Ducting, manifolds and airflow components are among the very best applications for SLS, and once you understand why, it is hard to unsee. These parts often feature curved internal passages, channels that merge and split, and thin walls, exactly the kind of geometry that is awkward to machine, costly to mould and almost impossible to support in other printing processes, but completely natural for a powder bed that supports every surface as it builds.
Because SLS needs no internal supports of any kind, it can print smooth, continuous channels in a single piece with nothing blocking the flow path. That is precisely why we see so much airflow and ducting work come through our MJF & SLS printing service from automotive, industrial and product design customers alike, many of whom have struggled to make the same part any other way.
Smooth internal passages
In SLS, the inside of a duct is supported entirely by powder as it prints, so there are no support marks or ridges left behind to disrupt the airflow once the part is cleaned. The channel can twist, branch, narrow and change cross section freely, which means you can design purely for efficient airflow rather than constantly compromising the shape to suit how it will be manufactured or how a tool would have to pull apart.
After printing, the loose powder trapped inside the passages is flushed out through carefully placed escape holes, leaving clean internal surfaces. Those escape holes are an essential part of designing any hollow airflow component, so they are planned in from the start rather than added as an afterthought once powder is already stuck inside.
One piece beats many
A complex duct that would otherwise be moulded in two halves and then bonded together can instead be printed as a single sealed part. That removes the joints, the glue lines and every potential leak path that comes with them, and it usually makes the finished part both lighter and stronger than a bonded equivalent would be, with no seam to split under pressure.
Consolidating several separate fittings and connectors into one printed component also cuts assembly time and reduces the number of places where a leak could ever develop, which is a real benefit for parts that have to hold pressure or move air efficiently around an engine bay or a machine.
Smoothing for cleaner flow
Where airflow efficiency really matters, the naturally matte internal surface can be vapour smoothed to reduce roughness inside the passages, which lowers turbulence and pressure loss along the channel. Smoothing also seals the slightly porous nylon, which helps a duct hold low pressure without weeping through the wall.
It is not needed on every part, since many ducts perform perfectly well with the standard finish, but for performance airflow work it is a worthwhile step. Tell us the flow and pressure your part has to handle and we will advise whether smoothing earns its place on your duct. We can also dye smoothed ducts black at the same time, which gives a clean finished look for parts that are visible inside an engine bay or on a display rig.
Designing airflow parts
For the best results, keep wall thickness consistent throughout the part, add generous radii on bends so air flows smoothly, and include powder escape holes at the low points so no powder is trapped inside. PA11 is well worth considering where the part has to flex slightly or absorb vibration without cracking over time.
Our CAD team can optimise a duct for both flow performance and printability at the same time, balancing the two so you do not have to choose. Send your concept through with a get a quote and we will help you get it right.