Why is there an under-injection phenomenon in injection molding production? Injection filler masterbatch manufacturers help you analyze
2019-03-04 10:40 来源:凯杰塑料填充母料厂家作者:熊猫 Time: 2019-03-04 10:40 Source: Qiagen manufacturers of plastic filled masterbatch: Panda
There are many reasons for under-injection in the production of injection molded products. The manufacturers of injection filler masterbatch will analyze for you what common reasons can cause this problem.
有没有效果。 Under-injection of injection-molded products often occurs in the production of injection-molded products. Although Kaijie produces injection-molded filling master batches , it has also encountered many customers who have consulted this question among customers who usually receive it, and many customers have asked to add our injection molding. There is no effect of filling the masterbatch .
In general, if you have a problem of under-injection of the masterbatch before, Kaijie's injection filler masterbatch can be tried, because Kaijie's filler masterbatch is made of high mesh powder and imported lubricants. Compared to many injection-filled masterbatches on the market, our flow performance is very good, so the improvement of under-injection is more obvious. However, there are many reasons for underpayment, so we still have to analyze and solve it in a targeted manner. The following editors will take you to understand the main reasons for underpayment.
1 Improper equipment selection: When using equipment, the maximum injection volume of the injection molding machine must be greater than the total weight of the plastic parts and the nozzle, and the total injection weight cannot exceed 85% of the plasticization volume of the injection molding machine.
2 Insufficient feeding: The current commonly used method to control the feeding is the constant volume feeding method, whether the amount of rollers and raw materials are uniform, and whether there is a "bridge" at the bottom of the feeding port. If the temperature at the feeding port is too high, it will also cause the blanking to be unsmooth. In this regard, the feeding opening should be unblocked and cooled.
3 Poor fluidity: When the fluidity of the raw materials is poor, the structural parameters of the mold are the main reason that affects the under-injection. Therefore, the stagnation defects of the mold pouring system should be improved, such as the reasonable setting of the runner position, the enlargement of the size of the runner, runner and injection port, and the use of larger nozzles. At the same time, an appropriate amount of additives can be added to the raw material formula to improve the flow properties of the resin. In addition, you should also check whether the amount of recycled material in the raw material is excessive and reduce its amount appropriately.
4 Excessive amount of lubricant: If there is too much lubricant in the raw material formula and the wear clearance between the injection screw check ring and the barrel is large, the severe backflow of the melt in the barrel will cause insufficient supply and cause under-injection. In this regard, reduce the amount of lubricant, adjust the gap between the barrel and the injection screw and the check ring, and repair the equipment.
5 Cold material impurities blocking the sprue: When impurities in the melt block the nozzle or the cold material blocks the gate and flow channel, the nozzle should be folded down to clean up or expand the mold cold material cavity and flow channel cross section.
6 The design of the gating system is unreasonable: When the mold has multiple cavities, the appearance of the plastic part is often defective due to the unreasonable balance design of the gate and runner. When designing the gating system, pay attention to the balance of the gate. The weight of the plastic parts in each cavity must be proportional to the size of the gate, so that each cavity can be filled at the same time. The gate position should be selected at a thick wall. Design scheme of balanced arrangement. If the gate or runner is small, thin, and long, the pressure of the melt during the flow will be too great, and the flow will be blocked, which will easily cause poor filling. In this regard, the cross section of the runner and the area of the gate should be enlarged, and if necessary, a multi-point feeding method can be adopted.
