Re: Climb Milling

Fred,

Nice post!

In climb cutting the full chip load is taken at the beginning as each
flute of the cutter enters the material. The chip load is reduced as
the cutting edge moves through the material toward the "already cut"
surface. This means that as the heat from the friction of the cut is
building, the area within the chip for the generated heat to
dissipate is getting smaller. So the heat builds up, since chips are
the MAIN way of dissipating the heat of a cut.

With conventional milling the chip load starts at zero and INCREASES
through the cutting action. The cutting edge will "skid" if it is not
sharp enough to enter the material... This friction will dull the
cutter, and the cycle repeats.

Visualise this by thinking of cutting a taper in a piece of wood with
a handsaw. If you start at the "thin" end (the point) you are
conventional cutting, and you may find that the saw is hard to start.
Flip the board around(which will be akin to climb cutting), and you
begin the cut in the "thick" end quite easily. When you get to the
thin part, the material will sometimes "split" before the cut is
complete. The sharper the saw(or cutter) the easier it is to deal
with the "thin" part, regardless of which direction you are cutting.
However, the climb cut will be easier to maintain with a cutter that
is less-sharp, all else being equal.


______ start here to simulate conventional cutting
| /|
| / |
| / |
|_ /___|
|
Start here to simulate climb cutting

Hope this helps.

Ballendo

P.S. If you think about this, you will see why a stiffer machine is
needed for climb cutting. Since the chip load is BEGUN at maximum,
the shock is transfered to the machine abruptly. With conventional
milling, the chip load starts small and increases steadily through
the cut, and the machine does not get the same kind of "shock
treatment". Imagine holding onto a rope (vertically) where weights
are being steadily added to the other end. Now imagine that the
weight you are/were able to hold this way is dropped all at once onto
the end of the rope. Make sense?

--- In CAD_CAM_EDM_DRO@y..., "Fred Smith" <imserv@v...> wrote:
> --- In CAD_CAM_EDM_DRO@y..., ron ginger <ronginger@r...> wrote:
<snip>
> Ron I think you have mixed up the purpose for backlash
compensation.
<snip>
> 2) Backlash compensation or other kinds of machine error correcting
> in software will place the tool in a more accurate position, which
> means that you can make a part with tighter tolerances with a less
> accurate and less expensive machine. Usually this results in the
> ability to accurately and reliably machine to tolerances 1/2 as
wide
> or 1/3 as wide. If you can hold +/- .003 without error
compensation,
> with it you can probably hold +/-.001 to +/-.0015. A fantastic
> improvement in real capability with just a software cost, not the 2-
3
> times the machine cost that it would cost you to do it with a more
> accurate milling machine and tooling.
>
> Aside from the "supposed" improvements in surfaces from climb
> milling, the real reason to use climb milling is for roughing, not
> finishing. It takes approximately 1/3 the horsepower to climb mill
> as compared to conventional mill the same material. This applies
to
> the spindle motor and the axis drive motors. This is one reason
that
> coolant becomes mandatory with CNC machining of metals. The amount
of
> cutting is dramatically greater and the heat build up in the
material
> and the chip, can become catastrophic if not constantly doused with
> coolant.
>
> Best Regards,
>
> Fred Smith
> IMService