Overview

OSSM Actuator overview showing the assembled linear actuator

The OSSM linear actuator converts rotary motor motion into linear thrust via a GT2 belt drive on an MGN12H linear rail. This page covers printing, hardware, and assembly.

Print Settings

Setting	Value
Walls	6
Infill Type	Cross Hatch or Gyroid
Infill Percentage	15%
Supports	None
Filament Estimate	200g
Recommended Filament	PLA+

Print all parts in the default file orientation. Printing threaded components in other orientations causes structural weakness.

For the 24mm Clamping Thread, use 2 raft layers to improve bed adhesion.

All OSSM print files are also available on MakerWorld.

Printed Parts

Quantity	Part
1	OSSM - Body - Middle
1	OSSM - Body - Lower
1	OSSM - Belt Clamp - Tensioner
1	OSSM - Belt Clamp - Top
1	OSSM - Belt Clamp - Bottom
1	OSSM - Body - Cover
1	OSSM - 24mm Jam Nut
1	OSSM - PCB Mount Base
1	OSSM - PCB Mount Lid
1	57AIM Ring v1.1
1	PitClamp v1.1 Lower Standard
1	PitClamp v1.1 Upper + Handle
1	PitClamp Dogbones Hex
1	PitClamp Dogbones Round

Troubleshooting: 24mm Clamping Thread

If you have issues printing the 24mm Clamping Thread, use the Non-standard 24mm Thread and Belt Clamp files instead. These require additional hardware:

(Qty 2) M3x8
(Qty 1) M3x16
(Qty 3) M3 Hex Nut

Bill of Materials

Motor and Linear Rail

Quantity	Part
1	57AIM30 Gold Motor
1	MGN12H Linear Rail (350mm suggested)

Calculate your rail length: desired maximum stroke + 180mm.You must use an MGN12H rail. The “H” designates a longer bearing block than “C” for greater stability. The “12” indicates a 12mm rail width.

Hardware

Part	Qty
M3x8mm socket cap screw	18
M3x20mm socket cap screw	3
M3 hex nut	10
M4x25mm socket cap screw	2
M4 hex nut	3
M5x20mm socket cap screw	6
M5x35mm socket cap screw	4
M5 hex nut	8
M6x16mm socket cap screw	2
M6 T-Nut for 30x30mm t-slot extrusion	2
5x11x4mm bearings	6
8mm bore 20T pulley	1
10mm GT2 belt	50cm

Assembly

Animated exploded view showing how actuator components fit together — Animated exploded view of actuator assembly

Exploded view of actuator from front angle — Exploded view - front angle

Exploded view of actuator from alternate angle — Exploded view - alternate angle

Before You Begin

Ensure all printed threads are clean and free of stringing. Test-fit the 24mm threaded parts by hand only.
Lightly deburr belt paths and bearing seats on printed parts as needed.
Gather metric hex keys and a small flathead screwdriver for set screws and terminal blocks.

Do not power the actuator until you complete belt routing and verify smooth motion. Avoid forcing the rail carriage — binding indicates misalignment.

Build Steps

Prepare the linear rail

Verify your rail matches the required spec (MGN12H). Slide the carriage through its full travel; it should feel smooth with no catches.

Carriage moves freely across the entire rail without binding.

Assemble the body stack

Position Body - Bottom and Body - Middle. Align mounting holes and loosely fasten the parts so you can make minor adjustments during alignment. Add Body - Cover later after belt routing.

Start all screws before tightening to maintain alignment.

Install bearings and tensioner

Press-fit the MR115-2RS bearings into the Belt Tensioner and any designated idler pockets in the body. The bearings should seat flush and spin freely.

All bearings are fully seated and rotate without rubbing printed walls.

Mount the pulley

Fit the 20T GT2 pulley (8mm bore, 10mm width) on the drive shaft and align it with the belt path. Secure set screws against a flat on the shaft if available.

Keep the pulley aligned with the belt centerline to prevent tracking issues.

Route the belt (reference images below)

Feed the 10mm GT2 belt through the body following the Tensioner → Body → Belt Clamp path. Leave equal tail length at the clamp for final tensioning.

Belt teeth fully engage pulley teeth; belt is not twisted.

Install the 24mm clamping interface

Assemble the 24mm Clamping Thread - End Effector and Belt Clamp with the two 24mm 5-sided nuts. Hand-tighten only during initial fit.

If your print has poor first-layer adhesion on these parts, use a raft (2 layers recommended) and reprint.

Set belt tension and close the body

Use the Belt Tensioner to remove slack until the belt is taut and tracks true during manual motion. Once satisfied, install the Body - Cover and tighten all hardware progressively.

With light hand motion, the carriage moves smoothly and returns without skipping teeth.

Belt Routing

Route the GT2 timing belt through the actuator body following these reference images:

Tensioner

Body

Belt Clamp

Next Steps

Flash firmware

Use the web flasher to install the latest firmware on your OSSM or RADR.

Wire your motor

Connect the Gold Motor (57AIM30) correctly before first power-on.

Program your motor

Configure third-party motors before first use.

Getting Started

Standard Printed Parts

Motor

OSSM PCB v2.3

OSSM Mods

Known Issues

Print Settings

Printed Parts