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Drone Propeller Guards & Ducts in 3D printed nylon

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Quick answer

A propeller guard is a sacrificial impact part, so ductility — not stiffness — picks the material. PA11 powders are the grades that flex and spring back: Formlabs Nylon 11 at 40% elongation at break, Arkema Rilsan Invent PA11 at 45%, EOS PA 1101 at 30% in-plane and 15% in Z. Glass-filled grades (4–9% elongation) and PA12 loaded across layers (EOS PA 2200: 4% in Z) are the brittle choices that crack on the first hard contact. Print the ring flat so impact bending runs in-plane, and hold roughly 1–2% of propeller diameter as tip clearance.

The propeller guard has an unusual job description: it exists to be hit. On cinewhoops and indoor aircraft it is also a duct that shapes the airflow, but structurally it is a bumper — first contact with walls, branches and the ground, at the largest radius on the aircraft, where every gram costs agility. Its design problem is the mirror image of the motor mount’s: survive bending, not resist it.

The incumbent guards are injection-moulded PP or ABS on consumer aircraft and bent carbon or wire at hobby scale — all cheap, all tied to one fixed airframe geometry. Printed nylon enters where the airframe is custom, the guard must integrate with printed mounts and ducts, or replacements are needed faster than shipping allows.

Choosing the material: the reasoning chain

Start from the working condition: the guard’s defining load is impact — a bending shock applied at the ring, repeatedly, in any direction the aircraft happens to meet the world. The material property that decides survival is elongation at break, and the datasheet spread in this database is wide: 45% for Arkema Rilsan Invent PA11, 40% for Formlabs Nylon 11 (XY), 30% for EOS PA 1101 (XY).
Orientation halves the choice again. A ring printed flat bends in-plane; stood on edge, the same impact loads the Z direction. EOS PA 2200’s split — 18% elongation in XY, 4% in Z — shows what that costs in PA12; EOS PA 1101 keeps 15% in Z, the strongest cross-layer ductility among the EOS powders, which matters for tall duct rings that cannot be printed perfectly flat.
Stiffness still matters, but it is a geometry problem, not a material problem. The ring must not deflect into the propeller disc under a side load. A closed ring with a taller-than-thick section gets that stiffness from shape; chasing it with glass filler buys modulus (EOS PA 3200 GF: 3200 MPa) at the price of 9% elongation — the wrong trade for a part whose job is to flex.
MJF is the credible alternative process: HP’s PA 12 lists 18% elongation in XY and 10% in Z — a notably smaller orientation penalty than SLS PA12’s 4% Z — so an MJF guard in PA 12 is a reasonable second choice where PA11 is not available. The FDM filaments are not: Polymaker’s CoPA, the most ductile filament in this database in-plane at 12.7%, drops to 1.3% in Z, and a guard is precisely a part that gets loaded across layers.
Verdict: PA11 powder, SLS first choice, ring printed flat; HP PA 12 via MJF as the fallback. Filled grades and FDM are for guards that only need to look the part.

Every figure in that chain is a datasheet value from the grade's own page in this database — follow the grade links in the table below, or open the shortlist in the material comparison tool.

Design numbers for this part

Design point	Value	Basis
Propeller tip clearance	≈ 1–2% of propeller diameter	Engineering rule of thumb for printed guards and ducts: enough gap that ring deflection and print tolerance never let the tips strike, small enough that the duct effect and protection are not given away. On a 5-inch propeller that is roughly 1.3–2.5 mm.
Absolute minimum wall (process floor)	0.6 mm vertical / 0.3 mm horizontal	Formlabs SLS Design Guide for the Fuse series (Nylon 12 Powder) — a printability floor, far below what an impact part needs.
Ring wall (structural)	1.5–2.5 mm, with a taller-than-thick section	Engineering rule of thumb: the ring gets its stiffness from section height (radial depth), not from wall thickness, so it can still flex along its length and absorb the hit.
Print orientation	Ring flat, in the XY plane	So impact bending runs along layers. Datasheet basis: elongation at break collapses in Z — 4% vs 18% (EOS PA 2200), 15% vs 30% (EOS PA 1101).
Strut-to-ring junctions	Generous fillets, no sharp internal corners	Engineering practice: the strut roots are the fatigue and fracture site on this part; a sharp corner there concentrates exactly the cyclic bending the guard lives under.
Enclosed sections	Escape holes ≥ 3.5 mm, at least 2 per cavity	Formlabs SLS Design Guide — applies if the guard or duct is designed as a hollow closed section: trapped unfused powder adds weight at the worst possible radius.

Where the basis column names a manufacturer document, the value is that document's. Where it says rule of thumb or engineering practice, the value is this site's engineering guidance, labelled as such — not manufacturer data.

