The factory modified excavator boom is a very important component, and the key to the excavator's participation in the construction depends on the functionality of the excavator arm. There is a saying in the machinery industry: structure determines function. So, what kind of structure does the same factory modified excavator boom have, and what kind of function does the excavator have?

The structure and manufacturing points of the boom

The integral curved boom is the main form of the factory modified excavator boom, and the downward bending form is mainly used to achieve a larger excavator depth. The boom is composed of two straight upper and lower sections and three curved sections in the middle. The whole boom is welded. In terms of structure, the integral bending boom is a symmetrical closed hollow box-shaped welded structure, usually the hinged joints of the upper and lower ends are steel castings, and the middle three sections are high-strength high-quality steel plates.

Inside the boom, especially the hinge joint with the boom cylinder is generally welded with ribs to further strengthen the local strength and ensure that the boom has a higher bending and torsion strength as a whole.

Due to the bending and processing technology, there is unavoidable welding deformation and stress concentration at the bending part of the bending boom, so the processing technology and strength are very important. In the production process, ultrasonic testing is usually used, and the boom without any micro cracks is considered a qualified product.

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

Arrangement of boom cylinder

The boom cylinder is connected to the body and the boom, and is the power element for lifting the entire working device and materials. Most of the small and medium-sized excavators, which are mainly backhoes, adopt the lower-mounted 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 placed 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 excavator is placed on both sides of the middle of the boom, while the upper hinge point of the boom cylinder of the small excavator is placed on the lower plate of the middle of the boom. The reasonable arrangement of the boom cylinder is of great significance to ensure the normal exertion of the excavator's digging force and the smooth progress of the digging process.

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

Boom angle

The bending angle of the boom of small excavators on the market is relatively small, which seems to be much more curved than that of medium 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 excavators. The layout of the boom cylinder of the machine is different, and the bending angle of the boom is reduced in order to increase the digging depth of the boom.

According to the data of related literature, the range of the boom angle is generally 110°~140°. Within the range of these values, a smaller bend angle is beneficial to increase the excavation depth, but will reduce the maximum excavation height, and is detrimental to the strength of the structure, because the bending part will cause stress concentration due to the structure and welding process. The smaller the value, the more serious the stress concentration, and the greater the possibility of cracking at the bending part of the boom during machine use.

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