Additive manufacturing in tool making
Conformal cooling and repair welding with laser cladding.
1. Introduction: Tool making as a pioneer of additive manufacturing
Tool and die making was one of the first industries to recognize the economic benefits of metal 3D printing on an industrial scale. This is rarely about weight reduction, but rather about cycle time, wear resistance and process stability in subsequent series production.
This white paper shows how PBF (powder bed fusion) and DED (laser deposition welding) are revolutionizing the design and maintenance of injection molds and stamping tools.
What is conformal cooling?
In classic mold making (CNC), cooling channels can only be drilled straight. You often have to keep a large distance from the contour in order not to break through. In 3D printing, the channels are printed curved - they follow the contour exactly (3-5 mm below the surface). The result is a significantly more homogeneous and faster cooling of the plastic.
2. Injection molds: The turbo through conformal cooling
In plastic injection molding production, the bottleneck is the cooling time (the time that the hot plastic has to harden in the tool). It often accounts for over 60% of the total cycle time.
- Reduction in cycle time: Through additively manufactured tool inserts (made of maraging steel 1.2709) with conformal cooling, the cycle time can be reduced by 20% to 40%. With millions of pieces, the expensive use of 3D printing often pays for itself after just a few weeks.
- Increase in quality: Since the plastic part cools evenly, thermal stresses are reduced. The risk of warping and sink marks in the end product is reduced dramatically.
3. Repair and maintenance using DED
Large punching, drawing or forging tools experience extremely high local wear (e.g. on edges or radii). If a large casting tool breaks, this typically means massive damage and a production stoppage.
- Laser deposition welding (DED): Instead of re-milling the entire tool, the defective area is milled out and rebuilt precisely using DED. A powder is often used that is even more wear-resistant than the base material (applied armor / cladding).
- Advantage over manual welding: The laser input is more precise, the heat input is lower (less distortion) and the structure has a significantly higher metallurgical quality.
4. Hybrid manufacturing: The best of both worlds
A metal 3D print (PBF) builds up relatively slowly. Printing a complete, massive injection mold weighing 200 kg would be completely uneconomical. Therefore, smart tool making uses hybrid approaches.
- The hybrid structure: A solid steel block (the later base of the tool) is prefabricated conventionally on a CNC machine. This block is then clamped into the 3D printer (PBF) as a building platform. The printer only builds up the top 5 centimeters (with the fine, conformal cooling channels) additively.
- Result: 90% of the material is cheap steel, 10% is printed with high complexity. This is the “sweet spot” of profitability.
5. New materials for mold making
In addition to the classic 1.2709 (maraging steel), new alloys are increasingly becoming established:
- Hot work steel H13 (1.2344): Known from die casting, offers high heat resistance. Challenging in printing (PBF) as it tends to form cracks (requires machines with high-temperature heating of the build platform >500°C).
- Copper alloys: Since copper conducts heat fantastically, tool inserts made of copper alloys (now excellently printable with green lasers) are used to quickly dissipate heatspots (hotspots). To protect the soft copper surface from wear, it is subsequently coated.
6. Conclusion
For modern tool making, metal 3D printing is no longer a future scenario, but rather everyday life. Contract manufacturers and in-house tool shops that do not have conformal cooling and DED repairs in their portfolio (or purchase externally) will lose out in the long term against competitors with significantly shorter cycle times.