Additive manufacturing enables large-format die casting tools

Researchers at the Fraunhofer Institute for Laser Technology ILT, in collaboration with MacLean-Fogg and Toyota, have manufactured a large-volume die-casting tool inlay using laser powder bed fusion (PBF-LB/M) for the first time. The basis for this is the newly developed L-40 tool steel, which allows the additive manufacturing of heavily loaded tools and, for the first time, enables near-contour cooling in large-format aluminum die-casting molds. The process was successfully demonstrated using the example of a hybrid tool for the transmission housing of the Toyota Yaris Hybrid.

Additive manufactured die casting tool inlay — Additively manufactured die-cast tool inlay made from tool steel L-40: The large volumetric mold was produced at Fraunhofer ILT using laser powder bed fusion with conformal cooling.

New material and machine technology for large-volume applications

Until now, additive manufacturing of large-format die casting molds has been limited by restricted build volumes and the high susceptibility to cracking of conventional tool steels such as H11 or H13. With the gantry-based 5-laser system developed at Fraunhofer ILT, the build volume has now been expanded to 1,000 × 800 × 350 mm³. In combination with a heatable build platform that reaches up to 200 °C, thermally induced stresses can be significantly reduced.

“To overcome this limitation, a new generation of machines and materials specifically tailored to large-format tools is needed,” explains Niklas Prätzsch, group manager for LPBF process technology at Fraunhofer ILT.

“It is precisely this combination that was the subject of the developments that have now been realized.”

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Werkstoff L-40 mit hoher Prozesssicherheit

Der von MacLean-Fogg entwickelte Werkzeugstahl L-40 wurde gezielt auf die Anforderungen der additiven Fertigung abgestimmt. Er weist im Vergleich zu konventionellen Stählen eine geringere Rissneigung auf und erreicht bereits im as-built-Zustand hohe mechanische Kennwerte: 48 HRC Härte, 1420 MPa Zugfestigkeit und über 60 J Kerbschlagzähigkeit. Damit eignet sich der Werkstoff auch für großvolumige Werkzeugeinsätze mit komplexen Geometrien und frei gestalteten Kühlkanälen.

Graphical comparison of the service life of conventionally manufactured and additively manufactured tools made of L-40 — Comparison of the service life of conventionally manufactured and additively manufactured tools made from L-40: The optimized near-contour cooling specifically tempers critical zones, reduces the thermal load and increases the service life. In earlier projects, the service life of the tools increased almost fourfold.

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Hybrid manufacturing shortens throughput times

The project partners combined additive and conventional processes for tool manufacturing. The mold insert, which is built on a preform, contains a dense network of contour-hugging cooling channels that enable targeted temperature control of critical areas, thereby significantly extending service life. Previous applications have already shown up to four times longer service life compared to conventional tools made of H13 steel.

After assembly, industrial heat treatment and precise milling of the functional surfaces followed. Due to the high dimensional accuracy of the additive base body, only minimal post-processing was required.

Additive manufacturing as a pioneer of efficient tool strategies

The technology opens up new perspectives for OEMs who are adapting their production architectures to the requirements of electromobility. In the future, large-volume tools can be manufactured faster and more flexibly – with shorter development times, lower material usage, and longer service life.

“With L-40, we set out to push the boundaries of additive manufacturing for die casting tools,” says Harald Lemke, Director of Product Management at MacLean-Fogg Component Solutions. “This project shows that large-format, heavy-duty inserts are economically feasible. Additive manufacturing is ready for industrial scale.”

Wide range of potential applications

The developed process chain, consisting of scalable PBF-LB/M technology, new materials, and hybrid construction, is not only suitable for aluminum HPDC tools, but also for hot and cold forming tools, punching, threading, or injection molding inserts. Wherever complex cooling structures and high load-bearing capacity are required, additive manufacturing can offer significant efficiency advantages in the future.