What Is Involved in Sheet Metal Laser Cutting?

The laser cutting machine focuses the laser light emitted from the laser into a high power density laser beam through the optical path system. The laser beam is irradiated to the surface of the workpiece, so that the workpiece reaches the melting point or boiling point, and the high-pressure gas coaxial with the beam blows away the molten or vaporized metal.

Compared with traditional cutting processes such as oxyacetylene and plasma, the laser cutting speed is fast, the slit is narrow, the heat-affected zone is small, the edge of the slit is perpendicular, and the edge is smooth. At the same time, there are many types of materials that can be laser cut, including carbon steel , Stainless steel, alloy steel, wood, plastic, rubber, cloth, quartz, ceramics, glass, composite materials, etc. With the rapid development of market economy and the rapid development of science and technology, laser cutting technology has been widely used in automobiles, machinery, electricity, hardware, and electrical appliances. In recent years, laser cutting technology is developing at an unprecedented speed, and it is growing at a rate of 15% to 20% each year. Since 1985, China has been growing at an annual rate of nearly 25%. At present, the overall level of laser cutting technology in China still has a big gap compared with advanced countries. Therefore, laser cutting technology has broad development prospects and huge application space in the domestic market ^[1]

Laser is a kind of light. Like other natural light, it is caused by

1. Vapor cutting.
In the process of laser gasification cutting, the temperature of the surface temperature of the material rises to the boiling point temperature so fast that it is sufficient to avoid melting caused by heat conduction, so part of the material vaporizes into steam and disappears, and part of the material is ejected from the bottom of the slit as auxiliary gas The stream blows away. Very high laser power is required in this case.

To prevent material vapor

There are two types of laser cutting technology: One is pulsed laser suitable for metal materials. The second is the continuous laser suitable for non-metallic materials, the latter is an important application area of laser cutting technology.

Laser cutting machine system generally consists of laser generator, (outside) beam transmission components, workbench (machine tool), microcomputer numerical control cabinet, cooler and computer (hardware and software).

1) Machine tool part: the machine part of the laser cutting machine, the mechanical part that realizes the movement of the X, Y, and Z axes, including the cutting work platform. It is used to place the workpiece to be cut and can move accurately and accurately according to the control program. It is usually driven by a servo motor.

2) Laser generator: a device that generates a laser light source. For the purpose of laser cutting, except for a few occasions where YAG solid-state lasers are used, most of them are CO2 gas lasers with higher electro-optical conversion efficiency and higher output power. Because laser cutting requires high beam quality, not all lasers can be used for cutting. Gaussian mode is suitable for less than 1500W, low-order mode carbon dioxide laser 100W-3000W, multi-mode 3000W or more.

3) External light path: refraction mirror, which is used to direct the laser in the required direction. In order to prevent the beam path from malfunctioning, all mirrors must be protected by protective covers, and clean positive pressure protective gas should be passed to protect the lenses from contamination. A good set of lenses will focus a non-divergent beam into an infinitely small spot. A lens with a focal length of 5.0 inches is generally used. 7.5-inch lenses are only available for> 12mm thick materials.

4) Numerical control system: control the machine tool to realize the X, Y, Z axis movement, and also control the output power of the laser.

5) Regulated power supply: connected between laser, CNC machine tool and power supply system. It is mainly used to prevent interference from external power grids.

6) Cutting head: It mainly includes parts such as cavity, focusing lens holder, focusing lens, capacitive sensor and auxiliary gas nozzle. The cutting head driving device is used to drive the cutting head to move in the Z axis direction according to a program, and is composed of a servo motor and a transmission member such as a screw rod or a gear.

7) Operation table: used to control the working process of the entire cutting device.

8) Chiller: used to cool the laser generator. A laser is a device that converts electrical energy into light energy. For example, the conversion rate of a CO2 gas laser is generally 20%, and the remaining energy is converted into heat. Cooling water removes excess heat to keep the laser generator working properly. The chiller also cools the optical path reflectors and focusing mirrors outside the machine tool to ensure stable beam transmission quality and effectively prevent the lens temperature from being deformed or cracked due to excessive temperature.

