Timing Belts for Linear Motion
Timing Belts for Linear Motion
Linear motion systems convert the rotary output of a motor into precise straight-line movement of a carriage, slide, or tool head. The timing belt is the critical link between the motor-driven pulley and the moving platform. In linear motion, the belt must provide near-zero elongation under load, repeatable positioning accuracy, and long service life under continuous high-cycle operation. Polyurethane timing belts with steel tensile cord are the industry standard for this application, available in open-end rolls that can be cut and joined to any travel length.
Material: Polyurethane body with steel tensile cord (standard)
Format: Open-end (cut to length, joined with mechanical connector or weld)
Elongation: 0.02% under load (steel cord)
Profiles: T5, AT5, T10, AT10, AT20, HTD 5M, 8M, GT2
Applications: Gantry systems, CNC routers, pick-and-place, actuators, 3D printers, laser cutters
Why Open-End Urethane with Steel Cord
Standard closed-loop neoprene timing belts are designed for rotary-to-rotary power transmission, where the belt wraps continuously around two or more pulleys. Linear motion drives work differently: one end of the belt attaches to one side of the carriage, wraps around a motor-driven pulley, and the other end attaches to the opposite side of the carriage. The belt does not form a continuous loop. This requires an open-end belt that can be cut to the exact travel length plus attachment allowance.
| Property | Open-End Urethane / Steel Cord | Closed-Loop Neoprene / Fiberglass |
|---|---|---|
| Format | Open-end roll. Cut to any length. | Closed loop. Fixed circumference. |
| Elongation under load | 0.02% (steel cord) | 0.3-0.5% (fiberglass cord) |
| Positioning accuracy | Excellent. Carriage position corresponds directly to motor shaft rotation. | Position drifts with fiberglass stretch over time. |
| Body material | Polyurethane. Chemical, oil, and moisture resistant. | Neoprene. Degrades in wet/chemical environments. |
| Joining method | Mechanical connector, welded splice, or clamp-on ends | Endless (factory made). No field joining. |
| Custom length | Yes. Any travel length. | No. Must order exact circumference from catalog. |
| Cost per foot | Higher (premium material and cord) | Lower |
| Best for | Linear motion, gantry, actuators, CNC, pick-and-place | Rotary power transmission, conveyors, general drives |
Profile Selection for Linear Motion
The right profile depends on your carriage weight, acceleration requirements, and whether the equipment uses European (T/AT) or global (HTD/GT) pulleys.
| Application Class | Carriage Weight | Recommended Profile | Typical Width |
|---|---|---|---|
| Micro / desktop | Under 1 kg | GT2 2mm | 6 mm |
| Light duty | 1-10 kg | T5 or AT5 | 10-16 mm |
| Medium duty | 10-50 kg | T5, AT5, or HTD 5M | 16-25 mm |
| Heavy duty | 50-200 kg | T10, AT10, or HTD 8M | 25-50 mm |
| Very heavy duty | 200-500 kg | AT10 or AT20 | 50-75 mm |
| Maximum duty | 500+ kg | AT20 or HTD 14M | 75-150 mm |
Linear Motion Applications by Machine Type
| Machine Type | Motion Requirements | Recommended Belt | Notes |
|---|---|---|---|
| 3D printers | Light carriage, fast acceleration, precision XY positioning | GT2 2mm, 6mm wide, urethane steel cord | Industry standard. 16T or 20T pulleys. |
| Desktop CNC routers | Medium carriage, moderate speed, cutting forces | T5 or GT2 3mm, 10-16mm wide | Steel cord for positioning. Open-end. |
| Industrial CNC routers (large format) | Heavy gantry, long travel, high acceleration | AT10 or 8M, 32-50mm wide | Dual-belt setups common on wide gantries. |
| Laser cutters and engravers | Light carriage, very high speed, smooth motion for cut quality | GT2 2mm or T5, 6-16mm wide | Vibration damping critical for cut edge quality. |
| Waterjet cutting tables | Heavy gantry with cutting head, long travel, precision | AT10, 50-75mm wide | Wet environment. Urethane resists water exposure. |
| Pick-and-place systems | Medium carriage, fast cycle time, repeatable positioning | AT5 or 5M, 16-25mm wide | Steel cord essential for repeatable pick positions. |
| Packaging indexing | Precise carton or product spacing at high speed | 5M or XL, 15-25mm wide | Registration accuracy for label/seal alignment. |
| Palletizers and material handling | Heavy loads, long travel, moderate speed | AT10 or AT20, 50-100mm wide | Dual-belt for heavy palletizer gantries. |
| Medical and lab automation | Light carriage, precision, clean environment | T5 or AT5, 6-16mm wide | Urethane body for cleanroom compatibility. |
| Semiconductor and electronics | Ultra-precision, anti-static, cleanroom | T5 or AT5, 10-16mm wide | Anti-static urethane available. ESD safe. |
Tensile Cord Options for Linear Motion
| Cord Type | Elongation | Best For | Limitations |
|---|---|---|---|
| Steel cord | 0.02% | Precision positioning. CNC, pick-and-place, packaging registration. The standard for linear motion. | Lower flex life than Kevlar around very small pulleys. Heavier. |
| Kevlar (aramid) | 0.1-0.2% | High flex life. Serpentine paths. Small pulleys. Applications where moderate stretch is acceptable. | More stretch than steel. Not for ultra-precision positioning. |
| Fiberglass | 0.3-0.5% | Not recommended for linear motion. | Too much stretch for repeatable positioning. Use only for rotary drives. |
Open-End Belt Joining Methods
Open-end timing belts must be joined to the carriage or to themselves to create the complete linear drive. The joining method affects positioning accuracy, load capacity, and service life.
