Conti Synchroflex AT5 GEN III 690

Conti Synchroflex AT5 GEN III 690 – compact timing belt for precise motion transmission

When a timing belt needs to be replaced correctly, the profile, pitch length and number of teeth are the first data that must be correct. The Conti Synchroflex AT5 GEN III 690 has the AT5 GEN III profile, 5 mm tooth pitch, 690 mm pitch length and 138 teeth. This makes the product unique in terms of length and profile, while the belt width is selected separately on the product side. The belt is manufactured as an endless Conti Synchroflex PU timing belt with steel cord. The GEN III version is the reinforced high-performance construction with red high-performance polyurethane and a denser, two-filament steel cord. It should therefore be treated as a separate product series and not as the regular standard version.

The most important product data

• Pitch length: 690 mm
• Number of teeth: 138
• Tooth profile: AT5 GEN III
• Tooth pitch: 5 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

The metric AT geometry has trapezoidal teeth with a larger tooth volume than the standard T profile. The purpose is to distribute the load advantageously in the tooth mesh and achieve higher tooth strength without making the drive unnecessarily large. The profile requires suitable AT timing belt pulleys with the same pitch; a visual similarity to other profiles is not evidence of compatibility.

Belt construction

The belt body consists of wear-resistant polyurethane, which encloses high-strength steel cord. The materials each have their own function: PU forms the teeth and protects the belt against mechanical wear, while the cord tensioning elements provide high longitudinal stiffness and limit post-elongation. Continental describes the design as maintenance-friendly and lubrication-free. This does not mean that the drive can be ignored; pulleys, alignment and pretension should still be checked.

The specific product version

GEN III is the reinforced high-performance version of the Conti Synchroflex series. The construction uses red high-performance polyurethane, more densely packed steel cord tension elements and a two-filament construction with balanced S and Z cords. Continental states up to 25% higher power transmission than the corresponding AT or ATP standard series. GEN III can use the standard profile timing belt pulleys, but the belt still needs to be dimensioned for the specific drive.

How to identify the correct replacement belt

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.

Where is this profile used?

The profile series is used in practice for tasks such as machine tools, pu , textile machines and positioning and conveying systems. Common to these machines is the need for a fixed transmission ratio and controlled tooth engagement. 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.

From basic width to desired width

The belt width is not written in the product name because the same pitch length is collected on one product page. The starting pu is 6 mm. Integer widths from 6 to 50 mm can be selected on this product page. The original supplier widths for this length are 6, 8, 10, 12, 16, 20, 25, 32 and 50 mm. Other intermediate sizes are offered as cut-to-size versions of the same type of timing belt sleeve when they are within the selection shown. The number of teeth, pitch length and profile do not change when the width is changed.

Gear ratio, enclosure and tooth contact

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 5 mm pitch and the correct AT5 GEN III tooth shape, and check that the flanges do not damage the belt edge.

Correct splice in the timing belt tensioner

The timing belt pulleys must be parallel and in the same plane. Even minor misalignments can cause the belt to move towards a flange and cause edge or cord damage. The belt should be installed without being twisted, sharply bent or pressed over a flange with a tool. The center distance is adjusted to achieve the calculated preload. Too high a tension increases the bearing and cord load, while too low a tension can cause tooth jumps at load peaks.

Operating conditions of PU timing belt

Continental specifies a temperature range of up to +100 °C for the GEN III series. When operating close to the temperature limits, the drive must still be dimensioned according to the specific load and environmental conditions. The timing belt operates without lubrication, and oil or grease should therefore not be added to dampen noise. The polyurethane is described as resistant to aging as well as simple oils, grease and petrol and to certain acids and bases. In the case of permanent contact, cleaning chemicals or unknown media, material compatibility should be specifically clarified.

Wear patterns and troubleshooting

A properly running timing belt should move smoothly without continuous contact against one flange. Regularly check the teeth for deformation, the back for ctiming bars and the edges for frayed areas. Abnormal noise or heat can be an early sign of incorrect tension or pulley failure. A systematic check of pulleys and belt is more effective than trying to hide symptoms with lubricant.

Technical questions about the product

Conti Synchroflex AT5 GEN III 690: when should the timing belt pulleys be replaced?

Pulleys should be evaluated if the tooth grooves are worn, sharp, crooked or damaged. A new belt on worn pulleys may have poor load distribution and short life. Also check flanges for bars and side contact and the grooves for foreign objects.

Conti Synchroflex AT5 GEN III 690: 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 AT5 GEN III 690: 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 AT5 GEN III 690: what temperature can the belt work at?

The GEN III series is rated for temperatures up to +100°C. When operating close to the limit, load, cooling and environment must be assessed separately.

Conti Synchroflex AT5 GEN III 690: why is GEN III not merged with the standard version?

GEN III has a different material construction and capacity data than the standard belt. The higher cord density, two-filament construction and high-performance polyurethane make it a separate product line, even though the pitch length and tooth profile may be identical.

Conti Synchroflex AT5 GEN III 690: why is the number of teeth important for spare parts?

The number of teeth links the pitch of the profile to the nominal length of the belt. For this size, 138 teeth at 5 mm pitch gives a length of 690 mm. It is a simple check that often reveals faults that are not visible by a quick comparison of two loose belts.

Conti Synchroflex AT5 GEN III 690: how does preload affect operation?

Correct pretension keeps the teeth in stable engagement and reduces the risk of tooth jump. Too low a tension can cause impact and jump under load, while too high a tension increases the load on the cord, pulleys and bearings. The correct value must be determined based on the drive's dimensioning.

Is the Conti Synchroflex AT5 GEN III 690 welded?

No. The Conti Synchroflex series is manufactured as cast, endless timing belts. The belt therefore does not have a welded joint around the circumference. The cast process provides a uniform tooth pitch around the entire belt and a strong bond between the polyurethane and the cast steel cord tension elements.

Brief summary

The product brings together the specified AT5 GEN III 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 690 mm pitch length and 138 teeth. In case of doubt about load or pulley compatibility, the drive should be calculated before ordering the belt.