How to Changing the head lens? How often?

[Williamhaxy]

Hi All,
I have recently started using my first laser, a Bysprint 2.2Kw machine. I am looking for some advice on how often the lense in the head should be changed. Bystronic say take it out and clean it every shift and if there are ANY marks which do not come of then you should change the lens! At £200 each, i dont want to change them unnecessarily so is this true - or can you get away with the odd mark, or light scratch if it is still cutting well? Are lens really that fragile that a scratch can make them heat up and brake?

When cutting 4-5hrs a day, ive been told i should get 6weeks or so out of a lens... does this sound right?

Thank you for all advice given, much appreciated!

[Vgzofmsan]

I just clean mine when needed.

[GregoryDrus]

After some time using, you will find some visible change of the focus. Then it is the time for changing. Otherwise, the beam will become weak and inaccurate, and the focus will heat up sometimes and the cracks will become larger.