Acrylic injection moulding

In addition, our company has established cooperative relationships with plastic raw material suppliers, printing manufacturers, etc. to ensure the supply of raw materials and printing quality. Through our rich experience and perfect supply chain, our company can provide customers with high-quality customized acrylic injection moulding products to meet their specific needs. At the same time, we have 10 years of professional foreign trade service experience, understand the foreign trade process, and better serve our customers. For acrylic injection moulding products, we can make corresponding plastic parts, which is mainly done through injection molds.

Acrylic, chemically known as (PMMA), is renowned for its exceptional optical clarity, excellent weather resistance, high surface hardness, and good processing properties. The injection molding process is similar to that of ordinary plastics, but specific requirements are imposed on the details due to the material's properties.

The entire process is also divided into three main stages: pre-molding preparation, the injection molding cycle, and post-molding processing and inspection.

Stage 1: Pre-molding Preparation (Extremely Critical)

For acrylic, this stage is crucial for success; improper handling can lead to irreversible defects.

Raw Material Selection and Pretreatment:

Material: Injection-molding-grade PMMA granules. Various grades are available, including standard clear, impact-resistant, UV-resistant, and various colors, depending on your needs.

Drying: This is the most critical step. PMMA is highly hygroscopic, and the moisture content must be controlled to <0.03% (typically <0.02%). If the raw material moisture content is too high, hydrolysis will occur during high-temperature injection molding, resulting in the following defects within the product:

Silver streaks: Hair-like streaks.

Bubbles: Small bubbles inside or on the surface of the product.

Cloud-like defects: Reduced transparency.

Reduced molecular weight: Increased brittleness and decreased mechanical properties.

Drying Method: A dehumidifying dryer must be used, drying continuously at 80-90°C for at least 2-4 hours. Conventional hot air dryers are strictly prohibited, as the hot air will carry moisture back into the hopper. If the dried pellets are exposed to air for more than half an hour, re-drying is recommended.

Mold Preparation:

Mold Design: To achieve a high-quality surface finish, the mold cavity must be made of high-quality mold steel (such as NAK80, S136, etc.) and be mirror-polished. Runners and gates should be designed to minimize weld marks and facilitate air venting.

Surface Cleaning: Before closing the mold, the mold cavity must be thoroughly cleaned with a dust-free cloth or high-purity alcohol. Any tiny specks of dust, oil, or moisture will permanently remain on the transparent acrylic part, causing defects.

Phase 2: Injection Molding Cycle (Core Process)

Injection molding parameters must be finely tuned based on the characteristics of PMMA.

1. Mold Closing

The movable and fixed molds are closed and locked under high pressure.

2. Injection and Holding Pressure

Barrel Temperature: PMMA has a narrow processing temperature range, typically between 210-270°C. Temperatures that are too low will result in poor melt flowability and incomplete filling. Temperatures that are too high (over 280°C) can cause material decomposition, discoloration, bubbles, and black specks.

Injection Speed: Use a medium-to-low speed. While high injection speeds facilitate filling, they can also cause excessive shear, leading to melt decomposition (producing black specks) and gas entrainment. For thick-walled products, a slow injection speed is recommended; for thin-walled products, the speed can be increased appropriately to prevent material from cooling.

Holding Pressure: The holding pressure and time are crucial for minimizing shrinkage marks. However, the pressure should not be too high, and the holding time should not be too long. Otherwise, significant internal stress will be generated, leading to deformation during subsequent annealing or stress cracking during use.

3. Cooling

Mold Temperature: Mold temperature has a significant impact on the quality and internal stress of PMMA products. Mold temperature is generally controlled between 60-80°C.

Too low mold temperature: The melt surface cools rapidly, "freezing" the molecular chains, resulting in difficult filling, noticeable weld marks, and high internal stress.

Too high mold temperature: The cooling time is long, resulting in mold sticking and low production efficiency.

Sufficient cooling time is critical for ensuring product finalization.

4. Mold Opening and Ejection

Because PMMA has a high surface hardness but is also brittle, the ejection system must be designed to be balanced and uniform, avoiding the use of sharp ejector pins to prevent whitening or cracking of the product. Typically, large-area strippers or gas-assisted ejection are used.

