Re: Better luck machining aluminum

On 2010-07-30, Ed Huntress <huntres23@xxxxxxxxxxxxx> wrote:

"Ignoramus18915" <ignoramus18915@xxxxxxxxxxxxxxxxxxxx> wrote in message
news:jOCdnfuOhpcfeM_RnZ2dnUVZ_sOdnZ2d@xxxxxxxxxxxxxxx
On 2010-07-30, Ed Huntress <huntres23@xxxxxxxxxxxxx> wrote:

"Ignoramus18915" <ignoramus18915@xxxxxxxxxxxxxxxxxxxx> wrote in message
news:wp6dnQHE4_XaTc_RnZ2dnUVZ_uqdnZ2d@xxxxxxxxxxxxxxx
On 2010-07-30, Jon Elson <elson@xxxxxxxxxxxxxxxx> wrote:
Ignoramus5687 wrote:
I have decided to dial way down this time. Again, I am making a mold
cavity in aluminum for making a kids wax toy (toy railroad supports).

This time I am using 1200 RPM and 1 IPM, and in addition I use WD-40.

The good news is that nothing gums up, the bad news is that the speed
is ridiculously slow. Yes, it is CNC, but still.

Next thing on my list is getting coolant to work. I have a
professional coolant tank with motor etc and also a little 1/70 HP
pump that works great in plastic buckets. I think that I will use the
latter Then I can go at the same 1200 RPM but at much higher feeds.

I'm not sure coolant really helps pick up the feedrate. From the other
thread it seems you are
using a 3/8" endmill? I'd probably use 1800 RPM there, and for a
4-flute cutter I'd feed at
about 10 IPM. And, much better to take lighter cuts and keep the
cutter
moving rather than taking a deep cut and crawling.
At least, that's MY method.

I think that part of my problem is that I use a ball endmill. I will
mess more with it on the weekend.

It can be difficult to get adequate surface speed near the center of a
ball-nose cutter. It's tricky to program them for complex cuts, and
plowing
through solid metal with one is problematic.

You usually use them to get the radius you need when you're cutting only
on
one side, and even then, you have to program speeds and feeds carefully
so
you aren't pushing the center of the ball at a rate faster than it will
actually cut chips. Profiling is especially tricky.

As for speeds, you can't run an ordinary mill at surface speeds in
aluminum
that are too fast for a carbide cutter. With a 3/8" endmill, you can't
turn
it too fast for HSS. And that's even running dry.

Maybe I should change the whole program. I need to cut out a circular
area of two nested cones:


\__ __/
\___/

Maybe I should get a regular square end mill and mill out two circular
pockets (wider on top and narrower on the bottom). Then change tool to
ball endmill and finish the sides and bottom.

i

That's how it's generally done. If you can find some info on CNC moldmaking,
you'll learn a lot about this kind of job. I haven't checked recently but
some of the CAD and CAM companies have, in the past, had illustrated online
descriptions of their pocketing, profiling, and contouring routines.

If my old articles on the subject were still online, I could point you to a
couple of them. <g> I covered the subject for _Machining_ and _Machine Shop
Guide_.

That's why I don't want to do CNC at home. It's too close to what I did for
work.


I do computer programming at home, and at work, I like it. No C++ at
home though.

i
.

Relevant Pages

  • Re: Better luck machining aluminum
    ... latter Then I can go at the same 1200 RPM but at much higher feeds. ... 4-flute cutter I'd feed at ... I think that part of my problem is that I use a ball endmill. ... one side, and even then, you have to program speeds and feeds carefully ...
    (rec.crafts.metalworking)
  • Re: Better luck machining aluminum
    ... This time I am using 1200 RPM and 1 IPM, and in addition I use WD-40. ... 4-flute cutter I'd feed at ... I think that part of my problem is that I use a ball endmill. ... one side, and even then, you have to program speeds and feeds carefully ...
    (rec.crafts.metalworking)
  • Re: Better luck machining aluminum
    ... This time I am using 1200 RPM and 1 IPM, and in addition I use WD-40. ... much better to take lighter cuts and keep the cutter ... I think that part of my problem is that I use a ball endmill. ... As for speeds, you can't run an ordinary mill at surface speeds in aluminum ...
    (rec.crafts.metalworking)
  • Re: Better luck machining aluminum
    ... This time I am using 1200 RPM and 1 IPM, and in addition I use WD-40. ... much better to take lighter cuts and keep the cutter ... As for speeds, you can't run an ordinary mill at surface speeds in aluminum ...
    (rec.crafts.metalworking)
  • Re: Machining A Flywheel
    ... O/D was a bit larger than the OP's flywheel. ... getting through the hard surface skin but anything less than 100 rpm would ... insert catalogue suggests anywhere from 200 to 500 for grey cast iron ... somewhere in the middle seems to accord exactly with the speeds I use ...
    (uk.rec.models.engineering)