Skip to content 
Benefits of Injection Molded Surface Finishes
Injection Molded Surface Finishes Specification
Specification |
Description |
|---|---|
| SPI A1 – A3 (High‑Gloss) | Precision diamond‑polished mold surfaces; SPI A1 is mirror‑grade flawless, A2–A3 are near‑perfect high‑gloss. Ideal for lenses, display covers, and premium cosmetic housings. |
| SPI B1 – B3 (Semi‑Gloss) | Fine grit polish; smooth, low‑sheen finish with minimal reflection. Balances appearance and ease of manufacturing for general visible parts. |
| SPI C1 – C3 (Matte / Satin) | Stone or fine grit finish; non‑reflective, smooth satin feel. Resists fingerprints and hides minor mold marks; perfect for medical devices and control panels. |
| SPI D1 – D3 (Textured / Blast) | Etched or bead‑blasted surface; uniform matte or subtle stipple texture. Hides wear and defects, improves grip for functional components. |
| VDI 12 – VDI 45 | Standard European texture codes; lower numbers finer/smoother, higher numbers deeper/more pronounced grain. Covers matte, orange peel, and patterned finishes. |
| Custom Grain / Texture | Mold‑etched or laser‑textured patterns including leather, geometric, stipple, or anti‑slip profiles. Matches ergonomic, branding, or functional requirements. |
| As‑Molded | Unmodified surface straight from the tool; retains natural mold finish with minimal processing. Best for internal or cost‑critical functional parts. |
| Pad / Screen Print | Crisp, durable text, logos, or markings applied post‑molding. Precise registration for control panels and branded components. |
| UV / Clear Coat | Transparent protective layer; boosts scratch, chemical, and UV resistance while preserving or enhancing base finish. |
| Metallization / Plating | Vacuum‑deposited chrome, gold, silver, or brushed metal effect; delivers premium metallic look without heavy plating. |
| Soft‑Touch Coating | Rubber‑like, non‑slip, velvet‑feel layer; improves grip and comfort for handheld devices and controls. |
Design & Tooling Considerations For Injection Molded Surface Finishes
Finish selection directly impacts draft angles, material choice, and mold design. Gloss surfaces need 0.5°–1° draft and high‑quality steel; textures require extra draft per depth and hide minor marks. Always specify SPI/VDI codes early, align wall thickness, and position gates/ejectors carefully to ensure consistent results, avoid rework, and balance quality with cost.
Draft Angles
Smooth/gloss finishes need 0.5°–1° draft. Textured finishes require +1° extra draft per 0.025 mm depth to prevent drag or ejection marks.
Texture Depth
Deeper grains need more draft and may increase tool wear; keep textures uniform across adjacent faces where possible.
Gate & Ejection
Gloss surfaces highlight gate marks and witness lines—position gates on hidden faces or use post‑finishing. Textures help mask these marks.
Material Fit
Amorphous plastics (ABS, PC) hold high‑gloss best; semi‑crystalline materials (PP, POM) suit matte/texture more reliably.
Tolerance Impact
Most finishes add negligible thickness, but heavy coatings or deep texture should be accounted for in critical fit dimensions.
Injection Molded Surface Finishes Materials
We work with a wide range of certified, traceable materials selected to match your performance, regulatory, and application requirements. Our engineers provide DFM guidance to optimize your plastic and metal parts design for manufacturing. Contact us or upload a CAD file for material options, instant quotes, and custom production solutions.
CNC milling services supports a wide range of additional metals, plastics, and composites.
Visit our materials page for a full list.
Injection Molded Surface Finishes
Medical CNC parts require surface finishes that meet strict regulatory, biocompatibility, and sterilization standards. Unlike general industrial machining, every finish must be cleanable, corrosion-resistant, and traceable with no crevices where bacteria or contaminants can harbor.
