CNC Milling newbie

[weiyungst]

Hi,

I am a fresh newbie, currently working on milling off copper leads on computer chips. The whole square copper surface on the top of the computer chip has to be milled off. I'm using the EMCO Concept Mill 55 machine for CNC implementation. This machine is currently equipped with a 0.125" dia. 30 degree helix - rhs/rhc submicron grain carbide tool (http://www.garrtool.com/viewitempublic.jsp?edp=13070).

Can anyone suggest on how I should decide on the feed rate, spindle speed, and entering angle?

Using technical data recommendations from the supplier, I tried calculating using SFM = 375 and ipt = 0.00145

This gives me a calculated spindle speed of 11460rpm and 66.47ipm feed.

The speed range on my machine is only 150 - 3500rpm and thus it is clear that it is impossible to reach the calculated value. What should I do from here? Is it advisable to run my machine at 3500rpm, or should it be slightly lower to avoid killing the machine? How should I change my feed accordingly?

Also, what is the shortest path for milling off a complete square surface? Currently, it's in simple zig-zag pattern. When starting the milling, should there be an entering angle or can I mill straight in from the side?

I am totally new to this art and so any feedback would be valuable!


P/S: I noticed that even though i have a fixed spindle speed in my CNC coding, when the feed is increased, the machine increases the spindle speed automatically as well. Is that normal?