Problems in injection mold processing and introduction of improvement methods


Author: MULAN -Plastic Molding Manufacturer

The main function of injection mold processing is to require the quality of the mold to clearly guarantee the quality of the product during the molding process. Different types of plastic molds and molding processes of different products have different requirements on the material, function and shape of the mold. With the emergence of high-speed molding machinery, the production speed of plastic molds and molds has accelerated.

Because the molding temperature is generally between 160-350, some have poor fluidity and fast molding speed, the molding surface temperature of mold parts will exceed 400 in a short time. When the working temperature of the mold is high, the hardness and strength of the mold will be reduced, resulting in early wear or plastic deformation of the mold. In order to ensure the precision and small deformation of the mold in use, the mold steel should have high heat resistance.

In order to reduce the temperature rise, the mold steel should have good thermal conductivity and low thermal expansion coefficient. In the processing of injection molds, the working conditions of molds with sufficient working temperature are mostly very harsh, and some molds often bear a large load, resulting in brittle fracture. The extrusion pressure is generally 10~35MPa.

Therefore, in order to avoid the sudden brittle fracture of the mold parts during the working process, the mold should have high strength and toughness. With the expansion of the use of wear-resistant plastic products, inorganic materials such as glass fibers often need enhanced plasticity. Due to the addition of additives, the fluidity of the plastic is greatly reduced, resulting in mold wear, so the mold is required to have outstanding wear resistance.

Adding flame retardant and polyvinyl chloride to ABS resin may release corrosive gas during the molding process, sometimes causing corrosion and damage to the mold in the air flow channel, so the mold steel is required to have excellent corrosion resistance. The prominent cutting function in injection mold processing is accompanied by the increase in size, complexity and precision of plastic products, which requires mold steel to have outstanding cutting function and less work hardening during cutting. In order to avoid the impact of mold deformation on precision, it is hoped to control the machining residual stress within a small range.

Mirror polishing The inner and outer surfaces of the cavity are lubricated, and the molding surface is required to be polished to a mirror surface, and the outer surface roughness is less than Ra0.4m, so as to ensure the appearance of the plastic pressed parts and facilitate demoulding. Precision mold inserts have high processing precision and high matching precision, and the cavity size precision is generally 3~5 grades. The joint surface of the mold cavity should be tightly sealed to prevent the molten material from entering the gap and causing leakage.

Many plastic items are beautified with striped pictures on the outside. In the leather industry, large embossed leathers are used, which requires die steels with better picture lithography properties. Common problems such as excess glue, potting, shrinkage, cracks, insufficient filling, wrinkling, pits, overflow, weld marks, warping, deformation, etc. before batching.

In addition to some of these problems can be improved by adjusting the machine on the injection molding machine, they can also be controlled by a few points in the injection mold design process: 1. The wall thickness should be as uniform as possible, and the draft should be large enough; 2. The transition part should be gradually and smoothly transitioned to prevent sharp corners. Sharp edges, especially pc products must not have gaps; 3. The gate runner should be as wide and short as possible, and the position of the gate should be determined according to the shrinkage and condensation process. If necessary, a cooling well should be added.

4. The surface of the mold should be smooth, with low roughness, less than 0.8mm; 5. Vent holes. The groove must be sufficient to discharge the air and gas in the melt in time; 6. Except for pet, the wall thickness should not be too thin, generally not less than lmm. In the large-scale injection molding process, in order to prevent the injection mold from being poorly formed due to poor reflow or uneven cooling, resulting in surface defects and deterioration, the above points can effectively avoid bad problems.

For more information about injection molds, please visit the official website of Xingye:

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