In this increasingly competitive commercial society, improving production efficiency is a matter of considerable concern. Through this article, you will learn how to increase the efficiency of the injection molding machine, and at the same time, you can fully understand the working principle and injection molding knowledge of the injection molding machine.
Injection Cycle The injection cycle of a hydraulically driven injection molding machine refers to the time from the start of mold clamping to the next mold clamping.
Clamping is generally divided into four sections: fast closing, slow closing, low pressure protection and high pressure locking. The injection starts after the completion of high-pressure mode-locking and is also divided into multiple stages. Molten plastic fills the mold cavity during injection. When the cavity is filled, the pressure swells, so the end of the injection is also called the packing phase. When the control is not appropriate, the finished product will have flashes.
The hold pressure starts after the injection is completed. In fact, the cooling starts after filling the cavity, that is, starting from the holding pressure. As the mold cools, the finished product shrinks cold. The function of holding pressure is to pass through the cold flow path that has not been solidified, fill the depression formed by the shrinkage with a holding pressure that is generally lower than the injection pressure, and make the finished product full (no dent) when it is released from the mold.
When the cold runner solidifies, it is meaningless to hold the pressure again and the pressure can be stopped. The packing pressure can be divided into multiple sections. The holding pressure of each section is different (usually decreasing by segment) and divided by time. The total dwell time is determined by the weight of the scale or the finished product without dents. From the short dwell time, adjustments are made to increase the dwell time for each injection, until the weight of the finished product no longer increases or dents are acceptable. The dwell time does not increase.
The "cooling time" parameter set on the injection molding machine is a period of time from the completion of the pressure holding to the opening of the mold, but cooling has already begun after the mold cavity has been filled with plastic. The purpose of the "cooling time" is to allow the finished product to continue to cool and solidify until it has been ejected without being deformed by ejection. It should be said that the "cooling time" is derived from the test.
At the beginning of the "cooling time", the addition is carried out at the same time. The "cooling time" is displayed longer than the feeding time. It is also possible that the feeding time is longer than the “cooling timeâ€, in other words the lack of plasticizing capacity of the screw indicates a bottleneck. Therefore, increasing the plasticizing capacity is the method of shortening the cycle time in this case. The goal is to return to the short feeding time of Figure 1.
"Cooling time or "After completion of the addition, the mold is opened and the product is ejected one or more times. After retreating, the mold is closed and the next cycle begins.
The recently designed toggle injection molding machine has a regenerative mold clamping circuit to achieve a higher clamping speed. Under the premise that the mold is not subject to high impact, it is suitable for use.
The high-pressure mode-locking uses the lowest clamping force that can produce no burrs on the finished product, and can shorten the time required for the high-pressure clamping section. Moreover, the molds, rods, toggles, and stencils of the injection molding machine will also have a longer life due to the low clamping force. If a mold with 50t clamping force is sufficient, 51t clamping force is not needed, although your injection molding machine has a higher clamping force.
The injection can be used with the highest injection speed in the case where the finished product does not generate bubbles or black spots due to burning of the plastic. Especially for thick-walled injection molding, there is a large amount of gas storage space in the mold cavity filled with molten plastic. Too high injection speed makes the air in the mold cavity not reach the outside of the mold, resulting in bubbles.
Using the lowest injection pressure can reduce the required clamping force (expansion mold force) accordingly, while using the lowest barrel temperature can shorten the "cooling time."
The shortest dwell time can be determined from the finished product weight or acceptable dents. There are many thin-walled products that do not have to hold pressure because the inner layer of the finished product will solidify almost immediately after the injection.
Cooling time heard a saying: mold is a heat exchanger. It is true that the mold is constantly taking the heat away from the cold water channel, and the properly designed mold can improve the heat exchange efficiency.
However, when allowed, ice water cooling can shorten the "cooling time." If the ice water cooling is used to make the mold condensation, the dry blower and the sealed mold clamping device can reduce the degree of dew point and prevent condensation.
If the addition of plasticizing capacity is not enough to create a bottleneck, the following processing may be performed during screw design and parameter adjustment:
1. Barrier screws increase plasticizing ability.
2. Large diameter (C) screws increase plasticizing ability.
3. Increasing the groove depth of the screw can increase the plasticizing ability.
4. Increasing the rotational speed of the screw can increase the plasticizing ability (some shear-sensitive plastics such as PVC, PET, etc. cannot be used).
5. Reduce the back pressure as much as possible, otherwise it will increase the rate of plasticization.
6. The use of hydraulic sealing nozzle, so that plastic mold can also open and close.
7. The use of a pre-plasticizer design allows the screw to plasticize in addition to the injection and holding time during the cycle.
8. The pressure holding device is adopted so that the screw can also be plasticized in the pressure holding section.
Methods 1 to 5 try to turn the case of FIG. 3 into the case of FIG. 1 .
Methods 6 to 7 use parallel actions, and the addition is driven by an independent oil circuit or circuit.
The method 8 is most suitable for thick-wall injection molding. In order to avoid dents, thick-walled pressure-keeping time may be lengthy.
Before pouring the cable before and after feeding, it is better to replace it with a spring nozzle or a hydraulic sealing nozzle to save the reverse cable action.
Open the mold at the highest speed without tearing the finished product and without generating a large open mold noise. Some exquisite injection molding machines have decompression equipment before the mold is opened, and even high-speed mold opening will not produce noise. In order to achieve a precise mold stop position at high speeds, a brake valve or closed loop control can be used.
Ejection on top of a small injection molding machine with a small top output, pneumatic ejection can be used, higher than the hydraulic ejection speed. Electric jacking is faster than pneumatic jacking. The mold can be designed to drive the ejector by the mold-opening action instead of the ejection device on the injection molding machine. Only this method can only be ejected once. This is the simplest method for ejecting the mold edge.
Spandex Covered Polyester Yarn
Spandex Covered Polyester Yarn,Polyester Yarn For Socks,Covered Polyester Yarn For Socks,Spandex Single Covered Polyester Yarn
Shaoxing Shiffon Textile Co., Ltd , https://www.shiffontex.com