Metal Filament 3D Printing of 316L Stainless Steel on a Prusa i3

In the recently published ‘Metal Filament 3D Printing of SS316L: Focusing on the printing process,’ thesis student Karthikesh Gante Lokesha Renukaradhya for the Machine Design track in Industrial Engineering and Management program at the Royal Institute of Technology explores additive manufacturing with metal. Analyzing previous studies, the author notes previous challenges and obstacles like expense and lack of availability for all users.

Product development cycle

Here, the author focuses on a new AM technique using a metal-polymer composite filament to create a stainless steel 316L part on an FDM 3D printer. With the use of a Prusa 3D printer, two comparisons were offered, beginning at the technical level using polymer techniques, and then the material level using stainless steel filament.

In the research, the following impacts were also analyzed:

• Printing temperatures
• Nozzle types
• Printing patterns
• Adhesion between layers

Previous studies have shown that fused filament fabrication (FFF, FDM) has great potential for manufacturing with metals, and especially those with complex geometries:

“Additionally, FFF technology proves to have an edge over other methodologies, in terms of simple and effortless change of material. The tailored Fused Filament Fabrication allows printing green parts out of 316L stainless steel feedstock effortlessly, however, the surface properties obtained were not found to be satisfactory for the surface critical applications without after treatment. Scope for further research could possibly be a combination of green part printing and surface polishing procedure in one print head,” states the author.

While FDM 3D printing is popular for fabrication with polymers, previous studies have shown that metal filament is not as easy to come by and can be cost-prohibitive too. The researchers note that with the use of infill and a significant increase in density, ‘both the mechanical strength and production cost will increase proportionately.’

The internal geometry of the printed part with different infill density

Samples were assessed in terms of printing parameters, with samples showing better success when printed at 210◦C rather than 235◦C. The sample exhibited a ‘well-packed structure’ with no signs of cracking at all. The geometric resolution was good too.

Microscopic (5x) images of green body test specimen printed at 210◦C

There were some issues with debinding because of a rapid rise in temperature. The author found that slow and steady temperature increases led to greater success along with the use of supports and good airflow.

 “The main practical conclusion of this study was the results obtained with different printing parameters, the structural integrity which influences the mechanical property and geometric resolution. Another advantage of this developed FDM process is that the system allows for a straightforward change of material, as only a new filament has to be inserted into the print head, unlike the other AM techniques which are a time-consuming process,” concluded the researchers.

“Debinding and sintering of the sample was the most challenging part and to control all the parameters added up to the challenge. After a series of trials, a set of parameters and equipment were selected with minor parameter alterations if necessary. It was also found out that the shrinkage rate from the green part of the final metal part varied in x, y and z directions. Virtual foundry stainless steel 316L is an upcoming and encouraging way of producing metal Additive Manufacturing parts and there is always space for future investigation in this area of Additive Manufacturing.”

Metal 3D printing has just continued to grow and has garnered interest not only by industrial users but many researchers too as they perform studies on how to eliminate porosity, combine traditional and new metal printing techniques, and create new superalloys. What do you think of this news? Let us know your thoughts! Join the discussion of this and other 3D printing topics at 3DPrintBoard.com.