Jack Saldono for Getty Images
Though small and seemingly humble, the nozzle of a fused filament fabrication-style 3D printer plays a big role in the success or failure of an FFF print job.
An FFF printer feeds a spooled thermoplastic filament through a heated nozzle onto a horizontal build platform. The printer, loaded with ABS, PLA, or other polymer filament, builds parts layer by layer from the bottom up.
FFF, often referred to as FDM (fused deposition modeling)—a technology patented by Stratasys in 1989—is a relatively low-cost, reasonably fast way to print objects. These characteristics make FFF the most popular style of 3D printer, especially among home hobbyists and companies with limited budgets.
Anyone using an FFF printer should be familiar with the different types and diameters of nozzles, as the nozzle selected will have a tremendous effect on part quality, productivity, and operating cost. The first thing to know is that FFF filaments come in two diameters: 1.75 mm and 2.85 mm. Along with ABS and PLA, other common materials include nylon, polycarbonate, and TPU. There’s also a host of additives that can be mixed with these materials, such as carbon fiber, metal, wood, colorants, and even rock.
As for nozzle selection, Paul Brutskiy, technical support specialist for Micro Swiss LLC, Ramsey, Minn., said the first step is to find one that’s compatible with the 3D printer being used. “Nozzles have various specifications, such as thread size, length, and pitch, as well as the overall nozzle length and filament diameter,” he said. “To simplify the selection process, manufacturers usually list compatible printers for each nozzle in the fitment section of their user guide or website.”
Another consideration is the nozzle material. The base filaments listed earlier are not abrasive and will work well with a low-cost, thermally conductive brass nozzle. Filament additives, however, tend to increase the material’s abrasiveness, calling for a nozzle made from a harder metal.
Here again, a wide variety of nozzle materials are available. A2 tool steel, for example, provides a nice balance of wear resistance and thermal conductivity, while one made of M2 tool steel is extremely durable but less conductive.
Some manufacturers offer stainless steel nozzles, which should be used when printing food-grade or medical components. Tungsten-carbide nozzles provide the longest life, albeit at a higher price. And ruby, sapphire, or diamond tips are sometimes added to brass nozzles, greatly extending their lifespan, as does plating them with nickel or chrome.
Finally, hybrid nozzles made of copper with a hard metal insert are coming online, as are nozzles that incorporate “core heating technology.” This design element, available from Bondtech AB of Värnamo, Sweden, speeds material melting by splitting a filament into thinner strands.
The company’s product manager, Nuno Santiago, offered several nozzle selection recommendations. “Consider the detail level of your application,” he said. “Are you aiming to build very detailed parts or very large ones? How quickly do you need to build those parts, and what is the smallest feature’s minimum dimension? For instance, a 0.4-mm nozzle cannot build geometric features smaller than that value in the X-Y plane, hence the relevance of nozzle size regarding the level of detail.”
Standard FFF filaments come in two diameters: 1.75 mm and 2.85 mm. Getty Images
Santiago suggested that a part’s mechanical requirements and weight also play a role in nozzle selection. For example, a small nozzle might be used to make thicker, stronger walls, but more passes will be needed to fill a given area. This approach allows the material to cool between each pass, thus lowering bond quality.
Additionally, as nozzle diameters shrink, the printer must move more quickly to maintain equivalent volumetric flow. It’s often better to lay a thicker bead with a larger nozzle, provided that the printer’s “hotend”—the part of the printer that melts the material—has sufficient time and heat to melt the material properly, and the part’s geometry and accuracy requirements allow the lower detail level.
“To maximize build speed, a calculation needs to be made to determine what nozzle size can deliver the desired output while remaining below the machine’s top speed threshold,” said Santiago. “Some nozzle sizes may be outside your printer’s capacity to deliver good parts at a specific build speed. Those will be useless.”
See More by Kip Hanson
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The Additive Report focuses on the use of additive manufacturing technology in the real world of manufacturing. Today’s manufacturers are using 3D printing technology to create tools and fixtures, and some are even using AM for high-volume production work. Their stories will be covered here.
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