Vacuum casting, also known as urethane casting or polyurethane casting is a versatile manufacturing process primarily used for highly accurate and detailed prototypes or parts in small batches. It involves pouring liquid material into a silicone mold under vacuum. Then, the material fills the mold without air bubbles or defects. Moreover, you have many vacuum casting materials options to choose from. It facilitates the best-fit material resin according to the desired properties and functionalities in the final part.
The popular vacuum casting resins are ABS-like resins, PC-like resins, PPMA, and soft rubbers. Each of these resins offers unique properties and benefits for vacuum cast parts. This article will discuss the various resins to guide you through vacuum casting material selection.
Significance of Material Selection in Vacuum Casting
The properties of final vacuum casting products directly depend on the raw material you choose at first. It influences the functionality, aesthetics, and durability of the casting part. The reason is that different materials offer varying degrees of flexibility, strength, hardness, appearance, heat resistance, and optical clarity.
Here are the significances of material selection in vacuum casting;
Performance and Durability
The material choice significantly impacts the performance and longevity of vacuum-casted parts. For example, materials with high tensile strength and heat resistance are essential for components exposed to stress and high temperatures. Conversely, applications requiring flexibility and impact resistance benefit from softer materials.
Aesthetics and Finish
Another significance is aesthetics and finish. The flow characteristics of the chosen material decide the finish quality. It will result in a fine and superior finish if the molten material flows smoothly inside the cavity.
Furthermore, it is crucial for prototypes and high-quality parts where visual appeal is as important as functionality, such as consumer electronics and high-end automotive components.
Cost of Vacuum Casting Project
The raw material cost takes a large share of the overall vacuum casting cost. Therefore, how expensive the chosen material affects how cost-effective the project will be.
Some materials offer a more economical solution without compromising quality, making them ideal for prototypes and small production runs. Additionally, the choice of material can affect the mold’s lifespan, directly impacting the overall cost of production.
Compatibility with Application Requirements
The material you select must align with the specific requirements of the intended application. For instance, medical devices demand biocompatible materials, and outdoor applications may require UV-resistant materials. Additionally, application requirements also involve production scale as some materials could take a long time to process and make mass production unfeasible. Nevertheless, there are several reasons to use vacuum casting for rapid prototyping, regardless of any cycle-time limitations.
Types of Materials Used in Vacuum Casting
Since we understand the significance, let’s elaborate on typical vacuum casting materials. So, you can make the decision based on which one suits your requirements.
ABS-Like Resins
Among the several materials, ABS-like and polyurethane (PU) resins offer strength, durability, low viscosity, and thermal stability. It results in parts with a smooth surface that can be easily painted or finished for aesthetic purposes. Additionally, the dimensional stability of ABS keeps the products structurally intact for a long -period.
| Key Properties | Applications | |
| PU8150 | Resistant to abrasion & wear, high strength, hardness, semi-transparent, and chemical & oil inertness. | Gasket and hoses for various applications. |
| PU8260 | It is a flexible polyurethane resin with high Impact & tear resistance, durability, flame retardancy, elasticity, and shock absorption capacity. | Flexible joints, automotive seals, protective casings, bent tubes. |
| PU8263 | Wear and high-temperature resistance, excellent mechanical strength, and flame retardancy. | Suitable for high flame retardancy applications ( UL94 V-0 and 5VA), industrial machinery components, and automotive under-hood parts. |
| PX100 | It is a rigid resin that offers an excellent blend of strength, impact resistance, and low viscosity. | Parts requiring similar properties to thermoplastics, aerospace components, and electronics housings. |
| PX215 | Dimensional stability, heat resistance, soft touch, and balance of flexibility & toughness. | Wearable devices, high-impact resistance products, grips, and soft-touch prototypes. |
| UP4280 | An easy-processing polyurethane with toughness, detail accuracy, and no inherent colors. | Detailed prototypes, complex parts with a blend of mechanical properties. |
PC-Like Resins
These resins mirror the properties of polycarbonate plastic in vacuum casting. It contains Polyol & and Isocyanate in appropriate ratios. Meanwhile, it also provides optical clarity as PC plastic does.
