Views: 0 Author: Site Editor Publish Time: 2022-08-12 Origin: Site
To better understand, use and maintain the injection molding machine and to develop good injection molding operation habits, it is beneficial to improve the life of the injection molding machine and production safety.
Before starting the Injection molding machine, you need to inspect the machine to see if the various safety devices are effective and if the stroke switches are standard. Check the amount of lubricant, and lubricate the Injection molding machine.
① Check whether there is water and oil in the electrical control box. If the electrical components are damp, do not start the machine, the maintenance personnel should blow the electrical components dry before starting the machine.
② Check whether the power supply voltage meets the requirements. Generally should not exceed 15%.
③ Check whether the emergency stop switch and front and rear safety door switch are standard, verify whether the rotation direction of the motor and oil pump is consistent, and check whether the electrical joints are loose.
④ Check whether each cooling pipeline is smooth and passes cooling water into the oil cooler and the cooling water jacket at the end of the barrel.
⑤ Check whether there is a lubricant (grease) in each moving part and add enough lubricant.
⑥ Turn on the electric heating switch and heat each barrel section. When the temperature of each section reaches the requirement, keep warm for some time to stabilize the injection molding machine's temperature. The holding time varies according to the requirements of different equipment and plastic raw materials.
⑦ Add enough plastic to the hopper. According to the requirements of injection molding different plastics, some raw materials must be dried first.
⑧ The heat insulation cover on the hopper should be covered, which can save electricity and prolong the life of the electric heater and current contactor.
According to the characteristics of plastic and material supply, raw materials' appearance and process performance should be checked before molding. If the plastic used is in powder form, such as polyvinyl chloride (PVC), and should also be dosed and dry mixed; if the plastic parts have coloring requirements, then the appropriate amount of coloring agent or masterbatch can be added.
The supplied granules often contain varying degrees of moisture, solvents, and other volatile low molecular substances. Some plastics that tend to absorb moisture always contain more water than the limit for processing. Therefore, they must be dried and the moisture content measured before processing. The moisture content of polycarbonate (PC), which is sensitive to water at high temperatures, must be below 0.2%, or even 0.03%-0.05%, so it is often dried in a vacuum drying ovens.
The dried plastic must be adequately sealed and stored to prevent the plastic from reabsorbing moisture from the air and losing the drying effect. For this reason, using a dry hopper can continuously provide the injection molding machine with dry, hot material, simplify the operation, maintain cleanliness, improve quality, and increase the injection rate. The loading capacity of the dry hopper is generally taken. Injection, The loading quantity of the drying hopper is generally 2.5 times the hourly quantity of material used by the injection molding machine.
The injection molding machine's injection molded products need metal inserts embedded in the plastic parts for assembly and strength requirements. When the cold metal insert placed in the mold cavity is cooled together with the hot plastic melt during injection molding, the significant difference in shrinkage between the metal and the plastic often results in high internal stresses around the insert (especially for rigid chain polymers such as PS).
Such internal stresses can cause cracks around the insert, resulting in a significant reduction in the performance of the plastic part in use. This can be achieved by choosing metals with a high coefficient of thermal expansion (aluminum, steel, etc.) for the insert and by preheating the insert (extensive metal inserts). At the same time, the design of plastic parts, the use of larger wall thickness around the insert, and other measures.
When the newly purchased injection molding machine is used for the first time, or when it is necessary to change the plastic variety, change the raw material, color or find the decomposition of plastic in the injection molding production, it is necessary to clean or disassemble the barrel of the injection molding machine.
The cleaning barrel generally uses the heating barrel cleaning method, and the cleaning material generally uses plastic raw materials (or plastic recycling materials). For heat-sensitive plastics, such as polyvinyl chloride stock, available low-density polyethylene, polystyrene, etc., for transitional Cleaning, the new material is processed to replace the transitional cleaning material.
The mold release agent is a substance that can make plastic products easy to release. Zinc stearate is suitable for general plastics except for polyamide; liquid paraffin wax is used for polyamide plastic effect is better; silicone oil is expensive and troublesome to use, less used. The mold release agent should be controlled in the right amount, as little as possible or not. Spraying too much will affect the appearance of plastic parts and will harm the color decoration of plastic parts.