How to solve the dull surface of injection molded parts
Injection molding factories often encounter products with insufficient gloss when processing injection molded parts. Low gloss means the surface is dark and dull, and the transparency of transparent products is low. There are many reasons for poor gloss. General product surface gloss defects can be divided into the following three types: mold failure, improper molding conditions, improper use of raw materials.
1. Injection mold failure
Since the surface of the plastic part is the reproduction of the cavity surface of the injection mold, if the surface of the injection mold has defects such as scratches, corrosion, micro-holes, etc., it will be reproduced on the surface of the plastic part, resulting in poor gloss. If the surface of the cavity is oily and damp, the surface of the plastic part will be darker. Therefore, the cavity surface of the injection mold should have a good finish. The surface of the mold cavity must be kept clean, and oil and water stains must be removed in time. The type and amount of release agent should be appropriate.
The injection mold temperature also has a great influence on the surface quality of the plastic part. Generally, different types of plastics have different surface gloss under different temperature conditions, and the injection mold temperature cannot be too high or too low, which may lead to poor gloss.
In addition, the demoulding slope of the injection mold is too small, the thickness of the section is suddenly changed, the ribs are too thick, the gate and runner section is too small, the shearing effect of the gating system is too large, and the injection mold is not exhausted. quality, resulting in poor surface gloss.
2. Improper use of raw materials
Insufficient raw materials can also lead to poor surface gloss of plastic parts.
Reason: The moisture content in the molding raw material is too high, and the volatile components condense on the cavity wall of the injection mold and during the molding process, resulting in poor surface gloss of the plastic parts. Treatment method: The raw materials should be pre-dried.
Discoloration of raw materials or colorants results in poor gloss. High temperature resistant raw materials and colorants should be used.
The fluidity of the raw materials is too poor, the surface of the plastic parts is not dense, and the gloss is poor. Change to a resin with better flow or add the right amount of lubricant and increase the processing temperature.
If impurities are mixed in the raw materials, new materials should be replaced in time.
3. Improper molding conditions
If the injection speed is too fast or too slow, the injection pressure is too low, the holding time is too short, the booster pressure is not enough, the nozzle hole is too small or the temperature is too low, the dispersion of the fiber reinforced plastic is too poor, the cylinder temperature is too low, the melt Poor plasticization and insufficient supply may lead to poor surface gloss of plastic parts. The reasons for the occurrence should be analyzed in detail and then adjusted accordingly.
Of course, in daily production, the problems encountered may be far more than the above-mentioned aspects, so it needs to rely on rich past experience and related knowledge to solve.