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Scopri le basi delle pulegge GT2 per cinghie dentate: come scegliere tra le tre modalità di flangia (pulley / idler / none), selezionare numero di denti, larghezza della cinghia e diametro del foro, oltre ai consigli per la stampa 3D. La guida si concentra sulla configurazione standard 20T / 6 mm / 5 mm utilizzata con motori NEMA17 e sistemi CoreXY.

Top-down view comparing the three GT2 pulley flange modes (pulley / idler / none)

Guida alle pulegge GT2: denti, larghezza cinghia e modalità flangia

Pubblicato 2026-05-20 8 min di lettura

GT2 pulleys (timing pulleys) are toothed-belt pulleys with a 2 mm pitch widely used in 3D printers and robotics. The most common configuration is 20 teeth (20T), a 6 mm belt width, and a 5 mm bore, paired with NEMA17 stepper motors as the drive shaft of CoreXY and Cartesian mechanisms. This guide explains the basic structure of GT2 pulleys generated with meta-matic, how to choose between the three flange modes pulley / idler / none, how to select the number of teeth and belt width, and what to watch out for when 3D printing them.

What is a GT2 pulley?

GT2 is a toothed-belt standard that originated in the PowerGrip series from Gates Corporation, and is now widely used including aftermarket compatibles. It adopts a curvilinear (circular-arc) tooth profile rather than a trapezoidal one, making it well suited to low-noise, low-backlash, high-precision positioning. Related variants such as GT1.5 (1.5 mm pitch) and GT3 (3.0 mm pitch) also exist.

Figure 1: GT2 tooth profile. Pitch, tooth height, and root/tip radii are defined by the standard.

The meta-matic GT2 pulley generator carries these standard values internally as fixed parameters; you only need to specify four items: number of teeth / belt width / bore diameter / flange mode.

Puleggia GT2 - Generatore di file STEPGT2 PULLEYhttps://meta-matic.com/it/3d/gt2-pulley/

Based on common GT2 dimensions

This tool generates GT2-compatible shapes based on commonly used dimensions. Because subtle differences exist between manufacturers and product generations, always verify mesh engagement with an actual belt for precision applications.

Choosing between the three flange modes

The GT2 pulley generator lets you pick one of three modes based on the combination of flanges (the side rims) and an extended hub. Pick the shape that best fits your application.

pulley — with an extended hub

3D model of a GT2 pulley in pulley mode (flanges on both sides plus an axially extended cylindrical hub) — Figure 2: `pulley` mode. Adds an extended axial hub in addition to the flanges.

Use case : Drive pulleys mounted directly on a motor shaft, or whenever set-screw fixation is required
Pros : The hub provides a surface for set screws (grub screws) and increases the contact area with the shaft
Additional parameters : The diameter and width of the hub can be freely specified

idler — toothed idler (for tension, flanged on both sides)

3D model of a GT2 pulley in idler mode (with 1.5 mm-thick flanges on both sides) — Figure 3: `idler` mode. Automatically adds 1.5 mm-tall flanges on both sides.

Use case : When used as a tension pulley or guide pulley
Pros : Keeps the belt from drifting axially. Makes belt routing easier during assembly
Caution : In practical use, press-fitting a bearing into the bore is recommended

none — no flange

3D model of a GT2 pulley without flanges (20 teeth, 6 mm belt width, 5 mm bore) — Figure 4: `none` mode. The simplest toothed cylinder.

Use case : When designing custom shapes or printing the pulley in split parts
Pros : Unlike the other modes there are no overhangs, so it prints cleanly without supports
Caution : A separate physical mechanism is needed to keep the belt from drifting axially

Quick reference for mode selection

We recommend pulley for drive shafts such as motor shafts and for driven shafts that transmit power, idler for belt-tension adjustment and guiding, and none when designing complex shapes from scratch.

Parameter selection guide

How to choose the number of teeth

The number of teeth can be specified in the range of 16 to 120. Fewer teeth gives a more compact pulley suited for high-speed motion, while more teeth gives a larger diameter that provides greater belt engagement.