7 Poor mold venting: When a large amount of gas remaining in the mold due to poor venting is squeezed by the flow material, which generates a high pressure greater than the injection pressure, it will prevent the melt from filling the cavity and cause under-injection. In this regard, it should be checked whether the cold material cavity is set or the location is correct. For molds with deep cavities, vent grooves or vent holes should be added in the under-injected area; on the mold clamping surface, a depth can be set. Exhaust grooves with a width of 0.02 ~ 0.04mm and a width of 5 ~ 10mm. The exhaust holes should be set at the final filling position of the cavity. When using raw materials with excessive moisture and volatile content, a large amount of gas is also generated, resulting in poor exhaust of the mold. At this time, the raw materials should be dried and volatiles should be removed. In addition, in terms of the process operation of the mold system, auxiliary measures such as increasing the mold temperature, reducing the injection speed, reducing the flow assist force of the pouring system, reducing the mold clamping force, and increasing the mold gap can improve the exhaust failure.
8 The mold temperature is too low: After the molten material enters the low-temperature mold cavity, it will not be able to fill all corners of the cavity because it is cooled too quickly. Therefore, the mold must be preheated to the temperature required by the process before starting. When the machine is just started, the cooling water flow in the mold should be properly controlled. If the mold temperature cannot rise, check whether the design of the mold cooling system is reasonable.
9 Melt temperature is too low: Generally, in the range suitable for molding, the material temperature and the filling length are close to a proportional relationship, and the flow performance of the low temperature melt is reduced, which shortens the filling length. When the material temperature is lower than the temperature required by the process, check whether the barrel feeder is intact and try to increase the barrel temperature. When starting up, the temperature of the barrel is always lower than the temperature indicated by the gauge of the barrel heater. It should be noted that after the barrel is heated to the temperature of the gauge, it needs to be warmed for a period of time before it can be turned on. If it is necessary to take a low-temperature injection in order to prevent melt decomposition, the injection cycle time can be appropriately extended to overcome the under-injection. For screw injection molding machines, the temperature in the front section of the barrel can be increased appropriately.
10 The nozzle temperature is too low: During the injection process, the nozzle is in contact with the mold. Because the mold temperature is generally lower than the nozzle temperature, and the temperature difference is large, frequent contact between the two will cause the nozzle temperature to drop, causing the melt to be at the nozzle. freezing. If there is no cold material cavity in the mold structure, the cold material solidifies immediately after entering the cavity, so that the hot melt behind the plug cannot fill the cavity. Therefore, when the mold is opened, the nozzle should be separated from the mold to reduce the impact of the mold temperature on the nozzle temperature, and the temperature at the nozzle should be kept within the range required by the process. If the nozzle temperature is very low and cannot rise, you should check the nozzle heater for damage and try to increase the nozzle temperature, otherwise, the pressure loss of the flow material will cause too much injection.
11 Insufficient injection pressure or holding pressure: The injection pressure is closely proportional to the filling length. The injection pressure is too small, the filling length is short, and the cavity is not full. To this end, the injection pressure can be increased by slowing the injection advance speed and appropriately extending the injection time. In the case where the injection pressure cannot be further increased, it can be remedied by increasing the material temperature, reducing the melt viscosity, and improving the melt flow performance. It is worth noting that if the material temperature is too high, the melt will be thermally decomposed, affecting the performance of the plastic part. In addition, if the dwell time is too short, underfilling can also result. Therefore, the dwell time should be controlled within a suitable range, but it should be noted that too long a dwell time will also cause other failures, and it should be adjusted according to the specific conditions of the plastic when molding.
12 Injection speed is too slow: The injection speed is directly related to the filling speed. If the injection speed is too slow, the melt is slow to fill the mold, and the melt flowing at a low speed is easy to cool, which further reduces its flow performance and generates an underfill. In this regard, the injection speed should be appropriately increased. However, it should be noted that if the injection speed is too fast, it may easily cause other molding failures.
13 The structural design of the plastic part is unreasonable: when the thickness of the plastic part is not proportional to the length, the shape is very complicated and the molding area is large, the molten material is easy to flow at the entrance of the thin-walled part of the plastic part, making the cavity difficult to fill. Therefore, when designing the physical structure of the plastic part, it should be noted that the thickness of the plastic part is related to the limit flow length when the melt is filled.
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