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3D-printed sash deflectors, engineered for plastic.

A deflector's job is to stop the two weights in a sash box clashing — and that job is about shape, not mass. So you don't need lead. With a 3D printer and hard plastic we're free of the casting mould, which means we can design a better deflector: one that sockets onto your weight, stays put, and sheds the opposing weight off a smooth, edge-free surface.

See the designs ↓ How it works →

▶  45-second explainer · tap the video for sound

What makes these better than a cast deflector

01

It sockets onto the weight

Each cap has a locating skirt sized to its weight, so it sits centred and upright instead of perching loose like a cast deflector. A deflector that can't tip is a deflector that always presents its working face.

02

No edge to catch on

The round caps use a smooth ogive dome and the square caps a steep four-way hip. There's no flat top or sharp lip for the passing weight to snag — it always glances off. Casting can't easily make these shapes; a printer can.

03

Sized to the weight

Round or square, 38 mm or 50 mm — pick the cap that matches your weight so the footprint never fouls the pocket or the parting bead. Scale any of them in your slicer if your sizes differ.

04

Lead-free and free

No lead handling for the deflecting job, and the files cost nothing. Just remember plastic adds no real weight — if a sash needs more balance, that's still a job for a lead makeweight.

Choose by your weight

Round-section weight? Take a dome. Square-section? Take a hip. We've made every standard size — match yours, print, and slide it onto the cord.

Round-section weights · smooth dome

3D render of a smooth domed round plastic sash deflector sized for 25 mm round weights, with a 10 mm cord hole and a locating socket

Round dome — 25 mm

Fits Round weights, 25 mm diameter

  • Smooth ogive dome
  • Ø31 mm base · 23 mm tall · 10 mm cord hole
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3D render of a smooth domed round plastic sash deflector sized for 32 mm round weights, with a 10 mm cord hole and a locating socket

Round dome — 32 mm

Fits Round weights, 32 mm diameter

  • Smooth ogive dome
  • Ø38 mm base · 26 mm tall · 10 mm cord hole
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3D render of a smooth domed round plastic sash deflector sized for 38 mm round weights, with a 10 mm cord hole and a locating socket

Round dome — 38 mm

Fits Round weights, 38 mm diameter

  • Smooth ogive dome
  • Ø44 mm base · 29 mm tall · 10 mm cord hole
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3D render of a smooth domed round plastic sash deflector sized for 44 mm round weights, with a 10 mm cord hole and a locating socket

Round dome — 44 mm

Fits Round weights, 44 mm diameter

  • Smooth ogive dome
  • Ø50 mm base · 32 mm tall · 10 mm cord hole
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3D render of a smooth domed round plastic sash deflector sized for 50 mm round weights, with a 10 mm cord hole and a locating socket

Round dome — 50 mm

Fits Round weights, 50 mm diameter

  • Smooth ogive dome
  • Ø56 mm base · 35 mm tall · 10 mm cord hole
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Square-section weights · steep hip

3D render of a square hip plastic sash deflector sized for 25 mm square weights, with a 10 mm cord hole and a locating socket

Square hip — 25 mm

Fits Square weights, 25 mm

  • Steep four-way hip
  • 31 mm base · 24 mm tall · 10 mm cord hole
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3D render of a square hip plastic sash deflector sized for 32 mm square weights, with a 10 mm cord hole and a locating socket

Square hip — 32 mm

Fits Square weights, 32 mm

  • Steep four-way hip
  • 38 mm base · 28 mm tall · 10 mm cord hole
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3D render of a square hip plastic sash deflector sized for 38 mm square weights, with a 10 mm cord hole and a locating socket

Square hip — 38 mm

Fits Square weights, 38 mm

  • Steep four-way hip
  • 44 mm base · 31 mm tall · 10 mm cord hole
Download STL ↓
3D render of a square hip plastic sash deflector sized for 45 mm square weights, with a 10 mm cord hole and a locating socket

Square hip — 45 mm

Fits Square weights, 45 mm

  • Steep four-way hip
  • 51 mm base · 35 mm tall · 10 mm cord hole
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3D render of a square hip plastic sash deflector sized for 50 mm square weights, with a 10 mm cord hole and a locating socket

Square hip — 50 mm

Fits Square weights, 50 mm

  • Steep four-way hip
  • 56 mm base · 38 mm tall · 10 mm cord hole
Download STL ↓

⚠︎ Example designs — not load-tested. Print and use at your own risk, and always check the fit, clearance and security in your own window first. A part that works loose inside a sash box is a hazard.

How to print them

  • Material: PETG, ABS, ASA or nylon — tough and a bit heat-tolerant, and they resist creep under sustained contact. PLA prints easily but is more brittle and can creep over time; treat a PLA part as a test.
  • Strength: high infill (40–60%+) or thick walls. It takes knocks and rubbing, not big loads.
  • Orientation: print socket-down (dome/hip up) so the layer lines don't run across the cord hole or the thin tip. Supports usually aren't needed.
  • Fit: the socket allows ~0.6 mm clearance; if yours is tight or loose, scale by a percent or two in your slicer.

The full story

For what a deflector actually does, how it differs from a makeweight, and the material trade-offs, read the guides.

3D-printed deflectors: the guide → Makeweights & deflectors explained →