RE: [CAD_CAM_EDM_DRO] Re: Very Confused!! Need help.

A couple of things possibly.

I doubt whether the drill will be fast enough for a cutter of that diameter.
Most electric drills will go up to about 4000 rpm, people pick tools like
dremels because they want 10000 to 30000 rpm. I used to hand drill a lot of
PCB's many years ago, in those days cheap PCB drills were good for 10,000
rpm, a commercial machine was 30,000 rpm and was much less wasteful on drill
bits.

The second problem will be the judder, quite probably as it judders the
cutter gets pulled in to take a deeper cut. Sometimes if you feed in the
opposite direction it may be better. And a higher speed and shallow cut
might help. Most modern drills are plastic bodied, and the bearings are very
poorly held, so there is a lot of play in just the drill itself, also the
drill motors, chucks gearbox etc will probably not be that finely balanced
leading to more vibration. In this case cutter won't spin about the centre
of the cutter, but about the centre of balance. So may not be your gantry,
may just be the drill, or even resonance between the two of them.

Last thing I doubt whether the eccentricity of a drill chuck itself is good
enough. When I bought my hand hobby mill 17 years ago, a collet chuck was
too expensive. I thought a good drill chuck would do to hold mill bits, so I
bought a good precision rohm chuck. If you looked at the metal with a strobe
on a fine cut only one side of the cutter was being used, cutters jammed up
with swarf, lost their tips and broke frequently.



Regs Mark







_____

From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Johan Van Wyk
Sent: 05 January 2007 06:29
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: RE: [CAD_CAM_EDM_DRO] Re: Very Confused!! Need help.



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_ <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_ <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
DRO@yahoogroups.com] On Behalf Of lcdpublishing
Sent: Thursday, January 04, 2007 8:01 PM
To: CAD_CAM_EDM_ <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
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_ <mailto:CAD_CAM_EDM_DRO%40yahoogroups.com>
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]
>

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