The existing machine tools for laser cladding remanufacturing and surface strengthening of shaft parts have problems such as inconvenient clamping and centering, and complicated operation. In this regard, a machine tool for laser cladding remanufacturing and surface strengthening of shaft parts is designed. The design scheme of this machine tool is introduced, the structure of this machine tool is given, the functional characteristics and manufacturing requirements are analyzed, and the application effect is introduced. This machine tool has the advantages of reasonable design, simple structure, convenient clamping and centering of shaft parts, and has significant application effect in laser cladding remanufacturing and surface strengthening of shaft parts.

1 Design background

As typical parts commonly used in mechanical equipment, shaft parts are mainly used to support transmission parts, transmit torque, bear loads, etc. In actual use, shaft parts often fail due to wear, corrosion, deformation, fatigue, fracture, etc., resulting in the inability of mechanical equipment to use normally. Replacing shaft parts not only consumes time, but also reduces production efficiency and increases production costs. If the replaced failed shaft parts are directly scrapped, it will not only waste raw materials, but also increase the environmental burden, which is not conducive to environmental protection. With the transformation and upgrading of the manufacturing industry, remanufacturing technology has gradually attracted the attention and attention of various countries with its advantages of energy saving, material saving and high efficiency. In recent years, the country has vigorously promoted energy conservation and emission reduction and developed a circular economy. By remanufacturing failed parts, not only can the performance of the parts be restored and the service life be extended, but also energy and materials can be saved, making the cost lower. As a result, more and more research and applications on the remanufacturing of failed parts are being carried out. At present, the remanufacturing of shaft parts mainly adopts surfacing, spraying, plasma arc welding, etc. Although these methods have achieved good application effects, there are still some shortcomings. For example, the heat in the surfacing process is high, the parts are easy to deform, the coating bonding force after spraying is insufficient, and the performance improvement of the parts after remanufacturing is limited. As an advanced surface treatment technology, laser cladding has been increasingly used in industrial production with its advantages of less heat input, large bonding force and simple operation. It can be used for the remanufacturing of scrapped and failed parts, and can also be used for the surface strengthening of new parts. The processing of shaft parts has high requirements for horizontal centering and matching accuracy. The roundness, cylindricity, straightness and other irregularities of failed shaft parts are used. The general laser cladding machine tool has low processing efficiency. In order to realize the remanufacturing and surface strengthening of shaft parts more conveniently and quickly, the author designed a machine tool for laser cladding remanufacturing and surface strengthening of shaft parts.

2 Design scheme

The machine tool for laser cladding remanufacturing and surface strengthening of shaft parts is mainly composed of a workbench, a shaft part drive mechanism, an actuator, a laser, a control system, a cooling system, a powder feeding system, etc. The working principle is shown in Figure 1.

The shaft part drive mechanism mainly includes a frame, a power head, a hydraulic tailstock, etc. The power head is a drive system for the rotation of shaft parts. The spindle is supported by front and rear bearings to ensure good rigidity and meet the requirements for precision in the process of laser cladding remanufacturing and surface strengthening of shaft parts. The chuck and the front connecting plate of the spindle are connected together, and the shaft parts are clamped by the chuck and rotated under the drive of the drive system. The drive system adopts AC servo stepless speed regulation, constant torque output, stable speed, fast start and stop at low speed, and a wide speed adjustment range, which can meet the needs of laser cladding speed of various shaft parts.

The actuator mainly includes machine tool actuator and laser actuator. The machine tool actuator includes the machine tool control cabinet, moving guide rails, clamping chuck, and tightening components. The laser actuator consists of columns, longitudinal beams, and laser longitudinal, transverse, and vertical adjustment mechanisms.

There are many types of lasers, commonly used ones are carbon dioxide lasers, aluminum garnet crystal lasers, semiconductor lasers, fiber lasers, etc. The quality of the laser beam directly affects the effect of the machine tool on laser cladding remanufacturing and surface strengthening of shaft parts. According to the performance characteristics of different types of lasers and the requirements of laser cladding of shaft parts for spot size, laser power density, laser cladding quality, and efficiency, high-power semiconductor lasers are selected.

The control system has an important impact on the operability of the machine tool. The control system adopts the mainstream CNC system, embedded with an open programmable controller and macro instructions, and secondary development is carried out in the CNC system. The operator only needs to input the specifications of the shaft parts, including the diameter and cladding length of the shaft, in the human-machine interface of the CNC system, and set the laser cladding process parameters according to the technical requirements of the workpiece, such as laser cladding speed, pitch, etc., and start with one button. The machine tool will automatically feed powder, turn on the protective gas, and emit light according to the process parameters, and realize the laser cladding of shaft parts according to the set parameters.

