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Cleaning molds falls neatly into two categories: Offline and Online. From there the decisions start to vary depending on your needs, the mold, time and your Preventive Maintenance procedures.
Heat can help or hurt the process
Various cleaning solvents have different characteristics and work differently at different temperatures. For example, some solvents work well when the mold is at the bench and is at room temperature. The solvent has the time to clean and yet still evaporate quickly, leaving little or no residue to wipe off. However, if you use this same cleaning solvent on a warm or hot mold, it will flash off so fast it will do little to clean the mold.
If you want to keep the mold in the press (online,) a cleaning solvent specifically formulated to work at higher temperatures is a better choice. Even at higher temperatures the solvent will sit on the mold long enough to remove release, plate out or other contaminants before it evaporates.
There are myriad varieties of cleaner formulations with varying characteristics. Many formulations have completely eliminated chlorinated solvents. The EPA’s final assessment of the popular trichloroethylene (TCE) “characterizes the chemical as carcinogenic to humans...”
Though some manufacturers have changed formulations to use alternative chlorinated solvents, these too have some questionable effects so you now can find formulations that have completely eliminated chlorinated solvents.
The variety of formulations can seem overwhelming. Yet each cleaning formulation has been developed to solve cleaning challenges faced every day by molders. Some cleaners are water-based. Others meet requirements for processors of food packaging. Others use a higher concentration of cleaning solvent for tough residues. Talk to your supplier to simplify the selection process. Then get free samples to test on each different application in your facility.
Offline: Cleaning a mold at the bench
The requirements of offline cleaners are primarily to dissolve resins, grease, oil, mold release, and sometimes rust. These cleaners generally are required to have a very fast evaporation rate. The best cleaners are hydrocarbons and naphthas. They readily dissolve greases and oils by merely flushing the mold with a heavy spray from top to bottom.
Mold releases and resin build-up may require rubbing the mold with a cloth saturated with cleaner. We recommend using a new shop rag or disposable, pre-saturated wipe. Used shop rags can contain contaminants, even bits of metal that can scar or damage your mold.
There are several advantages to using pre-saturated cleaning wipe:
A finishing touch
Use a mold polish/cleaning compound. These products typically require manual application and removal. The typical mold polishing paste contains a combination of cleaning solvents and mild abrasives that are designed to aid with the removal of all contaminants from the mold or die surface.
Using polish results in sheen or luster left on the mold surface which serves as a natural lubricant and release. This reduces the need for a mold release when the mold is initially put back into production.
Online: Cleaning a mold in the press
Online cleaners are used to remove mold release build up, plate out of resins and light rusting of the mold while it is still warm and in the press. Often molds get plate out, which is due to the adhesion of resins, like acetals such as Delrin® or Celcon®, or fire retardant materials. Such build-ups must be removed from the mold surface in order to minimize potential part deformation. A resin-removing product can work to break down the material and to aid with the removal of the unwanted resin from the mold surface.
As stated earlier, cleaning solvents used on a warm or hot mold are formulated specifically for cleaning at these temperatures. A cleaning solvent formulated for use at room temperature will flash off a warm or hot mold before it has a chance to clean.
When cleaning solvents aren’t enough
There may come a point where a mold needs a deeper, more extensive cleaning as part of a preventive maintenance program. There are more comprehensive cleaning options available that you may find are necessary to get a troublesome mold working at its optimum level. An article in MoldMaking Technology authored by John Berg, Marketing Director from MGS Mfg., outlines their systematic approach to mold cleaning.