Corrosion is a major cause of expenses for the injection molding industry. In the plastics industry, the costs do not only pertain to mold damage or repair. The breakdown/shutdown of a machine can also be caused by corrosion, resulting in production delays and productivity losses.
Many factors determine how you can prepare for proper corrosion control. Plastics with fillers, for instance, are particularly abrasive and can eliminate the mold steel after several cycles.
Plastic with high melt temperatures exposes mold to greater heat and results in higher wear and tear than plastic with low melting points. Corrosive vapors or residues are emitted by certain materials, leading to extra cleaning and corrosion prevention. Complicated molds often get overlooked.
Mold presses, slides, lifters, and moving cores, as well as mechanics and hydraulics, are also susceptible to corrosion issues. This is especially so with an abundance of corrosion vapors from PVC molding and several other types of substances.
Sprue bushings are as important, if not more, than the interior surface of a mold. Rusty sprue bushings prevent the barrel nozzle from sealing properly. The bases that are damaged when they are clamped to the platens could cause issues with holding the mold halves parallel. This could cause flash or an excessive pressure on the clamp.
When a mold is put into production, the type of material used and the method of application can help prevent the bleed out of solvents and anti-rust coatings. When bleed-out occurs, components may be marked with antirust/grease/oil material for hours prior to the initial molding process.
When the mold protectant is unable to mold off in a proper manner then an solvent cleaner is typically used to eliminate it. In this process of removal, some solvent generally penetrates through the ejector pins , and it contaminates the lubricant within the box for pins. The result is thinning the ejector pin lubricant, which then oozes out past the pins, leaving marks on the part that was molded.
The right mold protection and corrosion preventive will provide about a year of protection while the mold is stored. The best part is that they won’t need to be scrubbed before starting up because they flash off during the initialization process. This reduces the risk of normal bleed out issues.
Certain rust-preventive products are great for long-term storage (3 or 5 years) however, they may require cleaning in order to get their residue from mold prior to manufacturing. Rust preventives should be formulated with neutralizers to ward off attack from acidic fingerprints.
Some have a light blue dye, which is easier to see areas of coverage. People those who mold PVC or other resins that are fire-resistant have to contend with the acid vapors that are released during molding.
Acid vapor neutralizers are constructed to be extremely durable to avoid corrosion due to the vapor that is released from those resins. You must take daily steps to clean the mold by the end of the day in order to perform proper mold maintenance.
Ensure that the next time you open your mold, it will keep producing like it did earlier in the day by cleaning it thoroughly with an excellent solvent cleaner and degreaser, and applying a rust preventive.