Comparison of GT2 pulleys with different tooth counts (top-down view of 20/40/60 teeth) — Figure 5: Outer-diameter comparison across different tooth counts

16–20 teeth (16T–20T) : Ideal for direct-drive motor shafts; off-the-shelf aluminum pulleys are widely available
30–40 teeth (30T–40T) : Often used in reduction stages or intermediate pulleys
60+ teeth (60T and above) : Used for high-torque applications or final-stage driven pulleys, though commercial products are scarce

Notes on selecting the number of teeth

This generator cannot produce GT2 pulleys with fewer than 16 teeth (16T). This stems from the physical bend-radius limit of GT2 belts: smaller pulleys impose higher bending loads on the belt. Considering belt life and positional accuracy, pulleys with 20T or more are recommended.

Travel per pulley revolution (basics of steps/mm calculation)

steps/mm = (motor steps per revolution × microsteps) ÷ (pulley teeth × belt pitch)

Since GT2 belts have a 2 mm pitch, the travel per pulley revolution can be calculated as "number of teeth × 2 mm". You need this value when configuring 3D printer firmware.

Teeth	Travel per revolution	Typical use
16T	32 mm	Compact mechanisms, direct-drive motor shafts (where compactness is the priority)
20T	40 mm	Standard for 3D printers (widely adopted in Voron / Ender families)
40T	80 mm	Reduction stages, driven side for high-torque applications

Table 1: GT2 timing pulley tooth count and travel per revolution (belt pitch 2 mm)

The 20T GT2 pulley is the most widely used in 3D printers. With 40 mm of travel per revolution, the steps/mm calculation combined with a stepper motor’s step angle works out cleanly, which is why 20T GT2 pulleys are widely adopted in Voron and Ender-family 3D printers.

Microstep settings

NEMA17 stepper motors have a 1.8° step angle, giving 200 steps per revolution. Configuring the microstep setting on the motor driver enables smooth, high-precision motion. steps/mm and travel can be computed with meta-matic’s steps/mm calculator.

How to choose the belt width

The belt width can be specified in the range of 3.0–20.0 mm. Commercial GT2 belts typically come in 6mm / 9mm / 15mm widths; match the pulley’s belt width to the belt you plan to use. Commercial pulleys are designed slightly wider than the belt itself.

Comparison of GT2 pulley belt widths (side view of 6mm / 9mm / 15mm) — Figure 6: Belt width comparison. Pick the one that matches a standard belt width.

6 mm wide : Widely adopted in 3D printer and small-robot designs
9 mm wide : High-load segments in mid-size robots and CoreXY mechanisms
15 mm wide : High-torque applications and CNC machine feed axes

How to choose the bore diameter

The bore diameter can be specified from 0 to 100 mm; specifying 0 generates a GT2 pulley with no bore. The basic rule is to match the motor shaft diameter, but you may design +0.1 to 0.2 mm larger to compensate for shrinkage during 3D printing.

5 mm bore : Standard shaft diameter for NEMA17 steppers
6.35 mm bore : 1/4-inch shaft (some RC and industrial motors)
8 mm bore : NEMA23 and larger steppers

When using keyways or D-cut shafts

This generator only supports circular bores. If you need to fit shafts with special profiles such as keyways, D-cut shafts, or splined shafts, set the bore diameter to 0 and then perform post-processing in CAD software such as Fusion 360 or FreeCAD.

Hub (`pulley` mode only)

In pulley mode you can specify the diameter and width of the hub. Setting the hub diameter to auto sizes it to match the flange diameter automatically. For set-screw designs, specifying a hub diameter about 10 mm larger than the shaft together with a hub width of 10–20 mm gives a stable result.

How to generate a GT2 pulley

The meta-matic GT2 pulley generator lets you download a STEP file instantly just by entering parameters in your browser.

