Formada3D Serial-bus servo cradle + horn arm for 2020 extrusion (fits Feetech STS3215 / Waveshare ST3215)
A cradle and a horn arm for the 45 x 25 mm serial-bus servo used in every SO-100, SO-101 and LeKiwi build, so spare servos can become pan-tilts, sensor turrets and test rigs. The cradle stands the servo on its idler-side face on a 5 mm plate with the case's four mounting holes, a pocket for the raised panel, a spin hole for the idler horn and side cheeks, and bolts to 2020 extrusion or any 20 mm grid with two M5 slots 60 mm apart. The horn arm bolts to the output horn's four holes on a 14 mm circle and gives a 25 x 63 mm arm with M3 holes every 10 mm. Sized from the servo maker's own CAD and drawing; printed to order in our Melbourne workshop with 4 walls and 25 % infill because it carries servo torque.
From A$8 for the cradle + horn arm set. Printed to order in Melbourne and shipped Australia-wide; we confirm the final price and lead time before anything is printed.
On the quote page choose Request a quote (no file needed) and name this part and the option you want.
Order status. All positions come from the servo maker's own STEP model and 2D drawing. Two things are not stated there: how M2 screws bite in the case's 1.6 mm holes and the horn's thread, so the free coupon checks both before your parts are printed.
What does it look like in use?
Renders are computer images of our own design, made from the same model we print. This family is made to order: real photos of our first prints are coming.
Specifications: material, size and what it fits
| Spec | Detail |
|---|---|
| Material | PETG, 4 walls, 25 % infill (load-bearing: the parts carry servo torque), 0.24 mm layers on a 0.6 mm nozzle, no supports. PETG-CF or PA-CF on request for arms loaded at full torque |
| Cradle | 75 x 32 x 15.4 mm, 5 mm plate: four 2.4 mm M2 holes counterbored 4.4 x 1.5 mm (3.5 mm clamp, so M2 x 6 reaches 2.5 mm into the case), panel pocket with 0.5 mm clearance, idler-horn spin hole with 1.2 mm clearance, cheeks 0.35 mm off the case sides, 2 x M5 slots 60 mm apart. About 11 g |
| Horn arm | 26 x 75.5 x 6 mm: 18.4 mm pad x 2.0 mm on the horn disc only, four 3.4 mm holes on a 14 mm circle with 6.2 mm counterbores (4.0 mm clamp: M3 x 6 gives 2.0 mm of thread in the 2.2 mm horn), 6 mm hole over the centre screw, 25 mm wide arm with M3 holes every 10 mm plus a 20 mm cross pair. About 6.6 g |
| Fits | Feetech STS3215 / Waveshare ST3215 serial-bus servos (45.22 x 24.72 x 32 mm body, 19.2 mm horn with 4 holes on 14 mm), from the maker's published 2D drawing and STEP model. Cradle clashed against the maker's STEP model: zero overlap; arm swept a full turn: zero contact |
| Hardware | Not included: cradle 4 x M2 x 6 self-tapping screws + 2 x M5 x 10 and T-nuts; arm 4 x M3 x 6 into the horn. Never use longer horn screws: the case is 0.15 mm behind the horn |
| Fit coupon | Free with an order: a horn pad and a cradle-face plate with the same holes, to check how the M2 screws bite and your horn's thread before the final print |
Feetech and Waveshare are trademarks of their owners, named only to describe fit. These parts are our own design, made to the maker's published dimensions, and not affiliated with or endorsed by them.
How much does it cost?
Guide prices for printed parts, in Australian dollars. Shipping is extra; we confirm the final price, including any business minimum, before printing. Bulk and custom sizes are quoted per job.
| Option | From |
|---|---|
| Cradle + horn arm set, PETG (4 walls / 25 %) | A$8 |
| Two sets (pan-tilt) | A$8 |
| Fit coupon | Free with an order |
| PETG-CF or PA-CF | Quoted on request |
Who it's for
SO-101 and LeKiwi owners with spare servos, university and school robotics labs, and makers building pan-tilts, sensor turrets and test rigs on 2020 extrusion.
Safety & use
Installation & use. Designed for the uses described on this page only. Fixings are not included: use the sizes listed, check they are tight before use, and check the parts regularly for wear or damage. Not for safety-critical or overhead load-bearing use. Damage caused by misuse, modification or overloading isn't a fault in the product.
Robots. Powered joints can pinch and move unexpectedly. Keep fingers, hair and cables clear while powered, check the full range of motion by hand after fitting, and use the screw lengths listed on this page. PETG softens near 70 degrees C. A printed bracket is for hobby, education, research and prototype loads.
Load. These parts carry servo torque (the servo is rated about 30 kg.cm at 12 V). Use the servo's torque limit, use the stated screw lengths, and use metal brackets for production machines.
This doesn't affect your rights under the Australian Consumer Law.
Common questions
Which servos does it fit?
Feetech STS3215 serial-bus servos, which Waveshare sells as the ST3215: the 45 x 25 mm body used in SO-100, SO-101 and LeKiwi arms. All hole positions come from the maker's 2D drawing and STEP model.
How does the cradle mount?
Two M5 slots 60 mm apart (three 20 mm grid steps) take M5 x 10 screws into T-nuts in 2020 or 2040 extrusion, or bolt to any deck with a 20 mm hole grid. The servo screws to the cradle with four M2 x 6 self-tapping screws into its case.
What can I mount on the horn arm?
The 25 x 63 mm arm has M3 holes every 10 mm plus a 20 mm cross pair: a camera, a sensor, a small gripper or the next servo's cradle. Two sets and a 2020 corner make a pan-tilt.
Is printed PETG strong enough?
For hobby, education and prototype loads, yes: customer parts are printed with 4 walls and 25 % infill because they carry servo torque. For arms loaded at full torque all day, ask for PETG-CF or PA-CF, or use metal brackets.
How do I order?
Use Get a quote and choose Request a quote, naming the number of sets. We confirm the price and lead time before anything is printed.
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Sensor brackets, suction-cup arms and ISO 9409-1 tool-flange adapters for 2020 extrusion
Limit-switch and sensor brackets, vacuum-cup arms and ISO 9409-1 (50-4-M6, 31.5-4-M5) flange adapters, in PETG.
Last updated 15 October 2026.