Shot Blasting Strengthening Machine for Crankshafts and Connecting Rods

Crankshafts and connecting rods are core components of the engine’s crankshaft-connecting rod mechanism, which converts the reciprocating motion of the piston into the rotational motion of the crankshaft, providing power for the operation of the engine. During the operation of the engine, these components are subjected to complex and alternating loads—including tensile stress, compressive stress, and bending stress—for a long time. In addition, they operate in harsh environments such as high temperature and high pressure, which easily lead to fatigue damage (such as cracks and fractures) on the surface and subsurface of the components. Fatigue damage is one of the main causes of engine failure, seriously affecting the reliability and service life of the engine. Shot blasting strengthening is an effective surface strengthening technology that can significantly improve the fatigue strength and service life of metal components. The Shot Blasting Strengthening Machine for Crankshafts and Connecting Rods is a specialized equipment designed for the surface strengthening of these core engine components. It uses high-speed projectile impacts to form a residual compressive stress layer on the surface of the components, inhibiting the initiation and propagation of fatigue cracks. This article will discuss in detail the working principle, structural characteristics, technical advantages, application scope, operational precautions, maintenance methods, and development trends of this specialized shot blasting strengthening machine.

The working principle of the Shot Blasting Strengthening Machine for Crankshafts and Connecting Rods is based on the theory of shot peening strengthening. When high-speed projectiles impact the surface of the crankshaft or connecting rod, the surface material of the component undergoes plastic deformation. Due to the constraint of the subsurface material (which is not deformed or slightly deformed) on the surface deformed material, a residual compressive stress layer is formed on the surface of the component. This residual compressive stress can offset part of the alternating tensile stress generated during the operation of the component, reducing the actual stress acting on the component surface, thereby inhibiting the initiation and propagation of fatigue cracks. At the same time, the plastic deformation caused by the projectile impact refines the surface grain of the component, improving the surface hardness and wear resistance of the material. In addition, the shot blasting process can also remove the oxide layer, oil stains, and other contaminants on the component surface, improving the surface cleanliness. Unlike other surface strengthening technologies (such as heat treatment and electroplating), shot blasting strengthening is a cold working process that does not change the chemical composition and overall mechanical properties of the component, and can be applied to components with complex shapes. The key parameters of the shot blasting strengthening process include projectile type, projectile size, projectile velocity, peening intensity, and coverage rate. For crankshafts and connecting rods, which are made of high-strength alloy steel (such as 42CrMo and 40MnB), the selection of these parameters is crucial to ensuring the strengthening effect. For example, steel shots with a diameter of 0.2-0.8 mm are usually used, and the peening intensity is controlled between 0.2-0.6 mmA (Almen intensity), while the coverage rate is required to reach 100% (i.e., every part of the component surface is impacted by projectiles).

The structural design of the Shot Blasting Strengthening Machine for Crankshafts and Connecting Rods is highly specialized, taking into account the complex shapes and high-precision requirements of crankshafts and connecting rods. The machine mainly consists of a clamping and positioning system, a blast wheel system, a shot circulation system, a dust removal system, a control system, and a protective cover. The clamping and positioning system is the core part of the machine, responsible for fixing and rotating the crankshaft or connecting rod during the shot blasting process. For crankshafts, which have multiple journals and crank throws, the clamping system adopts a two-end positioning method (using hydraulic or pneumatic chucks) to ensure the coaxiality of the crankshaft during rotation. At the same time, a servo motor is used to drive the crankshaft to rotate at a precise speed, ensuring that each journal and crank throw surface is evenly peened. For connecting rods, which have a hollow structure and irregular shape, the clamping system uses a special fixture to fix the connecting rod, and the fixture can be rotated and tilted to ensure that the inner and outer surfaces of the connecting rod (including the small end hole, big end hole, and rod body) are fully covered by projectiles. The blast wheel system is composed of multiple high-precision blast wheels, which are arranged according to the shape of the crankshaft or connecting rod. The blast wheels are made of high-wear-resistant materials (such as high-chromium cast iron) and are driven by a variable-frequency motor, which can adjust the rotational speed (and thus the projectile velocity) steplessly. The shot circulation system includes a shot storage hopper, a screw conveyor, an elevator, and a separator. The used shots are collected from the bottom of the machine, transported to the separator by the elevator, and separated from the debris (such as oxide layer and metal chips) by the separator. The clean shots are then returned to the shot storage hopper for recycling. The separator adopts a multi-stage separation structure (such as cyclone separation and screen separation) to ensure the purity of the recycled shots, which is crucial to maintaining the stability of the peening intensity. The dust removal system uses a combination of cyclone dust collector and bag filter to collect the dust generated during the shot blasting process, ensuring that the exhaust gas meets the environmental protection standards. The control system adopts a PLC + touch screen control mode, which can realize the setting and adjustment of key parameters (such as peening intensity, coverage rate, and rotation speed of the component). At the same time, the control system is equipped with a feedback device (such as an Almen gauge) to monitor the peening intensity in real-time and adjust the parameters automatically to ensure the consistency of the strengthening effect. The protective cover is made of high-strength steel plate and is lined with wear-resistant rubber to prevent the projectile from splashing and protect the operator and the surrounding environment.

