Vacuum Casting Materials: How to select?

Vacuum casting is a popular method for low-volume production because it is both fast and cost-effective. However, selecting the right material for a vacuum casting project is crucial to meeting product requirements, particularly when balancing appearance, functionality, and durability. Understanding how vacuum technology works is essential, as material choice significantly impacts the system’s performance.

The vacuum casting process provides access to a wide range of materials, each offering unique properties for various applications. In this article, we will explore some of the most commonly used materials in vacuum casting and what sets them apart.

Introduction To Vacuum Casting

Vacuum casting (also known as urethane casting) is a cost-effective method for producing rigid or rubber-like plastic parts, making it ideal for prototypes and certain end-use applications. It uses silicone molds to create a limited number of copies from a master model, which is typically CNC machined or 3D printed. This process is particularly suitable for parts with fine details, varying thicknesses, and complex shapes.

One major advantage of vacuum casting is its fast production time, with most parts ready in under two weeks. The process supports both rigid and flexible parts and allows for customization with colored or transparent materials. Careful material selection is essential to ensure the best quality and performance of the final part. We will explore this further in the next section.

Vacuum Casting Materials Chart

To walk you through each material, we have summarized a chart to guide you in selecting the right properties for your needs. Here it is:

ABS–like Materials

ABS-like polyurethane (PU) resins are a popular choice in vacuum casting because they offer strength, durability, and stability. They have low viscosity, which makes them easy to work with, and they can handle heat well. These materials produce parts with smooth surfaces that can be painted or finished to look great. They are suitable for many applications, including consumer products.

Hei-CAST 8150, ABS-like

Hei-Cast 8150 offer unique properties not typically found in standard urethane materials. It has well-balanced physical properties, cures effectively, and provides excellent dimensional stability, making it ideal for creating prototypes and testing the strength of injection-molded parts. With its high practical strength, Hei-Cast 8150 is also suitable for producing small batches of parts.

Hei-CAST 8160, ABS-like

The polyol and UP4280-2 (ISOCYANATE) are required to be utilized with ABS UP4280. It has no inherent colour but takes on the colour of whichever polyol it is combined with, changing to colours of off-white (C/2), black (K/2) or pale beige (N/2).

Hei-Cast 8160 has good elongation and is harder to break, making it closer to ABS in strength. Hei-Cast 8160 cures well at low temperatures, reducing the risk of cracks or deformation during demolding. It forms tough, heat- and impact-resistant resin layers, causes less wear on silicone molds, and produces evenly colored parts.

Axson PX 100, ABS-like

PX100 is a popular material for rapid prototyping due to its toughness, durability, and impact resistance. Made from isocyanate and polyol, it has a milky white appearance once combined. PX100 is used in silicone molds to create prototype parts and mock-ups, offering mechanical properties similar to thermoplastics.

Axson PX 215, ABS-like

PX215 is a blend of ABS and unreinforced polycarbonate, known for its strong durability and dimensional consistency. It is UV-stabilized for enhanced durability in harsh conditions. PX215 is most commonly used in injection molding and vacuum casting.

Axson UP 4280, ABS-like

ABS UP4280 requires polyol and UP4280-2 (isocyanate) for use. It has no natural color but takes on the color of the polyol it’s mixed with, resulting in off-white, black, or pale beige. It has similar properties to filled ABS and polystyrene and can be vacuum cast in silicone molds to create high-quality prototypes.

PC–like Materials

PC-like resins are another commonly used vacuum casting materials because they replicate the properties of polycarbonate plastic. These resins, made with the right ratios of polyol and isocyanate, offer optical clarity similar to PC plastic. PC-like resins are ideal due to their excellent dimensional stability, ability to mold into complex shapes, and durability. They are strong and resistant to impacts and stresses, making them perfect for applications that require strength. Additionally, they offer versatility in shape and size, thermal resistance, and are a cost-effective alternative to glass parts.

Axson PX 223 HT, PC-like

PX223HT urethane is only available in black with no color variations. This material is easy to cast due to its low viscosity and offers excellent impact resistance. It is also temperature-resistant and has high flexural strength, good for durable and reliable applications.

Hei-Cast 8098, PC-like

This polyurethane resin is created by combining Polyol (A) and Isocyanate (B) in a mixing ratio of 100:250. It has an impact strength of 10 KJ/m² and a de-mold time of 60 minutes. PU8098 (PC-like) is commonly used by manufacturers to produce high-quality products through vacuum casting. It also offers a heat deflection temperature of 120°C (1.80 MPa), making it suitable for applications requiring heat resistance.

PMMA/Acrylic-like Materials

PMMA/Acrylic-like materials are known for their optical transparency, mechanical rigidity, strength, thermal stability, and resistance to wear and scratches. They are produced through the polymerization of methyl methacrylate monomer, often in bulk, solution, or suspension, resulting in a durable polymer that combines the aesthetic appeal of glass with excellent durability. Vacuum casting PMMA is perfect for applications like lenses, light guides, and transparent housings.

AXSON UPX 5210, PMMA / Acrylic-like

UPX5210 is a transparent, anti-UV urethane resin designed for casting in silicone molds. It can produce parts with wall thicknesses of up to 50 mm and is created by combining isocyanate and polyols. This material offers low shrinkage, is easy to process, and provides excellent transparency. It is also resistant to UV rays and can be easily polished for a high-quality finish.

