It is possible to create precise parts with lost wax casting, and this article will show you how. This technique was used for centuries in jewelry making and other crafts before the invention of metal molds. It has been popularized again by 3D printing, which can be traced back to lost wax casting as well.
The technique basically involves making a wax model, coating it with ceramic material which is baked, and then melting out the wax while using the remaining form to cast new metal parts.
Precise parts are needed for modern machines and tools including cars, cell phones, utensils and many other items. Lost wax casting can be used to make precise models for these items from scratch or make replacement parts when original components become damaged or worn out. In addition, lost wax casting can create objects that would be difficult or impossible to make via other methods such as machining from solid materials.
Let’s examine how this process works in more detail starting with the creation of a wax model. There are differing schools of thought on creating a model depending on what the object is going to be used for. If it will need to fit a certain mold, the model should be created based on an existing part to ensure a good result. If it will not be inserted into a mold, there is also a school of thought that the model should be made from scratch as this allows more freedom in design.
In either case, creating a wax model involves first identifying what type of wax to use and then how detailed the final model must be. Some factors that impact these decisions include:
- Wax form size
The bigger or smaller the part being replicated, the thicker or thinner its wax form can be without sacrificing too much detail since portions of it won’t have to fill every cavity in the mold
- Wax material type
Higher melting point waxes are need for larger parts while lower melting point waxes can be used for smaller objects
- Wax surface finish
Polished, sanded or unpolished? This is somewhat of a personal preference. An unpolished wax surface provides better detail but is more difficult to paint later on.
- Ambient conditions
If the model will be cast outside of the oven, it’s best to use an easily melted wax like beeswax or an inside job if possible
Once you’ve determined what kind of wax will work best, the next step is making your model. The ideal method involves creating your design in 3D modeling software and then slicing into thin layers that will then be printed by a 3D printer.
This allows you to create precise features and ensures a uniform thickness in the wax model. If your 3D modeling software is not up to par or you don’t have access to a 3D printer, another option is getting creative by using different materials such as clay.
Once you’ve created your model it’s time to add some color! To provide contrast when the part is being printed by a machine, it’s best to use white wax rather than other colors. However, if your final product will be unpainted then any color works just fine.
Next, coat the finished design with mold release compound which will help keep air bubbles out once the wax form has been dipped into ceramic slurry that will eventually harden into plaster. If you plan to use a foundry with your model, remember that they cannot use certain materials such as rubber so it’s best to avoid using any materials containing these unless you want to pay for extra work down the road.
Once everything is dipped and dried, it’s time to fire up the kiln. Kilns can be made at home out of household items such as flower pots and coffee cans but if you’ll be doing this regularly then investing in a professional model may be worth it. This is where many people run into trouble since most ceramic ovens won’t accommodate precise features like those seen on 3D printed models due to uneven heating and burnout. Enthusiasts note that heating times based on whether or not your model has solid or hollow cavities can vary between 10 and 24 hours!