Benefits:
- PC-like resins withstand impacts and stresses without cracking.
- Versatility in shape and size.
- Thermal resistance.
- Cheaper alternative to glass parts or products.
Moreover, they are ideal for creating durable, transparent parts with high precision. It makes them a favorite vacuum casting material in industries requiring clear & strong components.
| Key Properties | Applications | |
| PU8098 | It is highly heat resistant up to 120 °C, less dense, offers valuable mechanical strengths, and is durable. | Automotive bumpers and dashboards, durable industrial components, and hosing for tools. |
| PX510 | High strength, stiffness, UV resistance, and superior thermal stability. | Transparent prototypes, electrical and lighting fixtures, models & toys, under-hood automotive parts, etc. |
| UP6160 | Easy to process, high-temperature resistance, and detail casting capability. | Low-weight automotive components, thermal applications, electronic casing, and enclosures for medical devices. |
| PX223HT | It opposes the impact forces & offers low viscosity, toughness, chemical inertness, and excellent thermal resistance. | Thermal resistant applications, machinery parts, aerospace cabin components, and electrical insulators. |
PP-Like Resins
What makes polypropylene different from other thermoplastics? It is the thermal stability, low weight, fatigue resistance, and chemical inertness. Hence, PP-like resins bring these properties to the vacuum casting parts.
These vacuum casting materials or resins are achieved by polymerizing propylene with a catalyst, creating adjustable polymer chains for various applications. Meanwhile, adjusting parameters during polymerization allows flow properties, impact resistance, and thermal stability customization.
Benefits
- High Flowability: The resin’s flow properties ensure it can fill silicone mold effectively, capturing intricate details of cavities.
- Low Shrinkage: Minimal shrinkage during cooling results in parts with high dimensional accuracy.
- Flexibility and Toughness: They offer a balance of flexibility and toughness for durable parts that resist cracking and fatigue.
| Key Properties | Applications | |
| 8550 | Dimensional stability, excellent elongation, moderate impact resistance, and good clarity. | PP& PE plastic prototyping, Transparent or translucent components, automotive prototypes. |
| PU8570 | Wear resistance, durability, good toughness, and outstanding flexibility. | Seals and gaskets in machinery, automotive interiors, joints, and connectors. |
| UP5690 | High toughness, impact-resistance, flexibility, and inert to many chemicals & solvents. | Vibration-damping components & bumpers, dashboards, machinery enclosures, and consumer electronics casings. |
PMMA/Acrylic Materials
It is known for optical transparency, mechanical rigidity, strength, thermal stability, and wear & scratch resistance, among many materials.
Furthermore, the production of Acrylic/PMMA involves methyl methacrylate monomer polymerization. Generally, in a bulk, solution, or suspension. This process yields a polymer that combines the aesthetic appeal of glass with durability.
Benefits
- Aesthetically appealing: PMMA offers an excellent appearance (countless colors are possible). Additionally, it does not fade away with light (UV) and weather over time.
- Precision and Detail: Vacuum casting can cast PMMA parts with intricate details and tight tolerances. They closely replicate the master model design.
- Versatility in Applications: The optical clarity makes it suitable for various applications, including lenses, light guides, and transparent housings.
| Key Properties | Applications | |
| PX5210HT | High transparency, minimal shrinkage, excellent UV resistance, and high toughness | Automotive lighting, medical device components, and optical lenses |
| UPX5210 | Good impact strength, is easy to paint and color, and has UV stability. | Electronics casings, decorative items, and protective covers. |
| X522HT | Superior thermal resistance, high clarity, and durability. | Outdoor fixtures, aerospace components, and high-temperature applications |
Transparent Soft Rubber
This innovative vacuum casting material combines the elasticity and flexibility of rubber with the clarity of glass. Soft rubbers are typically made from silicone or thermoplastic elastomers. Moreover, it gives diverse application possibilities for engineers and product developers.