Axson PX 225, PMMA / Acrylic-like

Axson PX 225 is a PMMA/Acrylic-like material used for creating thermoplastic-like prototypes and mock-ups. It offers a flexural modulus of elasticity close to 2,500 MPa, similar to materials like polycarbonate and ABS. PX 225 provides high impact and flexural resistance, is easy to color with various pigments, and has low viscosity, making it simple to cast.

Axson PX 522 HT, PMMA / Acrylic-like

X522HT is a translucent urethane resin designed for creating high-quality transparent items through vacuum casting in silicone molds. Its clear appearance and ability to allow light to pass through make it an excellent choice for applications like greenhouses, where it also serves as an effective heat barrier. Additionally, it is highly processable and heat-resistant up to 100°C.

PP-Like Materials

Polypropylene stands out from other thermoplastics due to its thermal stability, lightweight, fatigue resistance, and chemical resistance. PP-like resins bring these qualities to vacuum casting parts. They are made by polymerizing propylene with a catalyst, allowing the polymer chains to be customized for different applications. Adjusting parameters during this process can further enhance flow properties, impact resistance, and thermal stability. PP-like resins offer high flowability to fill molds and capture fine details, low shrinkage for accurate dimensions, and a balance of flexibility and toughness for durable, crack-resistant parts.

Hei-Cast 8550, PP-Like

Hei-Cast 8550 is created by mixing Polyol and Isocyanate in a 1:2 ratio, resulting in a transparent black-and-white appearance. Its excellent elongation makes it ideal for producing elastic parts. Key features include a low flexural modulus, high elongation, long pot life, and suitability for molding large-sized products.

Hei-Cast 8570, PP-like

High-Cast 8570 is a polyurethane resin designed for vacuum casting and is ideal for producing tough PP-like prototypes. With a high flexural modulus, it is well-suited for creating interior and exterior automotive parts. It offers heat resistance up to 90°C, a long service life, and is ideal for making large cast products.

Axson UP 5690, PP-Like

This polyurethane resin is used for casting prototype parts and mock-ups with mechanical properties similar to PP and HDPE, such as instrument panels, bumpers, equipment boxes, covers, and anti-vibration tools. The resin’s mechanical qualities can vary depending on the proportions of the materials used in its production. It offers high elongation at break, high impact strength, excellent flexibility, and is easy to process.

PA(Nylon)-Like Material

PA (nylon)-like materials are commonly used in vacuum casting due to their strength, flexibility, and durability. They are ideal for creating parts that need to endure wear and tear. Additionally, these materials offer good heat resistance and are easy to process, ensuring high-quality results for both prototypes and functional components.

Axson PX 245, PA-like

Axson PX 245, PA-like, is used in vacuum casting with silicone molds to produce prototype parts and mock-ups with mechanical properties similar to thermoplastics like polyoxymethylene and polyamide. It offers a high flexural modulus of elasticity, excellent reproduction accuracy, and is available in two reactivity options (4 and 8 minutes). The resin can be easily colored with CP pigments and features fast demolding.

Rubber-Like Flexible Material

Rubber-like materials are widely used in vacuum casting due to their flexibility and ability to mold into complex shapes. They are durable, cost-effective, and reusable, adding to their efficiency and practicality for various applications.

Axson UPX 8400, Rubber-like

UPX8400 is a three-component polyurethane material designed for vacuum casting. It offers very high elongation and is easy to process. The mechanical properties of the material depend on the proportions of the three components used.

Hei-Cast T0387, Rubber-like

T0387 is a translucent polyurethane elastomer designed for vacuum casting applications. With a pot life of about 5 minutes and 30 seconds, its mechanical properties depend on the proportions of its three components: two polyols and one isocyanate. T0387 is perfect for producing parts that require a high degree of elasticity due to its excellent elastic properties.

Factors To Consider When Choosing Vacuum Casting Materials

When choosing vacuum casting materials, it’s important to consider several factors to ensure the best fit for your needs. Here’s what to keep in mind:

Product Requirements

Start by identifying the properties your final product needs. Different materials offer unique features like impact resistance, heat resistance, UV stability, and hardness. For example, if your product will face high stress, choose a material like Axson UP 4280 which had a great stength.

Operating Environment

Think about where the product will be used. Environmental factors like temperature, humidity, chemical exposure, and UV light can affect material performance. For example, a PC-like material like Axson PX 223 HT is great for outdoor use because it resists harsh conditions.

Cost

Budget matters too. While quality is important, you can find cost-effective materials that don’t compromise performance. For high-volume production, raw material costs become less significant, giving you more room to balance price and performance.

Selecting the Right Material for Your Vacuum Casting Project

Now that you have an idea of vacuum casting materials and the factors to consider when choosing them, you can narrow down which resin best suits your application. The selection depends on factors like the application environment, required mechanical properties, production volume, lead time, and project specifications.

For the best results, it’s always a good idea to consult experts in vacuum urethane casting services. At KUSLA Prototype, we bring over a decade of experience in a wide range of industry applications. Our engineers can help you choose the right materials for your project with a detailed Design for Manufacturability (DFM) analysis. Upload your design today, and let us assist you with high-quality vacuum casting solutions!

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