Benchmarking: How Do Metal 3D Printers Really Compare?

As additive manufacturing (AM) has taken hold as a production method, companies that wish to take advantage of this technology are also inherently concerned with quality. AM is still a young process and 3D printers can vary widely in terms of capabilities and consistency. 

Ensuring repeatability across metal 3D printers was a topic of discussion during AM In-Depth, an educational series housed within IMTS Spark. Brenna McCornac, additive manufacturing engineer with Cumberland Additive, shared a benchmarking experiment in which the company compared two of its powder bed fusion (PBF) metal 3D printers from different builders.

The two 3D printers were run through a series of tests using Ni718 powder from the same lot as a way of better understanding how they function during normal use and the particular strengths or weaknesses of each system when using this material. 

The 3D printers were evaluated on the following factors:

• Plate heating. Interestingly, the build plate temperature reported by each system was less than that found by thermocouples placed on top of their print surfaces, due to plate heaters being located below the plate; understanding this discrepancy could help users achieve better consistency through longer preheating steps or by checking temperatures independent of the system sensors.
• Tensile properties. Test builds with artifacts scattered across the plate resulted in parts with better elongation than indicated by either 3D printer manufacturer, but slightly less yield and ultimate strength than expected. Additive manufacturing users have an obligation to evaluate the tensile properties of builds themselves, she says, rather than rely on documentation from the printer supplier. 
• Geometric capability. In several cases the metal 3D printers were found to be more capable than manufacturers’ guidelines suggested; one system successfully printed an overhang of 35 degrees, for instance, despite a minimum overhang recommendation of 45 degrees. Holes, pins and thin walls were also evaluated, with the results indicating that some 3D printers may be more capable and reliable at creating certain features. 
• Gas flow. One of the 3D printers suffered from a dead zone with poor gas flow in one corner, resulting in a degradation of mechanical properties there. In this case, Cumberland Additive worked with the printer manufacturer to upgrade the system and correct the issue. In cases where that is not possible, having an accurate benchmark of build locations within a machine can help ensure quality by guiding part placement. 

For more detail on the benchmarking tests used as well as some advice for additive manufacturers pursuing benchmarking in service of serial production, see the recorded session.