CN102430904A - Laser heating assisted milling method and device - Google Patents

Abstract

The invention discloses a laser heating auxiliary milling method and a laser heating auxiliary milling device. The laser focusing head is arranged on a traditional numerical control milling machine, and laser is guided in through the optical fiber to improve the temperature of a local workpiece, so that the purpose of improving the processing performance of the material is achieved. On the premise that the laser focusing head and the milling cutter are relatively fixed, a rotary workbench is additionally arranged, and the incident direction of the workpiece relative to the laser is changed by rotating the workpiece, so that the laser heating auxiliary milling processing of the complex part is realized. The invention overcomes the defect that the processing direction can not be changed in the heating auxiliary milling processing, and provides a new method for processing complex parts made of difficult-to-process materials.

Description

Laser heating assisted milling method and device

technical field

The invention relates to a mechanical processing method, especially a laser heating-assisted milling processing method, which is mainly used in the field of mechanical processing, and is suitable for processing difficult-to-machine materials such as high-hardness metals, engineering ceramics, and composite materials, and can increase tool life. Improve processing efficiency and improve processing quality. The invention also relates to a laser heating assisted milling device for realizing the processing method.

Background technique

Laser heating assisted cutting technology is to focus a high-power laser beam on the surface of the workpiece in front of the cutting edge. In a short time before the material is cut, the local heating is heated to a very high temperature to change the machinability of the material at high temperature, and then Processing with cutting tools. By heating the material, the plasticity of the material can be improved, the brittleness of the material can be converted into ductility, the yield strength of the material can be reduced below the fracture strength, the cutting force can be reduced, the tool wear can be reduced, the generation of sawtooth chips can be suppressed, and cutting vibration can be prevented. chatter, so as to achieve the purpose of improving processing efficiency, reducing costs and increasing surface quality.

Laser heating assisted milling is a way of laser heating assisted cutting. Since milling is an intermittent cutting process, the impact of the workpiece on the tool is more likely to cause tool damage. Therefore, laser heating-assisted milling technology can reduce the cutting force, reduce the impact of the tool on the workpiece, improve tool life and improve the quality of the processed surface. Foreign scholars have conducted experimental research on laser heating-assisted milling of stellite materials, which proves the advantages of heating-assisted milling, which can reduce tool wear while improving processing efficiency. For ceramic materials that are brittle and difficult to process, the laser heating-assisted milling technology can transform the material from brittle to plastic, significantly reduce the cutting force during processing, make chips continuous, and obtain a good processed surface. However, the processing characteristics of milling and the structure of the milling machine bring difficulties to the combination of laser and milling. The relative position of the laser and the milling cutter cannot be adjusted, resulting in that the processing position can only be in one direction relative to the milling cutter. For complex workpieces with complex grooves, cavities and other structures, laser heating and softening can only be achieved by re-clamping, which greatly limits the application range of the technology. Therefore, it is necessary to comprehensively consider the processing method and device to solve the problem of combining laser and milling machine in order to realize the processing of workpieces with complex shapes.

Contents of the invention

The purpose of the present invention is to make the laser heating-assisted milling technology applicable to the processing of complex workpieces, and proposes a laser heating-assisted milling complex trajectory processing method and a processing device in which the laser focusing head and the milling cutter are relatively fixed. This method can be used to mill complex straight lines and curved paths, and realize the processing of complex-shaped workpieces. The laser heating assisted milling processing device proposed by the present invention is characterized in that it includes: CNC milling machine table, CNC rotary table, spindle, milling cutter fixed on the spindle, focusing head fixing adjustment device, laser focusing head, optical fiber, YAG Optical fiber output laser, industrial computer, the workpiece is fixed on the rotary table through heat-insulating fixtures, YAG optical fiber output laser can output laser with specified energy by adjusting the current, the laser enters the laser focusing head through optical fiber transmission, and the laser focusing head is fixed on the focusing head. On the adjustment device, the focusing head fixing adjustment device is fixed on the milling head of the machine tool, and the industrial computer is connected with each workbench and laser through cables.

The present invention also relates to a laser heating assisted milling processing device, which is characterized in that it includes a CNC milling machine table, a CNC rotary table, a two-dimensional mobile table, a main shaft, a milling cutter fixed on the main shaft, a focusing head fixing adjustment device, Laser focusing head, optical fiber, YAG optical fiber output laser, industrial computer, the rotation center of the rotary table coincides with the center of the spindle, the two-dimensional mobile table is fixed on the rotary table, and the workpiece is fixed on the two-dimensional mobile table by a heat-insulating fixture. The YAG fiber output laser can output laser with specified energy by adjusting the current. The laser is transmitted into the laser focusing head through the optical fiber. The laser focusing head is fixed on the focusing head fixing adjustment device. Connect with each workbench and laser through cables.

