Application Technology

In environments where extremes are the norm – be it scorching temperatures, corrosive substances, or the void of high vacuums – traditional fasteners often fail. Here, Analisa Russo, senior application engineer at Nano Dimension – a company specialising in 3D printing solutions for polymers, ceramics and additive manufactured electronics, explains how robust and versatile 3D printed ceramic threaded fasteners could provide the innovative alternative to meet exacting functionality requirements head on.

Ceramic threaded fasteners stand as barriers against extreme conditions, with highly sought after properties including electrical insulation,
non-magnetism, resistance to corrosion, as well as high temperatures. However, finding the perfect fit for harsh environments is akin to finding a needle in a haystack, especially for custom or low volume needs.

Producing a custom ceramic fastener begins with an ‘as designed’ model, drawing from existing screw thread standards or crafting bespoke designs for specific applications. Parts printed from ceramic slurries undergo a high-level of shrinkage during sintering, so applying precise scale factors to a design prior to printing is essential for precisely matching ‘as designed’ dimensions. Female threaded features typically require a slight increase in diameter to achieve a snug fit with mating threads.

Through 3D tests it was determined that orienting screw threads so that the axis is perpendicular to the build plate, yielded the most precise results, as well as adhering to best practices for UV dose to prevent dilation of the geometry due to overcuring. Mating features were also printed in the same build, in the same orientation, to maintain uniform shrinkage and thread pitch between parts designed
to interconnect.

Cleaning and post-processing

The work does not stop once the 3D printer’s hum subsides. Careful post-processing is also needed to maintain the fidelity of printed threads. Airbrushing is an effective non-contact cleaning method that prevents marring of delicate surface features, which can be used with warm water or solvents such as DPM. 

As part of an internal production and testing project, 3D printed ceramic screws meeting metric standards ranging from M6 to a delicate M2 were made, alongside corresponding ceramic nuts. In the design iteration process, screws with highly accurate diameter and tooth pitch using typical Alumina printing scale factors were produced. The corresponding nuts required a diameter offset up to 0.4mm to achieve a snug fit, while keeping tooth geometry and thread pitch constant. 

Spanning imperial screw sizes such as 8mm – 32mm, 10mm – 32mm, and 12mm – 24mm, ceramic female threads accommodate ‘off the shelf’ hardware, underscoring the technology’s versatility across different standards, as well as use in multi-material assemblies. Beyond conventional fastening applications, some models employ thread-like features that do not need to precisely mate to external hardware. To demonstrate this concept an Alumina wire nut with internal conical cavity and coarse threads was designed and printed. Here, the action of twisting the wire nut compresses multiple wires together, forging a secure conductive connection. 

While 3D printing can be used for low volume production of standard threaded fasteners, or in the production of new or non standard screw and nut geometries, it is likely that customers will encounter threaded features as just one part of a more complex custom design. Ceramic 3D printing can handle these versatile design needs in addition to withstanding demanding applications and environments.