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Focal length is one of the most important parameters for any lens and any optical system. In simple terms, this is the distance from the center of the lens itself to the point where rays refracted by it converge. If it is configured incorrectly, it reduces efficiency of work and quality of result.
Important parameters for operation depend on focal length — spot diameter and depth of focus. You can’t say much about the diameter of the spot, roughly speaking it’s like the thickness of a saw blade, thinner, smaller cutting thickness. Depth of focus is the range of distances within which focus remains clear and allows you to make a high—quality cut or engraving. The thickness of material you can process directly depends on this indicator.
Kinds of lenses
Each type of lens is suitable for a specific type of task and to achieve desired result, it is important to pay attention to fact that:
- Long—focus lenses are optimal for cutting materials with a thickness of 8 mm or curved blanks.
- Medium—focus is a compromise solution suitable for both engraving and cutting fabrics with a thickness of less than 8 mm.
- Short—focus – used only for engraving.
How to choose the right focal length?
In laser machines, focal length is adjusted, in some it is done automatically, but it is also possible manually. If you have chosen to set it up yourself or your machine simply does not adjust it automatically, then here are a few steps and recommendations for setting it up.
The engraving? Cutting?
- Engraving is a process where a more detailed result is needed, so this is a task for short—focus lenses.
- Cutting — good beam penetration into material can be provided by a lens with a long and medium focal length.
Material thickness
- Thin — short-focus lenses (<40mm) are suitable for them.
- Thick — long-focus lenses (75mm or more) are great for, because of their ability to penetrate deeper and cut more efficiently.
Type of material
- Organic — wood or leather is a lot for imagination in working with machines, depending on the result that you want to get with these materials, you can use different focal lengths.
- Metals — cutting and engraving of such fabrics requires fine-tuning, as they can overheat and distort if focal length is incorrect.
Tests and calibration
- Test cuts and engravings will help to avoid unaccounted-for settings, especially if mass production is launched.
- Calibration of a machine is one of the primary stages, if you do not follow it, even with the correct focal length and compliance with above parameters, you simply won’t get the desired result.
Additional tools
- Auto focus — some modern machines are equipped with it, trust machine, it will significantly speed up the process.
- Laser measuring instruments are literally created to simplify the process, do not neglect such a useful assistant.
The thickness of material and focal length
We have determined that these two parameters are crucial for which result will come out from under the machine. Below we will provide more accurate data on the relationship between these two indicators.
Focal length — 38-64 mm, Material — up to 3 mm
Example: Paper, cardboard, thin acrylic, fabric, leather.
A short focal length minimizes beam scattering, allowing you to create clear and fine lines when working with small and complex details. For example, in the case of surface engraving of thin fabrics.
Focal length — 64-102 mm, Material — 3-10 mm
Example: Medium-thick acrylic, wood, plywood, plastic.
A balance between good penetration and precision. It is ideal for most types of engravings, for fabrics of medium thickness.
Focal length is more than 102 mm, the material is more than 10 mm
Example: Thick wood, thick acrylic, thick plastic and metal.
This focal length ensures easy penetration of laser beam, which is very important for such thick fabrics. This distance of beam’s focus reduces the angle of its scattering, which allows you to keep concentration of power even at great depths.
Laser power
In addition to focal length and material itself, there is another important component — force with which beam affects fabric. This fact adds some nuances, but we will explain everything now.
High power
As we have already learned, a short-focus lens has the smallest exposure area, and if the laser is of high power, it is fraught with excessive heating, and in extreme cases, melting of the material. To avoid this, it is better to use a lens with a medium or long focal length, they will distribute energy over a large area.
Low power
By analogy with high power and overheating of fabric with a short-focus lens, if power is not enough, then a lens with a long focal length simply won’t be effective. Low power is great for precise engraving.
Conclusion
For a laser machine, key parameters are focal length, laser power, and type of fabric being processed. The correct choice of one depends on the other two. For precise and detailed results on thin materials, a short-focus lens and low power are suitable. Average distance is universally suitable for engraving and cutting, but if thick fabrics are used, then only a lens with a long focal length and high power is suitable.
Do not forget about calibrating your machine and conducting test runs before starting production, even in small batches. Proper management and knowledge of important aspects will allow you to unlock the potential of your device, and if you want to learn more about laser machines themselves, read our article about it.
