Conti Synchroflex AT3 GEN III 399

Conti Synchroflex AT3 GEN III 399 – durable PU timing belt with stable tooth pitch

Conti Synchroflex AT3 GEN III 399 is an endless, cast polyurethane timing belt with 133 teeth, 3 mm tooth pitch and a pitch length of 399 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 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. The GEN III version is the reinforced high-performance construction with red high-performance polyurethane and denser, two-filament steel cord. It should therefore be treated as a separate product series and not as the regular standard version.

Fixed specifications

• Pitch length: 399 mm
• Number of teeth: 133
• Tooth profile: AT3 GEN III
• 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.

Why the correct profile is crucial

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.

Cast polyurethane and steel cord

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.

The execution must be correctly identified

The red GEN III construction is not just a color variant. It is developed with higher cord density and a special steel cord construction that provides increased tensile strength, better grooveing and the ability to carry higher loads. The catalog also specifies a temperature range up to +100 °C. Standard and GEN III must therefore be created and selected as separate products, even when the length and profile are the same.

Relevant machine tasks

Continental cites small power drives, handling equipment, compact positioning axes and light synchronous drives as examples for this profile family. The examples describe the general application area of ​​the profile, but are not an approval for any specific installation. The final belt width and pretension must be selected based on the transmitted torque, starting and shock loads, operating time, pulley sizes, speed and the number of teeth in simultaneous engagement. For safety-critical or heavily loaded drives, an actual calculation should be made.

How the width variants work

This product line has been created with 6 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 6 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.

The discs are part of the overall solution

A belt with the correct length can still function poorly if the pulleys have the wrong profile, are worn or are misaligned. Therefore, check the tooth grooves, flanges, shaft alignment and the number of teeth on the pulleys. For AT3 GEN III, the nominal tooth pitch is 3 mm. The fixed tooth mesh makes the gear ratio reproducible, but only when the belt has sufficient wrap and does not run with constant side pressure.

Pre-tensioning and disc alignment

When installing, the cord pullers must be protected against kinks and local pressure damage. The belt must not be pinched with pliers or a screwdriver, and it should not be folded sharply. Check that the pulleys have the same pitch and profile as the belt and that they are not worn out. A stable drive is achieved through the right combination of alignment, wrapping and calculated pretension.

Checking when replacing

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.

Prevention of early belt damage

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.

Maintenance-free does not mean control-free

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 cast 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 can be signs of misalignment, too low tension or worn pulleys.

Questions and answers about this timing belt

Conti Synchroflex AT3 GEN III 399: 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 AT3 GEN III 399: 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 AT3 GEN III 399: are the standard widths the only possible widths?

The documented supplier widths for this size include 6, 8, 10, 12, 16, 20, 25, 32 and 50 mm. The product page may also show intermediate sizes as cut widths when they are within the allowed range. This does not change the tooth profile or length, but the price is calculated based on the base width.

Conti Synchroflex AT3 GEN III 399: 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.

Conti Synchroflex AT3 GEN III 399: 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 GEN III 399: why is 6 mm chosen as the basic width?

6 mm is the width of the supplier item whose SKU is used as the main product's stock reference. Other widths are handled as choices under the same product because they are cut from the same type of timing belt sleeve. The base width also determines the percentage-based pricing in the webshop.

Conti Synchroflex AT3 GEN III 399: what happens if the discs are not aligned?

Misalignment can cause the belt to wander towards a flange, causing edge pressure, heat and wear damage. It can also affect tooth engagement and reduce service life. Check both the parallelism of the shafts and the alignment of the pulleys.

The product in brief

In summary, this is a Conti Synchroflex PU timing belt with a fixed geometry of 3 mm pitch, 133 teeth and 399 mm pitch length. The width is selected separately, but does not change the length or number of teeth. A safe replacement requires that the entire designation and the specific version match the machine documentation.