Key principles.
Critical
Variable wall thickness causes sink marks visible through transparent material. Keep walls uniform.
Mold cavity
Mold cavity must be polished to optical finish for clear plastic transparency. SPI A1 grade.
Pre-dry essential
Most clear plastics absorb moisture. Pre-drying before injection essential. Wet material = bubbles.
Avoid optical zone
Gate marks visible. Place gate in non-optical area, use cold-runner system.
Avoid scratches
Surface scratches show. Polished mold + careful demolding + protective film during handling.
For impact resistant
PC bendable; PMMA scratches and stress-whitens. Choose material per impact requirement.
FAQ
Acrylic (PMMA): scratch-resistant, brittle, cheap, 92% transparency. PC: tough, scratches easier, 88% transparency.
Plastic: lighter, cheaper, formable. Glass: clearer (95%+), more scratch-resistant, brittle.
CNC machining: edge cloudy. Needs flame-polish or buffing for clear edge. Specify.
Add hydrophilic coating to prevent fog. Specialty coating, premium cost.
PMMA UV-stable. PC yellows with UV unless UV-stabilized. Specify UV grade for outdoor.
Injection molding economical at 1000+ pieces. CNC for prototypes (1-100). Both can produce optical quality.
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