Wall thickness in 3D printing is the specification most likely to be copied from a different process and quietly cause problems. A wall that is perfectly sensible for injection moulding can be too thin to survive a laser sintering build, and a wall that is thick enough to print can still deform if the rest of the part is not built to match it.
Here are the numbers we actually work to, why the recommended range sits above the absolute minimum, and the failure mode most people do not expect, which is that thin walls usually break during cleaning rather than in service.
What Is the Minimum Wall Thickness for SLS 3D Printing?
The minimum wall thickness for laser sintering is 1 mm, and walls between 1.5 mm and 3 mm print more accurately and more durably. That is the figure on our own design guidelines for SLS, and it is the number we quote against.
Treat 1 mm as the floor rather than the target. A part designed at exactly 1 mm throughout will usually print, but it gives up all of its margin: any local thinning from the CAD model, any slight variation across the build volume, and any handling during depowdering all eat into a wall that has nothing to spare. Designing at 1.5 mm costs almost nothing in material and removes most of that risk.
The full set of feature minimums is worth having in one place, since wall thickness rarely fails on its own.
| Feature | Our published SLS guideline |
|---|---|
| Wall thickness | Minimum 1 mm, with 1.5 mm to 3 mm giving more accurate and durable walls |
| Consistency | Keep wall thickness consistent through the part to reduce deformation as it cools |
| Clearance between features | Minimum 0.5 mm |
| Hole diameter | 1.5 mm minimum, and larger on thicker walls |
| Corners | Fillets in preference to sharp corners, for cleaning and to reduce stress points |
| Hollow spaces | Never fully enclosed, and at least two clean-out ports of 6 mm or larger |
| Embossed or engraved text | Bold, no smaller than 14 point, at least 0.8 mm deep |
| Standard tolerance | Plus or minus 0.25 mm up to 50 mm, plus or minus 0.38 mm from 50 mm to 75 mm, and above 75 mm plus or minus 0.38 mm plus 0.05 mm for every 25 mm over |
| Layer thickness | 100 micron high resolution, or 120 micron mid resolution |
Consistent Beats Thin
If you only take one rule from this, take this one: keeping wall thickness consistent matters more than making it thin. Our guidelines call for consistent thickness specifically to reduce deformation as the part shrinks, and that is a process constraint rather than a style preference.
The reason is thermal. A sintered part cools from melt temperature after the build, and thick sections hold heat longer than thin ones. When a thick boss meets a thin wall, the two cool at different rates and the part pulls itself out of shape at the junction. The result is warp, bow, or a subtly out of flat face that no amount of tolerance tightening will fix, because it is built in.
So a part with 2 mm walls throughout will generally come out truer than a part with 1 mm walls and a 6 mm block in one corner. Where you genuinely need a thick section, core it out and blend into it gradually rather than stepping straight from thin to thick.
Use Ribs Instead of Thicker Walls
When a wall is not stiff enough, the instinct is to thicken it. That is usually the wrong move in sintering, because stiffness rises far faster with depth than with thickness, and thickening the wall reintroduces the cooling mismatch you were just trying to avoid.
A rib standing off a thin wall buys much more stiffness per gram than adding the same material to the wall itself. For robot tooling that trade is the whole game, since every gram of tool is a gram off the payload, which is why ribbed thin wall structures dominate the end-of-arm tooling we build.
Two practical notes. Keep the rib itself within the same wall thickness guidance, since a rib is just another wall and a 0.8 mm rib is as unprintable as a 0.8 mm wall. And fillet where the rib meets the wall, which our guidelines already recommend in general and which matters doubly at a junction that is both a stress concentration and a powder trap.
Large Flat Areas and Unsupported Spans
Thin walls fail differently depending on how much unsupported area they cover. A 1.5 mm wall spanning 20 mm is fine. The same wall spanning 200 mm as a flat panel is a different part, because flatness, not strength, becomes the limit.