The Shot Blasting Strengthening Machine for Crankshafts and Connecting Rods has significant technical advantages in improving the performance of engine components. Firstly, it greatly improves the fatigue strength of the components. Tests have shown that after shot blasting strengthening, the fatigue life of crankshafts can be increased by 2-5 times, and the fatigue life of connecting rods can be increased by 1.5-3 times. This is particularly important for high-performance engines (such as those used in automobiles, ships, and aircraft), which require long-term stable operation under high loads. Secondly, it improves the surface hardness and wear resistance of the components. The plastic deformation caused by the projectile impact refines the surface grain of the component, increasing the surface hardness by 10-20 HRC. This reduces the wear between the crankshaft journal and the bearing, and between the connecting rod and the piston pin, improving the overall reliability of the engine. Thirdly, it has high processing precision and consistency. The use of servo motors and precise control systems ensures that the peening intensity and coverage rate of each component are uniform, avoiding the problem of uneven strengthening effect caused by manual operation. This is crucial for mass production of engine components, ensuring the consistency of product quality. Fourthly, it is suitable for complex-shaped components. The adjustable clamping and positioning system and the multi-angle arranged blast wheels enable the machine to process the complex surfaces of crankshafts and connecting rods (such as the fillets of crankshaft journals and the inner walls of connecting rod holes), which are difficult to process by other strengthening methods. Fifthly, it has high production efficiency. The machine can realize automated feeding, processing, and discharging, with a processing capacity of 30-60 crankshafts or 100-200 connecting rods per hour, meeting the needs of mass production in the automotive and engine manufacturing industries. Finally, it is environmentally friendly and energy-saving. The closed structure and efficient dust removal system minimize dust emissions, and the shot circulation system reduces the consumption of abrasive materials. In addition, the variable-frequency motor used in the blast wheel system can adjust the power according to the processing needs, reducing energy consumption.

The application scope of the Shot Blasting Strengthening Machine for Crankshafts and Connecting Rods covers a wide range of fields, mainly including the automotive industry, shipbuilding industry, aerospace industry, and agricultural machinery industry. In the automotive industry, it is widely used in the production and maintenance of engines for passenger cars, commercial vehicles, and new energy vehicles. For example, in the production of automotive engines, crankshafts and connecting rods must undergo shot blasting strengthening to meet the performance requirements of the engine. In the shipbuilding industry, large marine diesel engines have higher requirements for the fatigue strength of crankshafts and connecting rods due to their high power and long-term operation. The shot blasting strengthening machine can effectively improve the reliability of these components, ensuring the safe operation of the ship. In the aerospace industry, aero-engines operate under extreme conditions (high temperature, high pressure, and high speed), and the fatigue life of crankshafts and connecting rods is crucial to the safety of the aircraft. The shot blasting strengthening machine is an essential equipment for the surface treatment of these components, ensuring the high reliability and long service life of aero-engines. In the agricultural machinery industry, engines used in tractors, harvesters, and other equipment operate in harsh environments (such as dust and vibration), and the surface strengthening of crankshafts and connecting rods can improve the wear resistance and fatigue resistance of the components, reducing the frequency of maintenance and improving the operational efficiency of the equipment.

