Timing belt CXP 688 8M - CONTI® SYNCHROFORCE

Timing belt CXP 688 8M - CONTI® SYNCHROFORCE

Timing belt CXP 688 8M - CONTI® SYNCHROFORCE is a technical rubber timing belt in the CONTI® SYNCHROFORCE CXP version. The belt has an HTD 8M CXP profile, an effective length of 688 mm and 86 teeth. It is used in timing belt drives where power and movement must be transmitted precisely via tooth meshing.

Product data

• Effective length: 688 mm
• Number of teeth: 86
• Tooth profile: HTD 8M CXP
• Tooth pitch: 8 mm
• Profile type: HTD 8M in CXP version
• Tooth height: 3.4 mm
• Belt height: 5.6 mm
• Standard widths: 20 mm, 30 mm, 50 mm and 85 mm
• Length tolerance: ±0.30 mm
• Material: Chloroprene rubber
• Reinforcement: Fiberglass reinforcement
• Tooth surface: Prepared polyamide tissue on the tooth side
• Series: CONTI® SYNCHROFORCE CXP

Construction and materials

The CXP series is distinguished by incorporating a strong fiberglass reinforcement into a chloroprene-based belt. The tooth surface is covered with a specially treated polyamide fabric, which reduces friction in the tooth engagement and protects the tooth during operation. The back and teeth are made of chloroprene-based rubber, while the fiberglass reinforcement is located as the load-bearing reinforcement in the belt. This results in a belt that can absorb tensile forces and still maintain synchronous function, while the rubber part can bend around the timing belt pulleys during repeated rotations.

The polyamide fabric on the teeth is an important part of the belt's wear surface. It lies between the tooth rubber and the profile of the timing belt pulley and contributes to lower friction, smoother engagement and better protection of the tooth surface. In a CXP belt, the material layers are not separate functions, but parts of an overall construction where flexibility, tensile strength and tooth stability must work simultaneously.

Profile and tooth engagement

CXP 8M uses a metric tooth pitch of 8 mm. The HTD tooth shape has a semi-circular profile, which provides a large and stable engagement surface between the belt and the timing belt pulley. This shape is known for its high safety against tooth skipping, because the tooth can engage deeply and smoothly into the profile of the timing belt pulley. For this belt, the 688 mm effective length means that the belt has 86 teeth distributed around the endless belt.

The semi-circular tooth shape provides a large engagement surface in the timing belt pulley and is suitable for power transmission with good safety against tooth skipping. The profile is also part of the CXP series, where ContiTech has combined tooth shape, reinforcement and rubber compound for operation under demanding loads. The technical length tolerance for this length class is ±0.30 mm. The tolerance covers the manufacturer's effective length and pulleybase deviation.

Operating characteristics

CONTI® SYNCHROFORCE CXP is designed for high belt speeds and high dynamic loads and can be used at belt speeds of up to 50 m/s. The high load capacity is due, among other things, to the specially developed reinforcement and the strong material bond between rubber, reinforcement and tooth surface. This gives the belt high residual tensile strength and improved resistance to tooth shearing under heavy loads.

The belt transmits motion synchronously, so that the driving and driven shafts maintain a fixed speed ratio. It works without lubrication and is designed for maintenance-free operation. The optimized profile matching between the timing belt and timing belt pulley, together with the polyamide fabric on the tooth side, contributes to quiet operation. In demanding operation, this is an important property, because both tooth engagement and load variation can affect the sound level and stability.

Resistance to operating environment

The CXP version is temperature resistant from -20 °C to +100 °C depending on the application. The belt is ozone resistant, suitable for tropical climates, conditionally/moderately oil resistant and electrically conductive according to ISO 9563. These properties make the belt suitable for industrial environments where temperature, air, oily influences and static electricity can affect operation.

The rubber-based construction also provides some damping in the drive. The timing belt can therefore be used in solutions where a quieter and lighter transmission is desired than chain or sprocket drives. The function of the belt still depends on the mechanical structure around it, but the CXP construction itself is made to maintain strength and flexibility under repeated loads.

