Lens & mirrors
Mirrors and lens in your machine is actually very important.
The beam created in the laser tube travels between (at least) three mirrors and one lens before hitting your material.
The first upgrade everyone should do to their K40 is to upgrade the mirrors and lenses, as the provided ones with the machine are budget stuff noone should use, throw it away.
I don´t say this because we want to sell mirrors, order from Ebay if you want, but atleast change your mirrors, you will be happily surprised when you installed the new mirrors and lens.