What is the structure of the excavator boom?

Release Time :

2025-01-22

The structure and manufacturing points of the boom

The integral bending boom is the main form of the factory-modified excavator boom. The downward bending form is mainly to achieve a greater excavation depth. The boom consists of two straight arms and three curved arms in the middle. The entire boom is welded. In terms of structure, the integral bending boom is a symmetrical closed hollow box-shaped welded structure. Usually, the upper and lower hinges are cast steel parts, and the three middle sections are high-strength high-quality steel plates.

The inside of the boom, especially the hinge with the boom cylinder, is generally welded with reinforcing ribs to further strengthen the local strength and ensure that the overall boom has high bending and torsional strength.

Due to the bending processing technology, the bending arm inevitably has welding deformation and stress concentration at the bending part of the bending arm, so the processing technology and strength are very important. Ultrasonic testing is usually used in the production process, and only booms without any microcracks are qualified products.

In order to meet the needs of heavy-duty operations, many excavator manufacturers will optimize the design of the boom structure. For example, Sumitomo brand excavators use a two-stage boom structure with forged parts at the upper and lower hinge ends. According to the comparison of market users, the boom of Caterpillar excavator will be relatively strong and durable. It is worth noting that long-term installation of breaker hammers and heavy-load excavation operations will cause great damage to the boom of the excavator.

Boom cylinder layout

The boom cylinder connects the vehicle body and the boom, and is the power element for the entire working device and material lifting. Most small and medium-sized excavators, mainly backhoes, adopt a lower boom cylinder design, that is, the boom cylinder is located at the front and bottom of the boom.

The lower hinge point of the boom cylinder is located on the front flange of the turntable and is lower than the lower hinge point of the boom in the vertical direction. The upper hinge point of the boom cylinder of the medium-sized excavator is located on both sides of the middle of the boom, and the upper hinge point of the boom cylinder of the small excavator is located on the lower plate in the middle of the boom. The reasonable layout of the boom cylinder is of great significance to ensure the normal performance of the excavator's excavation force and the smooth progress of the excavation process.

In order to meet the needs of heavy-load operations, many excavator manufacturers will optimize the boom structure. For example, Sumitomo brand excavators use a two-stage boom structure with forged upper and lower hinge ends. According to the comparison of market users, the boom of Caterpillar excavator will be relatively strong and durable. It is worth noting that long-term installation of breaker hammers and heavy-load excavation operations will cause great damage to the boom of the excavator.

Boom angle

The boom bending angle of small excavators on the market is relatively small, and it looks much larger than the boom bending angle of medium-sized excavators. This is because small excavators use a single boom hydraulic cylinder, and the position of the cylinder hinge point is similar to that of medium-sized excavators, but the layout of the boom cylinder is different, which reduces the boom bending angle to increase the digging depth of the boom.

According to the data of relevant literature, the arm inclination angle range is generally 110°~140°. Within this numerical range, a smaller bending angle is conducive to increasing the digging depth, but it will reduce the maximum digging height and is not conducive to structural strength, because the bending part will cause stress concentration due to reasons such as structure and welding process. The smaller the value, the more serious the stress concentration, and the greater the possibility of cracking in the bending part of the boom during the use of the machine.

In summary, the advantages of the integral curved excavator boom are simple structure, light weight, high rigidity, which can make the excavator have a greater digging depth and is currently the most widely used structure. The disadvantages are that there are few replaceable working devices and poor versatility, and it is mostly used on excavators with similar long-term working conditions.


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