Mirror-Steel Clear Plastic Injection Mold

Mirror-Finish Tooling for Clear Molded Components

The clear plastic injection mold is developed for parts where transparency, gloss and visual consistency form part of the functional requirement. Optical covers, medical housings, light guides and transparent windows can reveal minor cavity marks, trapped gas or uneven resin flow that would remain unnoticed on opaque components.

S136 mirror mold steel provides the corrosion resistance and polishing response needed for clear PC and PMMA molding. After precision machining and heat treatment, the cavity passes through several polishing stages until the surface reaches an optical-grade Ra≤0.02 μm finish. This refined cavity surface helps reproduce smooth, bright parts without transferring cutter marks or polishing waves onto the molded component.

Controlling Flow Marks, Bubbles and Optical Distortion

Transparent molding depends on the relationship between gate position, vent depth, cooling layout and cavity finish. An unsuitable gate can create visible flow lines or weld marks across the viewing area. Restricted venting may trap air, causing burns, bubbles or incomplete filling. Uneven cooling can introduce shrinkage and optical distortion.

The mold structure addresses these risks before steel cutting begins. Flow direction, wall thickness changes and visible surfaces guide the placement of gates and vents. Cooling channels manage temperature across the cavity, while controlled assembly protects the polished surface from mismatch at inserts and parting lines.

Technological Process

1. Product & Mold Design: Optimize gate, venting and cooling solutions based on clear part structure, complete 3D mold design and 2D machining drawings.
2. Steel Cutting & Rough Machining: Cut S136 mirror steel to size and perform rough milling to remove most of the excess material.
3. Semi-finishing & Heat Treatment: Semi-finish the mold components and perform quenching treatment to stabilize S136 hardness at HRC48-52, improving wear resistance and polishing performance.
4. Precision Machining: Multi-axis CNC finish the cavity and inserts; wire-cut EDM process holes; EDM finish sharp corners and ribs.
5. Ultra-Mirror Polishing: Perform multi-step polishing on the cavity to optical standards, achieving Ra≤0.02μm mirror finish to eliminate flow marks and defects.
6. Mold Assembly & Trial Molding: Complete mold assembly, conduct multiple trial moldings and adjustments to ensure light transmittance, appearance and dimensions of clear parts meet requirements before delivery.

Core Advantages & Applications

Common Applications

• Optical Industry: Molds for lenses, prisms, light guides and other optical transparent parts
• Medical Industry: Molds for syringes, infusion sets and transparent consumable housings
• Consumer Electronics: Molds for mobile phone lens protectors, home appliance transparent panels and LED lampshades
• Industrial Products: Molds for transparent windows, protective covers and sensor housings

Trial samples are reviewed under direct light to reveal haze, flow lines, bubbles, gloss variation and surface distortion. Dimensional checks cover the viewing area, assembly edges and functional mounting points. Before release, the clear plastic injection mold undergoes repeated molding adjustments until the transparent part meets the required appearance, fit and light-transmission criteria.

Specification Table