One of the Parts for Volvo Engines: Crankshafts

There are many parts for Volvo engines, and the crankshaft is one of them. The crankshaft is one of the important parts in the internal combustion engine, the spine of the engine, and the key part to withstand shock loads and transmit power. The working environment and force conditions of the crankshaft are very complex, and it is subject to the combined effects of periodic changes in gas pressure, centrifugal force, and inertial force during operation, so it is easy to malfunction.

Although there are many varieties of crankshafts, and some details of the structure are different, the processing process is roughly the same. The following will introduce you to the main processes in the crankshaft machining process.

(1) Crankshaft main journal and connecting rod journal external milling machining

When machining crankshaft parts, due to the influence of the structure of the disc milling cutter itself, the cutting edge is always in intermittent contact with the workpiece and has impact. Therefore, the gap link is controlled in the whole cutting system of the machine tool, which reduces the vibration caused by the movement gap in the machining process, thereby improving the machining accuracy and the service life of the tool.

(2) Grinding of crankshaft main journal and connecting rod journal

The tracking grinding method is to take the center line of the main journal as the rotation center, and complete the grinding of the crankshaft connecting rod journal in turn (can also be used for the grinding of the main journal grinding) in a clamping, and the realization method of grinding the connecting rod journal is to complete the crankshaft processing feed by CNC control of the feed of the grinding wheel and the linkage of the two axes of the workpiece rotary movement. The tracking grinding method completes the grinding of the crankshaft main journal and the connecting rod journal on a CNC grinding machine in turn, which can effectively reduce equipment costs, reduce processing costs, and improve machining accuracy and production efficiency.

(3) Crankshaft main journal and connecting rod journal radius rolling machine

Rolling machines are used to improve the fatigue strength of crankshafts. According to statistics, the life of the ductile iron crankshaft can be increased by 120%~230% after rounded rolling; The life of forged steel crankshaft can be increased by 70%~130% after being rolled with fillet fillet. The rotational power of rolling comes from the rotation of the crankshaft, which drives the roller in the rolling head to rotate, and the pressure of the roller is implemented by the cylinder.

The most common fatigue failure of the crankshaft, the main stressed part of the engine, is metal fatigue failure, that is, bending fatigue failure and torsional fatigue failure, and the probability of occurrence of the former is greater than that of the latter. Flexural fatigue cracks first develop at the connecting rod journal or main journal fillet and then develop towards the crank arm. Torsional fatigue cracks arise in poorly machined oil holes or fillets, and then develop in a direction with the axis. Metal fatigue failure is the result of variable stress due to periodic changes over time. Statistical analysis of crankshaft failure shows that about 80% is caused by bending fatigue.

Precautions for crankshaft maintenance:

When it comes to crankshaft repairs, every step of the way needs to be meticulous to ensure that it is restored to optimal working condition. The following is a list of critical repair considerations designed to help technicians perform their crankshaft repair tasks better.

1. Comprehensively check the condition of the crankshaft

In the initial phase of the crankshaft repair, the technician needs to carry out a comprehensive inspection of the crankshaft. This includes, but is not limited to, inspecting the surface of the crankshaft for potential defects such as cracks, bending, or twisting. If these defects are not detected and dealt with in time, they will have a serious impact on the performance and life of the crankshaft. At the same time, the wear of the main and connecting rod bearings needs to be carefully assessed to ensure that the wear of these critical components is within acceptable limits.     In addition, it should be ensured that the mating clearance between the main journal and the main bearing, and between the connecting rod journal and the connecting rod bearing, is within the allowable range specified by the manufacturer to maintain the normal operation and performance of the engine.

2. Pay attention to the high-incidence areas of crankshaft cracks

Crankshaft cracks are a special concern during the repair process. As a rule of thumb, crankshaft cracks occur at the transition fillet between the crank arm and the journal, as well as at the oil holes in the journal. These areas are more prone to cracks due to their complex structure and stress concentrations. During the inspection, the technician should pay special attention to these areas and use professional tools for detailed inspection to ensure that cracks are found and treated in a timely manner.

3. Make sure the flywheel runs balanced

When repairing a compound crankshaft, it is important to ensure that the flywheel is balanced. As an important part of the engine, the balance state of the flywheel directly affects the running stability and performance of the engine. Therefore, before installing the crankshaft, the flywheel should be subjected to a strict balance test and adjusted according to the test results to ensure that the flywheel remains balanced during operation.

4. Comprehensive overhaul after major accidents

When a major accident occurs, the crankshaft tends to suffer serious damage. In this case, a complete overhaul of the crankshaft is particularly important. At the same time, the crankshaft needs to be cleaned, inspected and repaired as necessary to ensure that it can be restored to optimal working condition.

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