The cooling system is an important part of the machine tool, mainly used for cooling the laser and laser control unit. The laser will generate a lot of heat during operation, and the heat generated needs to be exported through heat exchange to ensure the stable operation of the laser. The cooling system uses a domestic high-end double-circulation water cooler to ensure that the machine tool can operate stably for a long period of time during the laser cladding remanufacturing and surface strengthening of shaft parts.

An accurate and stable powder feeding system is the key to ensuring the laser cladding remanufacturing and surface strengthening effect of shaft parts. The powder feeding system mainly includes a powder feeder, a powder feeding nozzle, and a horizontal, vertical, and up and down moving mechanism for adjusting the distance between the powder feeding nozzle and the shaft parts.

3 Structure

Before designing the structure of the machine tool for laser cladding remanufacturing and surface strengthening of shaft parts, a comprehensive survey of the laser cladding machine tools on the market was conducted. In view of the shortcomings of existing laser cladding machine tools in the process of laser cladding of shaft parts, such as inconvenient clamping and centering, complex equipment operation, low powder utilization, limited applicable size, and low processing efficiency, the structure design was carried out in combination with the requirements for machine tools in the production process of laser cladding remanufacturing and surface strengthening of shaft parts. The structure of the machine tool for laser cladding remanufacturing and surface strengthening of shaft parts is shown in Figure 2.

4 Functional features

(1) Easy to operate. The machine tool is mainly used for laser cladding remanufacturing and surface strengthening of shaft parts, solving the problems of inconvenient clamping and complex operation of general laser cladding machine tools during laser cladding of shaft parts. When in use, you only need to clamp the shaft parts on the machine tool, pre-load the required laser cladding powder in the powder feeder, and operate the machine tool control panel to easily and quickly adjust the laser cladding parameters and fully control the machine tool cooling system, powder feeding system, actuator, laser, etc., with a high degree of automation and easy operation.

(2) Easy to clamp. When designing the machine tool, the structure, manufacturing difficulty, and ease of operation are comprehensively considered to make the designed machine tool simpler and more reasonable. In order to facilitate the clamping of shaft parts, a clamping assembly is designed. The clamping assembly includes a clamping control box, a motor, a support seat, a clamping shaft, a center, etc. The horizontal distance between the clamping assembly and the rotating chuck is adjusted by the meshing movement of the gear and the rack. The motor and the clamping shaft are controlled by the clamping control panel, so that the center can clamp the shaft parts, and the clamping of the shaft parts can be completed conveniently and quickly.

(3) Large processing range and high efficiency. The machine tool adopts a horizontal four-axis structure, uses a large-size rotary chuck, increases the height of the longitudinal beam, and extends the length of the workbench. The maximum diameter of the machined shaft parts is 800mm and the maximum length is 3500mm, which can basically meet the needs of laser cladding remanufacturing and surface strengthening of shaft parts of common mechanical equipment. A high-power semiconductor laser is selected, and the spot is set to a large-size rectangular spot to obtain a large laser cladding path width, thereby improving the laser cladding processing efficiency of the machine tool for shaft parts. After the shaft parts of various sizes are clamped on the machine tool, the horizontal, vertical, and up and down moving mechanisms can be controlled through the machine tool control panel to quickly adjust the distance between the powder feeding nozzle and the shaft parts, which is not only conducive to improving the laser cladding quality of the machine tool, but also greatly improves the working efficiency of the machine tool.

(4) High powder utilization rate and cost saving. On the one hand, the machine tool adopts a high-precision powder feeder to achieve precise control of the powder delivery during laser cladding of shaft parts, thereby avoiding powder waste as much as possible from the source. On the other hand, a powder recovery tray that is easy to disassemble and fix is ​​designed on the moving guide rail of the machine tool workbench. In the process of laser cladding remanufacturing and surface strengthening of shaft parts by machine tools, some incompletely reacted powders are inevitably present. These powders can be recovered through the powder recovery plate, thereby improving the powder utilization rate and saving production costs.

(5) Broad application prospects. Machine tools can be applied in many industries. They can be used for laser cladding remanufacturing and surface strengthening of shaft parts commonly used in machinery, metallurgy, coal mining, electricity, petroleum, automobile and other industries, including crusher main shafts and tunneling machine shafts in the machinery industry, rolling mill transmission shafts and rollers in the metallurgical industry, hydraulic support columns and conveyor gear shafts in the coal mining industry, motor main shafts and turbine shafts in the metallurgical industry, sucker rods and drill strings in the petroleum industry, crankshafts and automobile wheel axles in the automobile industry, etc. In the context of the country’s vigorous promotion of energy conservation and emission reduction, the development of circular economy, and the transformation and upgrading of the manufacturing industry, laser cladding remanufacturing and surface strengthening machine tools for shaft parts have broad application prospects.