SPI A-2 High Gloss (Diamond Buff)
Passivation process
Industry-standard high-gloss mold finish achieved by polishing the mold cavity with #6 diamond buff. Produces a mirror-like, highly reflective plastic surface the smoothest and glossiest injection molded finish. Used for automotive interior trim, cosmetic enclosures, consumer electronics housings, and any part requiring a premium glossy appearance that reflects light uniformly.
SPI B-2 Semi-Gloss (400 Grit Paper)
Passivation process
Industry-standard semi-gloss mold finish produced by finishing the mold cavity with 400-grit sandpaper. Produces a uniform satin surface with moderate reflectivity smoother than matte but less reflective than high gloss. The most commonly specified finish for consumer products, appliance housings, and general-purpose injection molded parts where a refined, non-mirror appearance is desired.
SPI C-2 Matte (400 Grit Stone)
Passivation process
Industry-standard matte mold finish produced by finishing the mold cavity with 400-grit grinding stone. Produces a uniform low-gloss, non-reflective matte surface that hides fingerprints, minor scratches, and flow marks. Used for industrial enclosures, power tool housings, medical device casings, and functional parts where a durable, non-glare matte appearance is preferred over cosmetic gloss.
SPI D-2 Satin (Dry Blast)
Passivation process
Industry-standard satin mold finish produced by glass bead blasting the mold cavity. Produces a uniform matte satin, non-reflective surface with a fine, consistent grain texture that hides weld lines, flow marks, and surface defects. The most popular finish for medical devices, consumer electronics, and industrial components where a clean, uniform, non-glare surface is required at moderate cost.
Custom Mold Texture (Mold-Tech / Grain)
Passivation process
Custom surface texture created by chemical etching (photo-engraving) the mold cavity to reproduce patterns such as leather grain, wood grain, stipple, geometric designs, or branded textures directly onto molded parts. Adds tactile grip, hides surface defects, and simulates premium materials. Used for automotive interior panels, consumer product grips, power tool housings, and any part requiring a specific textured surface for ergonomic or aesthetic purposes.
Vapor Polished
Passivation process
Post-molding chemical process that exposes transparent plastic parts (acrylic, PC, PETG) to solvent vapor, melting and smoothing the surface micro-layer to dramatically improve optical clarity and gloss. Removes molding lines and produces crystal-clear transparent parts essential for lenses, light guides, display windows, fluidic chambers, and medical components requiring optical transparency that cannot be achieved by mold polishing alone.
Painted
Passivation process
Post-molding spray painting in any custom RAL/Pantone color, including metallic, matte, satin, or gloss finishes. Applied over a primed molded plastic surface for uniform color and adhesion. Allows injection molded parts to match final production aesthetics widely used for automotive bumpers and trim, consumer electronics enclosures, appliance housings, and marketing/showcase components requiring exact brand color matching.
Chrome Plated
Passivation process
Post-molding electroplating process that deposits a bright mirror-like chrome metallic layer over ABS or PC/ABS plastic substrates. Produces a highly reflective, premium metallic appearance with excellent scratch resistance. Used for automotive grilles, emblems, trim, decorative hardware, appliance components, and consumer product parts requiring a realistic chrome metallic finish to validate production aesthetics and durability.
Pad Printed / Silk Screened
Passivation process
Post-molding decoration process that transfers ink graphics, logos, text, symbols, and button labels onto molded plastic surfaces via pad printing (for curved/irregular surfaces) or silk screening (for flat surfaces). Produces crisp, durable, multi-color graphics with precise registration. Used for remote controls, keypads, instrument panels, electronic enclosures, and any injection molded part requiring permanent branding, labeling, or functional graphics.
Hydro Dipped / Water Transfer Printing
Passivation process
Post-molding decoration process that transfers printed patterns (carbon fiber, wood grain, camouflage, marble, custom designs) from a water-soluble film onto the entire 3D surface of molded plastic parts, including complex curves and recesses. Produces a seamless, full-coverage decorative pattern with excellent adhesion. Used for automotive interior trim, consumer electronics, sporting goods, and any injection molded part requiring a premium patterned finish that conforms to complex geometries.