Application

The endless construction makes the belt suitable for continuous operation because there is no welding or joining in the belt. This contributes to uniform strength all the way around the belt. Higher power machines, shaft drives, production equipment, conveyor systems and other belt drives where load and speed work together. It can be used in industrial systems where there is a need for synchronous operation, high efficiency and stable power transmission without lubrication. The CXP series is particularly relevant in fast-running drives where a standard timing belt does not provide the same load reserve.

The effective length of 688 mm and the CXP 8M profile make this belt a specific dimension in the series. The belt fits into timing belt pulleys with a corresponding tooth pitch and tooth shape. When timing belt pulleys and belt have the same tooth profile, the load is distributed over the teeth that work in mesh and the movement is transmitted without the slip known from friction-based belt types.

Installation and ongoing operation

In a synchronous belt drive, belt tension, the condition of the timing belt pulleys and the parallelism of the shafts are important for the life of the belt. A CXP belt works best when the tooth surfaces can move cleanly in and out of the profile of the timing belt pulleys. Too low a tension can cause unstable tooth engagement, while unnecessarily high tension can increase the load on bearings, shafts and reinforcement. A correctly constructed transmission utilizes the strength of the belt without overloading its materials.

The belt is endless without joints. This provides a uniform structure all the way around and is an advantage in dynamic operation because the belt does not have a weaker joint pu . The same construction makes the belt suitable for repeated accelerations, uniform rotational speed and operation with continuous tooth engagement.

Question about the belt

What does the fiberglass reinforcement in the belt do?

The fiberglass reinforcement acts as reinforcement and helps the belt maintain its length under load. This is important in synchronous belt drives, where tooth position and the effective length of the belt have a direct impact on operation.

Why is polyamide tissue on teeth important?

The polyamide fabric protects the tooth surface, reduces friction in the engagement and contributes to smoother operation between the belt and the timing belt pulley. This is especially relevant at higher speeds and repetitive loads.

Can CXP run without lubrication?

Yes. SYNCHROFORCE CXP is a timing belt for dry, synchronous power transmission and does not require lubrication. This distinguishes it from chain drives, where lubrication is typically part of the operation.

What does an HTD tooth shape mean?

HTD stands for High Torque Drive. The semi-circular tooth shape provides good protection against tooth skipping and is suitable for power transmission with high torque.

What does tooth division mean?

The tooth pitch is the center-to-center distance between two adjacent teeth measured along the belt's pitch line. An 8M belt has a tooth pitch of 8 mm.

The CXP design is particularly relevant when the belt is to operate at high belt speeds. The CXP series can operate at belt speeds of up to 50 m/s and is therefore one of the reinforced timing belts for dynamic drives. This does not mean that all belt drives can automatically operate at this speed; the actual operation depends on the timing belt pulleys, center distance, load, width, shaft alignment and the machine structure. However, the belt type itself has been developed with materials and tooth structure that are suitable for this type of load.

Backflex and the use of a tension roller can be included in certain CXP designs when the belt drive is dimensioned for it. The flexibility of the belt and rubber-based construction make it suitable for dynamic grooves, but the bend radius, roller size and belt tension always have an impact on the load in the reinforcement and the tooth root.

The dimensions of the profile affect how the belt bends and how the tooth carries the load in the timing belt pulley. For 8M, the tooth pitch is 8 mm, the tooth height is 3.4 mm, and the total belt height is 5.6 mm. These measurements describe the profile itself and are not the same as the belt width, which depends on the individual belt variant.

The rubber matrix of the belt provides cushioning and flexibility, while the fiberglass reinforcement absorbs the tensile load. The timing fabric on the inside is the part of the belt that works directly against the timing belt pulley. In practice, these parts must work together: the rubber must be able to bend around the timing belt pulleys, the reinforcement must limit length change, and the tooth surface must resist wear from repeated engagement.

The CXP belt is designed for timing belt pulleys with a similar tooth profile and tooth pitch. For this belt, this means that the tooth shape and 8M pitch must match the timing belt pulleys in the drive. When the belt and timing belt pulley operate with the same tooth profile, the load is distributed more evenly across the teeth that are engaged.