Hi

I am new in the world of CNC and i would like to ask a question.

I try to make a small piece in aluminium 6061. My DOC is 0.25 and feed rate is 900mm/min at 11000RPM. My probleme is that I got chatter only when my x and y go up. when is go down it like to cut butter. My end mill is HSS 3mm and the shank 6mm

thank you and sorry i try to make my best im french :/