9) Gas cylinder: It includes the working medium gas cylinder and auxiliary gas cylinder of the laser cutting machine, which is used to supplement the industrial gas for laser oscillation and to supply the auxiliary gas for the cutting head.

10) Air compressor, air storage tank: Provide and store compressed air.

11) Air-cooled dryer and filter: used to supply clean dry air to the laser generator and the beam path to keep the path and the mirror working normally.

12) Exhaust dust collector: extracts the smoke and dust generated during processing, and performs filtering treatment to make the exhaust emissions comply with environmental protection standards.

13) Slag discharge machine: Eliminate the leftovers and waste materials generated during processing.

In the 1950s and 1960s, the main methods used for cutting blanks were: oxyacetylene flame cutting for medium and thick plates; cutting with a shearing machine for thin plates; stamping in large quantities for complex parts; vibration shears for single pieces. After the 1970s, in order to improve and improve the quality of flame cuts, the precision flame cutting and

Beam collimation with beam expander

The beam waist diameter is inversely proportional to the far-field divergence angle. The larger the beam waist diameter, the smaller the far-field divergence angle. At present, the beam expander is mainly divided into two types: refractive and reflective, and its principle is equivalent to an inverted looking glass. The main effect is to reduce the far-field divergence angle by increasing the beam waist diameter, thereby improving the instability of the focus size and focus depth due to changes in the length of the optical path. At present, there is not much research on beam alignment in China, most of which All are aimed at the refraction type, and the research on the reflection type is less. Refractive beam expanders are easy to design, process, and adjust, but because the lens easily deforms the lens due to excessive temperature rise, the refractive beam expanders are only suitable for beam collimation of low-power lasers. For collimation of high-power beams such as laser cutting machines, reflective beam expanders are generally used. However, the mirror curvature radius of the reflective beam expander is difficult to determine by analytical methods and can only be obtained by numerical fitting. Therefore, it is difficult to design, manufacture and adjust. For this reason, the beam path compensation method of the laser cutting machine through the beam collimation method is used to compensate the optical path of the laser cutting machine. The effect is very small ^[1]

When the laser cutting machine is working, if the failure is very dangerous, novices must be trained by professionals to operate independently. According to experience, 13 details of the safe working of the laser cutting machine are summarized:

1. Observe the general safety operation rules of the cutting machine. Start the laser in strict accordance with the laser startup procedure.

2. The operator must be trained, familiar with the equipment structure and performance, and master the relevant knowledge of the operating system.

3 Wear labor protection articles in accordance with regulations, and wear protective glasses in accordance with regulations near the laser beam.

4 Do not process a material without knowing if it can be irradiated or heated with a laser to avoid the potential danger of smoke and steam.

5. When the equipment is running, the operator must not leave the post or entrust the person to manage it without permission. If it is really necessary to leave, the operator should stop or cut off the power switch.

6. Keep fire extinguishers within easy reach; turn off lasers or shutters when not processing; do not place paper, cloth, or other flammable materials near unprotected laser beams.

7. When an abnormality is found during processing, the machine should be stopped immediately, and the fault should be rectified or reported to the supervisor in time.

8. Keep the laser, bed and surrounding area clean, orderly, and free of oil pollution. Workpieces, plates, and waste materials should be stacked in accordance with regulations.

9. When using gas cylinders, avoid compressing the welding wires to avoid leakage accidents. The use and transportation of gas cylinders shall comply with the gas cylinder supervision regulations. Do not expose cylinders to direct sunlight or heat sources. When opening the bottle valve, the operator must stand on the side of the bottle mouth.

10 Observe the high voltage safety regulations during maintenance. Every 40 hours of operation or weekly maintenance, every 1000 hours of operation or every six months of maintenance shall be performed in accordance with regulations and procedures.

11. After starting the machine, manually start the machine at low speed in X and Y directions, and check whether there is any abnormal situation.

12. After entering the new workpiece program, it should be tested first and checked for its operation.

13. When working, pay attention to the operation of the machine to prevent the cutting machine from going out of the valid stroke range or the collision between the two.

