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  • What are the common problems with polyurethane sole moulding?

    pu release agent

    In the molding process of polyurethane sole, the following problems usually occurred:

    (1)
    The B component does not dissolve or appear the turbidity phenomenon.
    Reason: ① heating is insufficient, ② B component and H2O reaction, ③ B component heating time is too long, the temperature is too high; the ④ B component expires.

    Solution: ① Confirm oven temperature and B material heating time: ② Replace B component.

    (2) The sole demoulding stricks to the metal mold.
    Reason: ① coating is not uniform, ② release agent is not suitable for water or Dmf;③ release agent ratio is not suitable; ④demoulding time is premature

    Solution: ① coating film removal agent, ②-③ change release agent, use Sakurai release agent MK-WB309 & MK-PU-111 has strong demoulding force&power. ④ adjustment ratio, ⑤ prolong demoulding time.

    (3) Mold demoulding expansion, and even completely cracked.
    Reason: ① demoulding time is premature, ② injection quantity is too much, ③ proportion is unsuitable, b material is surplus, and ④ wood core drying is insufficient

    Solution: ① Prolong demoulding time, ② reduce injection amount, ③ adjust proportion, ④ dry wood core.

    (4) Shrinkage deformation of forming products.
    Cause: ① injection amount is too small, ②a material in addition to excessive amount of water, ③ ratio is not suitable, a material overdose; ④ demoulding time is premature.

    Solution: ① Increase Injection Quantity: ② change resin, ③ adjust proportion; ④ prolong demoulding time.

    (5) A part of the epidermis of the molded product falls off.
    Reason: ① mold temperature is too low: ②a material in the water is too high, ③ injection balance is not good; ④ Release agent coating uneven

    Solution: ① Mold Temperature control in 45-55℃;② replacement resin; ③ Balanced injection: ④ re-coating the release agent

    (6) Blister in parts of molded products.
    Reason: ① washing solvent leakage: ② resin leakage, ③ pressure instability, ④ metering pump pulse: ⑤ resin mixed with bubbles.

    Solution: ① repair of the washing nozzle valve: ② adjustment three-way valve adjustment throttle hole: ⑧ replacement pump, ④ check mixing, piping;

    (7) The hardness is too high.  
    Reason: ① ratio is unsuitable, b material surplus, ② density is too high, ③ ambient temperature is too low.

    Solution: ① adjustment ratio, ② adjust density, ③ test hardness at standard temperature.

    (8) The match ratio is often changed.    
    Reason: The ① raw material temperature change is big, ② in the material tank does not have the pressure, the A and B material tank liquid level difference is big, ③ pump’s rotational speed change is big, ④ stirring head part has the sundry.

    Solution: ① Adjust the temperature to keep the material temperature stable, ② to reduce the level of liquid level, ③ repair metering pump, ④ cleaning stirring head.

    (9) The front of the forming bottom or the direction of the above into sponge-like.
    Reason: ① die exhaust bad: ② with more than a material, ③ emulsification time is too short, ④ die temperature is too high, ⑤ initial flow balance is not suitable.

    Solution: ① The exhaust hole on the mold, ② adjust the proportion, ⑧ reduce the catalyst dosage, ④ reduce the mold temperature, ⑤ check the instantaneous proportion.

    (10) The forming bottom has concave.   
    Reason: ① release agent coating too much: ② mold temperature is too high, ③ density is too low or due to the mold gas caused by the separation of liquid, ④ with more than a material, ⑤ initial flow balance is poor.

    Solution: ① Mold Spray release agent after the cloth to wipe the mold. or choose suitable release agent, ② adjust mold temperature, ③ increase density or open vent hole on die: ④ adjustment ratio: ⑤ Adjust initial flow balance.

    (11) Corrosion of epidermis.
     Reason: ① release agent is superfluous, ② demoulding agent is not suitable, ③ mold temperature is too low: ④ mix is too much than B material. 
    Solution: ① Clean Release agent: ② selection of suitable release agent, ③ improve mold temperature: ④ adjustment ratio.

    (12) The internal bubble hole is too large, the surface of the following part of the pouring liquid formed pinhole.
    Cause: ① mixed bad: ② stirring head impeller rust, ⑧ mixing rate is not suitable: ④ density is too low, ⑤ mix is not normal, ⑥ color paste quality problems.

    Solution: ① A ② change stirring, ③ improve stirring head rotational speed, ④ increase density, ⑤ adjust ratio: ⑥ change color paste.

    (13) The soles turn yellow too fast.
    Reason: ① liquid selection is not suitable, ② spraying state is poor, ③ in the workshop has oxidation gas.

    Solution: ① Choose to have yellowing effect of the original liquid: ② Inspection Spraying method is standard: ③ to keep the workshop ventilated; ④ to avoid sunlight, use thick packaging materials.

    (14) Forming the bottom bubble more.
    Reason: ① mold pattern is too deep, the pattern is complex, ② emulsification time is too short, ③ mold temperature is too high, ④ die exhaust is not good, ⑤ injection method is not suitable, ⑥ mould angle is not suitable.

    Solution: ① Adjust the assembly of the mold, or modify the pattern of the mold, ② reduce the dosage of the catalyst, ③ reduce the mold temperature, ④ on the mold to add vent hole, ⑤ in the place to concentrate the gas leakage, ⑥ adjust the mold placement angle to match the pattern.

    (15) The top of the forming bottom has big bubbles.
    Reason: ① casting head and mold between the distance is too long, injected in the mold in the impact of the formation of bubbles; ② mixing chamber and stirring head of the sealing state is not good to form bubbles, injected when the bubbles come out: ⑧ two of chloroform mixed with the original liquid together out of the clip. Solution: ① reduce the distance between the pouring head and the mold, ② check the mixing chamber and the stirring head seal; ③ Check two of the chlorine methane valves for leaks.

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