Acrylic is a versatile plastic material that can be injection molded to create a variety of products. But can acrylic actually be injection molded? And what does the process look like?
In this complete guide, as a professional plastic injection molding manufacturer, I’ll walk you through everything you need to know about acrylic injection molding.
What is Acrylic?
Before diving into acrylic injection molding, it’s important to understand exactly what acrylic is.
Acrylic, also known as polymethyl methacrylate (PMMA), is a clear plastic that resembles glass but is less fragile. It is made from acrylic acid and methacrylic acid polymers.
Some key characteristics of acrylic:
- Optical clarity – Acrylic transmits 92% of visible light, giving it excellent transparency
- Impact resistance – Acrylic withstands impacts 10x better than glass
- Weather resistance – It resists yellowing and remains glossy when exposed to UV light
- Lightweight – Half the weight of glass
- Versatile – Can be tinted, mirrored, or made opaque
This unique combination of properties makes acrylic useful for all kinds of applications from signage to aquariums.
The Acrylic Injection Molding Process
Now that you know what acrylic is, let’s look at how acrylic injection molding works.
Step 1: Mold Preparation
Acrylic injection molding starts with creating a custom mold. The mold consists of two halves – the cavity side and core side. When closed, it forms a hollow chamber that gives the acrylic its shape.
Molds require precision CNC machining and must withstand high temperatures and pressure. Stainless steel and aluminum alloys like 6061 are common mold materials.
Step 2: Heating the Acrylic
Acrylic pellets are loaded into the injection molding machine’s hopper. An internal screw feeds the material forward where heaters melt it into a liquid state.
Typical acrylic melt temperatures range from 425°F to 572°F (220°C to 300°C). Careful temperature control prevents overheating and material degradation.
Step 3: Injecting the Acrylic
After melting, the liquid acrylic flows into an accumulator. Once there is enough molten plastic, the injection ram pushes it into the mold at high pressure – usually between 15,000 to 30,000 PSI.
The pressure forces acrylic to fill every crevice of the mold cavity, ensuring accurate replication of even the smallest features.
Step 4: Cooling and Solidifying
Cooling channels circulate water to bring down the temperature inside the mold. This solidifies the acrylic into its final plastic form.
Cooling time depends on part thickness but is typically under 2 minutes. Fast cooling prevents distorted or warped parts.
Step 5: Part Ejection
Opening up the mold ejects the finished acrylic part. Ejector pins help separate the part from mold surfaces without damage. Some parts may also require additional trimming to remove excess plastic.
After ejection, the mold closes and repeats the injection molding sequence for the next part. Automated machines produce thousands of identical acrylic parts per day.
Benefits of Acrylic Injection Molding
There are several notable benefits that make acrylic well-suited for injection molding:
Low Cycle Times – Acrylic flows easily into molds and solidifies quickly, enabling fast production cycles under 1 minute.
Dimensional Stability – Cured acrylic parts maintain precise dimensions without shrinkage or warpage.
Optical Clarity – Injection molded acrylic retains its crystal clear transparency, an important advantage over other plastics.
Complex Geometries – Smooth flow translates to easy molding of intricate product shapes and fine details.
Weather Resistance – Unlike other plastics, acrylic resists yellowing, fading, and cracking from UV exposure.
Lower Costs – Acrylic material is inexpensive compared to exotic engineering plastics, further reducing manufacturing costs.
Recyclability – Scraps and rejects can be reground and remolded instead of ending up in landfills.
Applications of Acrylic Injection Molding
Thanks to its versatility, acrylic finds use across many industries:
Signage
Storefront signs, displays, letters, logos, exhibit graphics.
Lighting
Lenses, light pipes, lamp covers, LED housings.
Automotive
Headlamp assemblies, taillights, mirror housings.
Medical
Inhalers, medical device housings, orthodontics.
Consumer
Appliances, electronics, furniture, cosmetics, housewares.
This list just scratches the surface of injection molded acrylic applications – new uses are constantly being explored as designers tap into acrylic’s potential.
Design Considerations for Acrylic Injection Molding
Certain design principles must be followed when injection molding acrylic to prevent defects:
Uniform Wall Thickness
Sudden changes in part thickness can lead to uneven filling. Keep walls a consistent thickness wherever possible.
Avoid Sharp Corners
Sharp corners act as stress concentration points. Rounded edges improve impact strength.
Draft Angles
Tapered walls and surfaces allow parts to slide out of molds easily during ejection.
Proper Gate Placement
Gate location influences how acrylic flows into the mold. Make sure gates promote uniform filling.
Factoring in these guidelines upfront prevents downstream manufacturing issues and improves part quality.
Is Acrylic Suitable for Injection Molding?
So after going over the acrylic injection molding process – can acrylic actually be injection molded?
The answer is a definite yes. Acrylic offers many benefits that make it an ideal injection molding material:
- Flows easily into molds
- Cures rapidly
- Maintains excellent optical clarity
- Produces intricate, detailed shapes
- Resists environmental degradation
Injection molded acrylic brings designers one step closer to replacing glass with shatterproof, crystal clear plastic. And continued advances in acrylic formulations open up even more possibilities across industries and applications.
So if your project calls for clear molded parts with fine details, acrylic is an excellent material option worth considering. Reach out to an injection molding company to explore your acrylic manufacturing options further!
