PU timing belt AT3 252 - Conti® Synchroflex

Conti Synchroflex AT3 252 – durable PU timing belt with stable tooth pitch

The Conti Synchroflex AT3 252 combines a precise AT3 tooth geometry with a molded polyurethane body and longitudinally stable steel cord tension elements. The product has 84 teeth and a 252 mm pitch length, which corresponds to a tooth pitch of 3 mm. The belt is used in synchronous drives where uniform movement and reproducible position are more important than the elasticity normally associated with a conventional V-belt or flat belt. This is the standard version in the specified profile. It should not be confused with a possible GEN III version or a double-sided DL belt with the same pitch length.

Dimensions, profile and number of teeth

• Pitch length: 252 mm
• Number of teeth: 84
• Tooth profile: AT3
• Tooth pitch: 3 mm
• Material: cast polyurethane with steel cord
• Brand: Conti Synchroflex

The technical data below describes the part of the product that does not change when a different belt width is selected. Pitch length, tooth pitch and number of teeth remain identical for all width choices. However, the width affects the available belt cross-section width and the price calculated on the product page. Correct sizing must always take into account torque, speed, number of teeth in mesh, pulley diameters, service factor and any counter-bending.

How tooth geometry works

The AT profile has been further developed from the classic T profile. The larger tooth volume provides a higher tooth shear strength, and the profile is designed for a favorable tooth engagement with reduced engagement shocks. This makes the AT series suitable when a drive must be compact and at the same time transmit motion precisely. Continental states that the AT profile can perform up to 50% more than a corresponding T profile, but the actual capacity always depends on width, discs, speed and load profile.

Belt construction

The endless PU construction combines low dead weight with high longitudinal rigidity. The steel cord tension elements are cast into the belt and are not intended to be exposed, damaged or sharply broken during installation. The wear resistance of the polyurethane and the strong bond to the cord are central to the belt's lifespan. Correct handling is therefore just as important as the correct choice of profile and length.

Standard, GEN III or DL ​​– this version

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.

Checking when replacing

It is not enough to compare the total circumference of a belt. The correct replacement must have the same pitch, tooth profile and number of teeth as the existing drive. The width must match the pulleys and the required capacity, and a DL or GEN III version must be identified separately. If in doubt, pictures of the marking, tooth profile and pulleys can be used as a supplement, but a documented spare part designation is best.

Areas of application

The profile series is used in practice for tasks such as small power drives, handling equipment, compact positioning axes and light synchronous feeds. Common to these machines is the need for a fixed transmission ratio and controlled tooth meshing. A timing belt can transmit both force and position, but the capacity cannot be assessed based on length alone. Width, profile version, wrap angle and load cycle are among the data that must be included in the selection.

Width selection and price calculation

The basic price applies to 4 mm, and the other widths are calculated with the same percentage logic as the existing PU timing belts in the webshop. Integer widths from 4 to 50 mm can be selected on this product page. A width of twice the basic width therefore costs 100% more, while a width of one and a half times the basic width gives approximately 50% extra. This price rule is a webshop calculation; it does not replace a technical dimensioning of the belt's load-bearing capacity.

Selection of discs for the profile

The pulleys and belt should be considered as a single tooth engagement. Correct AT3 geometry ensures that the load is distributed over the tooth flanks rather than concentrated on tooth tips or edges. The drive ratio is selected by the number of teeth on the pulleys, while the belt's 84 teeth and 252 mm pitch length determine the required combination of pulleys and center distance. When changing the drive, the geometry should be calculated.

Practical advice for installation

The belt must be able to be placed on the pulleys without force. If it can only be mounted by forcing it over a flange, the center distance or mounting procedure is incorrect. The pulley shafts must be aligned and the flanges must be smooth and undamaged. In the case of multi-shaft or counter-bent drives, the diameter and position of the rollers must be assessed separately. Correct pretensioning reduces the risk of tooth skipping without unnecessarily loading the bearings.

Operating conditions of PU timing belt

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.

Prevention of early belt damage

Uniform light polishing of the tooth flanks may be normal, but localised spalling, ctiming baring or severe wear should be investigated. Wear on one edge often indicates misalignment or persistent flange contact. Damage to tooth tips may be due to incorrect profile, foreign bodies or inadequate engagement. If cord becomes visible or the belt has a sharp break, it should not continue in service without assessment.

Answers to typical questions

Conti Synchroflex AT3 252: 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.

Conti Synchroflex AT3 252: can the belt be installed by pressing it over the pulley flange?

This should be avoided. The belt should be installed by adjusting the center distance or following the correct installation procedure for the machine. Forcing it over a flange can damage the cord pullers, teeth or belt edge. After installation, the pulleys must be parallel and the pretension must be correct.

Conti Synchroflex AT3 252: can the belt be turned upside down on the pulleys?

The standard version is single-sided with teeth on the inside and a smooth back. It must run with the teeth in the corresponding tooth grooves; the back is not an alternative tooth side.

Conti Synchroflex AT3 252: how to check if the length is correct?

Count the teeth and check the pitch. 84 teeth times 3 mm gives 252 mm pitch length. Then compare the profile and design with the marking or the machine parts list. A measurement around the outside of the belt alone is not accurate enough.

Conti Synchroflex AT3 252: 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 252: does this PU timing belt need to be lubricated?

No. The timing belt is designed for lubrication-free operation. Oil or grease should not be added to reduce noise as this may mask an alignment, pretension or worn pulley problem. Instead, keep the tooth mesh clean and check the cause of any abnormal noise.

Conti Synchroflex AT3 252: 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 252 mm. When the pitch length is divided by the tooth pitch, the belt has 84 teeth.

Conti Synchroflex AT3 252: what should be checked after the first run-in?

Check that the belt runs centrally, that there is no abnormal heat or noise, and that the edges are not constantly rubbing against the flanges. Also look for signs of too low or too high pretension. If the drive requires a re-tension check, the machine manufacturer's procedure must be followed.

Conclusion

Conti Synchroflex AT3 252 is the correct size when the drive requires AT3, 252 mm pitch length and 84 teeth. The belt is cast endless in PU with steel cord and must be used with timing belt pulleys that match the profile. Choose the width according to the technical load and always check the design, alignment and pretension before commissioning.