Most 3D printing technologies are direct; they directly create the finished object with no casting or further steps needed. These include Fused Deposition Modeling, Stereolithography, and many more. However, one lesser-known technique which 3D printing is also useful in is Lost Wax Casting, an indirect 3D printing process.
Also known as investment casting or precision casting, Lost Wax Casting involves creating a duplicate, or clone, of an original mold; usually from a metal such as gold or silver. The process has a rich history; it is believed to have been used since between 4500BC and 3500BC, with objects found in southern Israel created using Lost Wax Casting dated back to 3700BC. That’s over 5700 years ago!
Lost Wax Casting Process Steps
Part 1: 3D Design of Lost Wax Casting Part
When using 3D printing in Lost Wax Casting it is important to remember that you will struggle if you don’t have prior 3D design skills, unless you create something that is freely available online. This is because you will need to design the 3D printer model which you intend to create to 3D print the original mold. You can do this on any of the free or paid 3D software options out there – we’ve also written our own free 3D software ranking and professional 3D software ranking.
Once you’ve chosen your 3D software tool, it’s time to design. Simply create your chosen piece, whether it be a piece of 3D printed jewelry like a ring or pendant, or even a crazy 3D printed heart. Once you’ve designed it, export it as an STL file or similar compatible file type and prepare for printing with your 3D slicer.
For more information on Lost Wax Casting, there’s an example of a Lost Wax Casting YouTube video featuring a sprue mold created with Formlabs’ Form 2 SLA 3D printer.
Part 2: Wax 3D Printing the Mold
Once you’ve sliced the 3D model of your piece to use with Lost Wax Casting, you’re ready to print! To check for sizing and fit, it is recommended to try a test run on lower quality settings, and then once you’ve got a perfect fit to 3D print your final model on higher settings. Once you’ve got a model you’re happy with, you’re ready to create the inner, negative mold.
Printers such as 3D Systems’ Pro Jet range, resin 3D printers such as those by Formlabs, and FDM 3D printers like an Ultimaker can be used to 3D print the mold. There are a number of good wax filaments which are compatible, though the Pro Jet range is able to print supports in material that has a lower melting point, making the support removal process simpler. Stereolithography printers like the Form 3 naturally print in a wax-like resin, similar in consistency to the waxy texture required.
Part 3: The Second Mold
Once your original, 3D printed mold is ready, you need to create a sealed area, or sprue, where you can pour the material inside. After you’ve set this up, pour the molten material (either silicone, polyurethane, or other wax-like material) inside the sprue.
Once this has dried, remove the model. This is an exact negative of your original, 3D printed mold, and will form the basis of what will create your metal 3D printed piece.
Part 4: Creating the final metal piece using Lost Wax Casting
Once your negative mold is ready and dried, it is important to preheat it so it’s ready for the sudden bombardment of molten metal and subsequent heat.
Once your chosen metal has been heated to a high enough temperature and melted, pour it into your negative mold. This make a few tries to get right, and if not done properly can leave you without good enough detailing on your model. It is important to get this just right, or you’ll notice the imperfections forever. When it’s poured, leave it to cool down.
Part 5: Lost Wax Casting Post-Processing
Though nice and shiny, the metal object you’ve cast won’t look as pretty as it could. You’ll first need to cut off the excess metal that you poured into the negative mold. This cut will be rough, and will require polishing, sanding, or a similar process. Which process depends on the metal and it’s strength; soft metals like pewter can be shaped and refined far easier than metal or platinum.
Anything else beyond this is completely your choice. You may wish to accessorize your piece with extras that match your style and creativity. Beyond this, it’s all down to you!
Lost Wax Casting Materials
A variety of metals can be used in Lost Wax Casting rings, pendants, and more. However, since the uses are mainly jewelry, more precious and expensive metals are used most commonly. These include:
- Gold – Either 14K or 18K gold is commonly used in expensive, high-quality jewelry pieces.
- Silver – 925 silver (92.5% pure) is commonly used also as it is very malleable and has good thermal conductive properties.
- Bronze with copper – A cheaper option, it is worth remembering that it will tarnish if the metal isn’t varnished.
- Brass – Another lower-priced option.
- Copper – A viable low-priced alternative.
If you’re looking for the best wax for Lost Wax Casting 3D printing for the original wax mold, there are a few options. For FDM 3D printing, you can use Print2Cast wax filament or MOLDLAY filaments designed by Kai Parthy. These aren’t like typical filaments, and extrude at different temperatures to PLA or ABS (usually at lower temperatures). For SLA or DLP or LCD 3D printers, there are a variety of wax-like resins available, as well as for Multi Jet printers.
Applications: Lost Wax Casting Jewelry and Dentistry
Unsurprisingly, given that Lost Wax Casting excels at creating very precise geometric patterns of metals, the process is used extensively in jewelry. Pro Jet 3D printers are accurate up to 0.025mm in creating the original wax model, and this precision can then be passed on to the metal object. The jewelry can be created to perfectly set jewels like diamonds, emeralds, and rubies, making it a versatile and very attractive option for jewelers. Industrial 3D printer companies like EnvisionTEC, Formlabs, and 3D Systems make some of the best 3D printers for this purpose.
Lost Wax Casting Advantages and Disadvantages:
- Compared to alternative 3D printing technologies to create geometrically complex metal objects, Lost Wax Casting has low barriers to entry and is cheap to produce. You do not necessarily require a $300,000 Direct Metal Laser Sintering or Electron Beam Melting 3D printer, just the Lost Wax Casting kit and materials.
- Though not a concrete, scientific fact; it is just more satisfying to craft your own pieces. Other 3D printing processes are very detached in that you press a button, and a few hours later out pops the finished product. Lost Wax Casting is hands on, thus leaving you with the sense of satisfaction having completed the project.
- More hands on, and therefore slower and less scalable. Businesses looking to produce larger numbers of pieces quickly will prefer DMLS, Binder Jetting, or EBM, as they can create multiple pieces at higher speeds without the need for manual labor.
- Fairly steep learning curve. Pouring the molten metal correctly so every crevice is well-defined is a skill that takes time. Therefore, be prepared for failed projects, wasted materials, and much frustration