Lost Wax Casting is a metal casting process that broadly involves 4 stages.
First – the creation of master pattern,
Second – creating the ceramic mold on top of the pattern by spraying the ceramic slurry on the pattern,
Third – heating the ceramic mold to burn out the wax which leaves the negative cavity of the object to be casted and
Fourth – finally pouring molten metal into the mold to get the metal casting.
In ancient times, the master pattern was made out of beeswax with manual sculpting tools. In modern times, the master patterns are made with injection molding that first involves machining the mold which is very costly and time consuming. In recent times, the master patterns are directly 3D printed. The master pattern can be 3D printed with specific wax like materials (wax is a generic name) that are designated for lost wax casting application so that they burn out at elevated temperatures leaving the negative cavity in the ceramic mold.
Depending on the availability, costs and geometric details needed, various 3D printing technologies like Fused Deposition Modeling (FDM), Stereolithography (SLA), PolyJet Printing (PJP) or Multi Jet Printing (MJP) can be used to create the master pattern. It is advisable to select the material that has least ash content so that no residue is left after burn out.
Materials for Master Pattern
3D Systems’ Projet MJP printers are capable of printing accurate wax models with VisiJet iCast material that can capture very fine details of the object. Stratasys’ Polyjet Printing with VeroBlack material has the least ash content of only 0.02% making it ideal for lost wax casting. Formlabs offers Castable Wax 40 which is a resin specific for jewelry castings.
3D Printed master patterns are several times more affordable than having to develop the injection molds for creating the patterns. If there are no tiny and intricate details on the part being casted, Fused Deposition Modeling (ABS) with no additional surface polishing can be directly used as a master pattern.
3D printing is used to produce master patterns for automotive parts like gearbox casings, aerospace parts like turbine blades, jewelry applications and more.