Re: [CAD_CAM_EDM_DRO] Re: My Next Router

At 11:16 AM 9/30/02 -0000, you wrote:

>1)Replace the original <probably> grade 3 bearings with grade 5 or
>better. (this can make a BIG difference)

I see advice like this a lot ... the people offering it may not realize
that not only do bearings have different tolerances according to grade, but
they still also have different clearance classes within each grade. IOW,
simply replacing with higher class tolerances may not be enough. You also
have to consider the running clearance. It is sometimes a job for an
engineer, as not only must press fits be considered, but so must the
operating temp of inner and outer races. Otherwise the bearings may still
be noisy, or they may fail quickly from overload. Personally, I don't see
much point in second guessing the makers, at least not before checking on
what they did. The rest of the advice is good!

>Use of a high vacuum, low volume rotary vane pump (Available at
>graingers, or medical/electronics surplus) with home depot closed
>cell weatherstripping works well

I programmed and helpt set up jobs on a Showa a couple years ago. Found
that tool life is a big thing both for noise and efficiency. We cut a lot
of chipboard, which is hard to hold anyhow because roughness spoils vac.
But you need both high airflow volume and high vac! I was able to get full
sheet untilization by using foam strips around vac ports in a mask over the
table. We also went to a table with many-many narrow channels instead of
larger wider-spaced holes. Managment previously had even doubled up on vac
pump to tune of $20,000 more, w/o solving slippage problem. Despite
effectiveness of masks and seals, they decided instead to reduce
utilization enough to make skeleton grip the table regardless, with maybe
50% more losses of stock. This didn't do it either, in long term. Jobs that
ran early in my tenure didn't run later. Turns out they ran carbide tooling
til it was worn as much as .005" undersize, even started a friction fire on
table one day. Naturally the table wouldn't hold work, and talk about
cutting noise! And they just would NOT LISTEN to good advice. I haven't
been in such a frustrating sitch in a long time.

Tips for successful routing will include 1) masks and seal strips, esp for
smaller parts, 2) do all drilling, surface contouring, etc first while vac
is high, and take advantage of that by using highest feed rates, 3) make
short cuts and cut out smaller parts first, 4) may be necessary to make
cuts 98% or so of way thru, then second pass them to reduce final tool push
comensurate with loss of vac at cut-thru, 5) reduce feed rate progressively
as more vac is lost, 6) change tooling every 8 hours max, depending also on
job. 7) I also found that small separate bits of skeleton often got sucked
into chip control system, clogging it ... so as needed I used to completely
chip them instead or at least cut them to suitable non-clogging size/shape
mostly by removing cusps. 8) Also, reducing chip vac will sometimes
increase table grip by leaving the cuts partially filled, and by reducing
lift at the part. 9) Finally, I worked up a simple routine to sweep table
at high speed with a spindle brush barely touching it (no tool installed)
so we didn't have to blow chip with air hose; this was better for cleaning
and it also reduced air particulates like you wouldn't believe.

Good stuff, no? Anybody want to hire me?

Regards, Hoyt McKagen


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