Crankshaft production and manufacturing process

The crankshaft is the main rotating component of the engine. After installing the connecting rod, it is subjected to upward and downward (reciprocating) motion of the connecting rod and becomes circular motion. An important component of an engine, which is made of carbon structural steel or ductile iron, has two important parts: the main shaft journal and the connecting rod journal. The main journal is installed on the cylinder block, the piston rod neck is connected to the cylinder head hole, and the cylinder head hole is connected to the cylinder piston. It is a typical crank slider mechanism. So, let's learn about the crankshaft production and manufacturing process together!

Crankshaft lubrication mainly refers to the lubrication of connecting rod large metal and crankshaft connecting rod journal, as well as the lubrication of fixed points at both ends. The rotation of the crankshaft is the power source of the engine and also the power source of the entire mechanical system.

Working principle of crankshaft

The crankshaft is one of the typical and important components in an engine. Its function is to convert the gas pressure transmitted by the piston rod into torque, which serves as a power output to drive other power mechanisms and auxiliary equipment for the internal combustion engine.

Crankshaft machining process

There are many types of crankshafts with different structural details, but the processing technology is roughly the same.

Introduction to main processes

1) Milling of crankshaft and connecting rod journals

When machining crankshaft parts, due to the influence of the structure of the disc cutter itself, the cutter and the workpiece are always in intermittent contact, resulting in impact. Therefore, the entire machine tool cutting system controls the gap link, reduces vibration caused by motion gaps during the machining process, and improves machining accuracy and tool life.

Grinding of crankshaft and connecting rod journals

The tracking grinding method takes the center line of the main shaft journal as the rotation center, and uses a chuck to successively complete the grinding process of the crankshaft shaft journal (which can also be used for main shaft journal grinding). The method of grinding the shaft journal is achieved by controlling the feed of the grinding wheel and the rotational motion of the workpiece through a dual axis linkage. The feed tracking grinding method uses a one-time clamping process, and a CNC grinding machine to sequentially complete the grinding process of the crankshaft main shaft journal and the connecting rod journal, It can effectively reduce equipment costs, reduce processing costs, and improve processing accuracy and production efficiency.

Crankshaft main journal and connecting rod journal fillet rolling machine

The application of rolling machine tools is to improve the fatigue strength of the crankshaft. Statistical data show that the life of nodular cast iron crankshaft can be increased by 120%~230% after fillet rolling; The service life of forged steel crankshaft can be increased by 70%~130% after being rounded and rolled. The rotational power of the drum comes from the rotation of the crankshaft, causing the drum of the drum head to rotate, and the pressure of the drum is applied by the cylinder.

As the main load-bearing component of an engine, crankshaft fatigue failure is common in metal fatigue failure (i.e., bending fatigue failure and torsional fatigue failure), with the former having a greater probability of occurrence than the latter. Bending fatigue cracks first occur on the connecting rod journal (crank pin) or the journal fillet of the main shaft, and then develop towards the crank arm. Twisted cracks occur in poorly machined oil holes and fillets and develop parallel to the axis. Metal fatigue failure is the result of the action of variable stress that periodically changes with time. Statistical analysis of crankshaft fractures shows that about 80% of them are caused by bending fatigue. Main causes of crankshaft fracture

1) Deterioration due to long-term use of engine oil; Serious overloading and overloading lead to long-term overload operation of the engine, resulting in a tile burning accident. The crankshaft is badly worn due to the burning of the engine tiles.

2) After repairing the engine, the vehicle has not passed the wear period. In other words, overload suspension, long-term overload operation of the engine, and crankshaft load exceeding the allowable limit.

3) The crankshaft is repaired by overlaying welding, which destroys the power balance of the crankshaft and does not undergo balance verification, resulting in excessive imbalance, causing greater engine vibration, and causing crankshaft fracture.

4) Due to poor road conditions and severe overloading and overtaking of vehicles, the engine is often within the limit rotational speed of torsional vibration, and the shock absorber fails, resulting in torsional vibration fatigue damage and fracture of the crankshaft.

Precautions for crankshaft maintenance

1) During crankshaft maintenance, carefully inspect the crankshaft for cracks, bends, twists, and other defects, as well as the wear of the main bearing shells and connecting rod bearing shells. Check the wear of the main bearing shells and main bearing shells, connecting rod journals, and connecting rod bearing shells

2) Crankshaft cracks often occur in the transition fillet between the crankshaft arm and the journal, as well as in the oil hole in the journal.

3) When repairing and assembling the crankshaft, ensure that the flywheel operates in a balanced manner.

4) The crankshaft should be inspected after major accidents such as tile burning and cylinder striking occur in internal combustion engines.