Stage 3: Post-Processing and Inspection

Gate Removal: Carefully trim or punch out the gates and runners. Trimmed gates should be polished to maintain aesthetics.

Annealing (Stress Relief):

Purpose: Internal stresses generated during the injection molding process can significantly reduce the chemical resistance and cracking resistance of PMMA parts. Annealing eliminates these internal stresses.

Process: The part is placed in a circulating air oven, slowly heated to 70-80°C (typically 10-20°C below the heat distortion temperature), held at this temperature for 2-4 hours, and then slowly cooled to room temperature. Both the heating and cooling rates must be slow to prevent the introduction of new stresses.

Surface Treatment (Optional):

Polishing: For highly demanding optical components, fine polishing may be required to remove minor surface imperfections.

Hard Coating: A wear-resistant coating is sometimes applied to improve surface scratch resistance.

Full Inspection and Packaging:

Appearance Inspection: Carefully inspect under backlight for defects such as silver streaks, bubbles, black spots, scratches, shrinkage, and weld marks. This is a core step in transparent part inspection.

Dimensional Inspection: Use precision measuring tools to ensure critical dimensions meet standards.

Performance Inspection: This may include tests for light transmittance and haze.

Packaging: Each piece must be individually packaged in a soft, insulated material (such as a PE bag or foam pad) to prevent scratches on the surfaces.

We are a acrylic injection moulding manufacturer, providing high-quality acrylic injection moulding manufacturing. As long as you want to customize/develop acrylic injection moulding products, you can find us. We have professional injection mold design and mature manufacturing technology, providing you with one-stop service, from product design-mold making-product production-product packaging-product transportation, we can help you in every link. As long as you come to us, we will provide you with the ultimate service and satisfy you in terms of product quality, production time, information dialogue, etc.

Plastic Injection Mould making

Plastic molding specifications

Mold design:

Transaction process:

Mold testing:

Product packaging

Factory

We are Custom Plastic Mold factory. Our factory is plastic injection mold maker. we has 17 years of experience in professional custom plastic mold and 10 years of foreign trade experience. We are custom Plastic Mold supplier. We can provide custom Plastic Mold service. Our factory can make the Injection molded plastic parts, and the quality of the products will satisfy you.

We have more than 50 high-end machines and hundreds of engineers and designers. We can provide one-stop service, from product design - mold making - product production - product packaging - transportation. We have a complete production chain. We can meet all your requirements.

Services we provide:

Professional custom mold service, Plastic mold design and manufacturing .plastic product production, product design, mold design, blow mold customization, rotational mold customization, die-casting mold customization. 3D printing services, CNC manufacturing services, product packaging, customized packaging, shipping services.

We always adhere to the principles of quality first and time first. While providing customers with the highest quality products, try to maximize the production efficiency and shorten production time. We are proud to tell every customer that our company has not lost any customer since its establishment.If there is a problem with the product, we will seek a solution actively and take responsibility to the end.

FAQ

Q1: Are you trading company or manufacturer ?

A: We are manufacturers.

Q2. When can I get the quotation?

A: We usually quote within 2 days after we get your inquiry.

If you are very urgent, please call us or tell us in your email so that we can quote for you first.

Q3. How long is the lead-time for mold?

A: It all depends on the products' size and complexity. Normally, the lead time is 25 days.

Q4. I have no 3D drawing, how should I start the new project?

A: You can supply us a molding sample, we will help you finish the 3D drawing design.

Q5. Before shipment, how to make sure the products quality?

A: If you don't come to our factory and also don't have the third party for inspection, we will be as your inspection worker.

We will supply you a video for production process detail include process report, products size structure and surface detail, packing detail and so on.

Q6. What is your payment terms?

A: Mold Payment: 40% deposit by T/T in advance, 30% second mold payment before sending out the first trial samples, 30% mold balance after you agree the final samples.

B:Production Payment: 50% deposit in advance, 50% before sending out the final goods.

Q7: How do you make our business long-term and good relationship?

A:1. We keep good quality and competitive price to ensure our customers benefit for best quality products.

2. We respect every customer as our friend and we sincerely do business and make friends with them, no matter where they come from.