Investment Casting Wax Models

Investment casting, also called lost wax casting, is a process in which a pattern, also known as a master or master pattern, traditionally made of wax, is covered with a ceramic slurry. The wax pattern is normally produced with injection molding. The wax is melted out of the ceramic shell, which is pre-heated before molten metal is poured into it. After the metal cools, the ceramic is vibrated and blasted from the metal casting. Investment casting generally provides higher accuracy (+/- 0.005 inch (0.127 mm) tolerance is normal) and surface finish (typically 125 micron RMS (3.125 micron Ra)) than other casting processes. It is generally used in applications that have relatively low production quantities and changing product designs.

The Need of 3D Printer in Investment casting Industry

The wax patterns used in investment casting are typically produced using an injection molding process. Tooling cost ranges from 10,000 to 2,00,000 and lead time to produce tooling is approximately one month. A big problem for many investment casting foundries is that they are not able to produce prototype castings until the injection mold is completed. At this time, problems are often discovered, such as interference with other components in an assembly. Additional time and money must be invested to fix the injection mold. In a worst-case scenario, it may be necessary to scrap the original tool and start over from scratch. Another problem with wax patterns is that their complexity is limited by what is feasible from an injection mold in the allotted time.

Fused Deposition Modeling (FDM) provides an alternative method for producing investment casting patterns that can provide dramatic time and cost savings. FDM technology is an additive manufacturing process that builds plastic parts layer by layer, using data from CAD files. FDM makes it possible for the foundry to produce a pattern that can also serve as a prototype for form and fit evaluation. In one day, the foundry can provide the customer with a prototype that provides a perfect match to the casting that would be produced if it becomes the pattern. The strength of the materials used in the FDM process makes it possible to put the FDM component into an assembly and perform testing. If any problems are discovered, the foundry can usually make the changes requested by the customer and build a new pattern in about 24 hours.

As soon as the customer approves the prototype, the foundry can move into production by using the FDM parts as patterns for investment casting. Since FDM is an additive process, the pattern can be as complex as needed without any impact on cost. (With injection molding increasing pattern complexity often requires a more complex and more expensive tool).

Other advantages of FDM patterns are that they have greater strength, toughness and accuracy than wax or other additive manufacturing technologies. This durability is important because it prevents damage that often occurs in the transportation and handling of patterns made of wax or other materials.

Process Overview

FDM

FDM patterns are direct replacements for traditional patterns that are injection molded with foundry wax. One significant difference is that FDM material does not melt like wax. It burns, which leaves a small amount of ash, typically 0.021 percent, in the shell cavity. The ash is later removed in a shell washing operation. Venting should be added to the ceramic shells to speed the burnout of the FDM pattern. Investment casting patterns need to be produced to close tolerances and with an excellent surface finish because any defects are reproduced in the finished part. Advancements in finishing technology have improved FDM parts to the point that hand finishing is no longer needed, making FDM a much stronger competitor in the investment casting market.

Castable Wax from Kudo3DPrinter

Kudo3D is a DLP Printer and this technology is far better thanFDM in terms of Accuracy and surface finish. From this Printer we can directly print a castable wax. Thus we can eliminate first step of investment casting process which is to prepare a die. Die is the costly step in this process ad we are eliminating that. This whole process has an incredibly high resolution of 25 μm (0.025mm) between each layer which allows to create pieces with a virtually unlimited level of detail.

Based on Lost Wax Casting, one of the oldest metal-forming techniques, Investment Casting is actually an industrial process which has been used for around 5000 years in different forms. Lost Wax Casting refers to modern process of investment casting.

The beeswax was initially used in earliest forms to form the patterns required for casting process. These days, more advanced refractory materials, waxes and specialist alloys are used for making certain patterns. Investment casting is known for its ability to produce certain components with repeatability, accuracy, integrity, and versatility in different high performance alloys and metals.

The fragile wax patterns should withstand the forces encountered in the process of mold making. Most of the wax used can be reused and reclaimed in investment casting. The lost-foam casting avoids some steps in this process as a modern form of investment casting.

Investment casting is known for the patterns which is being surrounded or invested with refractory material. Several materials are best suited for investment casting, such as brass, stainless steel alloys, aluminum, glass and carbon steel. The material is added into the cavity in refractory material which is simply a replica of the targeted part.

Because of the sturdiness of refractory materials, investment casting is likely to produce the products with great surface qualities that can avoid the requirement for secondary machine process. It can be used for both large castings of several hundred pounds and small ones of few ounces. It can cost most than sand casting or die casting. But with large volumes, it costs less on per unit basis. Investment casting is capable to produce complex shapes that can be impossible or difficult with other methods of casting. It can easily produce the products with low tolerances and great surface qualities with minimal machining or surface finishing needed.

Benefits of Investment Casting

• Great accuracy
• Superior finish
• No parting or flash lines
• Very intricate parts may be cast
• Virtually any metal is castable

Applications

Investment casting is widely used in power generation and aerospace industries to manufacture turbine blades with cooling systems or complex shapes. Blades manufactured through investment casting may include directionally solidified (DS), single crystal (SX), or equiaxed blades. Investment casting is also used widely to fabricate the firearm receivers, hammers, triggers, and other precision materials at affordable prices by the firearm manufacturers. Other industries using standard cast parts are medical, military, automotive and commercial. With the great availability of 3D printers of higher resolution, the 3D printing technology has started to make large molds in investment casting. We have used this technique to print the mold which is dipped in ceramic to form the cast with embedded cable routing. FIBROX 3D is the one-stop investment casting shop. We can produce high quality investment castings with lost wax method and wax models with complex shapes in high dimensional accuracy. Along with it, the process gives a great amount of freedom in material and design choices. We can incorporate your demands and wishes into castings.