There is no better way to learn new artistic skills and techniques than actually going through the process itself. Here, we take an up-close look at how 3D modeling, printing, and lost wax casting all come together for the creation of a piece of art— in this case, a wild boar sculpture.
Creation of 3D Digital Model with ZBrush
The first step is to use 3D modeling technology to create a virtual model from which to start. ZBrush is one of the best programs on the market today for creating highly realistic sculptures. However, before the modeling begins on the computer, it is important to have a clear artistic idea of what you envision the piece of art to become– in this case, a wild boar. The digital modeling can be aided with having photos nearby for reference and blueprints outlined on paper to ensure there is a solid concept before you even get on the computer. There are important details you have to pay attention to with digital modelling when you intend to create a 3D print out. For example, you have to calculate and print the holding and supporting armature—the outer skeletal support structure. Additionally, the walls of the mold should not be more than 0.5mm and 0.8mm, so when the model is ready it can be placed directly in the mold itself.
3D Printing with MOAI Printer
After the digital model is created on ZBrush and you are happy with the results, you then have to save it specifically as an STL file. Then you can go ahead and print out your digital work that will serve as the original wild boar model. MOAI 3D printers are a great option for this type of work.
Please note this part of the process traditionally is done either directly out of wax, or with clay that you would then create a mold of to finally pour the wax into in order to get a wax replica. 3D modelling and printing technology in this day and age makes this part of the process quite easy and concise.
Cleaning the 3D Printed Model and Preparation for Molding
Once the high-quality 3D model of the wild boar has been printed, the next step is to clean it and prepare it for molding with silicon. (Smooth-On Tin Cure silicone mold rubber is a great choice as it is a high-tear silicone.)
You coat your artwork in this silicone mold rubber that, once complete, you will use to create a wax copy. With the newly created wax model, you will then create the bronze sculpture through the lost-wax casting method. To prepare for the wax copy, it is important to create a good supporting armature with plasticine, clay, or other plastic materials. With regards to the specific type of wax, you do not need to use any special brand, but rather a normal industry-grade wax will do the trick. Keep in mind that, depending on the model, there can be one or more parts of the mold; in the case of this wild boar sculpture, there are four parts.
Lost Wax Casting
With the wax model complete and the support pieces created and in place, you can now begin the lost wax casting process for the wild boar that is outlined below:
Creation of Casting Tubes
The next step is to create the casting tubes through which the liquid metal is going to flow once it is poured. This is especially important because the air needs a way to escape to ensure there are no air-pockets and bubbles which can affect the quality or integrity of the bronze sculpture.
Add Investment Powder
Now you should cover the wax model of the wild boar with special fireproof material known as investment powder— Prestige ORO Investment Powder is great for this purpose. Mix the investment into water for about three minutes, followed by vacuuming it at the five-minute mark, in order to get out all of the remaining air inside. Overall, you don’t want to disturb the investment for longer than eight minutes total.
Once the vacuuming is complete, it is time to pour the investment mixture into the flask. Be sure to solidify the top of the flask with tape so that the mixture doesn’t spill over accidentally. Try your best not to pour the mixture directly onto the wax itself so as to not disturb the design.
Next, you want to vacuum the flask itself. Be sure to mark the flasks in a way that differentiates them if there is more than one— chalk works great for this. Vacuum the flask for approximately one and half minutes— it’s still important to try not to go over the eight-minute mark. Afterwards, leave it to sit for one and half to two hours before putting it into the kiln for the burnout process.
Once the investment powder has had a chance to dry and is hard enough, put it in the furnace and bake at 740°C, for 12 hours to start the burnout process, which gets rid of the wax. After this, the model should be hard enough to continue casting with liquid bronze.
Casting with Liquid Bronze
Now is the time to actually pour the liquid bronze for the creation of the wild boar in its final form. All of the previous steps should have resulted in a very accurate investment mold for this purpose. You should start to heat up the crucible and the metal. Be sure that the crucible is literally red hot before adding the metal. As soon as the metal is fully melted, add the flux, and stir it with a pre-heated carbon stirring rod.
Retrieve the flask from the kiln. Check for ashes so that they do not accidentally get stuck in the piece. Always be sure to have the utmost safety measures in place— in this case a large fireproof glove. Next, put the flask upside down on the casting table with the holes facing up, and go ahead and turn on the vacuum pump. Now it is the time to pour the metal. Start by positioning the crucible over the flask, making sure to keep the torch on the metal to retain consistent heat. You can go ahead and turn off both the vacuum pump and torch in the cooling process. Wait until the metal is no longer in a red-hot state before moving onto quenching it. With an alloy such as bronze, you will need to wait until it is completely cool to complete this step— about an hour or so.
After the bronze has fully cooled, remove the investment shell in order to get the artwork out. Then, you can begin to carefully remove the casting pipes. Once all the pipes have been removed, you can begin the process of sanding and polishing the wild boar down in order to get rid of any imperfections. A simple toothbrush is a great tool to help with this. You can also use an ultrasonic cleaner, or even good old vinegar as a cheap alternative. After the investment is removed, we add a patina of choice, based on desired final effect of the wild boar to look like. We also some times add a clear lacquer to help prevent oxidation of the metal. Finally, depending on preference, or, that of our customer, we mount the piece on a beech wood foundation for a high-end and luxury vision.
This breakdown of 3D modeling, printing, and lost wax casting using a wild boar sculpture as an example should help to provide a strong visual outline for how such a work is completed from start to finish. You can buy this figure wonderful figure from our store.