| Method | How It Works | Best For | Notes |
|---|---|---|---|
| Clamp-on ends | Belt ends clamp directly to the carriage using toothed clamp plates. | Most linear actuators and gantry systems. Simple, strong, adjustable. | Easiest installation. Belt length adjustable. Most common method. |
| Mechanical finger splice | Interlocking finger joints cut into belt ends and bonded. | Continuous loop applications where the belt must wrap around both ends. | Factory or field fabricated. Strong joint. Good for high-cycle applications. |
| Welded splice | Belt ends butt-welded using heat and pressure. | Open-end urethane belts. Creates a near-seamless joint. | Requires welding equipment. Strongest urethane joint. |
| Metal connector pins | Metal pins inserted through matching holes in the belt ends. | Quick field installation. Easy replacement. | Slight positioning discontinuity at joint. Acceptable for non-precision applications. |
Linear Motion Drive Design Considerations
- Travel length determines belt length. The belt must be long enough to cover the full travel distance plus wrap around the drive pulley and any idler pulleys, plus attachment allowance at both carriage clamp points. Measure total required length before ordering open-end belt.
- Belt width determines load capacity. Wider belts handle heavier carriages and higher acceleration forces. Use the profile selection table above to match width to carriage weight.
- Dual-belt drives for wide gantries. Gantries wider than approximately 600 mm often use two parallel belts (one on each side) to prevent racking and ensure the gantry moves squarely. Each belt is driven by a synchronized motor.
- Pre-tension is critical. Linear motion belts require proper pre-tension to prevent tooth skip under acceleration and deceleration loads. Follow the manufacturer's tension specification. Overtensioning increases bearing load and belt wear; undertensioning causes skip and positioning error.
- Idler pulleys must be smooth (non-toothed) on the back side. If the belt path requires backside contact with an idler, use a smooth flat or crowned idler. Running the toothed side over a non-matching pulley damages the teeth.
- Minimum pulley size matters. Smaller pulleys increase belt stress per revolution. Follow the minimum pulley tooth count for your profile. Using undersized pulleys reduces belt life dramatically.
Or call 888-203-2358. We stock open-end urethane belts and cut to your length.
Related Pages
Linear Motion Timing Belt FAQs
Open-end polyurethane timing belts with steel tensile cord are the industry standard for linear motion. The open-end format allows cutting to any travel length. Steel cord provides 0.02% elongation for precise, repeatable carriage positioning. Common profiles include T5, AT5, AT10, HTD 5M, and GT2.
Steel cord provides 0.02% elongation under load, compared to 0.3-0.5% for fiberglass. Over a 1-meter travel length, fiberglass stretch translates to 3-5 mm of positioning error that compounds with carriage weight and acceleration. Steel cord ensures that the carriage position corresponds directly to motor shaft rotation without drift. Fiberglass cord is not recommended for any linear motion application.
GT2 at 2mm pitch, 6mm wide, is the industry standard for 3D printer XY motion. Use open-end urethane with steel cord for the best positioning accuracy. Most 3D printers use 16-tooth or 20-tooth GT2 pulleys.
Belt width is determined by carriage weight, acceleration, and the profile's rated capacity per unit width. As a general guide: GT2 6mm for under 1 kg; T5/AT5 at 16mm for 1-10 kg; T5/AT5 at 25mm or 5M at 25mm for 10-50 kg; T10/AT10 at 32-50mm for 50-200 kg. For exact sizing, provide your carriage weight, acceleration rate, and travel length and we will calculate the correct width.
The most common method is clamp-on ends: toothed clamp plates bolt to the carriage and grip the belt on both sides. This is simple, strong, and allows belt length adjustment. Other methods include mechanical finger splices (for continuous loop configurations), welded splices, and metal connector pins. Clamp-on is the standard for most linear actuator and gantry installations.
Yes, for short travel lengths where a standard closed-loop belt circumference matches your drive geometry. However, closed-loop belts are only available in fixed circumferences from the catalog. For custom travel lengths, non-standard center distances, or long travel applications, open-end belts cut to length are the standard and preferred approach.
Yes. We stock open-end urethane timing belts in the most common profiles and widths and cut to your specified length. Tell us the profile, width, and length you need. Call 888-203-2358 or request a quote online.