What are the good operating habits of injection molding machines?

Update:04-12-2020
Summary:

1. Before starting up: (1) Check whether there is water […]

1. Before starting up: (1) Check whether there is water or oil in the electrical control box. If the electrical appliance is damp, do not turn it on. Maintenance personnel should blow-dry the electrical parts before starting the machine. (2) Check whether the power supply voltage is in compliance, generally should not exceed ±15%. (3) Check whether the emergency stop switch and front and rear safety door switches are normal. Verify that the rotation direction of the motor and the oil pump are the same. (4) Check whether the cooling pipes are unblocked, and pass cooling water into the oil cooler and the cooling water jacket at the end of the barrel. (5) Check whether there is lubricating oil (grease) in each movable part, and add enough lubricating oil. (6) Turn on the electric heater to heat each section of the barrel. When the temperature of each section reaches the requirements, keep it warm for a period of time to stabilize the temperature of the machine. The holding time varies according to the requirements of different equipment and plastic materials. (7) Add enough plastic in the hopper. According to the requirements of different plastics for injection molding, some raw materials are best to be dried first. (8) Cover the heat shield on the barrel, which can save power and extend the life of the heating coil and current contactor.
2. During operation: (1) Do not cancel the function of the safety door at will for convenience. (2) Pay attention to the temperature of the pressure oil, and the oil temperature should not exceed the specified range. The ideal working temperature of hydraulic oil should be kept between 45~50℃, generally within the range of 35~60℃. (3) Pay attention to adjusting each stroke limit switch to avoid impact when the machine moves.
3. At the end of the work: (1) Before shutting down, clean the plastic in the barrel to prevent oxidation of the leftover material or long-term thermal decomposition. (2) The mold should be opened to keep the toggle mechanism in a locked state for a long time. (3) The workshop must be equipped with lifting equipment. Be very careful when assembling and disassembling heavy parts such as molds to ensure production safety. Some knowledge in the use of injection molding machine 1. The function of back pressure The application of back pressure can ensure that when the screw is rotated and reset, it can generate enough mechanical energy to melt and mix the plastic. Back pressure also has the following purposes: to exhaust volatile gases, including air, out of the injection cylinder; to evenly mix additives (such as toner, color, antistatic agent, talc, etc.) and melt; to make the flow The melt through the screw length is homogenized; uniform and stable plasticized materials are provided to obtain accurate finished product weight control. The selected back pressure value should be as low as possible (for example, 4-15bar, or 58-217.5psi), as long as the melt has proper density and uniformity, there are no bubbles, volatile gases, and incomplete plastics in the melt. Modified plastic will do. The use of back pressure increases the pressure temperature and melt temperature of the injection molding machine. The magnitude of the increase is related to the set back pressure value. Larger injection molding machines (screw diameters over 70mm/2.75in) can have oil back pressure as high as 25-40bar (362.5-580psi). But it should be noted that too high back pressure causes the temperature of the melt in the barrel to be too high, which is destructive to the production of heat-sensitive plastics. Moreover, too high back pressure also causes the screw to be too large and irregular offside, which makes the injection volume extremely unstable. The amount of offside is affected by the viscoelastic properties of the plastic. The more the energy stored in the melt, the sudden backward jump of the screw when it stops rotating.Some thermoplastics have more jumps than others, such as LDPE, HDPE, PP, EV A, PP/EPDM composites and Compared with GPPS, HIPS, POM, PC, PPO-M and PMMA, PPVC is more prone to beating. In order to obtain the best production conditions, it is important to set the correct back pressure so that the melt can be properly mixed, and the screw's offside range will not exceed 0.4mm (0.016in). 2. Mold opening and closing Generally speaking, the mold opening and closing time used by most injection molding machines is slower than the quoted time (about 100-359%). This difference is related to the weight, size and complexity of the mold, and it is also related to the mold. The safety protection (to prevent mold damage during opening and closing operations) is related. The typical mold opening and closing time is as follows (tcm: time unit quoted by the injection molding machine): Traditional double-plate mold: 1-2tcm composite mold (including the use of side mold cores and screw-out devices) and multi-plate mold: 2-3.5tcm If the mold opening and closing time is 15% longer than the actual operation time, then you need to modify the mold or use another injection molding machine to shorten the time. Newer injection molding machines can provide faster opening and closing speeds, and use low mold opening and closing (mold sensing) pressure to activate the clamping force to close the mold. Injection molding machine debuggers often do not pay attention to the board speed or time of a particular injection molding machine, and use personal experience to set the mold opening and closing time, which often leads to a long operating time. In a ten-second operation, one second is reduced, and a 10% improvement is immediately obtained. This improvement often constitutes the difference between profit and loss

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