The operation of the Shot Blasting Strengthening Machine for Crankshafts and Connecting Rods requires strict adherence to operational precautions to ensure the quality of the strengthening effect and the safety of the operator. Firstly, before starting the machine, the operator must inspect the equipment thoroughly—including the wear condition of the blast wheel, the level and purity of the shots, the functionality of the clamping system, and the operation of the dust removal system. At the same time, the operator must check the surface condition of the crankshafts and connecting rods to be processed, ensuring that there are no large defects (such as cracks and severe deformation) that may affect the strengthening effect. Secondly, the operator must select the appropriate shot blasting parameters according to the material, shape, and performance requirements of the components. The peening intensity should be determined through pre-tests (using Almen strips), and the coverage rate should be checked using a coverage rate tester. During the operation, the operator must monitor the parameters in real-time and adjust them promptly if deviations are found. Thirdly, the clamping of the components must be firm and accurate to avoid displacement or rotation instability during the shot blasting process, which may lead to uneven strengthening. For crankshafts, special attention should be paid to the coaxiality of the clamping to ensure that each journal is evenly peened. For connecting rods, the fixture should be adjusted to ensure that the inner and outer surfaces are fully covered by projectiles. Fourthly, the operator must wear personal protective equipment (such as a protective helmet, goggles, and protective clothing) to prevent injury from projectile splashing and dust. At the same time, the operator should not stand in the direction of the blast wheel’s projectile emission to avoid potential hazards. Finally, after the operation, the operator must shut down the machine in sequence, clean the equipment (including the blast chamber, shot circulation system, and dust collector), and inspect the processed components. The processed components should be tested for surface hardness, residual compressive stress, and coverage rate to ensure that they meet the requirements. If any unqualified components are found, they should be reprocessed or scrapped.

Maintenance of the Shot Blasting Strengthening Machine for Crankshafts and Connecting Rods is essential to ensure its long-term stable operation and the consistency of the strengthening effect. The maintenance work can be divided into daily maintenance, regular maintenance, and overhaul. Daily maintenance includes cleaning the surface of the machine and the blast chamber, checking the level of shots and supplementing them in a timely manner, inspecting the tightness of the clamping fixture and adjusting it if necessary, and cleaning the dust collector (emptying the dust bin and cleaning the filter bags). Regular maintenance (conducted weekly, monthly, or quarterly) includes inspecting the wear condition of the blast wheel blades, impellers, and liners. If the wear exceeds the limit, these parts should be replaced in time to ensure the stability of the projectile velocity and peening intensity. It also includes checking the bearing temperature and lubrication of the motor, blast wheel, and conveyor system, and adding lubricating oil or grease as needed. In addition, the control system should be calibrated regularly to ensure the accuracy of parameter setting and feedback. Overhaul (conducted annually or every two years) involves disassembling the key components of the machine (such as the blast wheel, clamping system, and shot circulation system), inspecting their wear and damage, and replacing or repairing them. At the same time, the entire machine should be debugged to ensure that all systems operate in coordination. During the maintenance process, it is important to keep records of the maintenance content, replacement parts, and equipment operation status, which helps to track the equipment’s service life and predict potential faults.

With the continuous development of the engine manufacturing industry and the increasing demand for high-performance, high-reliability engines, the Shot Blasting Strengthening Machine for Crankshafts and Connecting Rods is facing new development opportunities and challenges. In the future, the machine will develop in the direction of intelligence, precision, and integration. On the intelligence front, manufacturers will integrate advanced technologies such as artificial intelligence, big data, and the Internet of Things into the equipment. For example, through the collection and analysis of processing data (such as peening intensity, coverage rate, and component surface quality), the machine can automatically optimize the processing parameters, realizing adaptive and intelligent processing. At the same time, remote monitoring and fault diagnosis functions will be added, enabling operators to monitor the equipment operation status in real-time and quickly diagnose and resolve faults, improving the efficiency of equipment maintenance. On the precision front, the manufacturing precision of the blast wheel and clamping system will be further improved, and more advanced measurement and control technologies (such as laser measurement and ultrasonic testing) will be adopted to monitor the peening intensity and component surface quality in real-time, ensuring that the processing precision meets the requirements of high-end engine components. On the integration front, the shot blasting strengthening machine will be integrated with other processes (such as cleaning, drying, and inspection) to form an automated production line. For example, after the shot blasting strengthening, the components are automatically transported to the cleaning station to remove residual shots, then to the drying station to dry the surface, and finally to the inspection station to test the surface quality. This integration reduces the intermediate links, improves the production efficiency, and ensures the consistency of product quality. In addition, with the increasing emphasis on environmental protection, more environmentally friendly abrasive materials and dust removal technologies will be adopted, making the shot blasting process more environmentally friendly and sustainable. In conclusion, the Shot Blasting Strengthening Machine for Crankshafts and Connecting Rods will play an increasingly important role in the engine manufacturing industry, contributing to the development of high-performance, high-reliability engines.