The numerical control code writing method proposed by the present invention utilizes the method of coordinate transformation to convert traditional three-dimensional numerical control codes into special numerical control codes used by complex workpieces. The core of the method is to transform the track direction of the tool to be processed to be parallel to the incident direction of the laser through the coordinate transformation method of translation and rotation, and to be on a straight line. After the transformation, the laser position can be continued without moving the position. When the processing trajectory is a curve, the curve is discretized into multiple small line segments to approximate the curve, so that the direction of the small line segment trajectory is parallel to the incident direction of the laser, and the processing trajectory is obtained by rotating while processing.

The method for selecting suitable process parameters proposed by the present invention is based on the results of the finite element model for selection and optimization. The temperature of the cutting area is the most important parameter of laser heating-assisted milling, which reflects the softening degree of the local workpiece. The selected parameters need to ensure that the temperature of the cutting area is within a certain range. The cost of obtaining suitable process parameters directly through experiments is relatively high, while Using the simulation method saves time, reduces costs, and can obtain suitable process parameters. According to the size of the actual workpiece, the model is divided into grids, the laser is regarded as the surface heat flux density, the thermal radiation and convection boundary conditions are loaded, and the boundary conditions are corrected through the temperature measurement test, an accurate temperature distribution prediction model can be obtained. According to the test system, the process parameters can be selected for simulation, and the temperature of the cutting area is the optimization target, combined with the selection characteristics of the milling process parameters, the final processing process parameters can be obtained.

The present invention also relates to a laser heating-assisted milling processing method realized by the processing device, which is characterized in that it includes the following steps:

- Place the workpiece on the CNC rotary table or the two-dimensional mobile table and fix it, and change the relative position of the CNC rotary table and the milling cutter by moving the CNC milling machine table;

-Adjust the relative position of the laser focusing head to control the incident position and diameter of the laser spot, so that it is irradiated at the position where the material will be removed;

- Plan the machining trajectory, calculate the moving coordinate value of the special rotation axis, and output the NC code;

-Through the finite element simulation of the temperature field, the processing parameters are selected and optimized, and the processing parameters such as laser power, cutting speed, feed rate, feed rate, warm-up time, distance between the center of the laser spot and the center of the milling cutter are obtained;

- Open the shutter, make the temperature of the cutting area meet the processing requirements through preheating, and process according to the given NC code;

- After the machining track is completed, the shutter is closed and the milling cutter moves to the next machining position.

According to another embodiment of the present invention, a complex workpiece is placed on a two-dimensional mobile worktable for processing, and the complex workpiece is a workpiece with three-dimensional shape features.

According to another embodiment of the present invention, it also includes the step of changing the relative direction of the workpiece, and writing new numerical control codes by adopting the coordinate movement method of adding a rotation axis on the basis of the traditional three-dimensional coordinate movement.

According to another embodiment of the present invention, the coordinate movement method of adding a rotation axis includes two types of linear trajectory and curved trajectory.

According to another embodiment of the present invention, the step of selecting and optimizing the processing parameters through the temperature field finite element simulation includes using the finite element method to establish the temperature field model of the workpiece, and taking the appropriate cutting area temperature as the heating target, and selecting and optimizing the laser heating assisted milling process. Process parameters.

The present invention has the following advantages:

1. The laser heating assisted milling system that needs to be established by this method does not need a complicated optical path system or a laser focusing head moving system. The system is simple, convenient, and easy to operate. It can meet the requirements by modifying the current CNC milling machine.

2. Laser heating-assisted milling of continuous straight and curved paths can be realized, meeting the processing requirements of difficult-to-machine materials with complex shapes.

3. The selection of process parameters does not require a large number of experiments, saving time and reducing costs.

Description of drawings

Fig. 1 is a schematic diagram of an apparatus for laser heating-assisted milling of a complex-shaped workpiece according to one embodiment of the present invention.

Fig. 2 is a schematic diagram of a device for laser heating-assisted milling of a complex-shaped workpiece according to Embodiment 2 of the present invention.

