What happens when you combine a technology that has been tried and tested for centuries with one that has just emerged in the last few decades? The answer seems to point more and more to increased cost savings, faster lead times and new design possibilities. Investment casting has been in use for centuries and 3D printing has only recently emerged, but it turns out, when the two are combined there are many synergies to be found. Casting offers 3D printing the ability to create metal parts with excellent mechanical properties, and 3D printing allows casting to create parts faster, cheaper, more accurately and with more complex designs.
The Investment Casting Process
The process for investment casting begins with the design and manufacture of a tool to create what will become the sacrificial pattern. This is the stage that adds much of the cost and lead time to the process. Depending on the size of the part, the design and manufacture of the tool can take up to a year and cost hundreds of thousands of dollars. After the tool is finally manufactured and delivered to the casting house, the tool is used to create the wax patterns. In investment casting, each wax pattern is only able to make one part, as the pattern is destroyed in the process.
Once the wax patterns are created from the tool, they are mounted onto an assembly sprue (tree) with the other parts in the batch. The tree is then dipped into liquid ceramic mold material and sand, which completely covers and surrounds the part; this process of coating the assembly tree is repeated multiple times until the eventual shell obtains the required thickness.
After the shell is created and dries, the tree is then placed in a furnace where the wax is melted out, creating an empty shell in the shape of the wax part. After the wax is burnt out, the metal is then poured in and left to cool and harden. When the metal has sufficiently cooled, the shell is removed, the casted metal parts are removed from the tree and the parts then go to post-processing.
The investment casting process with 3D Printing
With 3D printing, there is no need to create a mold tool to make the wax pattern. This saves an enormous amount of time and cost in the process as the patterns can simply be printed using PLA or wax resin, each of which are very low-cost materials.
The Advantages of using 3D printing for investment casting
There are several advantages for using 3D printing for investment casting including:
- Shorter lead times due to the lack of tooling required.
- Less expensive in low volumes, which enables companies to do more prototyping and reduce risk in the new product development process.
- Complex geometries are possible. One of the major advantages of 3D printing is being able to produce complex designs that are either expensive or impossible to manufacture with traditional methods.
- The investment casting process allows for the preservation of fine details and features. This also opens the opportunity to use generative design, whereby parts utilize a highly complex and optimized topology designed specifically for its function. This allows for reductions in weight and part count, which is a huge advantage of investment casting with 3D printing.
- Bridge production enables companies to utilize 3D printing to quickly get parts on a high-volume order in work while they are waiting for the mold tool to be completed.
- Low volume production allows for companies to utilize casting without having to invest time and resources in a tool.
- Investment casting can produce high accuracy parts with dimensional accuracy up to +/- 0.03mm.
Applications Being Used Today
One of the leading applications of investment casting with 3D Printing has been with jewelry. A wide variety of metals and alloys, including precious metals such as gold and silver can be used. This has created extensive opportunities in the jewelry industry to created precise, highly customized rings, bracelets and necklaces with fine details.
Investment casting with 3D printing is done by printing a plastic model of the desired item, usually with PLA or casting resin. A mold is created around pattern, after which the pattern is burnt out and the mold is filled with molten metal; in this case silver, bronze and gold.
Multiple unique items can be printed at once, opening the way for mass customization in a process that traditionally must run high volume batches to pay for the tooling. Each of these items are printed on the same build plate and each has a uniquely individual design.
3D systems created a large 2m pattern from an SLA printer. The pattern was broken up into pieces in the CAD program printed as multiple pieces and then bonded together. Were the same pattern to be created using traditional wax patterns, it would have taken 9-12 months to create the tool and half a million dollars. With 3D printing, the pattern was completed in under a week and the cost was brought down to under $20,000
Investment casting can create complex geometries with fine details and features.
Investment casting is being used in several industrial applications due to its ability to shorten lead times and cut costs of low volume production batches.
Interested in creating metal casted parts? Contact ZABFAB today to create your customized 3D printed patterns!