Check the motor shaft diameter and belt width
Verify the shaft diameter of the motor you will use (e.g., 5mm for NEMA17) and the width of the GT2 belt you will pair with it (the default 7mm is 1 mm wider than a 6 mm belt).
Decide on the flange mode
Choose pulley for the drive side, idler for the tensioner / idler side, and none if you are designing a complex pulley shape from scratch.
Decide on the number of teeth
Work backward from the desired reduction ratio or the torque you need. The gear ratio calculator lets you confirm the reduction ratio from the tooth-count ratio of the drive and driven pulleys.
Generate and download with the generator
Enter the values above and click "Generate STEP file"; the STEP file will be downloaded automatically.
Open in CAD software to verify
Open the file in Fusion 360 / SolidWorks / FreeCAD etc., and verify dimensions and mesh engagement within your assembly.

Puleggia GT2 - Generatore di file STEPGT2 PULLEYhttps://meta-matic.com/it/3d/gt2-pulley/

3D printing tips

Because GT2 pulleys have small, fine teeth, 3D printing settings matter. A layer height of 0.16 mm or smaller, a nozzle diameter of 0.4 mm or smaller, and slower print speeds near the tooth tips help produce accurate tooth profiles.

Material : PLA or ABS work well; PETG or Nylon are recommended for higher loads
Print orientation : Align the pulley axis with the Z axis (vertical placement) so the tooth profile is perpendicular to the layer direction, giving better accuracy
Supports : Generally not needed, but if the upper flange collapses due to overhang, splitting the print works well
Shrinkage allowance : Specify the bore +0.1–0.2 mm larger and finish it with a reamer after printing for a reliable fit

When slipping occurs

If the drive pulley slips, check the belt tension and the set-screw fixation. Switching to a higher-friction, wear-resistant filament (such as TPU) can sometimes improve the situation.

Frequently asked questions

QAre "GT2" and "2GT" the same thing?

In practice they are used as essentially the same thing. "GT2" comes from the Gates trademark PowerGrip GT2, while compatible and generic products are often labeled "2GT". The specifications — 2.0 mm pitch and a curvilinear tooth profile — are identical, so GT2 belts and 2GT pulleys can normally be combined as-is.

QHow do GT2, MXL, and T2.5 differ?

MXL (pitch 2.032mm) and T2.5 (pitch 2.5mm) are not compatible with GT2. The tooth profiles also differ, so be sure to match the belt and pulley to the same standard. GT2 uses a curvilinear tooth profile that delivers high accuracy and low backlash, which is why it is widely used in 3D printer and CNC parts.

QDo the teeth have a front/back orientation?

GT2 pulley teeth are symmetric, so there is no front/back orientation or rotation-direction specification.

QHow do I calculate the distance between two pulleys?

If the pulleys and belt are already chosen, you can use the GT2 center-distance calculator. Just enter the tooth counts and belt length, and it computes the center distance between GT2 pulleys automatically.

QShould I choose 16T or 20T?

When in doubt, 20T is the safer choice. With 40 mm of travel per revolution, steps/mm calculations result in clean integer values, and 20T is widely adopted as the direct-drive motor pulley in CoreXY and Cartesian mechanisms. Choose 16T when you want a more compact pulley for the same reduction ratio, but note that the sharper belt bend tends to shorten belt life slightly.

QAre 3D-printed pulleys practical?

Yes — they are practical for hobby and prototyping use. GT2 pulleys printed in PLA or PETG are widely used in low-speed, low-load prototypes and DIY robots. However, for high-speed, high-load, or continuous-duty applications, tooth-face wear can progress faster than with aluminum pulleys.

Related resources

For those who want to dive deeper, here are related tools and reference materials.

GT2 center-distance calculator — Automatically computes the center distance from the belt length you intend to use
Gear ratio calculator — Automatically computes the reduction ratio when selecting tooth counts
PowerGrip® GT belts — Explanation of tooth-profile features, allowable torque, and positioning accuracy