Neje A40640 Focus adjustment for engraving

hello, I’ve already watched several of your videos, where it is described that the lens should be set to 2.5mm for cutting.

How far do I have to unscrew the lens for an engraving?

The following text is written on neje Wiki.

Understand the principle of focusing: if you use it for engraving, you can focus on the surface of the object.
When the focus is adjusted to about 33mm from the light outlet with a flat-blade screwdriver, you can get a focus of 0.13*0.13mm, which is suitable for engraving and fast cutting of materials smaller than 10mm.

From the photo you can see that the focus is not 33mm from the surface of the material to the starting point of the light.
It’s more in the middle of the material. What is right ? Unfortunately I do not understand it.

Greetings Martin

When cutting thick materials, it is best to calculate the focal length from the half position of the thick material, so that the cutting surface will be more uniform

But I don’t want to cut. I want to engrave and there is no video how to adjust the lens. As a reminder, in a video you should set 2.5mm for cutting. But there is no value for engraving

This is not a fixed setting, the A40640 is adjustable focal length, we just adjusted one of the settings, for reference only, engraving can adjust the cutting speed, power, focal length

sorry, that’s not very helpful.
In the first post I put a picture and a description. there it is written that the perfect lens setting is 33mm from the object surface to the light exit. but in the picture the 33mm is in the middle of the object.

You can do the same setup as we tested