There are a few levels of mirror finish on injection molds. The finest, and most labor-intensive finish to achieve looks as crisp and flawless as a fine glass mirror. You can truly see your reflection in the finish. This type of finish is needed when the part’s cosmetics critical. So think if items such as automotive lens parts, glassware and light housings.
The work required to build this type of mold is labor intensive, requiring several steps to create the final finish. And when it is molding, a mirror finish mold creates more challenges for the molder. It is this type of finish that most likely to create part eject issues, especially for deep parts with little or no draft. This results in quality issues, longer cycle times and more rejects.
Maintaining this type of mold requires a different few steps to protect the finish.
No shop rags. No cleaning wipes. They can scratch or leave particulates on the surface.
Don’t touch. A fingerprint can show up as rust or oxidation in a matter of hours.
Moisture. As a mold cools, a thin film of condensation will form.
Clean. Use a cleaner you can spray and thoroughly flush the mold. The cleaner should evaporate quickly, or flash off. For tougher to remove residue, use a cleaner the stays on the mold longer and doesn’t flashing off too quickly.
Quick, add a rust preventive. These delicate finishes can quickly start to rust. Use a short-term preventive if you are going back on press with a day or so. It will displace moisture and neutralize acids in the air. A short term rust preventive should also “flash off” when the mold is first put back into production, eliminating the need to clean the mold before hand.