The picture description is as follows:

1-CNC milling machine table, 2-Rotary table, 3-Mobile table, 4-Workpiece, 5-End mill, 6-Milling machine spindle, 7-Laser focusing head adjustment device, 8-Laser focusing head, 9- Optical fiber, 10-laser, 11-industrial computer

Detailed ways

Below in conjunction with implementation method and accompanying drawing, the present invention will be further described:

Referring to Figures 1 and 2, the laser heating assisted milling processing device proposed by the present invention includes: a CNC milling machine table 1, a CNC rotary table 2, a two-dimensional mobile table 3, a main shaft 6, a milling cutter 5 fixed on the main shaft 6, Focus head fixing adjustment device 7, laser focus head 8, optical fiber 9, YAG fiber output laser 10, industrial computer 11. When processing a straight line, the machining accuracy is not high or the existing milling machine cannot meet the requirements of processing curves or brittle materials, the rotary table 2 is fixed on the CNC milling machine table 1, and the workpiece 4 is fixed on the rotary table 2 through the heat-insulating fixture. superior. When machining curves, brittle materials, or high machining accuracy are required for complex workpieces, the rotation center of the rotary table 2 coincides with the center of the main shaft, and a two-dimensional mobile table 3 is added, which is fixed on the rotary table 2, and the workpiece 4 is fixed on the two-dimensional mobile workbench 3 by a thermal insulation fixture. The YAG fiber output laser 10 can output laser with specified energy by adjusting the current. The laser is transmitted through the optical fiber 9 and enters the laser focusing head 8. The laser focusing head 8 is fixed on the focusing head fixing and adjusting device 7, and the focusing head fixing and adjusting device 7 is fixed on the machine tool. on the milling head. Before processing, adjust the focusing head fixing device 7 to change the incident direction of the laser and the diameter of the incident spot on the surface of the workpiece. During the processing, the laser and the milling machine are relatively stationary, and the worktable moves with a predetermined trajectory to realize the processing of the workpiece. The industrial computer 11 is connected with each workbench and the laser 10 through cables, and controls the movement of the workbench, the laser energy and the switch of the shutter.

The present invention can adopt the following two implementations for different processing workpieces and the original CNC milling machine: Embodiment one is to place a CNC rotary table on the ordinary CNC milling machine workbench to achieve the effect of changing the relative direction of the workpiece, and the milling machine itself works The table changes the relative position of the workpiece; the second embodiment is to place a CNC rotary table on the ordinary milling machine table, and the center of the CNC rotary table coincides with the center of the spindle to achieve the effect of changing the relative direction of the workpiece. The table is placed on the CNC rotary table to achieve the effect of changing the relative position of the workpiece.

Embodiment 1: For processing straight lines, the requirements for processing accuracy are not high or the existing milling machines cannot meet the requirements. The device schematic diagram of this method is shown in Figure 1. Using this scheme, the system is easy to establish. Just add a rotary table 2 to the ordinary CNC milling machine. First, adjust the position and process along one direction. When the processing direction needs to be changed, the milling cutter 5 is lifted. , the shutter is closed, the rotary table 2 is rotated to the next position, so that the processing direction is the same as the laser incident direction, and the table 1 is moved to the rotated processing position at the same time, and the milling cutter 5 is lowered for processing at the next position. However, since the relative position of the laser incident cannot be adjusted at any time during the processing, only a straight line can be processed.

Embodiment 2: For occasions that require processing curves, processing brittle materials, or requiring high processing accuracy. The schematic diagram of the method device is shown in Figure 2. The two-dimensional mobile worktable 3 is placed on the rotary table 2, the machine tool spindle 6 is coaxial with the center of the rotary table 2, and the rotary table 2 only changes the machining process during the rotation process. direction, without changing the position of the milling cutter 5 relative to the mobile table 3, the two-dimensional mobile table 3 and the z-axis of the milling machine form three axes in the milling process. At this time, it can be ensured that the relative position of the laser incident can be adjusted at any time during the processing, so the processing requirements of the curved track can be met. During processing, the workpiece moves with the movable table 3, and the relative angle between the laser incident position and the workpiece is changed with the rotation of the rotary table 2, and the position of the laser spot does not need to be changed. In the process of processing, after processing a straight track, the shutter first needs to be closed to prevent the laser from being irradiated at other positions during the rotation of the worktable. After the rotation of the worktable, the shutter is opened to start processing the next section of the track. The integration of shutter control In the CNC system to ensure the synchronization of the system.

When using the laser heating assisted milling processing device of the present invention to process workpieces, the workpiece 4 is clamped on the two-dimensional mobile worktable 3, or fixed on the numerically controlled rotary worktable 2, and the numerically controlled rotary work is changed by moving the numerically controlled milling machine workbench 1 The relative position of table 2 and milling cutter. Before processing, the process parameters are selected and optimized through the finite element simulation of the temperature field, and the process parameters such as laser power, cutting speed, feed rate, feed rate, warm-up time, distance from the center of the laser spot to the center of the milling cutter, etc. are obtained. Determine the machining trajectory according to the traditional machining trajectory formulation method, calculate the moving coordinate value of the special rotation axis according to the NC code writing method, and output the NC code. Open the shutter, make the temperature of the cutting area meet the processing requirements through preheating, and process according to the given NC code. After processing a track, the shutter is closed, the rotary table rotates to the next station, and the processing continues after the shutter is opened. After processing all discrete trajectories in this order, close the shutter, the processing is completed, and the tool moves to the next step.

