Low-pressure structural foam molding requires nitrogen gas and/or a chemical blowing agent to be mixed with the melted resin. This mixture is then injected into a mold under significantly lower pressure than traditional injection molding techniques. Structural foam molding produces very large parts with thicker walls, making them very durable.

Large plastic products can be produced in two ways, large-tonnage injection molding and large-tonnage structural foam molding. Both can produce products that can replace metal, wood, concrete, or fiberglass. Each process, however, has its benefits and specific applications, so it is important to understand the processes and their benefits.

Structural foam’s ability to withstand thermal expansion makes it ideal for products that will be exposed to a wide range of temperatures. Whether it is heat or cold, these products will not warp or lose their properties if exposed to extreme temperatures.

Barrel Temperature: This is typically controlled in three zones. The front zone ranges from 210 - 230°C, the middle zone from 220 - 240°C, and the rear zone from 200 - 220°C. Injection Pressure: A relatively high injection pressure, usually within the range of 80 - 130 MPa, is required to overcome the viscosity of the melt. Injection Speed: A fast injection speed is employed to reduce the melt's residence time in the mold cavity and lower internal stress. Holding Time and Pressure: Appropriate holding time and pressure help compensate for the melt's shrinkage, enhancing the product's dimensional accuracy and stability. Mold Temperature: It is commonly controlled at 60 - 90°C to facilitate the cooling and solidification of the product.

In the world of manufacturing, the injection molding process for acrylic, also known as polymethyl methacrylate (PMMA), is a technique that demands precision and expertise. Let's delve into the details of this fascinating process.

Working with a manufacturer who has large tonnage capabilities in both low-pressure structural foam molding and high-pressure injection molding grants you a wider range of manufacturing options so you get the best product possible.

At Port Erie, we will assess your part and help you determine which process is best for your product’s functionality and your budget. If you need, our engineering team can get involved to help optimize your design, so it is as compatible with its manufacturing process as possible.

Low-pressure structural foam molding can create parts with variable wall thicknesses. However, cycle time will be determined by the thickest part.  Uniform wall thickness is always best.  Also, due to the low pressure used in the process, there is a reduced risk of warping and deformation during the manufacturing process.

Polyethylene is a durable and lightweight resin that offers excellent load-bearing, shock absorption, vibration-dampening properties, and resistance to chemicals, grease, and moisture. Polypropylene is a rigid and lightweight resin offering excellent compression and impact resistance, as well as chemical, temperature, and moisture resistance.

The mold plays a critical role in the quality of the final product. The mold material must exhibit excellent wear resistance and corrosion resistance. A well-designed gate and runner system is essential to guarantee balanced melt flow, minimizing internal stress and deformation.

Injection molding requires plastic resin pellets to be melted down in the barrel of the injection molded machine. The melted resin is then forced into the mold through a high-pressure nozzle, forcing the material into all parts of the mold cavity. As the plastic cools and hardens, it retains the shape of the mold.

There are three common resins used in high-pressure injection molding: HDPE, ABS, and polypropylene. Again, each has its own advantages and is chosen based on the application of the product being produced.

Polypropylene is a lightweight, cost-effective, rigid resin. Its chemical and heat resistance along with its high tensile strength and impact tolerance make it a great choice for a wide range of products.

Port Erie’s large-tonnage injection molding creates large parts with walls thinner than 0.25 inches. Our machines are capable of handling up to 1,650 tons and can create parts up to 20 pounds.

Luckily, while the injection molding process doesn’t produce much waste, any unused or waste plastic produced can be recycled for future products.

Many parts of the injection molding process are being automated, including loading and unloading, inspection and quality control, assembly, and more. Using automation and robotics during the manufacturing process helps to reduce labor costs and production time, increasing your cost savings.

The dried acrylic pellets are loaded into the injection molding machine's barrel. The material is heated and plasticized until the melt achieves the desired fluidity. The melt is then injected into the mold cavity. Subsequently, the holding, cooling, and solidification stages take place.

To further enhance the quality and performance of the products, annealing treatment is often carried out. This process helps eliminate internal stress and improves the product's properties and stability. Annealing is typically conducted at a temperature of 70 - 80°C, with the annealing time depending on the thickness and size of the product. Additionally, surface treatments such as polishing and coating can be applied to improve the appearance and performance of the products.

HDPE, or high-density polyethylene, is a flexible and waterproof resin. It has good low-temperature resistance, chemical resistance, and corrosion resistance, and is easily processed at an affordable price.

Cycle times for injection molding are very short—sometimes only lasting a handful of seconds. It is also possible to use a multi-cavity to produce several different parts in one run, saving even more production time.

At Port Erie Plastics, we are dedicated to providing our clients with the highest quality plastic products possible. From engineering to injection molding or structural foam molding and value-adding secondary operations plus distribution and warehousing, we have you covered.

High-pressure injection molding is used to create many outdoor products, including DuraTrac outdoor floors and lawn or garden carts.

The most common resins used in structural foam molding are polyethylene and polypropylene. Both resins possess advantageous properties that make them ideal for this process.

Structural foam molding and these two resins are great for creating large industrial totes and grilles for lawn and garden tractors due to their durability and resistance to heat, chemicals, and moisture.

Injection molding can be used to produce large plastic products with thinner walls. These products tend to be lighter than those produced by structural foam molding, usually weighing less than 20 pounds.

This manufacturing process can produce identical parts over and over. Additionally, the high-pressure forces used force the plastic against the mold walls, creating highly complex designs with intricate details.

Structural foam molding also allows for the production of very large plastic products with thicker walls. These products are generally heavier than injection molded products, weighing 50 pounds or more. However, structural foam molded products are still more lightweight than solid plastic parts.

Our large tonnage structural foam molding produces parts up to 50 pounds with walls thicker than 0.25 inches. These parts are heavy but would weigh significantly more if they were solid plastic.

Choosing the right injection molding machine is paramount. The machine should possess precise temperature control and adjustable injection pressure capabilities. A suitable screw is also necessary to ensure uniform plasticization of the material.

In conclusion, the acrylic injection molding process is a complex yet rewarding manufacturing technique. Fine-tuning the parameters based on specific product requirements, equipment capabilities, and material characteristics is essential to achieving high-quality injection-molded acrylic products.

ABS is a very durable resin with high durability. It also has high tensile strength and is very resistant to physical impacts and chemicals.

Due to the lower pressure used in this molding process, the tooling used does not need to be as durable as high-pressure injection molding tools, saving you money.

The first step in the acrylic injection molding process is the careful selection and preparation of materials. High-quality acrylic pellets are essential to ensure the final product's purity and stability. These pellets need to undergo a drying process, typically at a temperature range of 80 - 90°C for 2 - 4 hours. Moisture removal is crucial as it prevents the formation of bubbles and silver streaks during the injection molding process.