all you need to know about vacuum casting - IN3DTEC

Welcome, curious minds and DIY enthusiasts, to our comprehensive guide on the fascinating world of vacuum casting! If you’ve ever wondered how intricate prototypes, unique jewelry pieces, or even mechanical components are manufactured with exceptional precision, you’re about to embark on an enlightening journey.

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In this blog post, we’ll delve into the depths of vacuum casting, uncovering its principles, processes, and endless possibilities. Whether you’re a beginner seeking an introduction to this innovative technique or an experienced maker looking to refine your skills, we’ve got you covered. So, let’s roll up our sleeves and explore the captivating realm of vacuum casting together!

Why and when choosing the vacuum casting?

When we talk about vacuum casting, we usually compare it with injection molding. So, let’s distinguish the difference between them first.

Cost difference， Let’s take the mobile case as an example, the mold of the vacuum casting is only tens of dollars, while injection molding costs thousands of dollars. On the other hand, the production fee of vacuum casting is tens of dollars per unit, while injection molding only costs 1 or 2 dollars.

In brief, vacuum casting has a lower front-end cost and a higher unit price, while injection molding requires a higher front-end cost, but the unit price is significantly lower。

Compared with 3D Printing（3DP), what’s the advantage of vacuum casting? Base on the same material, vacuum casting has higher smoothness, durable, and accuracy, and it has not limitation to the color as well. 

How does it compare to CNC? It is difficult to say which one is better, but if we consider the complexity of the prototype, production efficiency, and cost, vacuum casting will have more advantages. While the CNC has more material options, the material performance is better.

Being able to make soft materials quickly is one of the biggest advantages of vacuum casting. It supports materials from Shore 30A to Shore 95A, from Shore 10D to Shore 90D, in any customized Pantone No.

In conclusion, vacuum casting is not in conflict with and can’t replace other technologies, Instead, it is a supplement way, providing more flexible solutions for manufacturing.

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.

Contact us to discuss your requirements of vacuum casting parts manufacturer. Our experienced sales team can help you identify the options that best suit your needs.

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.

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.

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.

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.

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.

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.

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 PU 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.

Want more information on low volume manufacturing? Feel free to contact us.