When processing complex workpieces, the workpieces are clamped on the two-dimensional mobile worktable. The complex workpieces are workpieces with three-dimensional shape characteristics, which can be grooves and cavities with certain trajectories.

When performing the operation of changing the relative direction of the workpiece, it is necessary to write a new CNC code, and add the coordinate movement method of the rotation axis on the basis of the traditional three-dimensional coordinate movement. There are two types of coordinate movement methods that add rotation axes: straight line track and curved track. For straight line trajectory, the angle between the straight line to be processed and the processed straight line is obtained to obtain the rotation angle; for curved trajectory, the curve needs to be discretized, and the small line segments approach the curve to obtain the angle between each small line segment, thereby obtaining the rotation angle.

The steps of selecting and optimizing the processing parameters through the finite element simulation of the temperature field include establishing the temperature field model of the workpiece by using the finite element method, and selecting and optimizing the laser heating assisted milling process parameters with the appropriate cutting area temperature as the heating target.

Claims (7)

1. a LASER HEATING is assisted the Milling Process device; It is characterized in that; Comprise: CNC milling machine workbench (1), numerical control rotary table (2), main shaft (6), be fixed on milling cutter (5) on the main shaft (6), focus head fixedly adjusting device (7), laser focusing head (8), optical fiber (9), YAG optical fiber output laser (10), industrial computer (11); Workpiece (4) through heat insulation clamps on rotary table (2); YAG optical fiber output laser (10) can be exported the laser of prescribed energy through regulating electric current, and laser gets into laser focusing head (8) through optical fiber (9) conduction, and laser focusing head (8) is fixed on focus head fixedly on the adjusting device (7); Focus head fixedly adjusting device (7) is fixed on the lathe milling head, and industrial computer (11) connects with each workbench and laser instrument (10) through cable.

2. a LASER HEATING is assisted the Milling Process device; It is characterized in that; Comprise: CNC milling machine workbench (1), numerical control rotary table (2), two-dimentional travelling table (3), main shaft (6), be fixed on milling cutter (5) on the main shaft (6), focus head fixedly adjusting device (7), laser focusing head (8), optical fiber (9), YAG optical fiber output laser (10), industrial computer (11); Rotary table (2) pivot overlaps with the alignment of shafts; Two dimension travelling table (3) is fixed on the rotary table (2), and on two-dimentional travelling table (3), YAG optical fiber output laser (10) can be exported the laser of prescribed energy through regulating electric current to workpiece (4) through heat insulation clamps; Laser gets into laser focusing head (8) through optical fiber (9) conduction; Laser focusing head (8) is fixed on focus head fixedly on the adjusting device (7), and focus head fixedly adjusting device (7) is fixed on the lathe milling head, and industrial computer (11) connects with each workbench and laser instrument (10) through cable.

3. the auxiliary milling method of LASER HEATING that utilizes claim 1 or 2 described processing unit (plant)s to realize is characterized in that, may further comprise the steps:

-workpiece is placed on that numerical control rotary table (2) is gone up or two-dimentional travelling table (3) is gone up and fixing, through moving the relative position that CNC milling machine workbench (1) changes numerical control rotary table (2) and milling cutter;

The incoming position and the spot diameter of the relative position control laser facula of-adjustment laser focusing head make it to be radiated at the position that will remove material;

-plan machining locus, calculate the moving coordinate value of special rotating shaft, the output numerical control code;

-select to optimize working process parameter through the temperature field finite element simulation, obtain technological parameters such as laser power, cutting speed, the amount of feeding, feed speed, preheating time, laser facula centre distance milling cutter centre distance;

-open optical gate, make the cutting zone temperature reach processing request through preheating, process according to given numerical control code;

After-machining locus was accomplished, optical gate was closed, and milling cutter moves to next Working position.

4. method according to claim 3 is characterized in that, complex part is placed on the two-dimentional travelling table (3) processes, and said complex part is the workpiece with three-dimensional shape features.

5. according to claim 3 or 4 described methods, it is characterized in that, also comprise the step that changes the workpiece relative direction, be employed in the conventional three-dimensional coordinate and move the basis and go up the coordinate moving method that increases rotating shaft and write new numerical control code.

6. method according to claim 5 is characterized in that, the coordinate moving method of described increase rotating shaft comprises two types of straight path and curvilinear paths.

7. according to a described method among the claim 3-6; It is characterized in that; The step of selecting to optimize working process parameter through the temperature field finite element simulation comprises the models for temperature field of utilizing Finite Element Method to set up workpiece; For adding thermal target, select to optimize the auxiliary milling process parameter of LASER HEATING with suitable cutting zone temperature.

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