Wavy skin at the base of the piece

[Guil]

On some prints, i got a wavy skin at the base of the piece.

( https://flic.kr/ps/3Xc26o )

Somebody knows why it happen and how to avoid this ?

Thanks,

[fantasy2]

You need to clean your optics(mirror, glass window, galvo mirrors)

[Guil]

OK, thank you very much !