Best 3D Printing Materials For Investment Casting

3D printing is increasingly becoming the go-to solution for artisans, engineers, and industrial professionals. It offers a cost-effective and time-saving alternative to traditional investment casting methods, which often require costly and time-consuming tooling and pattern-making techniques. With 3D printing, complex designs can be achieved, and the time to produce parts is significantly reduced. Various materials can be used for 3D printing investment casting, each offering unique advantages. For example, PolyCast filament is designed for low burnout, resulting in minimal ash residue when cast. On the other hand, wax-based filaments are also popular for their ease of use and ability to create intricate details. Other materials such as PLA, ABS, and specialty resins are also used, depending on the specific requirements of the project. The choice of material depends on factors such as cost, complexity of the design, and the desired finish.

Wax vs plastic master patterns

When it comes to investment casting, the choice of material for the master pattern can be crucial. Two of the most common options are wax and plastic. Each has its own advantages and disadvantages, and the right choice depends on the specific requirements of the project.

Wax master patterns have been traditionally used in investment casting, also known as lost-wax casting. This process involves shaping the final part out of wax, adding a ceramic shell over it, and then melting the wax out to create a mould for the metal. The type of wax used is important—common varieties include filled pattern wax, non-filled pattern wax, runner wax, sticky wax, and water-soluble wax. Wax is easy to work with and can be reused and recycled, but it has lower strength and dimensional stability compared to plastic. It is also susceptible to shrinkage and distortion during cooling, which may require additional steps in the process.

Plastic master patterns, on the other hand, offer higher strength and dimensional stability. They are created using 3D printing technologies such as stereolithography (SLA) or MultiJet printing (MJP). Plastic patterns provide accurate, high-yield, large-size, complex, and lightweight investment casting masters with high dimensional stability. They are also more robust and easier to handle and ship. Additionally, 3D printing plastic patterns can be faster and more cost-effective than traditional wax pattern-making techniques, as it eliminates the need for costly and time-consuming tooling.

The choice between wax and plastic master patterns depends on the specific requirements of the project. Wax is a traditional option that is easy to work with and reusable, but it may not provide the same level of accuracy and stability as plastic. Plastic patterns, created through 3D printing, offer improved accuracy, stability, and speed but may be more expensive and less versatile than wax. Ultimately, both options have their advantages and can be successfully used in investment casting depending on the specific needs of the project.

MultiJet printing for wax casting patterns

MultiJet printing (MJP) is a highly effective method for creating 3D printed casting patterns. WaxJet 400, for example, is a large-size, high-precision, multi-jet wax 3D printer that can print casting wax patterns with a smooth surface and high fineness. It uses MJP technology to print wax patterns for casting, bypassing the traditional mould-making and retouching steps. This enables direct 3D model printing with model data, eliminating the need for mould-making and retouching and shortening the time to market by two-thirds.

MJP technology is also used by 3D Systems in its ProJet MJP 2500 IC wax 3D printer, which produces hundreds of RealWax™ patterns at a significantly lower cost and in less time than traditional pattern production for low to medium-volume jobs. This printer generates wax patterns that fit into existing investment casting processes, making it ideal for customised metal components, bridge manufacturing and low-volume production.

3D Systems' digital foundry solution, which includes the ProJet MJP 2500 IC wax 3D printer, VisiJet wax material and 3D Sprint software, enables a smooth transition from digital design to cast parts without intermediate tooling. This combination of tools enables investment casting foundries to transition from a digital design to a cast part without the need for additional tooling. The 3D Sprint software is particularly intuitive and easy to use, and its ability to analyse and optimise the placement of support structures ensures the best placement of parts within the build platform.

MJP technology and VisiJet RealWax material deliver industrial casting patterns that hold tight tolerances and are ideal for manufacturing complex precision metal components with reduced or no finishing work. This technology can help foundries improve and accelerate their prototyping services and increase their ability to supply pre-production series and products, especially in small to medium batches.

QuickCast SLA plastic technology

Instead of the SLA part being completely solid, QuickCast eliminates 95% of its internal mass by curing only the external surfaces and an internal lattice structure. This results in a 65-80% hollow part with a beehive-like lattice structure, providing tremendous structural integrity. QuickCast replaces traditional wax patterns with patterns created from more robust and durable materials, without the need for tooling and with minimal delay.

One of the key advantages of QuickCast SLA is its ability to produce intricate geometries that would be challenging or impossible with traditional methods. The 3D printing process allows for the creation of internal features, undercuts, and complex shapes that enhance the functionality and design of the final product. Additionally, QuickCast offers greater flexibility in material selection, accommodating a broader range of materials, including plastics and ceramics.

PolyCast filament

PolyCast is compatible with Polymaker's Layer-Free technology, delivering superior surface quality while minimising the need for post-processing after casting. It can be used on any FDM/FFF printer with excellent printability and is lower cost compared to other 3D printing technologies (e.g. SLA/DLP/SLS).

PolyCast is an ideal filament for investment casting as it produces investment patterns that significantly cut down both the cost and lead time by eliminating the tooling process. It is safe and easy to post-process and has excellent printability.

To ensure professional and dimensionally accurate results when using PolyCast, it is recommended to follow these printing tips:

• Minimise the need for support structures as much as possible when placing your model on the build plate. This will help improve the surface finish and printing time.
• Print your model with minimal infill (e.g. 10%) and a small number of shells (2-3) to facilitate the burnout process.
• Apply shrinkage compensation to the .STL file to compensate for the dimensional change in the metal between the molten and solid states. Modify the model size by the metal/alloy-dependent compensation factor, which is usually between 1.007-1.030. For example, the compensation factor for steel is 1.025-1.030.
• Use a layer height of 0.1-0.2 mm for optimal print resolution and post-processing.
• Store PolyCast under dry conditions (relative humidity of no more than 20%) as it absorbs moisture.

FDM technology

Fused Deposition Modeling (FDM) is an additive manufacturing technology that can be used to produce investment casting patterns that are more efficient and cost-effective than traditional methods. FDM technology offers a faster and more affordable alternative to traditional injection-molded wax patterns, which can take weeks or months to create and are limited in their complexity.

FDM patterns are built with thermoplastics, which burn and turn to ash instead of melting like wax. This ash can be easily washed out of the ceramic shell, making it a more convenient option. FDM technology eliminates the time and cost of tooling required in injection molding, as FDM parts are built layer by layer without any tooling and can be produced in a matter of days.

One of the biggest advantages of FDM is the design freedom it offers. FDM patterns can have non-uniform wall thicknesses, undercuts, and overhangs, allowing for more intricate metal parts. Size is also not a limitation, as patterns can be built separately and then bonded together, resulting in the same strength as if they were created as a single piece. This makes FDM ideal for creating complex and detailed patterns.

The durability of FDM thermoplastics is another benefit, ensuring that patterns maintain their shape and structure during transportation and in various environments. FDM parts can be put into assemblies for testing without the risk of damage that often occurs with wax patterns. Additionally, FDM technology delivers smooth finishes through secondary operations like sanding or vapor smoothing, providing injection-molded quality without the associated time and expense.

Frequently asked questions