Creating mirror finishes on injection molds is a labor-intensive and expensive process. The resulting mold is smooth and highly reflective (you can see your reflection on the surface). This type of finish is critical when the manufactured parts require that same smooth, flawless texture in addition to extremely low friction, geometric precision and tight tolerances (such as technical-grade pieces).
Some products that require the use of molds with a mirror finish include automotive headlight assemblies, eyeglasses/lenses, glassware and light housings – where transparency and clarity are paramount.
The lack of texture on molds with mirror finishes make it more likely that a part can get stuck in the mold and end up becoming damaged, or at least take longer to process. Thus, part-eject problems, especially for deep parts with little or no draft, become more numerous, resulting in quality issues, longer cycle times and more rejects.
Here are the necessary maintenance steps to protect molds with mirror finish:
Never use shop rags or cleaning wipes as they can scratch or leave particulates on the finish.
Fingerprints can show up as rust or oxidation in a matter of hours, so avoid touching.
Moisture can cause a thin film of condensation as a mold cools, so do everything possible to retard this.
Choose a spray mold cleaner to thoroughly flush the mold with fast evaporation or flash off. For residue that is tougher to remove, use a cleaner that stays on the mold longer with a slower flash off.
Add a rust preventive to prohibit these delicate finishes from rusting. A short-term rust preventive works best if you are going back on press in a day or so as it will displace moisture and neutralize acids. This rust preventive should also flash off when the mold is put back into production, eliminating the need to clean the mold beforehand.
Slide recommends the following mold cleaners with fast-evaporation benefits that should eliminate the need for any wiping to remove the mold cleaner and contamination: