Industry
A light fixture shines through its own plastic. Any flow line, weld line, or speck that would disappear on an opaque part shows up the moment the lamp turns on.
What each part does to the light
Clear, diffuse, reflective, or hidden. Each wants a different resin.
| Part | Job | Usual resin |
|---|---|---|
| Lens or optic | Shape the beam without scattering it | Acrylic for clarity, polycarbonate where impact matters |
| Diffuser | Hide the individual LEDs and spread light evenly | Diffusion grade PC or acrylic, or a textured surface |
| Light pipe | Carry light from a board to an indicator on the surface | Optical grade PC or acrylic |
| Reflector | Bounce light forward from a hot source | High heat PC or BMC, then metallized |
| Housing and bezel | Hold everything, seal it, and look good installed | PC, PC/ABS, or ASA outdoors |
Clear parts
Clear parts are judged lit, so the mold is designed for how the part will look with light behind it.
Aging
LEDs run cooler than old bulbs, but not cool.
Polycarbonate yellows under UV and long heat unless it is stabilized, and the yellow tint shifts the color of the light. Acrylic holds clarity in sun very well but is more brittle and softens at lower temperatures. Outdoor fixtures often use UV stabilized polycarbonate, or acrylic where impact is not a concern.
Heat also concentrates. A lens a short distance from a high output LED runs much hotter than the room, so the resin grade is chosen for the temperature at the lens, not the ambient.
FAQ
Acrylic is clearer, harder to scratch, and holds up in sun. Polycarbonate is far tougher and takes more heat. Fixtures that can be hit or dropped usually go polycarbonate, while fixed indoor optics often go acrylic.
In some designs, yes, with a two shot or overmolded clear window in an opaque body. More often they are separate parts joined by a seal, snaps, or welding, which is simpler to tool.
The texture is cut into the mold surface, so every part carries it with no extra step. The texture choice is tested with the actual LED layout, because it decides how well the individual LEDs are hidden.
The reflector body can be molded in a high heat resin with a very smooth surface, then metallized by a coating supplier. The molded surface finish decides how good the reflection is.
Keep reading
Clear parts, the resins behind them, and the defects light reveals.
Optics, gates, and polish.
LensesCarrying light to an indicator.
Light pipesThe main lens decision.
Polycarbonate vs acrylicClarity that holds up in sun.
Acrylic (PMMA)Bright marks near the gate.
Gate blushClearing up faces after molding.
Vapor polishingBMC reflectors for hot sources.
Thermoset moldingEvery sector page in one index.
Industries hubNext step
Upload CAD with the optical and cosmetic faces marked and the LED position noted. DFM places gates and weld lines away from the light path. NetProto manufacturing is ISO 9001 certified.
