Cycle of Plastic Injection Machine
The production cycle in the plastic injection process is very short and usually lasts from 2 seconds to 2 minutes. This process includes the following steps:
Close
Before injecting the material into the mold, the two halves of the mold must be locked together by the clamping unit. Both halves of the mold are connected to the device, but only one of them can move. Relying on hydraulic force, the clamping unit compresses the two halves of the mold together and keeps them stable and motionless during the injection process by applying sufficient pressure. The time required to close and press the two halves of the mold varies depending on the machine used: large machines (those with higher clamping force) will need more time. This time can be evaluated according to the no-load cycle time of the device.
Injection
The raw plastic material is usually fed into the machine in the form of plastic pieces and pushed to the mold by the injection unit. During this process, the material is quickly inserted into the injection mold due to the application of heat and melting pressure. Accumulation of pressure behind the material will lead to its greater density in the interior of the mold. The amount of material required to completely fill the mold space is called shot. Due to the complex and variable flow of materials in the mold, it is generally difficult to calculate and estimate the injection time. However, this time can be evaluated by considering the required shot volume, pressure and injection power.
Cooling
The molten material inside the mold will gradually lose its heat as soon as it comes into contact with its inner surface. At the same time as this cooling, the material will take the desired shape and form. However, during this period, the phenomenon of shrinking of the piece may also occur. Greater accumulation and flow of material into the mold during injection can reduce the amount of visible shrinkage. The mold remains locked and motionless until the end of the cooling period. Also, the cooling time can be estimated by considering the thermodynamic properties of the plastic and the maximum thickness of the part.
Exit the piece
After enough time has passed, the cooled part can be removed from the mold by the spring system installed in the back half of the mold. When the mold returns, a special mechanism is activated by applying pressure to eject the part. The need to apply this pressure is because the part gets smaller during cooling and is absorbed into the core of the mold. In order to facilitate the ejection of the part, sometimes before the injection operation, spraying an auxiliary element to the inner space of the mold cavity is used. The time required to open the mold and fully eject the part can be estimated from the idle cycle time of the machine. After pushing out the piece, the mold is locked again and ready for the injection of the next shot.
Methods of reducing costs
Minimizing the rate of returned parts (less than 1% of production target) Removing the issue of plating quality Reducing the energy consumption of the plastic injection machine Increased cycle time Eliminate unplanned machine downtime With the right choice of plastic injection machine, all the above items are taken into account.
Plastic Injection Machine
Fully hydraulic Fully electric Combined hydraulic and electric
The process of selecting the plastic injection machine
Knowledge about the parts that are going to be produced by plastic injection method. Choose the type of car: 1) hydraulic 2) hybrid 3) electric Calculation of the required tonnage of the clamp unit Calculate the volume of the injection unit