Re: Any "Best Practice" Recommendations for clearing chips and feed/speed when

I use a shop vac as the main power device to pull chips from my work
space. I use the standard shop vac with a short tube to a pre-
canister that is a 5 gallon bucket. The pre-canister collects the
bulk of the chips and since there is little actual duct, the main
chamber takes a long time to fill.

if you are trying to pull long stringy chips like those generated on
a lathe or drill press, you will find they get stuck in the pick up
tube. better to let them fall and sweep them up.

one note on the ampliphication of air flows, the Coanda effect is
really summed up that as air (or any fluid) passes a surface, the
boundry layer of the surface attracts the flowing fluid and the fluid
will then bend to conform to the surface. One of the most easily
demonstrated real world applications it the ceiling diffusers you
find in restaurants. The discharged air travels along the ceiling
for upwards of 50 feet before it drops down. The distance being a
factor of the velocity of the air through the diffuser. The diffuser
manufacturers call that throw. a typical diffuser will have 12 foot
throw for a class room or office.

another note about the induction of flows, a 25 cubic feet per minute
induction air stream (the push) will pull a much larger air quantity,
but not increase the velocity of the second air stream, in fact, the
air inducted will be slower and each time the pipe or chamber
expands, the velocity will drop, which is what you ultimatly want.

also, 1,400 feet per minute exhaust duct velocity is the velocity in
which rain will not fall down into an open exhaust stack. a good
number to remember for your vertical duct sections.

if you want to pick metal chips, you will need a high velocity air
stream. this means a small opening or higher power.

search on cyclone duct collectors or vernturi dust collectors and see
the the industrial units operate.

Dave

--- In CAD_CAM_EDM_DRO@y..., Bill Vance <ccq@x> wrote:
> You need a regular dust collection system, not a shop vac. One of
the best, and
> easiest to build is the vortex system, (see rec.crafts.woodworking
archives).
> It's the same thing with grain silos; Enough fine particulate
matter plus
> commutator/switch sparks equals instant explosion. There are
several ways to
> move the air into/from a dust collector, but you want a zero sparks
solution.
> One such solution would be to use an air amplifier. These work on
the Coanda
> Effect, which has to do with how gasses and liquids move across a
curved
> surface. Coanda was one of those multi-discipline geniuses who
lived back
> around the early part of the last century. His main gig was
organic chemistry,
> but he also designed, built, and flew, the first jet airplane. An
air
> amplifier is a three opening unit that acceptss air from a
compressor, and uses
> it to induce an airflow into one side, and out the other. The
specs I've seen
> indicate that it works on a 1:25 ratio; I.e., a 10 mph flow from
the
> compressor equals a 250 mph flow through the device. This spec is
the same
> from several manufacturers, so I presume this is the max for
practical air
> moving devices, though no doubt the figures and sizes are
different for denser
> stuff like liquids.
>
> While I'm on the subject, try to segregate as much as possible the
results of
> your aluminum work from your ferrous metal work. Rust, (ferrous
oxide), mixed
> with aluminum oxide equals thermite, which burns, (redox reaction),
in the
> neighborhood of 5 or 6 thousand degrees, and has been known to self
ignite.....
>
> Bill
>
> On Sun Dec 23 00:45:12 2001, glee@i..., <glee@i...> wrote:
>
> >Well, tonight I switched from cutting wood to machining 6061
aluminum with
> >my Sherline Mill using a 1/8" end Mill to Mill a part 1" x 1.6"
by .25"
> >
> >It was an education to say the least. In the process of
documenting the
> >results, I arrived at some questions:
> >
> >When I was practicing on plastic and wood, I ran the ShopVac with
the
> >intake nozzle next to the cutter. This way, it was a superbly clean
> >process.
> >
> >When cutting aluminum, I used WD40 From time to time to lubricate
the
> >cutter. I noticed that the WD40 label says "Highly Flammable -
propane." I
> >decided that I would not use the ShopVac and the WD40 at the same
time for
> >fear of starting a fire inside my ShopVac and making my ShopVac a
flame
> >throwing jet engine. (Am I correct in this concern)
> >
> >Since I was no longer using the ShopVac I now had a micro chip
problem.
> >This was further complicated by the WD40 (used in moderation) and
resulted
> >in an aluminum "Slurry" surrounding the cutter and resting on top
of the
> >part.
> >
> >No problem, I thought. I used an acid brush to brush away the
debris -
> >still wishing I could run my ShopVac.
> >
> >Well, combine the above with the lessons I learned about climb vs
> >conventional milling as well as and feed/speed rates, I have
probably
> >broken many rules tonight not to mention possibly destroying my
cutter. At
> >least I am learning and having fun while making chips.
> >
> >So, now that I have shared the gory details, I will ask for
> >feedback/correction:
> >
> >1. Any ideas on the removal of chips
> >
> >2. Any ideas on the lubrication of the cutter (It's an 1/8" end
mill)
> >
> >3. I experimented with feed rates and speeds as I was encouraged
to do. I
> >came up with 2500 rpm, 5-10" ipm on XY and 1 ipm on Z seemed to
work. I
> >would welcome some recommended rates for my sample part
> >
> > Spindle Speed?
> > Feed Rate XY?
> > Feed Rate Z?
> >
> >This is a learning adventure for me. I'm open to all kinds of
feedback so
> >fire away :-)
> >
> >Thanks. I cant wait to check my email in the AM to see what kind of
> >responses I get....
> >
> >
> >Eric Mack
> >glee@i...
> >
> >
> >P.S. I am documenting my adventure to try and write a tutorial to
help some
> >future lost soul do this. For now, I return to wood and plastic for
> >practice until I master the speed/feed stuff.
>
> --
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