Clogged Mold Vents – Causes, Consequences & Solutions

A common and often recurring issue in the plastic injection molding industry, clogged mold vents are a maintenance challenge that should be addressed regularly. It will inevitably affect part quality and reduce efficient machine operation. These shallow channels allow trapped gases and air to escape the mold cavity and can tend to collect residue due to their small size.

Vents become clogged as various materials accumulate over thousands of cycles. Molten plastic deposit is the most common cause but volatile gases and other impurities such as excess from mold release agents, lubricant remains or even factory dust could block the escape path in the vents.

When the air and gases cannot disperse fast enough, the consequences are often costly defects in the molded part. This can include burn marks, voids, short shots or poor surface finish/imperfections.

Maintenance Procedures

Methods while the mold is on cycle and in the press:

• Mold cleaners – Apply a non-chlorinating, quick-evaporating mold cleaner directly to the vents then follow with a blast of compressed air until the channels are clear. The Slide Resin Remover is ideal for this purpose per these instructions.
• Dry ice blasting – Solid CO2 pellets are propelled at the vents then become gaseous upon impact, removing contaminants. This method is effective and non-abrasive.
• Manual cleaning – Physically remove the buildup with fine tools such as a brass wire brush, a needle or a cotton swab with a suitable cleaner compound. Avoid scratching by not using anything harder than the mold steel.

Methods when the mold is removed (off-press, more thorough):

• Ultrasonic immersion – Disassembled components are placed in a cleaning solution and exposed to high-frequency sound waves, creating bubbles that thoroughly clean all surfaces.
• Chemical bath and scrubbing – Soak the plates in a specialized formula followed by manual scrubbing.
• Laser cleaning – Used to burn off contaminants with no contact needed. Requires special equipment but is very precise and works well for stubborn buildup.

An Ounce of Prevention

As with so many other facets of maintaining injection molding equipment, the best method to curtail clogs is prevention. Implementing a routine schedule for checking and cleaning vents is critical and often based on number of runs. Always use the proper tools such as dedicated mold cleaners and non-abrasive brushes and scrapers. Optimizing your procedural functions such as injection speed, melt and mold temperatures can also help avoid obstruction.

Slide’s team of distributors and factory experts are always available to assist with these or any other injection molding-related issues.

As production ramps up near year-end, molders feel pressure with constant color changes, back-to-back runs and no margin for downtime. Use of purging compounds becomes imperative in properly managing pigment transitions, especially when running bright, high opacity seasonal hues. Incorporating the purging process you can reduce waste, prevent contamination and maintain consistent output. Read more...