Benefits
- Design Freedom: Vacuum cast process with transparent soft rubber facilitates complex shapes and details. Those are not easily achievable with traditional manufacturing processes.
- Transparency: Similar to clear plastics or glass. Thus, casting the rubber can make visible internal components without sacrificing material integrity.
- Flexibility and Durability: Combines the ability to bend and stretch with resistance to impact and wear.
| Key Properties | Applications | |
| UPX8400 | High elongation, flowability, easy to work with casting and tear resistance | Medical prototyping, Wearable technology components. |
| T0387 | Durable resin, optical transparency, good elastic properties, thermal resistance, and flexibility. | Automotive lighting prototypes, consumer products, and various flexible components. |
Factors Influencing Vacuum Casting Material Selection
Now, you must get an idea of the features, properties, and potential applications of vacuum casting materials. Next, you need to choose which one fits your casting requirements.
Let’s discuss which factors affect the material selection.
Environmental Factors
It is critical to consider in which environment the vacuum cast part will operate. Each material resin behaves uniquely towards environmental factors like humidity, chemical or other solvent exposures, UV radiation, and temperature fluctuation. Therefore, identify the application’s environment. Then, consider it while choosing the material. For example, PC-like PX510 resin provides excellent breathability for outdoor applications.
| Material | Thermal Exposure | Humidity | Chemical and Solvents | UV Exposure |
| PU8150 | Moderate | High | High | Moderate |
| PU8260 | Moderate | Moderate | High | High |
| PU8263 | Highly suitable | Moderate | Highly suitable | Highly suitable |
| PX100 | Low | Moderate | Moderate | Low |
| PX215 | Moderate | High | Moderate | Moderate |
| UP4280 | Highly suitable | Moderate | High | Moderate |
| PU8098 | Highly suitable | Low | Moderate | Low |
| PX510 | Moderate | Moderate | Moderate | Moderate |
| UP6160 | Moderate | Moderate | High | Moderate |
| PX223HT | Highly suitable | Moderate | Highly suitable | Highly suitable |
| 8550 | Low | High | Low | Low |
| PU8570 | Moderate | Highly suitable | Moderate | Moderate |
| PU5690 | Low | Moderate | Low | Low |
| PX5210HT | Highly suitable | High | Moderate | Highly suitable |
| UPX5210 | Highly suitable | High | Moderate | Highly suitable |
| X522HT | Highly suitable | High | Moderate | Highly suitable |
| UPX8400 | Moderate | High | Moderate | Moderate |
| T0387 | Low | High | Low | Low |
Cost Considerations
The price of materials used in vacuum casting work can vary widely, impacting the overall project budget. For instance, high-performance material resins offer superior properties but cost more price. Thus, balancing the need for specific material properties with budget constraints is essential for affordable vacuum casting.
Additionally, also consider the per-part material cost. If it is for high-volume production, the raw material costs contribute less to the overall vacuum casting cost. Here, you can get more flexibility on cost and performance balance.
Production Volume and Lead Times
You might wonder how intended production volume affects the vacuum casting material selection. However, the production volume impacts the cost consideration, material availability, and casting cycle time. For example, a material like PU8150 is ideal for prototyping or small batches as it offers short cycle periods. So, you can cast a few replicates in a shorter time.
The lead time connects with the material selection as curing time is distinct for individual resins. For instance, if you need a faster turnaround, select such material that is easy to process and has a short curing period.
Selecting the Right Material for Your Vacuum Casting Project
Now you might know what type of resin suits your application after discussing the common Vacuum casting materials and selection considerations. As discussed, it depends on the application environment, necessary mechanical physical & properties, intended production volume, lead time, and other project specifications.
However, it is recommended to consult vacuum casting manufacturers and experienced professionals. In this context, no one can give the best vacuum casting services except RapidDirect. We have a decade of experience working on numerous industry applications. Our engineers can help suggest suitable vacuum casting materials for the project with a detailed Design for Manufacturability (DFM) analysis of your design. You can upload your design here.
