Lubrication of injection units
Lubrication of the injection molding machine is a crucial maintenance measure to ensure its proper operation and extend its service life. Moving parts within the injection molding machine, such as the screw, guide rails, and bearings, experience intense friction in high-speed, high-pressure environments. Poor lubrication can lead to increased component wear, increased resistance, increased energy consumption, and even malfunctions such as seizures and damage, impacting the normal production of the injection molding machine. Therefore, a scientific and rational lubrication system must be established to regularly and properly lubricate all moving parts of the injection molding machine to ensure optimal operation. For example, the rotation and reciprocating motion of the screw within the barrel require excellent lubrication; otherwise, frictional overheating will accelerate wear of the screw and barrel, affecting the plasticizing effect and metering accuracy.
The lubrication parts of the injection device mainly include the mating surface of the screw and barrel, the check ring and backing ring at the tail of the screw, the guide rail and slider of the injection seat, the gears and bearings in the gearbox, etc. Different lubricating parts require different types of lubricants and lubrication methods. For the mating surface of the screw and barrel, due to the high operating temperature (usually 150-350℃) and contact with the plastic melt, solid lubricants such as molybdenum disulfide or polytetrafluoroethylene are generally used. These lubricants have good high temperature resistance and chemical stability, will not contaminate the plastic melt, and can form a lubricating film on the friction surface, reducing friction and wear between the screw and the barrel. For components such as the check ring and backing ring, high-temperature greases such as lithium-based greases or polyurea greases are usually used. These greases have good adhesion and high temperature resistance and can maintain lubrication effect at high temperatures.
The guide rails and sliders of the injection seat are the moving parts in the injection device that bear heavy loads. Their lubrication condition directly affects the motion accuracy and response speed of the injection device. The guide rails and sliders are usually lubricated with lubricating oil. The lubricating oil is injected into the oil groove of the guide rails through a manual oil pump or an automatic lubrication system to form an oil film and reduce friction resistance. The selected lubricating oil must have appropriate viscosity and good oxidation resistance. If the viscosity is too low, the oil film will easily break and the lubrication effect will be poor; if the viscosity is too high, the motion resistance will increase and the flexibility of movement will be affected. For high-precision injection devices, a centralized lubrication system can be used to supply oil to the guide rails and sliders at a regular and quantitative time to ensure the uniformity and reliability of lubrication while reducing the workload of manual maintenance. In addition, the surface of the guide rails needs to be cleaned regularly to remove impurities such as oil stains and iron filings to prevent impurities from entering the interior of the slider and aggravating wear.
The gears and bearings within the gearbox are the power transmission components of the injection unit. They are primarily lubricated with gear oil, which must possess excellent extreme pressure, anti-wear, oxidation resistance, and anti-foaming properties to withstand the high pressure and impact forces during gear meshing and reduce tooth wear and galling. The viscosity of the gear oil should be selected based on the gearbox’s operating temperature and speed. Generally, medium-viscosity gear oil is used at room temperature, while low-viscosity gear oil is used under high-temperature or high-speed conditions. Gearboxes are typically lubricated using either splash lubrication or forced lubrication. Splash lubrication uses the rotating gears to distribute the gear oil to various lubrication points and is suitable for small gearboxes. Forced lubrication, on the other hand, uses an oil pump to pressurize the gear oil to various lubrication points and is suitable for large or high-speed gearboxes, providing more reliable lubrication. The gear oil level and quality must be checked regularly. A low oil level can lead to poor lubrication, while deterioration in oil quality (such as blackening or emulsification) requires prompt replacement. Gear oil should generally be replaced every 1,000 to 2,000 hours of operation.
Lubrication management for injection units requires strict regulations and rules, clearly defining the type of lubricant, lubrication cycle, and lubrication quantity for each lubricated area. These regulations must be performed and recorded by professionals. During the lubrication process, the following points should be noted: First, the lubricant selection must comply with the equipment manual. Different types of lubricants must not be mixed. For example, lubricating oil and grease cannot be mixed, as this will affect the lubrication effect. Second, impurities and old lubricant must be cleaned from the lubricated areas before lubrication to ensure that the new lubricant can fully function. Third, the lubrication quantity must be controlled. Too little lubrication will result in insufficient lubrication, while too much will cause waste and even contaminate the product or affect heat dissipation. Furthermore, the lubrication system must be regularly inspected and maintained, such as checking the proper functioning of the lubrication pump, the oil pipes for blockages, and the integrity of the oil nozzles. Any problems identified must be addressed promptly to ensure the proper operation of the lubrication system. Through scientific and standardized lubrication management, the failure rate of injection units can be effectively reduced, and the operating efficiency and service life of the equipment can be improved.
