1. Whether the focal length is adjusted properly.
2. Whether there is too much paper soaked in water on the engraved material, or whether there is too much water on the paper.
3. Whether the laser tube is aging.
4. Whether the optical path is correct. (Recorrect)
5. The lens is dirty and the dust is too thick.
6. Broken lens.
7. The laser tube head is contaminated.
Dutch 
English 
Spanish 
Portuguese 
Russian 
Arabic 
Italian 
French 
German 
Swedish 
Greek 
Czech 
Polish
I am regular reader, how are you everybody? This piece of writing posted
at this website is actually good.
Hi there, I found your site by means of Google even as searching for a related topic, your
website got here up, it appears great. I’ve bookmarked it in my google bookmarks.
Hello there, simply was aware of your blog through Google, and found that it’s truly informative.
I’m going to be careful for brussels. I will be grateful should
you proceed this in future. Many other people will be benefited from your writing.
Cheers!