1) The ductility and tension of the fabric

The fabrics used for low-pressure injection Bucket Moulding are all bottom non-woven fabric + foam layer + surface fabric layer. Due to the compression of the mold and the extrusion of the molten plastic, the longitudinal and transverse extensibility of the fabric are different, and the phenomenon reflected on the product is different. . The most prominent problems are: seepage, breakdown, and damage. That is to say, when the mold state is constant and the process conditions are constant, the characteristics of the fabric have a great influence on the quality of the product. Similarly, the longitudinal and transverse elongation has different adaptability to different molds. Some molds may require high longitudinal elongation due to design constraints, and some molds may require high transverse elongation. Therefore, it is necessary to comprehensively consider this issue when trial production of new products and new molds.

2) The fluidity of plastic

The index for evaluating plastic fluidity is: melt index MI value. Everyone knows that the flow of plastic on the fabric must be much slower than that on the smooth mold cavity. This is why the low pressure injection mold for the fabric has more gates than ordinary molds. The slow flow rate will inevitably affect other appearance problems of the product, such as bond marks and material shortage.

(1) Breakdown

The sharp corners of the product are prone to breakdown. The parting surface at the sharp corners is matched with a gap. When the material volume or speed increases, the molten plastic penetrates from the gap. Too thick wall at sharp corners can easily cause breakdown.

(2) Seepage

The corners of the product are prone to seepage, the gate temperature of the seepage part is too high, the mold temperature is too high, and the amount of the gate material at the seepage part is controlled too much.

Improvement plan:

1) The wall thickness at the sharp corners is too thick to cause breakdown, so the wall thickness at the sharp corners of the mold is relatively thinner to prevent the fabric from seeping or breakdown;

2) Product preventive design, try to make the product surface transition smoothly, reduce the step difference, and avoid the rapid product transition;

3) Adjust the injection molding process parameters, reduce the mold temperature and melt temperature, reduce the amount of plastic injection, and reduce the injection pressure.

(3) Shrink at the glue mouth

Reduce the shrinkage, the gate should be less than Φ3, the length of the cold runner is 15, and the gate will increase cooling.

4) Lack of materials

The sharp corners of the product are prone to lack of material. Reasons: mold temperature is too low, the temperature of the gate at the lack of material is low, the amount of material at the lack of material is too little, the wall thickness at the sharp corner of the mold is too thin, injection speed, compression The speed is low.

(5) Fabric crush

Reason: The temperature of the mold used in low-pressure injection molds is usually low (10-15 degrees). If the anti-rust measures are not done well, rust spots will occur on the parting surface of the press fabric frame and the slider, which will press the fabric during production. Excess, the ductility of the fabric is limited, thus crushing the fabric.

(6) Glow at the R corner

Check whether the R angle is at a sharp corner, whether the product has a large warping angle but the R angle is not large enough, and whether the ductility of the skin meets the requirements.

(7) Cuticle strain

Check whether the demolding angle is sufficient; whether the Paint Bucket Mould surface polishing meets the requirements.