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Injection molding process
by：CSSSLD
2021-01-23
Adjusting the wet process is a kind of plastic water content of post-treatment process, it is mainly used for moisture absorption is strong and easy to oxidation of polyamide plastic parts, etc.
Wet processing besides can eliminate the residual stress under heating condition, still can make injection molding processing parts in a heating medium to achieve balance of moisture absorption, in order to prevent the use process change size.
Wet processing medium is commonly used in the boiling water or potassium acetate solution, heating temperature is 100 -
121℃。
The thermal deformation at high temperature limit, instead take a lower limit.
Holding time and the thickness of plastic parts, usually take 2 -
9h。
after the pressure, piston or screw back, contact with molten material in the cavity pressure, at this point, the liquid pressure in the cavity will be higher than the pressure in front of the gate. If the gate has not been frozen, occurs in the cavity by melting casting system backflow phenomenon, make plastic parts produce the defects such as shrinkage, deformation and the soft. If removal of injection pressure, the gate has been frozen, the backflow phenomenon would not exist. Thus, backflow whether or go back to what extent, are related to the holding time.
annealing is molded parts in a fixed temperature of heating medium in the heat treatment process of heat preservation for a period of time. Using thermal return when, can accelerate plastic in macromolecule relaxation, thereby eliminating residual stress after plastic molding. A well annealing temperature in a plastic piece using temperature above 10 - 10-20 ℃ below the thermal deformation temperature To choose between 20 ℃ and control. Heat preservation time is associated with plastic varieties and the thickness of the plastic parts, can generally be calculated at every mm about half an hour. Cooling annealing, the cooling rate should not be too fast, or you will produce stress.
the holding time is longer, the holding pressure within the cavity on melt action time is longer, back is lesser, the contraction of plastic parts be mitigated. And the holding time short, the opposite situation. Cooling process of plastics within the mold refers to the plastic melt completely from the gate to freeze time have plastic parts from the mold cavity will launch so far all the process. At this stage, the feeding or back are no longer continue, within the cavity plastic cooling, hardening and finalize the design.
when parting, plastic parts with sufficient rigidity and does not produce warping and deformation. As the cooling process, the temperature continues to drop, plastic shrinkage cavity, pressure drop, to open mold, the pressure inside the cavity down to the lowest, but is not necessarily equal to the atmospheric pressure. Residual stress is positive, the demoulding is difficult, easy scratches or cracks, plastic, residual pressure is negative, the defective or internal vacuum bubble on the surface of the plastic. So, only in the residual stress is close to zero, parting is more convenient, and can obtain satisfactory plastic parts.
plasticizing good plastic melt in the injection molding machine piston or screw propulsion, at a certain pressure and velocity through the nozzle and the mould gating system to enter and full of mold cavity, this stage become mold filling. After the mold filling, the injection molding processing and injection molding machine piston or screw, driven by melt still keep pressure to fill material, make the continued melting of cylinder cavity, need to supplement the plastic shrinkage cavity. The holding time should be appropriate, long the holding time is easy to make the plastic produces stress cause plastic parts warp or crack.
the cooling speed of plastic parts should be moderate, if cooling too urgent. Or cavity in contact with the plastic melt temperature is different, each part will cause uneven cooling and shrinkage, produce plastic stress and warping deformations. Plastics can open mould after cooling, the introduction agencies, under the action of outside will launch mold plastic parts. Due to uneven plasticizing or due to plastic within the cavity of the crystallization, orientation and uneven cooling and partly due to the influence of metal insert, plastic internal inevitably exists some stress, resulting in plastic deformation in the process of using or cracking. In order to solve these problems, some appropriate on plastic parts for post-processing. Commonly used post-processing method has two kinds of annealing and wet.
more excellent articles: the parting surface design principles, click directly.
http://www。 csssld。 cn//html/2017/Info_0503/569。 HTML
nantong on suye's official website: http://www. csssld。 Cn / /
more wonderful articles, immediately search: changshu da plastic products factory smoothly
after the pressure, piston or screw back, contact with molten material in the cavity pressure, at this point, the liquid pressure in the cavity will be higher than the pressure in front of the gate. If the gate has not been frozen, occurs in the cavity by melting casting system backflow phenomenon, make plastic parts produce the defects such as shrinkage, deformation and the soft. If removal of injection pressure, the gate has been frozen, the backflow phenomenon would not exist. Thus, backflow whether or go back to what extent, are related to the holding time.
annealing is molded parts in a fixed temperature of heating medium in the heat treatment process of heat preservation for a period of time. Using thermal return when, can accelerate plastic in macromolecule relaxation, thereby eliminating residual stress after plastic molding. A well annealing temperature in a plastic piece using temperature above 10 - 10-20 ℃ below the thermal deformation temperature To choose between 20 ℃ and control. Heat preservation time is associated with plastic varieties and the thickness of the plastic parts, can generally be calculated at every mm about half an hour. Cooling annealing, the cooling rate should not be too fast, or you will produce stress.
the holding time is longer, the holding pressure within the cavity on melt action time is longer, back is lesser, the contraction of plastic parts be mitigated. And the holding time short, the opposite situation. Cooling process of plastics within the mold refers to the plastic melt completely from the gate to freeze time have plastic parts from the mold cavity will launch so far all the process. At this stage, the feeding or back are no longer continue, within the cavity plastic cooling, hardening and finalize the design.
when parting, plastic parts with sufficient rigidity and does not produce warping and deformation. As the cooling process, the temperature continues to drop, plastic shrinkage cavity, pressure drop, to open mold, the pressure inside the cavity down to the lowest, but is not necessarily equal to the atmospheric pressure. Residual stress is positive, the demoulding is difficult, easy scratches or cracks, plastic, residual pressure is negative, the defective or internal vacuum bubble on the surface of the plastic. So, only in the residual stress is close to zero, parting is more convenient, and can obtain satisfactory plastic parts.
plasticizing good plastic melt in the injection molding machine piston or screw propulsion, at a certain pressure and velocity through the nozzle and the mould gating system to enter and full of mold cavity, this stage become mold filling. After the mold filling, the injection molding processing and injection molding machine piston or screw, driven by melt still keep pressure to fill material, make the continued melting of cylinder cavity, need to supplement the plastic shrinkage cavity. The holding time should be appropriate, long the holding time is easy to make the plastic produces stress cause plastic parts warp or crack.
the cooling speed of plastic parts should be moderate, if cooling too urgent. Or cavity in contact with the plastic melt temperature is different, each part will cause uneven cooling and shrinkage, produce plastic stress and warping deformations. Plastics can open mould after cooling, the introduction agencies, under the action of outside will launch mold plastic parts. Due to uneven plasticizing or due to plastic within the cavity of the crystallization, orientation and uneven cooling and partly due to the influence of metal insert, plastic internal inevitably exists some stress, resulting in plastic deformation in the process of using or cracking. In order to solve these problems, some appropriate on plastic parts for post-processing. Commonly used post-processing method has two kinds of annealing and wet.
more excellent articles: the parting surface design principles, click directly.
http://www。 csssld。 cn//html/2017/Info_0503/569。 HTML
nantong on suye's official website: http://www. csssld。 Cn / /
more wonderful articles, immediately search: changshu da plastic products factory smoothly
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