Re: [CAD_CAM_EDM_DRO] Speeds and Feeds and Torque and Power

Frank wrote:

> I've finally got my gantry mill together and I am having problems
> getting the speeds and feeds right.
>
> I've been cutting aluminium with small HSS slotdrills, 3mm and 4mm.
> I've already broken 3 cutters, and I can't work out why. (one plus is
> my x/y/z motors have more than enough torque)
>
> I've been using Visual Mill to generate my gcode, and using its
> internal speed/feed calculator. For 4mm HSS slotdrill, cutting
> aluminium, it recommends...
>
> surface speed - 183 m/min
> spindle speed - 14562 rpm
> feed/tooth - 0.13mm
> cut feed - 3786 mm/min
>
> These numbers are way too scary for my first cuts, so I tried to wind
> them down a fair bit (which may be my problem) - sorry can't remember
> exactly what I used.

You don't mention depth or width of cut, or the alloy. It all
wakes a difference. Also, the stiffness of the workpiece and
fixture. .13 mm feed/tooth sounds WAY too aggressive for such a
small HSS cutter. My McDonnell-Douglas slide rule says under
1/2", the feed/tooth should scale with the inch size of the
cutter from .010" per inch. So, for 3mm, that should be about
.001"/tooth, or 0.03mm/tooth. I use a depth of cut no more than
1/2 the diameter when plunging full width into the work, and
reduce the feed considerably.

If you can see any deflection in the cutter, you are already
beyond the limits. I'd switch to carbide in these sizes, they
are quite cheap and very durable (just don't drop them).

Jon