8. Remove the clamping ring.
9. Take out the protective glass.
10. Clean the protective glass with a dry or damp cloth on
both sides.
11. If necessary take out the sealing ring and clean the
housing with a dry or damp cloth.
12. Insert the sealing ring again.
13. Now carefully insert the protective glass and clamping
ring and fixate the clamping ring using the key tool.
14. Fix back the protective glass housing on the laser head.