Mold makers have taken an interest in additive manufacturing when considering their most intricate designs.
By building a mold from the base up, the parts can include internal features such as conformal cooling channels. This change can lead to production processes being optimized for speed, price, as well as for material conservation.
Additive manufacturing allows for complex geometries that could never be achieved with traditional machining methods. Further than that, the design of the mold in CAD software can take place in the same room as the mold production, by the hands of the same operator and sometimes even within the same day.
As-printed parts have properties equivalent to those manufactured by conventional means with densities exceeding 99.5% of the theoretical density, +/- 0.2% dimensional tolerances, and fine surface finish. Achieving these densities allows for optimal hardness.
When printing a mold with a powder-bed fusion printer, the only material that is formed is the metal volume of the part itself. Most of the material can be returned to the printer and used again in the next print. Additionally, when using the selective laser melting (SLM) process there is not a need for sintering because parts are printed with 99.5% density and optimal HRC.
When using other methods of additive manufacturing, such as FDM and EBM, a part is printed with sub-optimal density, requiring the sintering process to bind the material closer together and achieve the necessary density and hardness. However, the heat causes thermal contraction, impacting your dimensional accuracy. Gauging this contraction can be difficult, especially in fine features, generally needing multiple iterations. This method could be helpful to produce secondary molds, but if the mold design is relatively basic and then it may not be cost efficient. With powder-bed fusion printing, the print’s do not require additional machinery for strong mechanical properties to be achieved and they can print features as small as 30 microns, giving the designer the freedom to create what is needed, and nothing more.
This challenges the traditional need for economies of scale because the price of one print equates to the powder usage and labor costs. This price would remain true each time that part was printed. With machines able to work without constant oversight, the time and additional materials that would have been needed to create a secondary mold can be eliminated and replaced with another direct mold being printed.
