Experience with Laser Welding Machines

Experience with Laser Welding Machines

Note: Laser maintenance must be carried out by specially trained personnel, otherwise serious damage may occur.

1) In order to ensure that the laser is always in normal working state, after two weeks of continuous operation or when it is stopped for a period of time, the components in the optical path such as the YAG rod, dielectric diaphragm and lens protection glass should be checked before starting the machine to determine the optical path. The components have no abnormal phenomena such as dust pollution and mildew. If the above phenomena are found, they should be dealt with in time to ensure that the optical components will not be damaged under strong laser irradiation. (If the equipment is used in a relatively clean environment, the above inspection can be extended to one month or even longer.)

2) The purity of the cooling water is the key to ensure the laser output efficiency and the life of the laser concentrating cavity components. During use, the conductivity of the inner circulating water should be checked once a week to ensure that its conductivity is 30.5MW·cm. For circulating deionized water, the conductivity of newly injected pure water must be 32MW·cm. Pay attention to the color change of the ion exchange column in the cooling system at any time. Once the color of the resin in the exchange column becomes dark brown or even black, the resin should be replaced immediately.

3) Equipment operators can often use black image paper to check the laser output spot. Once the uneven spot or energy drop is found, the resonator of the laser should be adjusted in time to ensure the beam quality of the laser output.

Tuning of laser resonators

Warning: This product belongs to Class 4 laser equipment. Direct strong laser irradiation can cause serious damage to human skin, especially blinding eyes. Debugging operators must have common sense of laser safety protection. special laser protective glasses.

Note: When the strong laser directly irradiates flammable materials such as wood, an open flame will be generated. During the debugging process, a ferrous metal material with good absorption performance should be placed on the optical path of the laser output as a beam terminator to prevent fire accidents.

Note: The adjustment of the laser must be carried out by specially trained personnel, otherwise other components on the optical path will be damaged due to the misalignment or polarization adjustment of the laser.

The adjustment steps of the laser resonator are as follows:

1. Check the reference light source

The red semiconductor laser is the benchmark of the entire optical path, and its accuracy must be ensured first. Use a simple height gauge to check whether the red light is parallel to the top surface of the optical bench guide rail, and is on the center line between the two guide rails of the optical bench. If there is any deviation, it can be adjusted by 6 fastening screws. After adjustment, pay attention to check again whether all fastening screws are fully tightened.

2. Adjust the position of the output mirror (output dielectric diaphragm)

Before adjusting the output mirror, the condenser cavity with the YAG rod should be removed, so as not to affect the adjustment accuracy due to the refraction deviation of the YAG rod in the optical path.

The exact position of the output dielectric diaphragm should be the exit hole that makes the red light at its center and can fully reflect the red light back to the red light, otherwise it should be carefully adjusted by the knob of the diaphragm holder. Note that after the adjustment, the locking ring on the adjustment knob of the diaphragm holder should be completely locked to ensure the stability of its position, and then check again whether the position of the reflected light remains in its original position.

3. Check the installation position of the YAG rod

Paste the two ends of the YAG rod sleeves with transparent tape, and observe whether the red light spot is in the middle of the two rod sleeves. If there is any deviation, it should be corrected by adjusting the position of the concentrating cavity. Then observe the position of the reflected light of the YAG rod, which should coincide with the exit hole of the red light. Otherwise, adjust the position of the concentrating cavity on the premise of keeping the red light in the center of the rod casing as much as possible, so that the reflected light is as close to the exit hole as possible. , at least it should be ensured that the deviation from the exit hole is less than 1mm.

4. Adjust the position of the total reflection mirror (the total reflection dielectric diaphragm)

Step 1: Check whether the red light is in the middle of the dielectric diaphragm, otherwise the installation position of the dielectric diaphragm holder should be adjusted so that the red light is in the center of the dielectric diaphragm.

Step 2: Coarsely adjust the knob of the dielectric diaphragm holder so that the red light is reflected back to the exit hole.

The third step: turn on the laser, about 200A, adjust the pulse width to about 2ms, adjust the repetition frequency to 0Hz, step on the foot switch to make the pulsed xenon lamp flash, at this time, put the fully exposed black image paper in front of the output mirror, you can When the laser output is observed, adjust the two knobs of the diaphragm holder repeatedly to make the output light spot the most round and uniform, and then gradually reduce the current to about 120A, and further fine-tune the knob repeatedly and carefully to make the light spot hit on the paper as far as possible. The circle and the strongest part are concentrated in the center of the spot.

Step 4: Check whether the laser is coincident with the red light, fix the image paper at the front of the laser output mirror and as far away as possible from the output mirror, send out a laser pulse, and observe whether the center of the spot on the image paper coincides with the center of the red light, such as If it does not coincide, you can fine-tune the output mirror and the total reflection mirror to make the light spot coincide with the red light, and then fix the image paper at a distance of 800~1000mm from the laser output mirror, and check again whether the light spot coincides with the red light. If it can coincide well, the laser is adjusted to the best state.

Step 5: Tighten the adjustment knobs and check again whether the light spot on the image paper is good and coaxial with the red light. Otherwise, it should be readjusted.

5. Check the position of the shutter. Manually rotate the reflective lens bracket, push the shutter to the light-blocking position, and observe whether the red light is in the middle of the lens, and whether the reflected light is located on the absorption cone in the center of the beam terminator. If the position is incorrect It can be adjusted slightly. Finally, special attention should be paid to carefully check whether the shutter reflector is clean, and the contaminated lens will burst quickly during use.

At this point, the adjustment of the laser part is completed.

Maintenance of the cooling system

1 The main content of cooling system maintenance

The main contents of maintenance include checking the water quality of cooling water, cleaning the water tank and pipes, and checking whether the protection circuit operates normally.

In the case of frequent use, the water quality must be checked once a week to ensure the quality of the cooling medium at any time. The inspection method is to place the multimeter in the 2MW resistance gear, and insert the exposed metal parts of the two test leads into the cooling water surface in parallel at a distance of 1cm. The resistance reading at this time should be at least 250kW. If the reading is lower than this value, the cooling water should be replaced immediately.

2 Check the protection interlock circuit

This cooling system is specially designed for the characteristics of laser equipment, and has designed protective measures such as over-temperature sound alarm, over-temperature interlock, flow switch interlock, and liquid level protection interlock. In use, the above protection circuits should be checked frequently to ensure that their functions are normal and effective. Inspection work can be carried out during a water change.

Precautions

In a high temperature or humid environment, you should always pay attention to observe whether the "condensation" phenomenon caused by the low water temperature occurs on the pipeline of the cooling water circulation or the laser concentrating cavity during the operation of the laser. The occurrence of "condensation" will cause YAG Damage to crystal facets resulting in a drop in output power or even no light output. Be careful when using it. If there is "condensation", the laser welding machine should be stopped immediately, and the condition of the YAG optical surface should be re-checked after the moisture on the surface of the concentrating cavity is naturally dried to determine whether to clean the YAG rod. Before starting the machine, pay attention to properly adjust the lower limit set temperature of the temperature controller.

During normal operation, you should also pay attention to observe whether there is frost on the titanium tube of the refrigeration system. If frost occurs, it may be caused by insufficient Freon in the refrigeration system. You should immediately ask the relevant professionals to supplement and check whether there is any leakage.