How To Focus The Laser

work guidelines

Laser cutting is a technique that uses a laser to cut materials, typically for industrial manufacturing applications, but is also starting to be used by schools, small businesses, and hobbyists. Laser cutting works by directing the output of a high-power laser, usually through an optical system. Laser optics and CNC (Computer Numerical Control) are used to guide the material or the resulting laser beam. A typical commercial laser used to cut material will involve a motion control system to follow the CNC or G-code of the pattern to be cut into the material. A focused laser beam is directed at the material, which then melts, burns, vaporizes, or is blown away by a gas jet, leaving an edge with a high-quality surface finish. Industrial laser cutters are used to cut flat material as well as structural and piping materials.

Factors affecting the dimensional accuracy of laser cutting

We confirm that a laser cutting machine manufacturer is excellent and cutting accuracy is the number one criterion. Therefore, how to determine whether the cutting accuracy is qualified will be considered from the following four factors

1. The size of the laser coagulation of the laser generator. If the light spot is very small, the cutting accuracy is very high, if the gap after cutting is small. The results show that the laser cutting machine has high precision and high quality.

2. The accuracy of the workbench. If the precision of the table is very high, the precision of the cutting will be improved. Therefore, the accuracy of the workbench is also a very important factor in measuring the accuracy of the laser generator.

3. The laser beam is condensed into a cone. When cutting, the laser beam is gradually tapered downward. When the workpiece is cut with a very large thickness, the cutting accuracy will be reduced, and the cut out gap will be very large.

4. Different cutting materials will also affect the accuracy of the laser cutting machine. In the same situation, the cutting accuracy of stainless steel and aluminum will be very different, the cutting accuracy of stainless steel will be higher, and the section will be smooth.

How to focus the laser

The laser beam is focused by a focusing lens. A focal length lens is like a magnifying glass and sunlight. For a 55mm lens, the laser beam passes through the lens and converges to a minimum point about 55mm from the edge of the lens. The laser beam is concentrated to a minimum size at this “spot”. Given that the lens is mounted in the focal tube, the question is how to place the material in the best position for engraving or cutting.

First, think about the desired result. Whenever we want to engrave, we want the laser beam to be focused to the smallest spot and the spot on the top surface of the material. Having the smallest spot size will give us the best resolution. Best DPI (dots per inch). The laser machine should be equipped with a manual height measuring tool. Some machines come with square pieces or acrylic to match the markings on the side of the focal tube. Other machines come with a feeler gauge that fits snugly between the focus tube nozzle and the top surface of the material.

The conventional adjustment method is to place the material on the table and then move the table height so that the top surface of the material is at the focal point of the laser beam. Use the measuring tool when moving the table to the proper height. Make sure not to move the table too far. You don’t want to damage bench surfaces, materials or focus components.

Most laser machines have movable table heights. If the table stage moves or has moved to the top, then the coke tube can move/slide up and down about 1.5 inches with some adjustment. First, loosen the focal tube nut (or screw). Second, move the focus tube to the desired height above the material surface. Finally, tighten the focal tube nut (or screw).

You might be concerned about using the provided tool to focus at the prescribed distance, but the focus doesn’t seem to be correct. Keep in mind that the best focal length may be slightly closer or further away from the lens. Place a piece of flat scrap (wood) under the focus component. Adjust the focal length so that the material is slightly closer to the focal length lens. Use the “Laser” button to make test points on the wood. The spot size will be larger than desired for engraving. Move the table a short distance away from the camera. Move the wood to a clean target location. Use the “Laser” button to make another test point. The spot size should become smaller. Continue to move the bench and make test points on the wood surface. You’ve just passed the focal point when the spot starts to get bigger. This is the easiest way to find the true focal length of a lens.

Get the best engraving….

1. Make sure the laser is focused on the material.

2. If the target material is an uneven surface, areas where the laser is out of focus may be found.

3. If your target material is a dowel and you are not using a swivel attachment. The laser will be out of focus in some parts of the image.

4. If your image looks blurry at the edges of the laser cut, but is in focus, then you may be trying to engrave at too high a speed. Set the engraving speed to a slower speed. You also need to lower the laser power percentage to avoid burning out the material.

5. If your material shows (scan) lines in the engraved area, you may need to reduce the “scan gap”. The “scan gap” is the amount of space that the track travels in the Y direction between the engraving machine scan passes. Setting the Scan Gap to a lower number will give better resolution. With some materials (anodized aluminum, hard plastic, and hardwood), a scan gap of 0.05 provides excellent results. A good environment for glass is 0.07. In soft plastics, a scan gap of 0.1 is required to ensure that the plastic does not crystallize. A setting of 0.1 is suitable for soft woods.

If you often engrave materials with different distances from the focal point, it might be a good idea to buy a focal length lens with a longer focal length. A longer focal length will focus more closely at greater distances.

type

There are three main types of lasers used in laser cutting. CO2 lasers are suitable for cutting, boring and engraving. Neodymium (ND) and Neodymium-Yttrium-Aluminum-Garnet (ND-YAG) lasers are the same in style and differ only in application. ND is used for drilling and requires high energy but low repetition. ND-YAG lasers are used where very high power is required and for boring and engraving. Both CO2 and ND/ND-YAG lasers can be used for welding.

Common variants of CO2 lasers include fast axial flow, slow axial flow, transverse flow and slab.

CO2 lasers are typically “pumped” by passing an electrical current through a gas mixture (DC excitation) or using radio frequency energy (RF excitation). RF methods are newer and more popular. Since DC designs require electrodes within the cavity, they may experience electrode corrosion and electroplating of electrode materials on glassware and optics. Since RF resonators have external electrodes, they are less prone to these problems.

CO2 lasers are used for industrial cutting of many materials, including mild steel, aluminum, stainless steel, titanium, task boards, paper, wax, plastic, wood and fabric. YAG lasers are mainly used for cutting and scribing metals and ceramics.

In addition to power, the type of airflow also affects performance. In a fast axial flow resonator, a mixture of carbon dioxide, helium and nitrogen is circulated at high speed through a turbine or blower. Cross-flow lasers circulate gas mixtures at lower velocities, requiring simpler blowers. Plate or diffusion-cooled resonators have static gas fields that do not require pressurization or glassware, saving turbines and glassware replacement.

Cooling is required for the laser generator and external optics, including the focusing lens. Depending on system size and configuration, waste heat can be transferred to the air via coolant or directly. Water is a common coolant, usually circulated through a cooler or heat transfer system.

A laser microjet is a water-jet guided laser in which a pulsed laser beam is coupled into a low-pressure water jet. This is used to perform the laser cutting function while directing the laser beam using a water jet, much like an optical fiber, by total internal reflection. The benefit of this is that the water also removes debris and cools the material. Other advantages compared to conventional “dry” laser cutting are high cutting speeds, parallel cuts and all-round cutting.

Fiber lasers are solid-state lasers that are rapidly growing in the metal cutting industry. Unlike CO2, fiber technology uses a solid gain medium, not a gas or liquid. The “seed laser” produces a laser beam, which is then amplified within the glass fiber. Fiber lasers with a wavelength of only 1.064 microns produce extremely small spot sizes (as small as 100 times smaller compared to CO2), making them ideal for cutting reflective metallic materials. This is one of the main advantages of fiber compared to carbon dioxide

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