Cutter Comp.

[camtd]

When using cutter comp.to program a cnc mill is it required or best practice to use a radius after the 90 degree or angular move and before the actual cut?

Thanks in Advance

[Prestimion]

The cutter's radius has to be set during the angular move before the actual cut. Here is an example for climb milling (cutter comp left):
G41 G01 D5 X.... Y..... F15.0
On HAAS controllers, the "D" number is the same as the tool number (T5) and the height number (H5) and is stored as a radius value of the tool (.500" for a 1.0" diameter tool). On FANUC controllers, the "D" number has to be different from the "T" and "H" values, but is still stored as a radius. I believe old FADAL controllers are like HAAS with the registry numbers, but take the cutter diameter rather than radius.
Also, make sure the angular move invoking cutter comp is equal to or larger than the radius of the cutter being used. Don't forget to disengage cutter comp after the cut with an angular move away from the part.
G40 X... Y....

[beege]

A radius move into the first cut helps blend into that cut, so that there aren't any lines from dwell/change of direction. Same goes for sweeping off when complete; use the same radius away from the part before turning off comp at the end.

[Prestimion]

Hey beege,
You're right, but I believe he was talking about the prep move, not the arc lead-in as you mentioned.

[camtd]

Hi

Here is a sample. I was wondering if the G3 radius move was needed.

N30G1Z1.063F10.
N40G41X2.0274Y.2504D2
N50G3X1.9439Y.3037I-.0684J-.0151
N60G1X1.9369Y.3021F20.
N70X1.9298Y.3004

What I have gathered from the answers is that it is needed to blend into the cut.

Thank You

[sinha_nsit]

Right.

[runangolee]

Everything above said is accurate. The only thing I might add is that when trying to avoid any dwell at the entrance of a finish cut is to have 2 lead-in moves, one to establish cutter compensation and then another at a very shallow angle in order to compensate for any dwell due to read-ahead lag. Though that may not be necessary depending on the machine, I have found this helps a lot on some older Fanuc controls.

As far as establishing cutter comp using a radius lead-in, this is generally what I do these days on the newer machines I run, and even when I'm not using cutter comp I'll use a radius lead-in just because dwell between moves is not an issue and a vertical lead-in always causes overcutting simply due to that lack of chip-load.

Naturally that all applies to lead-out as well.