This is a problem we often encounter, but it is also treated briefly. When the process method can not be dealt with, it can be considered from the die planning and manufacturing to improve, generally can be dealt with.

I. Equipment:

(1) The plasticizing capacity of injection moulding machine is small. When the quality of the product exceeds that of the injection machine, it is obvious that the amount of material supplied is more than enough. If the product quality is close to the injection quality, there will be a problem of inadequate plasticization. The material in the barrel is short of heating time, and the function can not supply the appropriate melt to the mould in time. In this case, only replacing the injection moulding machine with large capacity is needed to adjust the problem. Some plastics, such as nylon (especially nylon 66), have narrow melting planning and larger specific heat. It requires a high 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. Perhaps it is due to the aging or burning of the electric heating coil far from the temperature measuring point. The heating failure has not been found or replaced in time.

(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. If the flow cross-section area is too large, the unit area pressure of the plastic feed die will be low and the injection force will be small. For non-Newtonian plastics such as ABS, it is difficult to fill the mould because the viscosity of the plastics can not be reduced due to the lack of large shear heat. The cooperation between the nozzle and the inlet of the main channel is not good, and the phenomenon of overflow and unsatisfactory filling in the mould often occurs. The nozzle itself has 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 and the axis of the main channel to occur tilt displacement or axial compression surface to separate; the spherical diameter of the nozzle is larger than the spherical diameter of the main channel inlet, because of the vacancy of the edge, it is driven by the overflow. Increasing the axial push force of the nozzle step by step 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, excessive temperature in feeding section of machine barrel, improper selection of plastics grade, or excessive lubricant in plastics, the plastics will melt prematurely in the direction of shrinkage diameter of feeding port or deep groove of screw starting end. Particles and melts stick to each other to form a "bridge", block the passage or wrap the screw, and rotate with the screw to make the circumference 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 plastics unexpectedly rush into the inlet of the main runner and harden under the cooling of the template, 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 lowered, the storage of the barrel should be reduced, and the back pressure should be reduced to avoid the excessive density of the melt at the front end of the barrel.

(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

(1) There are some shortcomings in the mould casting system. The runner is too small, too thin or too long, which increases the fluid resistance. The diameter of the main channel should be increased, and the flow channel and the diversion channel should form a circular shape. The runner or bigger mouth is too big, and the injection force is not enough; 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 bad, which affects the material flow; the runner does not have a cold material well or the cold material well is too small, and the direction is not right; the multi-cavity mould should carefully arrange the balance of the runner and the huge subdivision of the gate, otherwise only one will appear. It is necessary that the cavity near the main runner may be filled with a thick and short gate while other cavities cannot 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. Mould overheating disorderly, colorful, inappropriate selection of inlet and outlet, too narrow runner, lack of gate quantity or inappropriate way; part of the product section is very thin, should increase the thickness of the whole product or part, or set auxiliary runner or gate near the filling shortage; the phenomenon of unsatisfactory parts is endless because of inadequate exhaust measures in the cavity, which mostly occurs in the products in production. The turning point, the deep depression, the thin-walled part surrounded by the thick-walled part, and the bottom of the thin bottom shell formed by side gate, etc. Planning for eliminating this shortcoming includes opening useful exhaust passages, selecting reasonable gate orientation to make air simply discharge in advance, specially making a part of the trapped area of the cavity into inserts when needed, so that air overflows from the gap of the insert; regarding the uneven distribution of the gate in the multi-cavity mould during a brief attack, the number of needle-punching cavities should be reduced when needed to ensure other types. Cavity parts are qualified.