The polarization properties of the laser beam. Lasers, like any other electromagnetic wave transmission, have electrical and magnetic vectors that are perpendicular to each other in two directions and both are orthogonal to the direction of laser transmission. It is generally considered that the direction of the electric vector is the polarization direction of the light beam. Beam polarization properties affect the absorption of beam energy by the material. Cutting parallel to the polarization direction of the beam results in a narrow cut with smooth and straight edges. If the cutting direction is at an angle with the plane of polarization, the energy absorption is reduced, the cutting speed is slowed, the cut is widened, and the edges are rough and not at right angles to the surface of the material. Once the cutting direction is perpendicular to the polarization direction, the edges will not be rough but the cutting speed is slower and the opening is wider. The cutting quality is significantly reduced. Although required in principle, it is difficult to keep the cutting direction parallel to the polarization direction during multi-axis motion. To overcome this instability, a phase delay is provided. Studies have shown that circularly polarized light is best suited for cutting metals. Most lasers produce polarized light at 45 degrees to the vertical. A phase retarder converts this linearly polarized light into circularly polarized light. This method is effective for cutting metal? But it does not work for other materials such as plastic and wood.

Auxiliary gas selection and air pressure setting. When cutting thin plate materials at high speed, the typical pressure value is 150-300kpa? Cutting 12-thick iron plates usually requires only 40-60kpa.

Cutting speed. When the speed is too slow, the plume Mars beams are directly downstream. When the speed is too fast, the plume Mars beams make an acute angle with the vertical direction and are unstable. Feathered Martian beams are at an appropriate speed when they make an obtuse angle to the vertical.

Set the air pressure. The auxiliary gas pressure is controlled by a CNC machine. The correct way is to select the automatic mode when calibrating the air pressure controller? Activate the program. After activating the program, press the Cycle button and follow the on-screen instructions. The program will automatically calibrate the air pressure system.

The price of laser cutting machines is not low, ranging from hundreds of thousands to millions. Therefore, prolonging the service life of the laser cutting machine as much as possible can better save production costs and win greater benefits. It can be seen that the daily maintenance and maintenance of the laser cutting machine is very important. The following mainly describes from six aspects:

I. Replacement of circulating water and cleaning of the water tank: Make sure that the laser tube is filled with circulating water before the machine works. The water quality and temperature of the circulating water directly affect the life of the laser tube. Therefore, it is necessary to periodically replace the circulating water and clean the water tank. This is best done once a week.

2. Cleaning of the fan: The long-term use of the fan in the machine will cause a lot of solid dust to accumulate in the fan, make the fan generate a lot of noise, and is not conducive to exhaust and deodorization. When the suction power of the fan is insufficient, the fan must be cleaned.

3. Lens cleaning: There will be some mirrors and focusing lenses on the machine. The laser light is reflected and focused by these lenses and emitted from the laser head. The lens can be easily contaminated by dust or other contaminants, causing laser loss or lens damage. So clean the lenses every day. At the same time when cleaning, please pay attention to: 1. The lens should be wiped gently to avoid damaging the surface coating; 2. The wiping process should be handled gently to prevent falling; 3. Be sure to keep the concave side down when installing the focusing lens.

4. Rail cleaning: Rails and linear shafts are one of the core components of the equipment. Its function is to guide and support. In order to ensure the machine has a high processing accuracy, it is required that the guide rails and straight lines have high guiding accuracy and good motion stability. During the operation of the equipment, due to the large amount of corrosive dust and fumes produced by the workpiece during processing, these fumes and dust have been deposited on the surface of the guide rail and the linear axis for a long time, which has a great impact on the processing accuracy of the equipment and will Corrosion spots are formed on the surface of the linear axis of the guide rail, which shortens the service life of the equipment. So clean the machine guide every half a month. Turn off the machine before cleaning.

V. Tightening of screws and couplings: After the motion system works for a period of time, the screws and couplings at the motion joints will loosen, which will affect the stability of the mechanical movement. Therefore, observe the transmission components during machine operation. There are no abnormal sounds or abnormal phenomena, and problems should be solidified and maintained in time. At the same time, the machine should be used to tighten the screws one by one after a period of time. The first solidification should be about one month after the equipment is used.

6. Inspection of the optical path: The optical path system of the machine is completed by the reflection of the mirror and the focusing of the focusing lens. There is no offset problem in the focusing lens in the optical path, but the three mirrors are fixed by the mechanical part and offset. It is more likely that although there is usually no offset, it is recommended that users check whether the optical path is normal before each work.

