High Gloss Mold - Kehui Mold Co., Limited

A high gloss mold (also called mirror finish mold or optical grade mold) refers to a mold with an extremely smooth cavity surface, typically achieving a mirror polish of Grade 2 or higher. Products manufactured with such molds can be directly assembled without additional surface treatment, making them ideal for industries demanding flawless aesthetics.

Key Characteristics of High Gloss Mold

High Mold Temperature (80-90°C)

Essential for eliminating defects like weld lines and flow marks in high gloss plastic molding.
Requires heating systems and resin insulation plates to maintain consistent mirror finish.

Precision Hot Runner System

Uses 6-8 hot nozzles with shut-off needles for high polish injection mold quality.
Electromagnetic valves and timers enable sequential injection, critical for optical-grade surface results.

Best Steel for High Gloss Mold

The primary mold steels include NAK80, S136-D, YH136, and 718H, among which S136-D offers the best optical-grade polishing performance, while NAK80 provides the highest cost-performance ratio. The selection depends on polishing grade, corrosion resistance needs, and budget considerations.

NAK80 Mold Steel (Pre-Hardened Mirror Steel)

Hardness range: HRC 37-43, ready for machining without heat treatment.
Excellent polishing performance, suitable for standard high-gloss applications (e.g., cosmetic cases, automotive parts).
Typical applications: TV light filter panels, precision threaded molds.

S136-D Mold Steel (High-End Corrosion-Resistant Steel)

Can be polished up to #18,000, achieving optical-grade surface quality.
Ideal for ultra-precise applications like transparent POM boxes and lens scales.
Compared to standard S136, it has better structural uniformity, avoiding defects like pitting and hazing.

YH136 Mold Steel (Cost-Effective Alternative)

Polishes up to #12,000, more affordable than S136-D.
Suitable for mid-to-high-end applications requiring defect-free surfaces (e.g., automotive reflector lenses).

718H Mold Steel (General-Purpose Pre-Hardened Steel)

Hardness: HRC 33-38, stable machinability.
Suitable for high-gloss molds with higher injection pressure.

Polishing Techniques for High Gloss Molds

Diamond Paste Polishing: Required for optical-grade molds (beyond #12,000 grit).
Electropolishing: Enhances corrosion resistance in high-gloss injection molding.
Hand Polishing: Critical for final mirror-like surface refinement.

Applications and Advantages of High Gloss Mold

Glossy Appearance: Products exhibit a flawless, shiny surface free from shrinkage and weld lines, ideal for high-end aesthetic requirements.
Direct Usability: Eliminates the need for post-processing, allowing immediate assembly.
High-Quality Standards: Demands superior mold steel and plastic materials to ensure product excellence.

Maintenance and Care for High Gloss Mold

Heating Treatment: Maintain proper heating during operation, often using resin insulation plates to prevent heat loss.
Regular Inspections: Periodically check heating systems and insulation to ensure optimal performance.
Precision Control: Use solenoid valves and time relays to precisely regulate injection timing and temperature, ensuring consistent product quality.

With over 15 years of expertise in high-gloss mold manufacturing, we specialize in delivering mirror-finish precision for automotive, electronics and medical applications. Our optical-grade polishing (up to #18,000 grit) using premium steels like NAK80 and S136-D ensures flawless surface quality. Contact our team today to discuss your high-gloss molding needs – let’s create something exceptional together.