How to Shorten the Daily Use Injection Mould Cycle Time

2021-05-15


What is Daily Use Mould Injection Cycle Time?

Everyday, we must use different kinds of plastic Daily Use Injection Mould Products, but most people don't have idea about where does these plastic parts from?

The injection cycle of a hydraulically driven injection molding machine refers to the start of mold clamping to the next mold clamping. Mold clamping is generally divided into four stages: fast mold clamping, slow mold clamping, low pressure mold protection and high pressure mold clamping.

Injection

The highest injection speed can be used when the finished product does not produce bubbles or black spots due to scorched plastic. Especially for thick-walled injection molding, a large amount of air-storing space in the mold cavity is filled with molten plastic. Too high injection speed prevents the air in the cavity from being discharged out of the mold, causing bubbles.

Using the lowest injection pressure can correspondingly reduce the required clamping force (expansion force), while using the lowest barrel temperature can shorten the "cooling time".

 

Hold pressure

Daily Use Mould need hold pressure,the shortest holding time can be determined from the weight of the finished product or the acceptable dent. There are many thin-walled products that do not need to hold pressure, because the inner layer of the finished product is basically solidified immediately after the injection is completed.


 

Cooling time

There is a saying: The Daily Use Mould is basically a heat exchanger. Yes, the mold continuously takes away the heat of melting through the cold water channel, and a properly designed mold can improve the efficiency of heat exchange. However, if allowed, ice-water cooling can shorten the "cooling time". If the ice water is cooled to make the mold condensation, the dry air blower and the sealed mold clamping device can reduce the degree of dew point and prevent condensation.

 

If the plasticizing capacity is not enough and it becomes a bottleneck, the following treatments can be done during screw design and parameter adjustment:

1. Barrier screw can increase plasticizing capacity. To

2. Large diameter screw can increase plasticizing capacity. ,

3. Increasing the groove depth of the screw can increase the plasticizing capacity. To

4. Increasing the speed of the screw can increase the plasticizing capacity (some plastics that are sensitive to shear, such as PVC, PET, etc., cannot use this method). To

5. Reduce the back pressure as much as possible, otherwise it will increase the plasticizing speed. ,

6. The hydraulic sealing nozzle is adopted, so that the mold can be plasticized when opening and closing the mold. To

7. The use of pre-plasticizer design enables the screw to be plasticized during the cycle except for the injection and holding time.

8. Adopt pressure-holding device, so that the screw can be plasticized in the pressure-holding section.


 

Open Mold

Use the highest speed to open the mold without tearing the finished product and producing a loud mold opening noise. Some sophisticated injection molding machines have decompression equipment before mold opening, and even high-speed mold opening will not produce noise. In order to achieve accurate mold stop position under high-speed mold opening, brake valve or closed-loop control can be used. 

 

Mold Ejector

On small injection molding machines with low ejection force, pneumatic ejection can be used, which is higher than hydraulic ejection speed. Electric ejection is faster than pneumatic ejection.

 

The Daily Use Mould can be designed to be ejected by the mold opening action instead of the ejection device on the injection molding machine. This method can only be ejected once. This is the simplest method of ejecting while opening the mold.

 

Using independent oil circuit, gas circuit or circuit control, it can realize the function of multiple ejection while opening the mold while ejecting. To

 

Equipped with video and computer equipment, it can quickly analyze whether the finished products are all dropped after one ejection. The second ejection is performed when not all of them are dropped, so 99% of the cycles in the above example are ejected only once, which saves the average cycle time. 

 

Retreat

Some finished products can be ejected by the vibration of the injection molding machine for multiple ejections. The thimble does not need to be fully retracted each time to shorten the time of multiple ejections.

 

The last ejection can be started at the same time as the mold clamping. Since the stroke of the thimble is shorter than that of the template, the thimble will always be fully retracted before clamping.

 

The shortest cycle time

The shortest cycle time consists of the time required for mold clamping, injection, pressure holding, cooling and mold opening. Feeding is carried out at the same time during the "cooling time" and mold opening and closing, and even while maintaining pressure. Multiple ejections are performed at the same time when the mold is opened, and the last ejection is performed at the same time when the mold is closed. In this case, up to three actions can be performed at the same time, and each action has an independent drive. It may be that all three are oil circuits (such as three oil pumps), and all three are circuits (electric injection molding machine) or a combination of oil circuits, air circuits and circuits. To

 

Electric Daily Use Mould injection machines generally have 4 servo motors to drive injection molding, feeding, opening, closing and demolding respectively. The advantage is that the parallel operation can shorten the cycle. In fact, the hydraulic injection molding machine can also achieve this goal when using 3 independent oil circuits. Therefore, this advantage is not a patent for electric injection molding machines.

Since injection cannot be made when the mold is opened, the four servo motors cannot operate at the same time.

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