1. Every other week must check the X-axis guide and lead screw, Y-axis guide and lead screw, Z-axis guide and lead screw lubrication, maintain the lubrication of each moving part, extend the X, Y, Z-axis guide and lead screw Service life. b. Check the pollution of the surface of the reflecting mirror and focusing lens irregularly (at least once a month) depending on the environment of the workshop, and clean the optical lens in time to ensure its service life (see the maintenance of optical lens for details)

2. Regularly clean up the debris in the exhaust vent to ensure the ventilation effect.

3. Regularly check the filters in the gas path to remove water and debris in the filters in a timely manner.

4. Regularly check whether the screws of the travel switch bracket and bumper bracket are loose.

5. The dust on the filter screen of the electric control cabinet ventilation fan should be cleaned in time to ensure good ventilation to facilitate the heat dissipation of the internal electrical components.

6. The bed is cleaned in time to protect the sundries in the leather cavity of the guide rail to avoid damaging the guide rail, thereby prolonging the service life of the guide rail.

7. After the machine tool is installed, after a period of use, the level of the machine tool should be readjusted to ensure the cutting accuracy of the machine tool

Lens cleaning

1. During the replacement process, care must be taken to prevent the lens from being damaged and contaminated during the placement, testing, and installation of the optical lens. After a new lens is installed, it should be cleaned regularly.

2. When the laser cuts the material, a large amount of gas and splashes will be released on the working surface, and these gases and splashes will cause damage to the lens. When contaminants fall on the lens surface, they will absorb energy from the laser beam, resulting in a thermal lens effect. If the lens has not developed thermal stress, the operator can remove and clean it.

3. in

   1. First of all, we must find out the production scope, processing materials and cutting thickness of our company, so as to determine the type, format and quantity of equipment to be purchased, and make a simple preparation for the later procurement work. The laser cutting machine applications include mobile phones, computers, sheet metal processing, metal processing, electronics, printing, packaging, leather, clothing, industrial fabrics, advertising, technology, furniture, decoration, medical equipment and many other industries. The mainstream on the market are 3015 and 2513, that is, 3 meters by 1.5 meters and 2.5 meters by 1.3, but the format is not a problem. Generally, companies will have a variety of formats for customers to choose from, which can be customized. [3]

   2. Professionals perform on-site simulation solutions or provide solutions, and can also bring their own materials to the factory for proofing.

   1) Fine cutting seam: laser cutting seam is generally 0.10mm-0.20mm;

   2) The cutting surface is smooth: There is no burr on the cutting surface of laser cutting. Generally speaking, the YAG laser cutting machine has a little burr, which is mainly determined by the cutting thickness and the use of gas. Generally there is no burr below 3mm, the gas is the best with nitrogen, the oxygen is the second, and the air is the worst. The fiber laser cutting machine has minimal or no burrs, and the cutting surface is very smooth and fast.

   3) Look at the deformation of the material: the deformation of the material is very small

   4) Power: For example, most factories cut metal plates below 6mm, so there is no need to buy high-power laser cutting machines. 500W fiber laser cutting machines can meet production requirements. If the production volume is large, worry about 500W efficiency Not as good as a high-power laser cutting machine. The best option is to buy two or more small and medium-power laser cutting machines. This will help manufacturers in controlling costs and improving efficiency.

   5) The core parts of laser cutting: whether the laser and laser head are imported or domestic. The imported lasers generally use more IPGs, and the domestic ones are usually Ruike. At the same time, other parts for laser cutting are also required. Note that if the motor is an imported servo motor, guide rail, bed, etc., because they affect the cutting accuracy of the machine to a certain extent. A special point to pay attention to is the cooling system of laser cutting machinescooling cabinets. Many companies directly use domestic air conditioners to cool them. The effect is actually clear to everyone, and it is very bad. The best way is to use industrial air conditioners, special machines. To achieve the best results.

   3. Any equipment will be damaged to varying degrees during the use process. In terms of maintenance after damage, whether the maintenance is timely and the level of charges has become a problem to be considered. Therefore, when purchasing, you must understand the after-sales service issues of the enterprise through multiple channels, such as whether the maintenance charges are reasonable and so on. ^[2]