Laser is a kind of light enhanced by stimulating radiation.
Because of its good directivity, high brightness and good monochromaticity, the laser is widely used, such as laser cutting, laser welding, laser engraving, laser drilling, laser marking and so on. Laser application has also become one of the most promising fields at present.
As the most important technology application in laser processing, laser cutting mainly has two kinds:
One is pulsed laser, which is suitable for metal materials; The other is continuous laser, which is suitable for non-metallic.
Now let’s introduce the application of laser cutting technology in the automotive industry.
Principle and advantages of laser cutting
Laser cutting is to use high-power density laser beam to scan the material surface, heat the material to thousands to tens of thousands of degrees Celsius in a very short time, melt or gasify the material, and then blow the melted or gasified material away from the cutting seam with high-pressure gas, so as to achieve the purpose of cutting.
Laser cutting has the following advantages in the production of auto parts:
(1) High precision, positioning accuracy is about 0.05mm.
(2) The slit is narrow, and the laser beam is focused into a small light spot, so that the focus reaches a high power density.
The material is heated to the degree of gasification and evaporates to form holes.
With the relative linear movement of the beam and the material, the holes continuously form slits with very narrow width.
(3) The cutting surface shall be smooth without burrs.
(4) Fast speed, much faster than wire cutting speed.
(5) Good cutting quality, non-contact cutting; little thermal influence on the cutting edge; basically no thermal deformation of the workpiece; completely avoid the edge collapse formed during material punching and shearing, and the cutting joint generally does not need secondary processing.
(6) Do not damage the workpiece, and the laser cutting head will not contact the workpiece surface to ensure that the workpiece is not scratched.
(7) Laser can process steel plate, stainless steel, aluminum alloy plate, cemented carbide and other materials without being affected by the hardness of the cut materials.
(8) It is not affected by the shape of the workpiece and has good flexibility. It can process any graphics and cut pipes and other profiles.
(9) Save the investment of molds.
Laser processing does not need molds, there is no mold loss, there is no need to repair molds, and the replacement time of molds is saved, so as to save the processing cost and reduce the production cost.
(10) Save materials and adopt computer programming to cut the whole plate of products with different shapes, so as to improve the utilization rate of materials.
(11) It can shorten the development cycle of new products.
The trial production of new products generally has a small number and uncertain structure. There is no need to manufacture molds, reduce waste and shorten the production cycle of new products.
(12) Non metallic materials can be cut.
Therefore, it is very feasible to use this equipment in production, and this equipment is also suitable for the production of small batch workpieces, which provides convenience for the preliminary trial production and development of parts and saves the cost.
Laser cutting equipment
There are many kinds of laser cutting equipment:
(1) 2D laser cutting machine is mainly used to cut plane workpieces.
(2) 3D laser cutting machine, which can cut workpieces in three-dimensional space.
(3) Laser cutting robot (Fig. 1) can cut more complex three-dimensional workpieces.
Fig. 1 Laser cutting robot workstation
With the development of the automobile industry, laser cutting robots are used more and more, and this type of laser cutting equipment can also cut plane workpieces and simple three-dimensional workpieces.
Therefore, the following focuses on the components of the laser cutting robot workstation.
Components of the laser cutting robot workstation:
(1) High precision trajectory robot realizes high precision, high speed, three-dimensional processing and cost reduction.
(2) Laser generator, including solid-state laser generator, gas laser generator and optical fiber laser generator, is the device for generating laser source.
(3) Cooler for cooling the laser generator.
(4) Optical fiber cable.
(5) Cutting head, mainly including cavity, focusing lens seat, focusing mirror, capacitive sensor, auxiliary gas nozzle and other parts.
(6) The workbench is used to place the cut workpiece and can move correctly and accurately according to the control program. It is driven by the servo motor.
(7) The numerical control system controls the workbench to realize the movement of X, y and Z axes, and also controls the output power of the laser.
(8) Operation console is used to control the working process of the whole cutting device.
(9) Gas cylinders, including working medium cylinders and auxiliary cylinders of laser cutting machine.
(10) Air compressor.
(11) Air cooling dryer and filter.
(12) Auxiliary equipment such as exhaust fan and dust collector.
Practical use of laser cutting robot in automobile manufacturing
The application of laser cutting robot in automobile parts processing is listed below.
Cutting of pipe parts
As shown in Fig. 2, the part is laser cutting all holes on the pipe (there are 4 holes in the left part and 5 holes in the right part).