Recommended grades in this database

Grade	Polymer	Process	Tensile strength	Elongation at break (in-plane)
Formlabs Nylon 11 Powder	PA11	SLS (Fuse series)	49 MPa	40 %
Arkema Rilsan Invent PA11	PA11	SLS	45 MPa	45 %
EOS PA 1101	PA11	SLS	50 MPa	30 %
HP 3D High Reusability PA 12	PA12	MJF	54 MPa	18 %

How this part fails

Brittle ring fracture on impact — the signature failure of the wrong grade: a glass-filled or cross-layer-loaded PA12 ring cracks through instead of flexing, usually at a strut root.
Ring deflection into the propeller disc under side impact: the guard survives, bends far enough to meet the spinning prop, and destroys both. Clearance and section stiffness, not material strength, prevent it.
Fatigue cracking at the strut-to-ring junctions under continuous propeller vibration — the cyclic-load version of the impact problem, arriving after hours of flight rather than one crash.
Sacrificial abrasion: guards are supposed to wear on contact faces. Thinned sections are a replacement cue, not a defect — the failure is flying a worn guard until the thinned ring becomes the fracture path.

Economics: printed nylon vs the conventional part

The incumbent is the injection-moulded guard bundled with a consumer airframe: per-part cost is minimal, but the mould only exists for that one frame, in that one size, and the design is frozen. Bent carbon rod and wire guards cover the hobby end with hand labour per part. Powder-bed printing inverts both: no tooling and no hand-forming, with cost driven by part volume and build packing — and the guard is a large, thin, mostly-air part, which is the shape powder economics handles best when builds are packed well.

Printed nylon wins for custom and low-volume airframes, for guards integrated with printed motor mounts and ducts as a single part, and for operators who treat guards as consumables and print spares on demand. It loses on stable, high-volume consumer designs, where moulding’s tooling has long since amortised — the honest break-even question is always “how many identical guards, of a design that will not change,” and the answer that favours printing is counted in singles to low hundreds per design.

As with every powder-bed part, the effective material cost includes the refresh term: unfused powder is reused blended with fresh powder at the manufacturer’s refresh ratio, so a big thin guard costs more than its fused volume alone. That term belongs in any per-part comparison against a moulded guard.

Related: the SLS vs MJF cost-structure comparison and the SLS & MJF design guide cover the process side of these numbers.

Frequently asked questions

Are 3D printed propeller guards strong enough?

In the right grade, yes — the guard’s job is to flex, and PA11 powders are built for it: 40% elongation at break for Formlabs Nylon 11, 45% for Arkema Rilsan Invent PA11. In the wrong grade — a glass-filled powder at 4–9% elongation, or PA12 loaded across layers — the same shape cracks on first contact. Strength here is a material-and-orientation decision more than a thickness decision.

What is the best material for a 3D printed propeller guard?

A PA11 powder, printed by SLS: Formlabs Nylon 11, EOS PA 1101 or Arkema Rilsan Invent PA11, chosen on elongation at break and on how much of it survives in the Z direction (PA 1101 keeps 15% in Z). HP’s MJF PA 12 (18% XY, 10% Z) is the sensible fallback. Avoid glass-filled grades for this part.

How much clearance should there be between the propeller and the guard?

A working rule of thumb is 1–2% of propeller diameter — roughly 1.3–2.5 mm on a 5-inch propeller. Less, and ring deflection or print tolerance lets the tips strike the guard; much more, and the guard stops guarding (and a duct stops ducting). The clearance has to be checked against the ring’s stiffness: a flexible ring on a crash-prone aircraft belongs at the top of the range.

Do ducted propeller guards increase thrust?

A well-shaped duct can improve static and low-speed efficiency — that is established aerodynamics, and it is why cinewhoops are ducted. On small printed multirotors the gain is easily eaten by the duct’s weight and by as-printed surface finish, so the honest reason to print a duct-guard is protection and integration, with any thrust effect a bonus rather than the design case. This site makes no numerical efficiency claim for printed ducts; no manufacturer publishes one for these grades.

SLS or FDM for a propeller guard?

SLS, and the datasheets show why. A guard is loaded across its layers in exactly the direction where FDM nylon is weakest: Polymaker’s CoPA filament, the most ductile FDM nylon in this database in-plane (12.7% elongation), manages only 1.3% in Z, and the carbon-filled filaments are lower still. Powder-bed PA11 keeps 30–45% in-plane and 15% in Z. FDM guards are acceptable as cosmetic bumpers on micro aircraft; structural guards belong in powder.

Sources

Last updated: November 2026