PU timing belts (polyurethane synchronous belts) are essential components in precision power transmission and linear motion systems. With their open-ended, cut-to-length design and wide range of pitch profiles, they offer maximum flexibility for custom machinery, conveying systems, and automation equipment.

This guide explains how PU timing belts work, the differences between pitch profiles, and how to select the right belt for your application.

1. What Is a PU Timing Belt?

A PU timing belt (polyurethane synchronous belt) is a toothed belt that drives precision equipment with a pattern of teeth that mate to timing belt pulleys or idlers [0†L45-L47]. It provides accurate, slip-free synchronous transmission with a constant rotation rate during operation.

Key characteristics include:

• Open-ended design – can be cut to any length from 1000-20000mm [2†L18-L20]

• Thermoplastic polyurethane (TPU) – excellent wear resistance, oil resistance, and chemical resistance [1†L46-L48][4†L18-L19]

• Steel wire or Kevlar core – high tensile strength and dimensional stability [2†L23]

• No dust generation – clean operation for sensitive environments [4†L14][4†L20-L21]

• Tooth surface fabric – reduces friction and noise

2. Open-Ended vs Endless – Why Choose Open-Ended?

✅ Choose open-ended for custom applications, conveyors, and linear drives where length flexibility is critical. Choose endless for standard OEM equipment with fixed length requirements.

3. Pitch Profile Selection – Choose the Right Teeth

The pitch profile determines the belt’s tooth shape, load capacity, and application suitability:

T Series (Trapezoidal) – Standard General Purpose

• T5, T10, T20 – Standard trapezoidal tooth profile [3†L10-L11]

• Best for general conveying and light to medium-duty power transmission

• T5: 5mm pitch – light-duty; T10: 10mm pitch – medium-duty; T20: 20mm pitch – heavy-duty

AT Series (Trapezoidal, Reinforced) – High Torque

• AT5, AT10, AT20 – Reinforced trapezoidal profile for higher torque [3†L6]

• Best for high torque, precision positioning, and linear drives

• AT5: 5mm pitch – high torque, light-duty; AT10: 10mm pitch – medium-duty; AT20: 20mm pitch – heavy-duty

XL, L, H (Imperial) – Inch Series

• XL – 5.08mm pitch, light-duty (0.2″) [3†L6]

• L – 9.525mm pitch, medium-duty (0.375″)

• H – 12.7mm pitch, heavy-duty (0.5″)

• Best for inch-based machinery and equipment

M Series (Metric, Curvilinear) – High Precision

• 3M, 5M, 8M – Curvilinear tooth profile for high precision

• Best for precision positioning, robotics, and automation

• 3M: 3mm pitch – precision; 5M: 5mm pitch – general; 8M: 8mm pitch – heavy-duty

S Series (Super Torque) – High Torque, High Precision

• S3M, S5M, S8M – High torque curvilinear profile [3†L13]

• Best for high torque, high precision applications

• Suitable for servo drives, CNC machines, and automation

RPP Series (Round Profile) – Smooth Operation

• RPP3M, RPP5M, RPP8M – Round tooth profile for smooth operation

• Best for high-speed, low-noise applications

• Suitable for packaging machinery and printing equipment

4. Tension Member Selection – Steel Wire vs Kevlar

✅ Choose steel wire for most industrial applications requiring high tensile strength and dimensional stability. Choose Kevlar for high-speed applications, chemical resistance, or food processing environments.

5. Width and Length Selection

Length:

• Open-ended belts can be cut to any length from 1000-20000mm [2†L29][2†L33]

• Cut tolerance: ±10 mm [2†L33]

• Consider the center distance of your pulleys and the required belt wrap

Width:

• Customizable to any width

• Standard widths available – contact us for options

• Width affects load capacity – wider belts handle higher loads

6. Applications Where PU Timing Belts Excel

7. Installation & Maintenance Tips

1. Measure accurately – Ensure the required belt length is measured correctly before cutting

2. Clean pulleys – Remove debris from pulleys before installation

3. Proper tension – Tension the belt according to the manufacturer’s recommendations

4. Alignment – Ensure pulleys are properly aligned to prevent belt tracking issues

5. No lubrication required – PU belts are self-lubricating

6. Inspect regularly – Check for wear, cracks, or damage

7. Clean belts – Remove dust and debris to prevent premature wear

8. Hole punching – For applications requiring holes, specify when ordering

8. Selection Checklist

• □ 

  Pitch profile: T, AT, XL, L, H, M, S, or RPP – match your pulley

• □ 

  Pitch: 3mm, 5mm, 8mm, 10mm, 12.7mm, 20mm – select based on load and speed

• □ 

  Length: 1000-20000mm – measure your required length

• □ 

  Width: Custom – match your application

• □ 

  Tension member: Steel wire (standard) or Kevlar (high speed/chemical)

• □ 

  Color: Black (standard) or White (food-grade)

• □ 

  Customization: Hole punching, teeth milling, coating – specify if required

• □ 

  Application: Packaging, printing, conveying, automation, medical

9. Conclusion

The PU open timing belt from Apex Coupling offers the perfect combination of flexibility, durability, and precision for custom industrial applications. With open-ended, cut-to-length design, T to RPP pitch profiles, steel wire or Kevlar tension members, and OEM customization, it is the ideal solution for packaging machinery, printing equipment, conveying systems, factory automation, and medical devices.

👉 Need a PU timing belt for your application? Contact us with your pitch profile, width, length, and customization requirements.