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Plastic mesh belt conveyor systems can use round shafts or square shafts; square shafts have the following advantages over round shafts: 1. They enable torque to be transmitted to the sprocket without the need for keys and keyways. 2. Allow the sprocket to move laterally in order to account for the inherent differences in thermal expansion and contraction between plastic and metal. Choosing the right size for the shaft is particularly important for the service life of the plastic conveyor belt; excessive bending of the drive shaft can cause misalignment between the plastic conveyor belt and the sprocket teeth, accelerating wear. This can also lead to uneven stress on the plastic conveyor belt, resulting in damage or movement of its pins. 3. When selecting the shaft size, it is necessary to take into account the torque exerted on the drive bearings. The tension in the plastic conveyor belt transfers torque to the drive shaft via the sprocket. Under the influence of product load and friction, the tension in the plastic conveyor belt remains constant, but the torque on the drive shaft varies depending on the size of the sprocket chosen. As the pitch diameter of the sprocket increases, so does the torque on the shaft. Proper alignment of the shaft helps ensure proper operation of the plastic conveyor belt and extends its service life ； In applications with heavy loads and where smooth conveying is required, the support rails can be extended between the sprockets; the ends of these rails should be bent downward, making sure that they do not come into contact with the sprockets or the shafts. Removing and installing the timing chain and sprockets is an important step in engine repair. Whether the installation is correct has a direct impact on the overall quality of engine repair. Even the slightest carelessness at work can result in difficulty starting the engine, or even prevent it from starting at all. Based on practical maintenance experience, the following key points should be kept in mind when removing and installing the timing chain and sprockets: (1) Remove the negative battery ground wire. (2) Remove the engine cover and any components that interfere with the work. (3) Rotate the crankshaft so that the piston of cylinder 1 is at the top dead center of compression, aligning the timing marks on the camshaft and crankshaft sprocket. There are two timing marks on the camshaft sprocket: one is the timing mark when the piston of cylinder 1 is at top dead center, at which point both the intake and exhaust valves of cylinder 1 are closed ； Second is the timing mark when the piston of cylinder 4 is at top dead center; at this point, both the intake and exhaust valves of cylinder 4 are closed. It is essential to determine which cylinder’s piston is at the top dead center of compression. (4) Remove the bolts from the camshaft sprocket, and take off the timing chain and the camshaft sprocket. (5) If it is necessary to replace the crankshaft sprocket, use a puller to remove the sprocket. When installing a new sprocket, align the chain with the sprocket teeth to prevent loosening. (6) Install the timing chain on the camshaft sprocket, secure the sprocket so that the chain hangs down, and align it with the timing marks on the camshaft and crankshaft sprockets. Align the positioning pin hole on the sprocket with the positioning pin hole on the camshaft, then install the sprocket on the camshaft. The tightening torque for the camshaft sprocket bolt is 20 N·m. (7) Lubricate the timing sprocket and chain with engine oil. (8) Turn the crankshaft two full turns to check whether the engine timing marks are aligned. If the timing marks are not aligned, repeat the process following the steps outlined above. If there are no timing marks on the camshaft gear, the following points should be taken into consideration during installation: ① Install the crankshaft sprocket. ②Install the timing chain vibration damping plate on the cylinder block. ③Align the timing mark on the crankshaft sprocket with the timing mark at the bottom of the timing damper. ④Lower the timing chain, secure the camshaft sprocket, and install the timing chain on the crankshaft gear. ⑤Align the centerline of the positioning hole on the camshaft sprocket with the timing mark on the top of the timing chain shock absorber plate. ⑥Align the positioning pin on the camshaft with the positioning hole on the camshaft sprocket. Install the sprocket on the camshaft; the bolt tightening torque is 100 N·m. ⑦Lubricate the timing chain and sprockets with engine oil. ⑧Rotate the crankshaft two full turns and check whether the engine timing marks are aligned.