I. Equipment:

(1) The plasticizing capacity of injection moulding machine is small. When the product quality surpasses that of injection moulding machine, it is obvious that the amount of material supplied is limited. If the product quality is close to that of injection machine, there will be a problem of insufficient plasticization. The material can not be heated in the barrel for a short time, so it can not supply the proper melt to the mould in time. This situation only needs to replace the large capacity of the bathroom machinery injection machine to adjust and handle the problem. Some plastics, such as nylon (especially nylon 66), have narrow melting scale and high specific heat. It requires a large plasticizing capacity injection moulding machine to adjust to ensure the supply of materials.

(2) The temperature flashed by the thermometer is unreal, high and low, and the material temperature is too low. This is due to the failure of temperature control devices such as thermocouples and their circuits or temperature difference millivoltmeters, or to the ageing or burning of electric heating coils far away from the temperature measuring point, the failure of heating without detection or timely repair and replacement.

(3) The diameter of the inner hole of the nozzle is too large or too small. If the flow diameter is too small, the specific capacity of the strip will increase, the feed passage will be blocked or the injection pressure will be consumed due to simple cooling, and if the flow cross section area is too large, the unit area pressure of the plastic feed die will be low, which will constitute a situation of low injection force. At the same time, the non-Newtonian plastics such as ABS can not make the viscosity decrease because of the lack of large shear heat, which makes it difficult to fill the mould.

The cooperation between nozzle and main channel inlet is not good, and the phenomenon of overflow and unsatisfactory filling often occurs. The nozzle itself has a great resistance to movement or blockage of foreign bodies or plastic carbonized sediments; the spherical surface of the nozzle or main channel inlet is harmful and deformed, which affects the excellent cooperation with the other side; the mechanical failure or error of the injection seat causes the nozzle to tilt away from the axis of the main channel or the axial compression surface; the spherical diameter of the nozzle is larger than that of the main channel inlet, because of the gap in the edge, it is driven by overflow. Increasing the axial push force of the nozzle will result in unsatisfactory injection of the product.

(4) Plastic frit blocked the feeding passage. Due to the melting and agglomeration of plastics in hopper dryer, the excessive temperature in the feeding section of machine barrel, the improper selection of plastics grade, or the excessive lubricant in plastics, the plastics will melt prematurely in the shrinkage direction of feeding inlet or in the deep groove of screw starting end. The glue structure of granules and melts will form a "bridge" to block the passage or wrap the screw, and the screw will rotate as a circumferential slippery. Moving, can not move forward, constitute a continuous supply or irregular and unswerving. In this case, only when the passage is drilled through and the material block is cleaned, the bottom can be adjusted.

(5) Injection of cold material into the nozzle. Injection moulding machines usually only have straight-through nozzles because of pressure loss. However, assuming that the temperature of the front end of the barrel and the nozzle is too high, or that there is too much material stored at the front end of the barrel under high pressure, the "salivation" occurs, which makes the plastic accidentally rush into the main channel inlet and harden under the cooling effect of the template without starting injection while the die opens, and prevents the melt from entering the cavity smoothly. At this time, the temperature of the front end of the barrel and the nozzle should be reduced, the storage of the barrel should be reduced, and the back pressure should be reduced to prevent the density of the melt at the front end of the barrel from being too high.

(6) Short injection cycle. Because of the short cycle, the material temperature can not keep up with the shortage, especially when the voltage is not firm. The period should be adjusted according to the supply voltage. When adjusting, needling and holding time are generally not taken into account. The first consideration is to adjust the period from the end of holding pressure to screw return, which does not affect the filling conditions, but also extends or shortens the preheating time of material particles in the barrel.

2. Mold aspect:

(1) The gating system of the mould is defective. The runner is too small, too thin or too long, which adds fluid resistance. The diameter of the main channel should be added, and the flow channel and the diversion channel should form a circular shape. The runner or gate is too big and lack of shooting force; the runner and gate are blocked by impurities, foreign bodies or carbides; the runner and gate are rough and scarred, or have sharp angles, and the surface roughness is not good, which affects the material flow.

The runner does not have a cold material well or the cold material well is too small and the opening direction is not right. As for the multi-cavity mould, it is necessary to carefully arrange the balance of runner and gate size distribution. Otherwise, it will appear that only the cavity near the main runner, which may have a thick and short gate, can be filled while other cavities can not be filled. The diameter of the runner should be appropriately increased to reduce the pressure drop of the melt flowing to the end of the runner, and the gate of the cavity farther away from the main runner should be increased so that the injection pressure of each cavity and the base of the material flow velocity can be combined.

(2) The die planning is unreasonable. Dies are overheated and disorderly, with many improvements, improper selection of inlet and outlet, too narrow runner, lack of gate quantity or improper method; the section of part of the product is very thin, the thickness of the whole product or part should be added, or auxiliary runner or gate should be set near the filling shortage;

The phenomenon of unsatisfactory parts caused by inadequate exhaust measures in the die cavity emerges in endlessly. Most of these defects occur at the turning point, deep depression, thin-walled part surrounded by thick-walled part and the bottom of thin bottom shell formed by side gate.

The plan of eliminating this defect includes setting up useful exhaust passage, choosing reasonable gate orientation to make air simply pre-discharged, specially making some part of the trapped area of the cavity into inserts when needed, so that air overflows from the gap of the insert. In the case of simple imbalance of gate distribution in multi-cavity dies, the number of needle-punching cavities should be reduced when needed in order to ensure other types of dies. Cavity parts are qualified.

3. Technological aspects:

(1) Improper scheduling of feeding, lack of feeding or multi-feeding. Incorrect feeding metering or improper operation of feeding control system, injection moulding machine or mould or operation