What is the common sense of operating a vertical injection molding machine?

What is the common sense of using an injection molding machine? In the process of using injection molding machine, there are many problems that need to be paid attention to. Aoxiang machinery has clarified some common sense of the use of injection molding machine:

1. Opening and closing of the mold

In general, most injection molding machines use molds with a slower opening and closing time than quote time (about 100-359%). That's the difference. It is related to the weight, size and complexity of the mold, as well as the safety protection of the mold (to prevent mold damage during opening and closing operations).

Typical mold opening and closing times are as follows: (TCM: a unit of time used by injection molding machines) :

Traditional double plate mold: 1-2TCM

Composite dies (including the use of side die cores and spinning devices) and multi-plate dies: 2-3.5TCM

If the opening and closing time of the mold is 15% longer than the actual operating time, the mold may need to be modified. Or use another injection molding machine to shorten the time. Compared to the new injection molding machine, it has a faster opening and closing speed and uses a lower mold opening and closing pressure to initiate clamping force.

Injection molding machine operators often do not pay attention to the speed or time of a particular injection molding machine plate, but use personal experience to set the opening and closing time of the mold, which often makes the operation time long. In a 10-second operation, a one-second loss produces an immediate 10% improvement, which usually makes up the difference between profit and loss.

2. The back pressure function and the application of the back pressure can ensure that the screw can produce enough mechanical energy when it is rotated and reset, so that the plastic can melt and mix. Back pressure can also be used for the following purposes:

The volatile gas (including air) is discharged from the injector cylinder; Mix additives (such as toner, colorant, antistatic agent, talcum powder, etc.) and melt evenly; Homogenize the melt flowing through the length of the screw; And provide a uniform and stable plasticizing material to control the weight of the finished product. The back pressure values selected should be as low as possible (e.g. 4-15bar or 58-217.5psi). As long as the melt has the proper density and uniformity, there are no bubbles, volatile gases and incomplete plasticized plastics in the melt.

The pressure temperature and melt temperature of the injection molding machine increase with the use of back pressure. The rise rate is related to the set backpressure value. Large-scale injection molding machines (with screw diameters larger than 70mm/2.75in) have tubing backpressures up to 25-40bar (362.5-580psi). It should be noted, however, that excessive backpressure can cause the melt temperature in the injector barrel to become too high, which can disrupt the production of heat-sensitive plastics.

In addition, too high back pressure will also lead to large screw, irregular offside, so that the injection volume is very unstable. The viscoelasticity of plastics affects their offside properties. The more energy is stored in the melt, and when the screw stops spinning, it suddenly jumps backwards. Compared with GPPS and HI, some thermoplastics have much more serious jump, such as LDPE, HDPE, PP, EVA, PP/EPDM composites and PPVC.