Mold opening and clamping control during plastic injection molding
Open mold control:
When the molten plastic is injected into the cavity and after the cooling is completed, the product is taken out as the mold is opened. The mold opening process is also divided into three stages. The first stage slowly opens the mold to prevent the part from tearing in the cavity.
The second stage quickly opens the mold to shorten the mold opening time. The third stage slowly opens the mold to reduce the impact and vibration caused by the mold opening inertia.
The mold clamping is to tighten the mold with a huge mechanical thrust to withstand the high-pressure injection of the molten plastic during the injection molding process and to fill the mold to cause a large opening force of the mold.
When the safety door is closed, each stroke switch gives a signal, and the mold clamping action starts immediately. The first is that the moving template starts at a slow speed. After a short distance, the control block that originally pressed the slow switch is disengaged, and the movable plate is turned forward to advance rapidly. When advancing to the end of the clamping, the other end of the lever is pressed against the slow switch, and the movable plate is again rotated at a slow speed and at a low pressure.
In the low pressure clamping process, if there is no obstacle between the molds, it can be smoothly closed to the high pressure switch, and the high pressure is to straighten the machine hinge to complete the mold clamping action. This distance is extremely short, generally only 0.3~1.0mm. When it is turned to high pressure, it will touch the mold closing limit switch. At this time, the action stops and the clamping process ends.
The clamping structure of the injection molding machine is fully hydraulic and mechanical linkage. Regardless of the type of construction, the final result is that the connecting rod is fully extended to perform the clamping force. The straightening process of the connecting rod is the process of opening the movable plate and the tail plate, and is also the process in which the four tie rods are stretched by force.
The clamping force can be obtained from the highest value of the instantaneous oil pressure gauge of the clamping die. If the clamping force is large, the highest value of the oil pressure gauge will be high, and vice versa. The smaller injection molding machine does not have a clamping hydraulic gauge. In this case, it is necessary to judge whether the mold is really tight according to the straightening condition of the connecting rod.
If the connecting rod is easily straightened when the injection molding machine is closed, or if it is "slightly" not straightened, or if one of the pairs of connecting rods is not fully extended, the mold will be expanded during injection molding. There will be flash or other problems.