Injection molding helps businesses produce high volumes of identical plastic parts, without causing too much financial pain. The molding process is straightforward: polymer granules are melted and injected into a mold, eventually cooling and solidifying. Many plastic parts used in machinery come from injection molding, from car parts to kitchen appliances.
Injection molding machines, also known as injection presses, have been around for decades. But, like all other forms of machinery, they degrade over time. Proper use and lubrication can prolong machine lifespans and avoid costly replacements or repairs.
Why Lubrication Matters
Injection molding machines, whether hydraulic, electrical, or mechanical, contain multiple contact points between parts. From screw motor drives to reciprocating screws, clamps, barrels, heaters, thermocouples, and ring plungers, there are plenty of areas that require preventative maintenance and ample lubrication.
Without good lubrication, both machine and part quality can suffer:
- Poor lubrication increases friction. Mold tools encounter friction as the hot resin is injected under great pressure. Too much friction can wear parts down, cause unusual noises or vibrations, generate excessive heat, and reduce production speeds.
- Poor lubrication reduces part quality. Molded parts are likelier to stick to the mold cavity or emerge with surface imperfections. They can also become difficult to remove from the cavity, which could damage the part further.
- Poor lubrication increases repair costs. Without proper lubrication, moving parts must work harder. This increases energy consumption, reduces machine efficiency, and makes it more likely to need repair or replacement.
Why the Type of Lubrication Matters
In injection molding, different lubricants have unique roles to ensure smooth operation. Three common types of lubricants are mold release agents, lubricating greases, and hydraulic fluids.
- Mold-release agents focus on preventing parts from sticking to the mold cavity. Silicone-based agents are often used here, because of higher heat resistance and plastic compatibility. Wax-based agents are a less expensive option for simpler applications.
- Lubricating greases focus on reducing friction with moving parts, like pins, sliders, and ejector mechanisms. Lithium complex greases are often used here because of high water resistance and heavy load management. Synthetic greases are also helpful for long-term performance needs.
- Hydraulic fluids are vital for power transmission within a hydraulic system. They lubricate pumps, valves, and cylinders, ensuring precise mold clamping pressure and injection force.
Why Application and Maintenance Matter
Even if you have the right type of lubricant for your injection molding machine, you’ll need to apply and maintain it effectively for optimal performance. For each of the common lubricant types, consider machine compatibility, plastic compatibility, potential chemical reactions, viscosity, and friction potential.
- For mold release agents, watch for any chemical reactions between the lubricant and the molded plastic material. Silicone-based agents have some degree of thermal stability and are less likely to corrode the mold. The agent should consistently coat the entire surface of the mold, no matter the shape. If applied too lightly, the part may stick to the mold. If applied too heavily, the mold release could bleed into the part.
- For lubricating greases, use a manual pump grease gun with a proper fitting. Apply a small amount of grease with slow, steady strokes. Don’t over-grease–apply a thin and even film of grease to all contact surfaces. Too much grease can attract dirt, create drag, and potentially contaminate the molded parts.
- For hydraulic fluids, monitor for signs of contamination or degradation. Discoloration, cloudiness, or the presence of metal shavings might indicate a problem. If the fluid viscosity is off, for example, the machine might overheat or reduce production.
Good lubricants can extend the lifespan of your injection molding machines. If you have any questions, contact our team and we can help choose the right lubricant solution for your needs.