Acrylic is one of the most versatile thermoplastics available. With properties like high optical clarity, good weather and UV light resistance, and excellent dimensional stability, it has a wide range of applications from construction materials to lenses and light diffusers. One of the most common ways to fabricate custom acrylic parts at scale is through injection molding. But can acrylic actually be used for injection molding? As a professional acrylic injection molding manufacturer, I will help you to find it out.
Can Acrylic Be Used for Injection Molding?
Yes, acrylic can absolutely be used for injection molding. The excellent melt flow properties allow acrylic to be readily molded into complex geometries through the injection molding process. Parts can be molded with fine details, dimensional precision, and low levels of internal stress when proper molding guidelines are followed.
Acrylic is commonly injection molded into:
- Lenses
- Light covers and diffusers
- Display cases
- Custom enclosures
- Transparent tubing
How Acrylics Flow
Acrylic flows very well compared to other clear thermoplastics like polycarbonate allowing intricate details and thin walls to be molded. The melt viscosity is temperature dependent though. As temperature increases, acrylic flows much more readily through the injection molding machine allowing for high cavity fill rates.
Shrinkage Control
Like all thermoplastics, acrylic shrinks as it cools down from its melted state. Controlling and accounting for shrinkage through proper tool design is critical for holding tight dimensional tolerances. Acrylic has relatively low levels of shrinkage compared to other materials, generally 0.4 – 0.8%.
Optical Quality
The optical clarity of molded acrylic parts depends heavily on the molding process. Contamination or high internal stresses can significantly reduce light transmission. Properly molded acrylic rivals optical glass with light transmission exceeding 92%.
Acrylic Injection Molding Process Overview
While conceptually simple on the surface, consistently injection molding high quality acrylic components requires careful control of the entire process. Here are the key processing steps when working with acrylic resins:
Drying
As a hygroscopic material, acrylic resins absorb ambient moisture. Exposure to moisture leads to aesthetic defects and potential processing issues. Prior to molding, acrylic pellets must be thoroughly dried to less than 0.02% moisture content. For most grades 3-4 hours at 180°F achieves proper drying levels.
Temperature Control
Maintaining tight control of barrel and mold temperatures is critical to producing high clarity parts free of defects. Typical barrel temperature profiles range from approximately 300 – 390°F. The mold temperature is normally held between 130 – 190°F depending on part geometry.
Injection Speeds
Faster injection speeds lead to higher molecular orientation levels in the molded acrylic part. This negatively impacts optical performance. Slower injection speeds are generally recommended, allowing the molecular chains to lightly flow into place. Typical injection speeds range from slow to moderate.
Hold Pressure
Applying hold pressure at the end of fill allows additional resin to flow into the mold cavities compensating for material shrinkage. This minimizes visible sink marks in the final acrylic part. Care must be taken not to apply excessive pressure leading to flash.
Acrylic Injection Molding Applications
Major markets utilizing injection molded acrylic components include:
Optics
Lenses, prisms, light pipes, display covers
Lighting
Lamp covers, diffusers, illuminated signs
Medical
Clear custom enclosures, fluidic cartridges
Consumer goods
Cosmetic cases, transparent handles
Transportation
Taillight covers, indicator housings
From tiny lenses to large illuminated panels, acrylic can be tailored to meet stringent application requirements through injection molding processes. Consistent quality depends on processing expertise and proper integration of the resin, tooling, and equipment.
Can acrylic be used for injection molding?
In summary, acrylic is an exceptional plastic for injection molding applications requiring:
- Optical clarity
- Precision
- Weather resistance
- Light weight
With careful control of the injection molding process parameters and tool design considerations, acrylic can produce molded parts rivaling optical glass. It enables creative shapes not possible with other transparent materials. Talk to an injection molding expert to determine if acrylic is a fit for your specific application.