Acrylic, known for its glass-like clarity and excellent weather resistance, is a popular material in various industries, from automotive to medical devices. Let’s dive into what makes acrylic injection molding so special, how the process works, and what you should consider to get the best results.
What is Acrylic Injection Molding?
Acrylic injection molding is a manufacturing process where acrylic resin is heated until it becomes a molten liquid. This liquid is then injected into a mold cavity under high pressure. Once cooled, the acrylic solidifies, taking the shape of the mold. This process allows for the creation of complex and detailed parts with high precision.
Why Choose Acrylic?
Acrylic, also known as polymethyl methacrylate (PMMA), offers several advantages:
- Acrylic delivers superior optical clarity, making it a top choice for transparent applications.
- It withstands UV light and outdoor conditions without yellowing or degrading.
- More impact-resistant than glass, it provides reliable performance in various applications.
- Acrylic is lighter than glass, making it easier to handle and transport.
- Generally more affordable than glass and other transparent materials, offering a budget-friendly option.
- Simple to cut, mold, and fabricate, allowing for flexibility in design and manufacturing.
Acrylic Material Properties
Here’s a table the properties of acrylic material:
| Category | Property |
|---|---|
| Density (g/cm³) | 1.13-1.19 |
| Shrinkage Rate (%) | 0.4-0.61 |
| Rockwell Hardness (R) | 71-102 |
| Tensile Strength at Yield (PSI) | 6,390-10,700 |
| Elongation at Break (%) | 3.0-12 |
| Flexural Modulus (PSI) | 247,000-509,000 |
| Flexural Strength (PSI) | 6,770-18,900 |
| Impact Strength (Izod, kJ/m²) | 1.0-1.2 |
| Heat Deflection Temp (°C) | 85-95 |
| Thermal Conductivity (W/m·K) | ~0.19 |
| Water Absorption (%) | ~0.3-0.5 |
| Drying Temperature (°C) | 75-91 |
| Drying Time (hrs) | 3.4-5.1 |
| Melt Temperature (°C) | 225-272 |
| Mold Temperature (°C) | 59.4-81.1 |
The Process of Acrylic Injection Molding
Here’s a step-by-step breakdown of how acrylic injection molding works:
- Material Preparation: Acrylic resin pellets are carefully selected and dried to remove any moisture that could affect the final product’s quality. Moisture can cause bubbles or imperfections during the molding process.
- Melting and Injection: The dried acrylic pellets are fed into an injection molding machine, where they are heated to a molten state. The molten acrylic is then forced under high pressure through a nozzle and into a precision-engineered mold cavity.
- Cooling and Solidification: Once the acrylic fills the mold cavity, it is rapidly cooled to solidify.
- Ejection and Post-Processing: After the acrylic has sufficiently cooled, the mold is opened, and the molded part is ejected. Depending on the requirements, post-processing steps such as trimming, polishing, or painting may be necessary to achieve the desired finish.
Key Design Guidelines for Acrylic Injection Molding
Here are some key injection molding design guidelines:
- Wall Thickness: Maintain a wall thickness between 0.025″ and 0.150″ (0.635 to 3.81 mm). Ensure consistent thickness throughout the part to avoid defects.
- Radii: Avoid sharp corners. Use a radius at least 25% of the wall thickness for improved moldability and reduced stress. For enhanced strength, aim for a radius of 60% of the wall thickness.
- Draft Angle: Implement a draft angle between 0.5° and 1° to facilitate easy ejection from the mold. For optically clear parts, a larger draft angle may be necessary for a smoother finish.
- Part Tolerance:
- Commercial Tolerance: For parts under 160 mm, tolerance ranges from 0.1 to 0.325 mm.
- Fine Tolerance: For parts 100 mm or smaller, achieve tolerances from 0.045 to 0.145 mm.
Proper processing is crucial to avoid common issues such as surface defects, dimensional inaccuracies, and thermal degradation.
- Acrylic absorbs moisture, which can lead to cloudiness and injection molding defects if not properly dried. Dry acrylic pellets for 3.4 to 5.1 hours before processing.
- Avoid overheating acrylic to prevent thermal decomposition, which causes brown or burn marks.
- Higher pressures are generally needed due to acrylic’s viscosity. Too high pressure can cause parts to stick, while too low pressure may lead to out-of-tolerance parts.
- Optimal speed prevents issues like burning and poor finish. Too fast speeds can cause defects, while too slow speeds may result in incomplete mold filling.
- Acrylic shrinks 0.4 to 0.61% during cooling. Account for this in mold design to ensure dimensional accuracy. Shrinkage is influenced by pressure, temperature, and holding conditions.
Advantages of Acrylic Injection Molding
Acrylic injection molding offers several compelling advantages, making it a popular choice for producing clear and durable plastic parts:
- Acrylic can be easily colored, textured, or coated to meet specific design and functional requirements.
- Requires less energy due to lower processing temperatures, reducing costs.
- Resists sunlight and rain, ideal for outdoor use.
- Maintains accurate dimensions, even in high-volume production.
- Withstands various chemicals, suitable for industrial applications.
- Offers high clarity with 91%-93% light transmittance.
- 100% recyclable, making it an eco-friendly alternative to glass.
Applications of Acrylic Injection Molding
Acrylic injection molding is used in a wide range of applications, including:
- Optical Lenses
- Display Panels
- Light Covers
- Automotive Tail Lights
- Protective Covers
- Medical Device Casings
- Signage and Displays
- Aquariums
- Phone Cases
- Cosmetic Containers
- Lighting Fixtures
- Glass Replacement Panels
What Temperature is Acrylic Molding?
In acrylic injection molding, the melt temperature ranges from 225°C to 272°C (437°F to 522°F), while the mold temperature is typically between 59.4°C and 81.1°C (139°F and 178°F). Proper temperature control is crucial for achieving high-quality, defect-free parts.
Top-Quality Acrylic Injection Molding
BOYI offers top-notch acrylic injection molding services, delivering clear, durable parts with precision. From custom solutions to high-volume production, trust us for quality and efficiency.
Ready to elevate your projects with high-quality acrylic parts? Contact BOYI today to discuss your needs and discover how our acrylic injection molding services can bring your vision to life.
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FAQ
The primary material used for acrylic injection molding is polymethyl methacrylate (PMMA), also known as acrylic glass. It’s a clear, durable thermoplastic with excellent optical clarity and weather resistance.
Acrylic injection molding specifically utilizes acrylic resins, known for their clarity and durability. It differs from other plastic molding methods in terms of material properties and the unique challenges that come with molding acrylic, such as controlling temperature and pressure to avoid warping or discoloration.
Acrylic offers benefits such as exceptional optical clarity, durability, and weather resistance. It’s also lightweight and can be easily formed into complex shapes. Additionally, acrylic can be recycled, making it an environmentally friendly choice.
Yes, acrylic injection molded parts are suitable for outdoor use due to their weather resistance and durability. However, it’s important to consider the specific application and environment to ensure proper material selection and design.
Yes, acrylic injection molded parts can be customized with colors, textures, or coatings during the molding process or as a post-processing step. This allows for a wide range of design options.
Catalog: Injection Molding Guide
This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.
