Originally Posted by
CaistorAl
I can see two things happening here.
You have programmed your tool to pocket it out in a zigzag pattern.
On the "zig" the cutter will climb (down) cut, on the "zag" it will conventional (up) cut.
In other words, in one direction the wood chip is starting in the uncut material , and on the return trip it's starting on the finished face.
May I suggest not using parallel linear pocketing, but parallel spiral from the inside out, climb cutting, then the finish pass will skim the pocket walls and leave a beautiful finish