Trivex is growing in popularity as a lens material, prized for its lightweight durability, optical clarity and impact resistance. But unlike other common lens materials such as polycarbonate, trivex isn’t made using the injection molding process. This has led many to ask: can trivex be injection molded? As a professional plastic injection molding manufacturer, I will help you find it out!
Can Trivex Be Injection Molded?
No, trivex cannot be injection molded. Trivex lenses are made using a cast molding process, which provides sharper optics compared to injection molding.
Why Not Injection Mold Trivex?
Injection molding is a much faster, higher-volume process than cast molding. Molten plastic is injected under high pressure into lens molds then rapidly cooled to set the lens material.
For most purposes this works well. But the extreme heat and pressures can result in internal molecular alignment and stress patterns that reduce optical performance.
These optical compromises are unacceptable for a high-end lens material like Trivex. So it is exclusively made using the slower, more optically precise cast molding method.
How Trivex Lenses Are Made
Trivex lenses start as a urethane-based liquid monomer, which is poured into heated molds. The liquid then hardens, or “cures”, resulting in a finished lens.
This cast molding process allows the liquid trivex to spread evenly into every part of the mold, producing a lens that maintains its optical integrity from edge to edge.
The Benefits of Cast Molding Trivex
There are a few key advantages to making lenses with a cast molding process rather than injection molding:
- Sharper optics: The even flow of liquid into the mold prevents internal stresses and optical distortion.
- More dimensionally stable: Trivex resists warping or changing shape over time better than injection molded lenses.
- Lower birefringence: Cast molding produces very low internal stresses in the lens, resulting in less vision-blurring birefringence.
How Trivex Compares to Polycarbonate
Polycarbonate lenses have long been the most popular lenses for impact protection and durability. Unlike Trivex, polycarbonate is almost always injection molded.
This allows polycarbonate lenses to be made inexpensively and in high volumes. But injection molded polycarbonate does suffer from some minor reduction in optics. Their lower Abbe value also results in more chromatic aberration and peripheral color fringing.
For most people, polycarbonate lenses work just fine. But the cast molded Trivex process offers better optics for those who want superior visual performance from their durable eyeglass lenses.
When Does Production Method Matter?
For single vision and lower prescription powers, both polycarbonate and Trivex provide excellent lens performance.
But with higher prescriptions, especially high-minus lenses over -6.00, subtle compromises from the injection molding process become more apparent through increased distortions at lens edges.
That makes Trivex an ideal choice for rimless frames or safety glasses, since the whole lens is utilized for vision. Their optical uniformity edge-to-edge provides optimal peripheral vision.
Can Any Lens Be Cast Molded?
Pretty much any lens material can be cast molded. Even polycarbonate can theoretically be cast into lenses rather than injection molded.
CR-39 plastic lenses have been cast molded since they were first introduced. Some high index plastics are also primarily made by the cast molding method.
But each lens material has its own specialized casting process tailored around its unique chemical properties.
Trivex in particular works well as a cast-molded material. Attempting to adapt it to injection molding would require chemistry changes to the raw formulation that would erase many of trivex’s inherent performance advantages.
The Takeaway
While technical details between lens materials may seem subtle to most eyeglass wearers, production methods significantly impact lens optics and durability.
Trivex has been engineered and optimized specifically for casting into lenses, making injection molding unfeasible. Yet for those demanding peak performance in rugged yet comfortable eyewear, cast molded Trivex hits a sweet spot between optical performance, weight, impact resistance and all-day wearability.
So in summary – No, trivex lenses cannot be made by injection molding. But their specialized cast molding process results in a best-in-class lens worthy of consideration by anyone wanting top-tier eyewear.
Frequently Asked Questions
Is injection molding cheaper than cast molding lenses?
Yes generally injection molding is a faster, cheaper process. But for optical quality lenses like Trivex, cast molding results in better and more consistent end products.
Why don’t they just cast mold polycarbonate too?
Polycarbonate lenses have been injection molded for decades, with huge existing manufacturing capacity optimized around this process. Switching formulations and re-tooling factories to cast mold would require massive industry investment.
Trivex was engineered from inception for optical quality cast molded production. This allowed its material properties and manufacturing to be designed in unison for maximum performance.
What’s the best lens material: polycarbonate or Trivex?
Both make terrific impact resistant eyewear materials, with more similarities than differences for most prescriptions. Polycarbonate wins on cost and thinness. Trivex offers better optics, lower weight, less allergy risk and greater chemical resistance – advantages that become more significant in higher prescriptions.
