Re: Very Confused!! Need help.

Johann,

My guess is that your main culprit is the fact your using a tool that wasn't designed to
handle side loads. There should be no shuddering when the chips are flying. As long as a
gantry is built rigid enough for the loads it's expected to handle its design is no worse
than any other.

Calculating the cutting speed takes a piece of info you need to get from the bit
manufacturer which is chip load. Aside from that the calculation is simple. Feed rate =
RPM * Chip load * number of flutes. The manufacturer will also tell you what you
maximum cut depth should be, but in my experience it's usually 1/2 to 1 x the diameter,
but smaller bits can be less.

I've estimated your feed rate should be 190 to 380 mm/min given hand drill speeds are in
the 1250 to 2500 rpm range and a conservative chip load of .05 mm. Since you're not
coming anywhere close to this I think you need to work out the shuddering problem
before you'll be able to get satisfactory results.

Regards,
Mike Nemesh (Aerowright)
Roswell, Georgia USA
http://webpages.charter.net/mnemesh

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Johan Van Wyk" <wykj@...> wrote:
>
> I'm using a bosch 800 watt hand drill fixed to the gantry, it has a
> variable speed and torque controller, so what I usually do is to adjust
> the speed till I get the best results on the plastic, so far I've been
> too chicken to actually try and put it through any metal type material.
> My favorite bit to use is a 3mm straight 3 flute HSS bit. At the price
> of those it's a unnerving experience when one of them break, and I've
> gone through 2 already.
>
>
>
> One thing that I saw is that there is a bit of a shudder on the drill
> when the chips actually start flying, I suppose that is one of the
> drawbacks of using a gantry style setup, the Z-axis is "hanging" off the
> rest of the machine, and I couldn't get it as rigid as I was hoping..
>
>
>
> One of you asked whether I calculated the cutting speed, and I have to
> confess, I'm really no machinist so no I haven't is there some specific
> formula for that? So far I've just been slowly in increments trying to
> ramp up the speed, I try to keep my cuts less that 5mm deep at a time,
> am I being too aggressive in how much I cut?
>
>
>
>
>
> Thanks so far anyways
>
>
>
> ________________________________
>
> From: CAD_CAM_EDM_DRO@yahoogroups.com
> [mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of lcdpublishing
> Sent: Thursday, January 04, 2007 8:01 PM
> To: CAD_CAM_EDM_DRO@yahoogroups.com
> Subject: [CAD_CAM_EDM_DRO] Re: Very Confused!! Need help.
>
>
>
> Johan,
>
> Along with all the other questions, let us know what spindle you are
> using? Is it a router, a dremel, etc.
>
> Seeing as you are breaking tools I am guessing you are using a
> dremel motor with tiny dremel bits?
>
> Chris
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com
> <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com> , "Johan Van Wyk" <wykj@>
> wrote:
> >
> > I recently finished my first homebuilt router pouter project, and
> was
> > doing some trial runs for a while now, just figuring out the best
> > software solution etc. etc. So basically I've been cutting air for
> 2
> > months now just to suss things out..
> >
> >
> >
> > One thing I now realized that I made a mistake on is my ever
> increasing
> > need for speed, so at the moment I got a good mix between speed and
> > torque.
> >
> >
> >
> > Now I started putting some wood and plastic under that cutter to
> see the
> > chips fly, and lo and behold all that speed was completely
> unnecessary,
> > I'm not able to cut anything at speeds more than approx. 5mm per
> minute,
> > what am I doing wrong??? I keep breaking bits if I go faster, or
> the
> > cuts become very dirty and especially plastics start chipping etc.
> So
> > why do I keep reading on these forums about xxxx ipm if all that
> speed
> > is wasted on everything except G00 rapids??
> >
> >
> >
> > Maybe one of the boffins on here have some idea of what I'm talking
> > about, and maybe able to help me understand this...
> >
> >
> >
> > Any help will much appreciated.
> >
> >
> >
> > BTW. To all the lurkers out like me out there, it really isn't that
> > complicated to make a machine so start already.....!!!! You'll be
> amazed
> > at the feeling you get inside the first time that machine starts
> moving
> > on it's own..
> >
> >
> >
> > Thanks
> >
> >
> >
> > Johann van Wyk
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>
>
>
>
> [Non-text portions of this message have been removed]
>