience and systematic solutions to ensure the project's Smooth progress.
1. Appearance surface has obvious hole structure
During the filling process, the melt is re-confluent after the shunting at the periphery of the hole, and then the weld line problem occurs at the confluent part. For the ordinary dyeing material, the weld line is only a thin line, and for the spray-free material Say, "visually" the color of the two sides of the weld line will be different, so that the appearance of the weld line is more obvious, therefore, the appearance of the surface has a clear hole-like product structure, generally not suitable for direct injection molding materials without direct injection molding.
2. Product structure with more screw posts, snaps, ribs, etc. on the back of the product
During the injection molding process, when filling the screw column, the melted plastic will produce a shunt, part of the melted plastic will longitudinally fill the structure of the screw column/snap, etc. Some of the melts will laterally fill the appearance of the product and cause the amount of glue in the lateral flow to decrease. This site has a problem of flow marks due to changes in the flow state of the stream.
3. Structure with uneven wall thickness and partially thinned middle position
During the filling process, the flow speed on both sides is significantly faster than the thinned part compared to the middle thinned part, and the two sides form a coating in the middle, so that a bonding wire is formed at the thinned end part.
to sum up:
Although spray-free coating has a variety of benefits, it is true that for these difficult-to-handle product structures, its application is still relatively limited, and product defects are also prominent. However, spray-free products are still widely used: refrigerator panels, air conditioning panels, decorative strips, speaker panels, bases, LCD TV panels, small appliances, cosmetics packaging.