The most commonly used method for cleaning plastic injection molds today remains the somewhat antiquated process of scrubbing tooling and plates, one piece at a time. Ask why, and the answers will probably be:

“This is the way we’ve always done it.”

“We can’t cost-justify other methods.”

“Other methods don’t clean as well, they don’t leave a bright and shiny surface.”

“We’re too busy. We don’t have time to experiment with or investigate other methods.”
These excuses can cost companies thousands of dollars a day in wasted time and worn tooling.

To realize a major reduction in the time required to clean molds, to maximize tooling life, to systemize cleaning and make it more consistent and predictable, more modern methods should be introduced in the mold shop, and hand cleaning should be limited to the areas where it works the best and damages the least.

Hand Cleaning
It is a safe bet that hand cleaning will never be completely eliminated, but it is an enormous waste of time and money to remove, clean, rinse, dry and replace every piece of tooling contained in a mold whenever it needs to be cleaned.

Hand cleaning tooling is a slow and damaging process. It is an effective cleaning method, however, for areas of plastic molds that normally have the most corrosion and contaminant build-up (rust), including:

front and rear clamp plates that directly contact the press platens

bubbler plates (non-stainless)

bushings and wear plate grease grooves

water lines (non-stainless) with heavy build-up

plates subjected to heavy internal condensation and clamp pressure (non-stainless

Managerial inertia sometimes leads a shop to keep using old, familiar (and ineffective) methods rather than deal with the mayhem that a change in cleaning culture can cause. Choosing the wrong type of cleaning system or having repair technicians reject the new method can cause disastrous repercussions, so they avoid making a change. I spent many years during my career hand cleaning my own plates and tooling (and being pushed to “hurry up”) while the company leisurely searched for effective alternatives.

We experimented with different types of spray cleaners, solvents and brushes, but they all required handling each piece of tooling several times, so none resulted in significant savings in cost or labor. Even extremely caustic cleaners, such as sodium hydroxide, sulfuric acid baths or MEK, were limited in the amount of rust build-up they would remove on unplated surfaces in a specific time frame. In the end, I found that the answer to heavy rust build-up is prevention—through more frequent cleanings, use of stainless steel plates and corrosion-resistant platings, and consistent application of spray-on rust inhibitors.