In the injection molding machine before starting, the injection molding machine to carry out a preliminary inspection to see whether a variety of safety devices are effective, as well as the various travel switch is normal, check the amount of lubricating oil, and lubrication of the injection molding machine.
Work that must be done before starting the injection molding machine
① Check whether there is water or oil in the electric control box, if the electric components are damp, do not start the machine. Should be blown dry by the maintenance personnel of the electrical components before starting.
② Check whether the supply voltage meets the requirements, generally should not exceed 15%.
③ Check whether the emergency stop switch, front and rear safety door switches are normal. Verify that the direction of rotation of the motor and the oil pump is the same. Check whether the electrical connectors are loose.
④ Check whether each cooling pipe is smooth, and pass the oil cooler and the cooling water jacket at the end of the material cylinder into the cooling water.
⑤ Check whether there is lubricating oil (grease) in each movable part, and add enough lubricating oil.
⑥ Turn on the electric heat switch and heat up the material cylinder sections. When the temperature of each section reaches the requirement, keep warm for a period of time to stabilize the temperature of the injection molding machine. Holding time varies according to the requirements of different equipment and plastic raw materials.
⑦ Add enough plastic into the hopper. According to the requirements of injection molding of different plastics, some raw materials need to be dried first.
⑧ should cover the material barrel on the heat shield, which can save electricity, but also can extend the life of the electric heating ring and current contactor.
Preparation work before injection molding
Pre-treatment of raw materials
According to the characteristics of the plastic and the supply situation, the appearance and process performance of the raw materials should be tested before molding. If the plastic used is in powder form, such as polyvinyl chloride (PVC), it should also be batching and dry mixing; if the plastic parts have coloring requirements, it can be added to the appropriate amount of coloring agent or masterbatch; the supply of granular materials often contain varying degrees of moisture, solvents and other volatile low molecules, in particular, some of the hygroscopic tendency of the water content of the plastic is always more than the processing of the permissible limits. It is therefore necessary to dry them before processing and to determine the water content. The water-sensitive polycarbonate (PC) at high temperatures requires a moisture content of less than 0.2%, or even 0.03%-0.05%, so it is often dried in a vacuum oven. Has been drying the plastic must be properly sealed and stored to prevent the plastic from the air again moisture absorption and loss of drying effect, the use of drying hopper can be continuously for the injection molding machine to provide dry hot material, to simplify the operation, to maintain clean, improve the quality, increase the rate of injection are favorable. Drying hopper loading generally take the injection molding machine hourly amount of material 2.5 times.
② insert preheating
Injection molded products for assembly and strength requirements, the need for metal inserts embedded in the molded part. During injection molding, when the cold metal inserts placed in the mold cavity and the hot plastic melt are cooled together, due to the significant difference in the shrinkage rates of the metal and plastic, it often produces a large amount of internal stress around the inserts (especially polymers such as PS and other rigid chains are more significant). The presence of such internal stresses can cause cracks to appear around the insert, leading to a significant reduction in the performance of the plastic part. This can be achieved by selecting metals with high coefficients of thermal expansion (aluminum, steel, etc.) for the inserts, and by preheating the inserts (especially large metal inserts). At the same time, when designing the molded part, a larger wall thickness is used around the insert, and other measures.
③ Cleaning of the barrel
Newly purchased injection molding machine before the initial use, or in the injection molding production needs to change the plastic varieties, replacement of raw materials, colors or found in the plastic decomposition phenomenon, the need for injection molding machine barrel cleaning or dismantling,
Cleaning barrel generally use heating barrel cleaning method. Cleaning material is generally used plastic raw materials (or plastic recycling materials). For heat-sensitive plastics, such as polyvinyl chloride stock, available low-density polyethylene, polystyrene, etc. for the transition of the material for cleaning, and then replace the transition of the cleaning material with the new material processed.
④Selection of mold release agent
Mold release agent is a substance that can make the plastic products easy to release the mold. Zinc stearate is suitable for general plastics except polyamide; liquid paraffin is more effective for polyamide plastics; silicone oil is expensive and troublesome to use, so it is seldom used. The use of mold release agent should be controlled in the right amount, as little as possible or not used. Spraying too much will affect the appearance of the plastic parts, the color decoration of the plastic parts will also have a negative impact.