5 Manufacturing requirements

Four aspects need to be paid attention to when manufacturing machine tools for laser cladding remanufacturing and surface strengthening of shaft parts.

(1) Since the frame of the machine tool is a welded structure of steel and steel plates, in order to ensure the stability of the machine tool during operation, the frame must be stress-relieved after welding.

(2) The laser is the core component of the machine tool. In order to ensure the safety of the laser, for the three-dimensional adjustment mechanism of the laser, in addition to setting electrical limit switches at the extreme positions of the stroke, mechanical limits must also be designed.

(3) In order to ensure the accuracy and precision of the machine tool’s laser cladding action on shaft parts, the slide used for laser adjustment is installed on a precision linear guide rail set on the longitudinal beam. The slide is driven by a transmission chain consisting of a servo motor, a precision planetary reducer, and a gear rack pair. During the operation of the machine tool, the slide drives the laser to move longitudinally, and the moving speed can be adjusted steplessly by AC servo to meet the needs of spiral cladding.

(4) Various control cables and pipelines of the machine tool are arranged in a dedicated cable drag chain, which can not only protect the cables and pipelines and extend their service life, but also make the overall layout of the machine tool neat and beautiful.

6 Application effect

Connect the power supply of the machine tool for laser cladding remanufacturing and surface strengthening of shaft parts, clamp the shaft parts to be processed on the machine tool according to the clamping requirements, set the laser cladding related parameters on the machine tool control panel, and execute the laser cladding command to realize the laser cladding of shaft parts.

The laser cladding work site of shaft parts is shown in Figure 3.

The machine tool has a stable structure and reliable operation during the laser cladding process of shaft parts. The machine tool can be used for both remanufacturing and surface strengthening of shaft parts. The application effect can be analyzed from two aspects.

In order to test the application effect of machine tools on laser cladding remanufacturing of shaft parts, the hydraulic support column of shaft parts was selected and remanufactured by laser cladding by machine tools. The comparison of the hydraulic support column before and after laser cladding remanufacturing is shown in Figure 4.

As shown in Figure 4, after the failed and scrapped hydraulic support column was remanufactured by laser cladding, the worn and corroded surface was covered with a uniform laser cladding layer. Laser cladding powder with good wear resistance and corrosion resistance was selected during laser cladding, which can form a laser cladding layer with good performance on the surface of shaft parts, restore the surface performance of shaft parts, and realize the remanufacturing of hydraulic support columns.

In order to test the application effect of machine tools on laser cladding surface strengthening of shaft parts, the hydraulic support cylinder of shaft parts was selected for surface strengthening. The complex environment under the mine has a corrosive effect on the hydraulic support cylinder. To improve the performance of the hydraulic support cylinder, the surface can be strengthened before use. The machine tool is used to perform laser cladding surface strengthening on the hydraulic support cylinder, and the comparison of the surface strengthening of the hydraulic support cylinder before and after laser cladding is performed.

As shown in Figure 5, laser cladding surface strengthening of the new hydraulic support cylinder can obtain a dense laser cladding layer on the surface. Selecting powder with excellent corrosion resistance during laser cladding can significantly improve the corrosion resistance of the surface of the hydraulic support cylinder and realize laser cladding surface strengthening of the hydraulic support cylinder.

7 Conclusion

Aiming at the phenomenon of failure and scrapping of shaft parts in mechanical equipment, combined with the large demand for remanufacturing and surface strengthening of shaft parts in actual production and the current situation of lack of special machine tools, a machine tool for laser cladding remanufacturing and surface strengthening of shaft parts is designed. This machine tool has a simple structure, is easy to clamp, easy to operate, and has a high powder utilization rate. It is suitable for the processing of shaft parts of various sizes in multiple industries and has broad application prospects.

A clamping assembly consisting of a clamping control box, a motor, a support seat, a clamping shaft, a center, etc. is designed in the machine tool, which can clamp and fix shaft parts simply and quickly. The machine tool adopts precision linear guides to ensure the movement accuracy of the machine tool.

The machine tool has been tested in practice and is stable and reliable when processing shaft parts. The laser cladding remanufacturing of shaft parts by machine tools has achieved remarkable results. The failed shaft parts remanufactured by laser cladding have restored their performance. For the surface strengthening of shaft parts, laser cladding layers can be prepared on the surface of new shaft parts to improve the surface performance of shaft parts. In summary, the designed machine tools for laser cladding remanufacturing and surface strengthening of shaft parts have achieved good application results.