1、 Lack of material
Une fois que le matériau en fusion entre dans la cavité du moule, il n'est pas complètement rempli, ce qui entraîne une pénurie de pièces en plastique.
Causes et contre-mesures:
(1)Improper selection of equipment: when selecting equipment, the amount of melt glue on the machine must be greater than the amount of melt glue on the products, and the weight of pièces moulées par injection can only account for 85% of the total amount of melt glue on the machine.
(2) Insufficient material supply: if there is bridging phenomenon at the feeding port, the screw injection stroke can be increased appropriately to increase the material supply.
(3) Poor fluidity of raw materials: improve the retention defects of the mold pouring system, reasonably set the pouring position, expand the gate, flow channel and the size of the injection gate, and use a larger nozzle to properly increase the temperature of raw materials.
(4) Unreasonable design of gating system: when designing gating system, attention should be paid to gate balance, which is proportional to the weight of plastic parts in the mold cavity and gate size. It is that each mold cavity can be filled at the same time. The gate position should be selected at the original wall position, or the design scheme of balanced layout of runner can be adopted.
(5) Mauvais échappement du moule: vérifiez s'il y a une cavité de matériau froid ou si la position est correcte. Pour le moule à cavité profonde, une rainure d'échappement et un trou d'aération doivent être ajoutés à la partie sous-injectée. La rainure d'évent avec une profondeur de 0. 02-0. 04 mm et une largeur de 5-11 mm peut être ouverte sur la surface de fermeture. Le trou de ventilation doit être réglé à la position de remplissage finale de la cavité du moule.
(6) In the aspect of process operation, we can improve the mold temperature, reduce the injection speed, reduce the resistance of the gating system, and reduce the closing force.
(7) La température du moule est trop basse: le moule doit être préchauffé à la température requise par le processus avant le démarrage -. Si la température du moule n'augmente pas, vérifiez si la conception du canal d'eau du moule est raisonnable.
(8) Insufficient injection pressure: the injection pressure and the length of the die are close to a positive proportion. The injection pressure is too small, the length of the die is short, and the cavity filling is not enough. Therefore, the injection pressure can be increased by slowing down the injection forward speed and extending the injection time appropriately.
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2、 Deformation
Parce que le retrait interne du produit est incohérent, la contrainte interne est différente et la déformation est provoquée.
Causes et contre-mesures:
(1) Orientation moléculaire déséquilibrée: afin de minimiser le gauchissement causé par différentes orientations moléculaires, des conditions doivent être créées pour réduire le gauchissement. Orientation de l'écoulement et relaxation des contraintes d'orientation: la méthode la plus efficace consiste à réduire la température du plastique et la température du moule. Lors de l'utilisation de cette méthode, il est préférable de combiner avec le traitement thermique des pièces en plastique, sinon l'effet de réduction de la différence d'orientation moléculaire est souvent de courte durée -. La méthode de traitement est que la contrainte d'orientation dans la pièce en plastique peut être largement éliminée lorsque la pièce en plastique est démoulée et maintenue à une température élevée pendant une certaine période de temps, puis refroidie lentement à température ambiante.
(2) Improper cooling: when designing the structure of plastic parts, the section thickness of each part should be consistent as much as possible, and the plastic parts must be kept in the mold for sufficient cooling setting time. For the design of mold cooling system, it must be noted that the cooling pipe should be set in the position where the temperature is easy to rise and the heat is relatively concentrated. For those parts which are easy to cool, slow cooling should be carried out as far as possible to make the cooling of all parts of the plastic parts balanced.
(3) the first mock exam is not enough. The edges are not light. The plastic parts have a slope when designing the mold. If a product & #39;s uneven slope is distorted, the product will be rough and rough. In the design and acceptance of the mold, the angle of the supporting film and the smoothness of the edge should be considered.
(4) Cooling time: when the vulcanized plastic is filled into the mold cavity, there must be cooling time. The cooling time will cause the product ejection deformation. The product is not sufficiently cooled. When ejection, the product will also deform if it is relatively soft. If it is too slow, the product will completely cool in the mold cavity and ejection has no elasticity. The hardtop product will also deform, so the cooling time should be set appropriately.
(5) Injection process: injection process, pressure, speed, time, location, can make the product deformation. When setting the parameters, it should be considered repeatedly. When adjusting the machine, adjust the parameters slowly in 1 unit to obtain the best parameters.
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3、 Phimosis
Lorsque le plastique fondu est expulsé du moule de la surface de séparation. Un flash se forme lorsque la cavité produit une feuille.
Causes et contre-mesures:
(1) Insufficient clamping force: when the clamping force of the injection molding machine is too low to maintain the clamping force of the mold, the flashing will occur. It is necessary to adjust the area of the plastic part and the molding pressure to see whether they exceed the rated clamping force of the equipment and improve the clamping force. If they exceed the limit, the machine with large tonnage can be replaced, and the injection pressure, mold temperature, injection speed, time and position can also be adjusted from the process of adjusting the machine.
(2) Material temperature is too high: the plastic temperature is too high, resulting in the melt viscosity is too low and the material overflows between the templates. You can manually spray glue to observe the fluidity of the raw materials. You should properly reduce the material temperature, and at the same time, try to precisely process the mold to reduce the mold gap.
(3) Mold defect: mold defect is the main cause of overflow flash. Carefully check whether there are sundries in the mold closing surface and guide pillar hole, resulting in the mold not being closed. Whether there is balance between the mold templates, whether there is bending deformation, and whether the opening distance of the template is adjusted to the correct position according to the thickness of the mold. Whether the lock module surface is damaged, whether the pull rod is deformed unevenly, and whether the exhaust slot hole is too large and too deep. If the formwork deformation is caused during forming, the supporting formwork or thickened formwork shall be added to prevent the formwork deformation.
(4) Improper control of process conditions: the injection speed is too fast, the injection time is too long, the injection pressure is not evenly distributed in the mold cavity, the filling speed is not balanced, and the feeding amount is too much, resulting in flash and drape. Taking corresponding measures to reduce the filling speed, especially the speed close to the completion of filling, the injection pressure and the holding pressure, can reduce the required clamping force and avoid using too low
