A Method for Precisely Controlling Lens Defocus During Equipment Tuning

When fine-tuning a laser engraver, the precise control of the focal length directly affects the engraving result.The researchers use a variety of techniques, such as basic parameter checks, layered testing, and sound-assisted judgment, to quickly determine the proper defocus range for different materials.Once adjustments are complete, the parameters must be recorded, and regular checks must be made to ensure that the equipment continues to run smoothly for a long time.Mastering these techniques can dramatically improve accuracy and efficiency, and avoid wasting materials and equipment.

Why does the amount of defocusing have such a large impact on the quality of the mark?

In a nutshell, depth of focus is the distance from the laser focus to the material surface.If the parameter is not adjusted properly, the engraved image will either be fuzzy or not deep enough, or may even burn the material.Different materials have different levels of sensitivity to focus. For example, metal requires very precise focus control, while plastic can tolerate a little bit more leeway. But in the end, it all affects the final product.

There are a lot of things that have to be done before the actual tuning.

Check the basic parameters of the equipment.

First, we need to make sure that the laser's power and frequency have been adjusted to the recommended values for the material.If these parameters are wrong, then adjusting the amount of defocus won't help.At this point the equipment instruction manuals and the supplier's data sheets come in handy.

Clean the work table and the lenses.

Dust or dirt will affect the laser's path, causing you to think that the diopter is not accurate, when in fact it is the lens that is dirty.Before adjusting the focus, use a dust-free cloth to clean the focusing lens and protective lens. Also clean the work table, removing any debris.

This is a practical method for gradually adjusting the amount of defocusing.

The initial parameter test method.

First, print a small sample using the equipment's default parameters for the amount of defocus. For example, a grid pattern with a 0.5 mm spacing.Check to see if the lines are smooth and continuous.If the edges are too soft, the focal distance might be too great. If the center is too deeply etched, the focal distance might be too small.

Layered testing.

We prepare five pieces of material and adjust the focus by 0.1 mm each time.The samples are then compared to determine which one best meets the requirements.Although this method is material intensive, it is especially suitable for beginners to quickly find a reasonable range.

Listen to the sound to aid in making a judgment.

When engraving, listen carefully to the sound of the laser at work.Under normal conditions, the sound should be a continuous "buzz." If you hear intermittent popping sounds, it could mean the focal point is off, resulting in a loss of energy.This approach requires experience, but once you have mastered it, you can quickly identify problems.

Don't forget these things after adjusting.

Record the combinations of parameters.

After finding the best amount of defocus, the corresponding material type, thickness, and laser power are also recorded.The next time you encounter similar material you can simply draw on your previous research, saving a lot of time.

Regular calibration checks.

After a while, the equipment may lose its accuracy. It is recommended that you check the focus with a calibration plate each month.This is especially true of work areas where operators are frequently rotated, which are more likely to have parameters inadvertently altered.