In previous articles, we introduced the three major processes used by the axle factory to ensure the strength and toughness of the trailer axle, which played a key role in the performance of the axle in subsequent use. However, if the quality of an axle is not up to standard, it depends not only on strength and toughness, but also on production accuracy.

Although the appearance of the trailer axle looks relatively simple and bulky, which seems not to match the word "precision", in fact, it is a veritable precision machinery, with nearly 100 components on a trailer axle. Because of this, it is very important to control the machining accuracy of the trailer axle.

Next, we will take Darong axle as an example to see which processes are used to ensure the accuracy of finished products in the production process.

1. Axle alignment

The straightening process is generally set after heat conditioning and sand blasting, which is used to correct all kinds of bending caused by the axle in the production and processing process.

Although the strength and toughness of the axle have been stimulated to a certain extent through the previous processes such as hot rotary rolling, thermal quenching and tempering, sand blasting, etc., it is still impossible to completely avoid the subtle bending phenomenon of the axle that cannot be recognized by the naked eye in the processing process, especially in the process of thermal quenching and tempering.

If it is not restored to deformation through the straightening process, it will directly affect the stress distribution of the axle beam or axle end parts in use. In light cases, it will produce body vibration and driving instability, in heavy cases, it will lead to axle cracks or direct axle breakage, affecting driving safety.

Darong axle adopts an automatic multi-point straightening machine with an accuracy of 0.4-0.5mm, which can automatically correct various bending phenomena of the axle in the process of processing or heat treatment, and provide a basis for the processing accuracy of the finished product.

2. NC machine tool processing

The NC machine tool processing is set after the primer process and before the medium frequency strengthening treatment, mainly for boring, turning and milling, drilling, precision grinding, etc. of the shaft body.

CNC machine tool processing is mainly aimed at the shaft head, providing the installation foundation for the hub, bearing, brake drum and other parts installed on the subsequent shaft head, which is the same as the foundation of high-rise buildings. The higher the processing accuracy, the better the foundation for the subsequent assembly accuracy, avoid unnecessary friction loss of wheel end parts, improve the operation reliability of wheel end system, and the longer the maintenance cycle.

Compared with ordinary machine tools, NC machine tools can write processing parameters into the NC device in the form of programs, such as the track size of the relative movement between the spindle head and the tool, the grinding process parameters and various auxiliary operation information, and then the NC device will send signals and instructions corresponding to the program for automatic processing after analysis and processing.

In this way, not only the processing efficiency is higher, but also the processing stability is stronger, because the operation of the NC machine tool is out of the continuous calculation, output and feedback control, which can ensure the accuracy of the relative position between the tool and the shaft head, avoid artificial errors, and the processing quality is more stable.

3. Automatic welding

In the production process of axle, the welding work is much less than that of trailer production, which is mainly used in the welding of brake base plate, spherical bearing, air chamber seat and other parts. After welding, semi-finished axle welding products can be obtained, which is also one of the main products of Darong axle.

The welding process of Darong axle adopts robot automatic welding, and uses the laser positioning system to track and identify the position of the weld, so as to ensure the consistency, aesthetics and firmness of the weld, and the welding quality is more stable.

4. Finished product assembly

Assembly requires the installation of wheel hubs, brake drums / discs, inner and outer bearings and other components on the basis of welding semi-finished products to obtain the finished axle. After that, the production process ends and the finished product quality inspection process begins.

The assembly accuracy mainly includes the dimensional accuracy, relative motion accuracy, mutual position accuracy, contact accuracy, etc. among them, the dimensional accuracy also includes the fitting accuracy and distance accuracy. The accuracy control of the assembly process is mainly divided into two points: the accuracy of the parts themselves and the accuracy of the assembly technology.

In order to better ensure the accuracy of parts, Darong axle chooses outsourced parts, such as bearings, hubs, brake drums, etc., all of which choose domestic strength brands, ranking first in their respective fields. On the one hand, these brands have been deeply cultivated in the accessories industry for many years, and their quality has been baptized and tested by the market, so they have the corresponding quality assurance ability; On the other hand, after the arrival of accessories, Darong will also carry out a series of tests on their strength and accuracy, which can be put into use only after they are qualified, adding another layer of guarantee to the quality.

In terms of assembly technical accuracy, Darong axle has chosen automatic assembly lines, coupled with high-precision guidance, positioning, feeding, adjustment, detection and other instruments, to ensure the high accuracy and consistency of the assembly process and fully reduce or reduce the unqualified rate in the highly repetitive assembly tasks.

In fact, in addition to the hot rotary rolling, hot quenching and tempering, medium frequency strengthening and axle alignment in this period, CNC machine tool processing, automatic welding, and finished product assembly mentioned earlier, the production process of Darong axle also includes raw material cutting, preliminary treatment of axle head, cold pushing, shot blasting, primer spraying, finish painting, axle head accuracy inspection and other processes, which complement and cooperate with each other, Jointly cast the quality cornerstone of the finished axle.