First, check if the material can absorb the 1064nm laser wavelength.
Second, pls kindly check fiber laser marking machine,if on the correct focus distance marking? What’s the output laser power? If it is bigger lens? Usually the laser will be weaker for bigger lens, also the depth of focus is relatively shallow, prone to this situation.
Third, check the marking content, if it is JPG or BMP format picture.
How to check on this situation?
Use a piece of stainless steel, type TEXT, HATCH line distance is 0.05, laser power is 80%, speed is 500, chose Continue, then marking, up and down marking head, then we will find where the problem from.