Fig. 2 Pipe parts
Due to the large number of holes and different hole sizes, if the die is used for blanking, the die is relatively complex, the number of dies is relatively large, the investment is relatively large, and the later die maintenance frequency is also high, which will occupy a lot of time and manpower, produce unqualified products, affect the quality of parts.
There should also be special quality inspection personnel for inspection to prevent the outflow of nonconforming products.
The use of laser cutting technology can not only reduce a lot of mold capital investment but also bring the following benefits:
(1) Ensure the quality of parts;
The cutting position of parts is accurate, and this non-contact machining can avoid the occurrence of corner collapse.
(2) Save the occupation of operators and equipment;
When laser cutting is adopted, after adjusting the program, only one worker can complete a series of work such as taking parts, loading parts and unloading parts;
If the die is used to realize, at least 3 sets of dies, 3 operators and 3 stamping equipment are required.
(3) Time saving and simple operation;
According to practice, the parts can be cut 400 sets a day, and the workers will not be too tired and the efficiency is high;
If the mold is used, 400 sets can be produced a day under normal conditions.
However, if the mold has problems, maintenance, mold installation and commissioning will consume a lot of time and manpower.
(4) Avoid missing cutting and wrong cutting;
In case of missing or wrong cutting in laser cutting, the equipment will give an alarm, so there will be no outflow of nonconforming products;
If the die has missed punching, it is not easy to be found. In this way, the outflow of nonconforming products will bring greater losses.
In order to ensure the quality of parts, the positioning of parts should be accurate, so it is necessary to make the positioning fixture of parts (Fig. 3).
The fixture structure is divided into three parts:
(1) The fixing plate is fixed on the workbench of the workstation by screws and pins.
There are screws and pins at fixed positions on the worktable, so the design of the fixture should be combined with the size of the worktable, and can not be designed blindly.
(2) For the positioning device of the part, according to the service characteristics of the part, the position between the hole and the end is the most important, so the positioning is set at the end of the part.
(3) For the clamping device of parts, because the parts have cutting parts in all directions, the parts need to be turned over with the workbench.
In order to prevent the parts from falling off when the workbench rotates, four sets of clamping cylinders need to be set.
Generally speaking, the fixture structure is simple and easy to operate, and the investment cost is also very low, but it can bring great benefits, which can be said to be more practical.
Fig. 3 Positioning fixture for making pipe parts
Cutting of profile
As shown in Fig. 4, the part needs to cut two large holes and two ends.
Fig. 4 Profile parts
When the holes and ends are punched by die, they will be deformed.
Therefore, in order to ensure the quality of the part, laser cutting is used to avoid part deformation.
The cutting of the part hole is relatively easy to achieve, but it will be difficult to cut the end of the profile.
The section of the profile is in the shape of B, and the cutting direction is 360 degrees in each direction.
Therefore, it is required that the laser cutting head can rotate 360 degrees, and there should be enough space for the cutting head to rotate.
If the space in the normal direction is not enough, then, under the condition of not affecting the use of parts, small angle cutting can be adopted.
Therefore, the setting of cutting track of cutting head needs to be tried continuously to finally ensure the quality of parts, reduce the cost of parts and improve the production efficiency.
The laser cutting fixture of the part is shown in Fig. 5.
Fig. 5 Positioning fixture fixed on the worktable
The structure of the fixture is similar to that of the pipe fixture, which is also divided into three parts:
(1) The fixed plate is fixed in the same way as the fixed plate of the pipe.
(2) The part positioning device has two very important installation holes on the part.
Therefore, the hole positioning method is adopted to make the position of the part accurate.
The positioning structure adopts the cylinder to drive the positioning pin, which can move back and forth to facilitate the taking and placing of the workpiece.
(3) The clamping device of the part is similar to the pipe part, but the clamping head changes with the shape of the part.
In the above two examples, the laser cutting fixture is relatively simple compared with the mold, which is composed of three parts: fixed plate, positioning device and clamping device.
At the same time, it shows that the application of laser cutting robot can solve many problems in the manufacture of automobile parts, and brings many advantages.
To sum up, laser cutting has outstanding advantages in the field of automobile processing, which adapts to the development trend of reducing cost and improving quality of automobile. Moreover, laser processing robot workstation is more and more widely used in the automobile industry, not only in laser cutting, laser welding, laser marking, laser engraving, etc, even in the application of non-metallic materials is very common.