Large flat thin areas are the geometry most prone to curling and bowing, since they present the most surface to cool unevenly and have the least inherent stiffness to resist it. The fixes are geometric rather than dimensional: break the plane with ribs or a gentle crown, add a return flange at the edges, or split the face into smaller panels. Any of those beats simply adding thickness, which increases the thermal mass you are fighting.
Unlike some other additive processes there are no support structures to worry about, because the surrounding powder cake supports the part as it builds. Design guidance for the process is standardised in ISO/ASTM 52911-2, the design standard for laser-based powder bed fusion of polymers.
Where Thin Walls Actually Fail: Depowdering
Most thin wall failures happen between the build finishing and the part reaching you, not in service. After the build, a part is buried in a cake of unsintered powder that has to be broken away, brushed and blasted off, and that process applies real mechanical load to every feature on the part.
A wall that is strong enough for its job in the tool can still be too fragile to survive that. Blast media hits thin unsupported areas hard, and a technician breaking a cake apart is working by feel. This is the reason the recommended range sits above the absolute minimum: the extra half millimetre is not there for service loads, it is there so the part arrives intact.
Features most at risk are thin unsupported fins, tall narrow projections, sharp unfilleted edges on thin sections, and thin walls around large hollow volumes where powder has to be worked out through a port. If a part has any of those, say so when you send it, and it can be handled accordingly or the geometry adjusted before the build rather than after a breakage. Finishing steps that follow are covered in our post-process options for SLS.
Hollows Need a Way Out
A fully enclosed hollow cannot be printed usefully, because the powder inside it has nowhere to go and stays there for the life of the part. Our guidelines require that confined hollow spaces are opened up, with at least two clean-out ports of 6 mm or larger so the powder can actually be removed.
Two ports rather than one matters more than it sounds. One port lets powder out slowly and awkwardly. Two give you somewhere to blow air in and somewhere for powder to leave, which turns a frustrating job into a quick one. Place them at opposite ends of the cavity, and put them where a plug or a fitting can close them afterwards if the cavity is part of an air path.
This is also where thin walls and hollows interact badly. A large internal void with thin walls means aggressive powder removal against the least supported geometry in the part, so either thicken those particular walls or make the ports generous enough that force is never needed.
How We Handle It
We are Anubis 3D Industrial Solutions. We design and manufacture end-of-arm tooling and produce parts by selective laser sintering in polyamide at our facility in Mississauga, Ontario, so wall thickness is a question we resolve on nearly every part that comes in.
When a model arrives with sections below the minimum, we flag them before printing rather than printing them and hoping. Usually the fix is small: bring a wall from 0.8 mm to 1.5 mm, add a rib instead of thickening a panel, blend a step between a thin wall and a thick boss, or open a second clean-out port. None of that changes what the part does, and all of it changes whether the part arrives straight and intact. The material behind these numbers is covered on our PA12 nylon page.
Wall Thickness Questions
What is the minimum wall thickness for SLS 3D printing?
One millimetre is the minimum, and 1.5 mm to 3 mm gives more accurate and more durable walls. Treat 1 mm as the floor rather than the design target, because a wall at exactly the minimum has no margin left for handling or depowdering.
Why do thin walls warp on 3D printed parts?
Because of uneven cooling rather than the thickness itself. Thick sections hold heat longer than thin ones, so a part that mixes the two pulls out of shape at the junction as it cools. Keeping wall thickness consistent through the part is what prevents it.
Is it better to thicken a wall or add a rib?
Add a rib. Stiffness increases much faster with depth than with thickness, so a rib gives more rigidity per gram and avoids creating a thick section that cools at a different rate. Keep the rib to the same minimum thickness as any other wall and fillet it into the surface.
Can SLS print fully enclosed hollow parts?
Not usefully, because unsintered powder stays trapped inside. Confined hollows need at least two clean-out ports of 6 mm or larger, ideally at opposite ends, so powder can be blown out and removed.
Not Sure Your Walls Will Print?
Send us the model and our team will tell you which sections are below the minimum, where the thickness changes too abruptly, and what to change before the build rather than after it.
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