Tool Steel Grade Selection and Cavity Shrinkage Tolerances
Selecting tool steel grades for precision cavities requires balancing grain direction, heat treatment distortion, and alloy verification to hold tight part tolerances.
NAK80 Core Inserts
Meaning
Pre-hardened tool steel inserts configured for high-aesthetic plastic injection molds provide excellent machinability and a high-gloss finish without the risk of dimensional distortion from post-machining heat treatment. Utilizing NAK80 core inserts ensures that complex mold cavities can be machined to tight tolerances with minimal risk of cracking or warping. This specialty steel is delivered pre-hardened to thirty-seven to forty Rockwell C, making it ready for immediate milling.
Mechanical Property
The steel’s composition includes nickel, aluminum, and copper to promote precipitation hardening, which results in a uniform hardness profile across the entire cross-section. This uniform hardness ensures that the steel machines consistently, even in deep cavities where other steels might have soft spots. It also provides good dimensional stability during the EDM process.
This makes it a reliable choice for intricate mold designs.
Polishing Performance
High-gloss consumer electronics and clear plastic parts require a mirror finish that can only be achieved with high-purity steel. The steel’s micro-structure allows it to be polished to a very high level with a low risk of pinholes or orange peel defects. This quality reduces the time required for hand polishing.
It results in a higher quality surface finish.
Wear Resistance
While the pre-hardened steel is softer than fully hardened steels like H13, it offers sufficient wear resistance for medium-volume production runs of up to five hundred thousand cycles. If the mold is used with abrasive resins, the wear rate will increase, requiring surface treatments or more frequent maintenance. Mold builders should select this steel for its ease of machining and superior polishing capabilities.
This selection helps reduce tooling lead times and costs. It is the ideal choice for projects where speed to market is a critical factor. This approach balances manufacturing speed with long-term mold durability.