Frequently Asked Questions about Molded Plastic Products

Frequently Asked Questions about Molded Plastic Products:
1. Molded plastic creates dents
2. Lack of plastic products
3. Molded plastic produces silver streaks
4. Deformation of molded plastic
5. Cracks in molded plastic
6. Stress cracking in molded plastic
7. Reticular cracks appear in the molded plastic
8. Molded plastic bleaching
9. Molded plastic fusion marks
10. Paste spots and so on.

Injection molding of electrical casing

Increase the injection pressure, prolong the injection holding time, reduce the barrel temperature and mold temperature, and force cooling at the place where the dent occurs. Fill in the edge where the dent occurs. When there is a narrow space on the edge of the material where the dent occurs, thicken the edge of this part. The difference in the thickness of the designed product should be completely avoided. For ribs that are prone to dents, the long and narrow shape should be kept as short as possible. Increase the temperature of the mold, the temperature of the feeding cylinder, increase the injection pressure, and add a gas escape groove (depth 0.02~0.04mm) on the parting surface with a width of 5~10mm. Increase the gate, increase the flow edge, in the case of a large number of molds per mold. If the cavity is short of material, the gate of that cavity will be enlarged, and the configuration of the flow edge will be changed, and the gas escape pin will be added to improve the finish of the mold. Avoid designing different thicknesses of products, add gates where the products are thicker, understand the occasions where the products are used, and try to use materials with good fluidity if appropriate.

Injection molding of portable power supply shell

Dry the material completely. (The effect of drying at high temperature for a short time is not good, generally drying at 85C for 4 hours) Increase the temperature of the mold, lower the temperature of the heating barrel, and keep the injection nozzle of the barrel warm.
Make the flow edge thicker. Avoid designing product thickness differences, and add gates where the product thickness is thick. Fully cool and solidify in the mold (extend the cooling time timer), increase the barrel temperature, and reduce the injection pressure.
Allow mold cooling to homogenize. To avoid the difference in product thickness, set the gate (1-1) at the place where the product thickness is large, because the straight line is easy to cause warping, and a large R curve is made. The reversible bending mold of the product increases the number of ejector rods and increases the demoulding slope.
Warpage of molded plastic products: It means that the shape of injection molded products deviates from the shape of the mold cavity, which is one of the common defects of plastic products. With the development of the plastics industry, people have higher and higher requirements on the appearance and performance of plastic products. As one of the important indicators to evaluate product quality, the degree of warpage has been paid more and more attention by mold designers. Mold designers hope to predict the causes of possible warping of plastic parts during the design stage in order to optimize the design. Thereby improving the efficiency and quality of injection molding production, shortening the mold design cycle and reducing costs.

abs injection molding

Influence of mold structure on warping deformation of injection molded products
In terms of mold design, the main factors affecting the deformation of plastic parts are pouring system, cooling system and ejection system.
1. Design of molded gating system
The position, form and number of gates of the injection mold gate will affect the filling state of the plastic in the mold cavity, resulting in deformation of the plastic part.
The longer the flow distance, the greater the internal stress caused by the flow and feeding between the frozen layer and the central fluid layer. Conversely, the shorter the flow distance, the shorter the flow time from the gate to the flow end of the part, the thickness of the frozen layer will be thinner when filling the mold, the internal stress will be reduced, and the warpage will be greatly reduced. If only one center gate or one side gate is used, the molded plastic part will be distorted because the shrinkage rate in the diameter direction is greater than the shrinkage rate in the circumferential direction. If multiple point gates or film gates are used instead, warping and deformation can be effectively prevented.
When spot casting is used for molding, also due to the anisotropy of plastic shrinkage, the position and number of gates have a great influence on the degree of deformation of plastic parts.
Due to the use of 30% glass fiber reinforced PA6, a large injection molded part with a weight of 4.95kg is obtained by molding. Therefore, many reinforcing ribs are provided along the flow direction of the surrounding walls, so that sufficient balance can be obtained for each gate. But it is not that the more molded gates, the better.
In addition, the use of multiple gates can also shorten the flow ratio (L/t) of the plastic, so that the material density in the mold cavity is more uniform and the shrinkage is more uniform. At the same time, the entire plastic part can be filled under a small injection pressure. The lower injection pressure can reduce the molecular orientation tendency of plastics and reduce its internal stress, thus reducing the deformation of plastic parts.

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