PU timing belt AT3 351 - Conti® Synchroflex

Conti Synchroflex AT3 351 – precise PU timing belt for synchronous power transmission

Conti Synchroflex AT3 351 is an endless, cast polyurethane timing belt with 117 teeth, 3 mm tooth pitch and a pitch length of 351 mm. It is intended for synchronous power transmission, where the driving and driven shafts must follow a fixed tooth ratio without the slippage known from friction-based belt drives. The pitch length is the nominal length measurement in the belt's cord line and is therefore the measurement that must be compared with the existing belt, the machine's spare parts data and the installed timing belt pulleys. This is the standard version in the specified profile. It must not be confused with a possible GEN III version or a double-sided DL belt with the same pitch length.

Technical information for this timing belt

• Pitch length: 351 mm
• Number of teeth: 117
• Tooth profile: AT3
• Tooth pitch: 3 mm
• Material: cast polyurethane with steel cord
• Brand: Conti Synchroflex

These specifications can be used as a check against the marking on the old belt or against the machine's spare parts list. The pitch length is not necessarily the same as a measurement across the outside of the belt, and the number of teeth is therefore often the safest additional check. If in doubt, both the belt and timing belt pulleys should be examined before ordering a replacement.

Function of the tooth profile

In a synchronous belt drive, the movement is transmitted through the tooth flanks. The geometry of the AT profile is therefore crucial for both load distribution, noise level and position accuracy. A correct AT pulley supports the teeth according to the profile to which they are cast. If the pulley's tooth shape or pitch deviates, the load can be concentrated at a few pu and cause abnormal wear, even though the belt can apparently be mounted.

Materials and endless manufacturing

With the cast manufacturing method, the finished belt becomes an exact copy of a precision-machined shape. This is a major reason for the uniform tooth pitch and reproducible length. The steel cord is integrated into the polyurethane and contributes to position and angular precision. The design is suitable for synchronous drives, where a conventional elastic friction belt does not provide the desired repeatability.

What does the version designation mean?

This item is a single-sided standard design. The teeth are located on the inside of the belt, while the back is smooth. It should not be confused with a double-sided DL version or the red GEN III series. If the machine is originally dimensioned for a specific variant, a change should only be made after a technical assessment of load, pulleys and preload.

Areas of application

The application examples in the catalogue include small power drives, handling equipment, compact positioning axes and light synchronous feeds. This shows that the profile can be used in both power transmission and motion control. However, the specific belt must only be finally selected when the machine's torque, speed, center distance and pulley geometry are known. When simply replacing a spare part, the safest method is usually to copy the documented profile, length, design and width.

Operating environment and maintenance

The standard material is specified for ambient temperatures from -30 °C to +80 °C. Applications close to the limits, especially below -10 °C or above +50 °C, may require special sizing. The molded PU belt is maintenance-friendly and does not require lubricant. Regular visual inspection is still relevant: look for ctiming bars, frayed edges, shiny tooth flanks, foreign body impressions and abnormal side contact. Sudden changes in noise or grooveing may indicate misalignment, too low tension or worn pulleys.

How the width variants work

This product line has been created with 4 mm as the base width because this is the width of the selected item and thus the SKU used for inventory control. Integer widths from 4 to 50 mm can be selected on this product page. The widths that appear as standard widths in the supplier data are marked separately in the options. The price surcharge is calculated as a percentage of the base width: doubling the width results in a surcharge of 100%. The technically necessary width should be selected according to the load and not only according to the price.

Selection of discs for the profile

The number of teeth on the pulleys affects both the gear ratio, deflection and how many belt teeth carry the load. A small pulley may be necessary in a compact drive, but it should not be selected without considering the minimum profile requirements and any counter deflection. Use timing belt pulleys with 3 mm pitch and the correct AT3 tooth shape, and check that the flanges do not damage the belt edge.

How to avoid unnecessary wear and tear

Proper installation begins with clean, undamaged pulleys with the correct profile. Teeth and grooves should be checked for deposits, bars and wear before the new belt is fitted. The pretension should be based on the drive's calculation and should not be selected based on a random hand feel. After the initial run-in, it is a good idea to check grooveing, noise, temperature and whether the belt runs centrally.

Signs of improper operation

Troubleshooting should start with pu location of the damage. Edge wear is typically associated with grooveing and alignment, while tooth skipping can be associated with too low tension, load peaks or too few teeth in mesh. Ctiming bars on the back can be caused by too small rollers, back bending or environmental influences. Do not simply replace the belt without also finding the mechanical cause.

Profile and length must match

When replacing a spare part, the marking on the existing belt should be compared with the product name. Check the profile designation, pitch length, number of teeth, design and width. If the text on the belt has worn away, the number of teeth can be counted and the pitch can be assessed by measuring over several teeth. A single external length measurement is less reliable because the nominal length of the timing belt is indicated in the pitch line.

Answers to typical questions

Conti Synchroflex AT3 351: what is the difference between tooth pitch and pitch length?

The tooth pitch is the distance from one tooth to the next and is 3 mm for this profile. The pitch length is the entire nominal circumference in the cord line and is 351 mm. When the pitch length is divided by the tooth pitch, the belt has 117 teeth.

Conti Synchroflex AT3 351: can an old V-belt be directly replaced by this timing belt?

No. A timing belt requires timing belt pulleys with the correct profile and pitch, while a V-belt works by friction in V-grooves. A conversion therefore requires new pulleys and a dimensioning of the entire transmission. The product is intended as a timing belt, not as a universal replacement.

Conti Synchroflex AT3 351: what temperature can the belt work at?

The standard version is specified for ambient temperatures from -30 °C to +80 °C. At temperatures below -10 °C or above +50 °C, adapted sizing may be required.

Conti Synchroflex AT3 351: can this belt be used at high speeds?

The Conti Synchroflex series is designed for precise and fast synchronous drives, but the permissible speed depends on the profile, pulley diameter, belt width, load and peripheral speed. A high speed must therefore not be approved based on the product name alone; the drive must be calculated.

How many teeth does the Conti Synchroflex AT3 351 have?

The belt has 117 teeth. The number of teeth is calculated by dividing the pitch length of 351 mm by the tooth pitch of 3 mm. The result is 117, and this number can be used as an additional check when identifying an existing belt. A different number of teeth means a different pitch length.

Conti Synchroflex AT3 351: why can a timing belt make noise?

Noise can be caused by incorrect pretension, skewed pulleys, poor tooth profile compatibility, excessive speed, resonance or worn tooth grooves. Lubrication is not the solution. First check alignment, tension, pulley condition and whether the belt runs without abnormal side contact.

Conti Synchroflex AT3 351: can a wider belt always transmit twice as much?

Not necessarily. A larger width provides a more active belt cross-section and can increase the permissible load, but the drive capacity also depends on the profile, number of teeth in mesh, pulley size, speed, load factor and preload. The width should be selected by an overall calculation.

Conti Synchroflex AT3 351: can the belt run with counter-bending?

The possibility depends on the profile, cord design, the diameter of the rollers and the specific belt routing. Counter-bending increases the bending load and must be included in the dimensioning. A roller on the belt back must have sufficient diameter and be positioned so that tooth engagement and grooveing are not impaired.

Conclusion

The product brings together the specified AT3 profile and length on one side, so that the appropriate width can be selected without creating a separate item for each cut. The main technical data is 351 mm pitch length and 117 teeth. If in doubt about load or pulley compatibility, the drive should be calculated before ordering the belt.