On Monday 24 November 2008, Andrew Ayre wrote:
>Gene Heskett wrote:
>> On Monday 24 November 2008, Andrew Ayre wrote:
>>> Gene Heskett wrote:
>>>> On Saturday 22 November 2008, Andrew Ayre wrote:
>>>>> Gene Heskett wrote:
>>>>> 30 IPM is an arbitrary value that I picked that I didn't feel
>>>>> comfortable going above. If I knew I could run it faster I would, but
>>>>> I'm just starting out.
>>>>
>>>> One of the problems that pushes the speed up is that the cuttings are
>>>> part of the bit cooling, they carry away the heat. Cut too thin (on
>>>> either edge) and the bits get hot too fast. If you are seeing burns,
>>>> slow the bit rpms down, speed up the move, or replace the bit, its
>>>> getting dull.
>>>
>>> This is an area I am still completely unsure about. I get chatter and
>>> nothing I seem to do helps. I've tried slowing the spindle down,
>>> increasing the feedrate, slowing the feedrate, etc. I guess it is slight
>>> runout in the spindle.
>>
>> The later dremels have an elastomer seat cushion for the spindle nose
>> bearing, and its rather loosely coupled to the motor shaft itself.
>> Another friend made a new alu nosepiece with a precision seat for that
>> bearing for his dremel and it works much much better. Also, the last one
>> I bought had a seriously defective 1/8" collet, it allowed, and demanded,
>> about a 20 thou runout. I spotted a card of collets at Lowes, and a new
>> one runs nicely.
>
>I had the collet problem when I first started. Solved with a new collet.
>
>> There is, and I forgotten the name, a german maker of such goodies that is
>> very highly thought of, maybe someone will chime in with more details. I
>> believe its about the same diameter as the dremel, but an inch or so
>> longer.
>
>I am planning on switching to a laminate trim router, perhaps by the end
>of the year. I just don't think a Dremel is up to the job.
It isn't, way too much rubber in the front shaft mounting.
How about something with a longer nose, like a Dewalt DW888? Or the higher
priced Makita that has an easily mounted body form.
>> I looked at that machine some time back and came to the conclusion it was
>> a 6 month machine. MDF warps over time when weight is applied, so I'd
>> think it would be hard put to maintain a flat bed over time.
>
>A slightly non-flat bed doesn't concern me too much right now. If needed
>I plan to skim the surface of a sacrificial bed every few months.
You may want to shrink it a bit in that event, just so you can skim it
completely. Edges sticking up are unhandy at best. :)
>I will
>likely do that if I switch to PCB milling, which requires depth
>precision. If you go to millpcbs.com the owner of the site is getting
>excellent results with an older FireballCNC machine, also made of MDF.
[...]
>I'm not running the rapids at full speed, which is the only time the
>problem showed with pre-2.2 CVS HEAD. Are you saying that I should now
>be able to go at the full speed of my PC?
>
I don't think so, unless you can scare up another 40 volts to feed the motors
drivers. At about 2.3 amps, and 27 volts, I'm seeing loss of torque when the
going gets hard at about 10 ipm. But my xy screws are 20 tpi too, so that's
actually decent motor rpm. Unloaded and well lubed, 30+ ipm, but don't ask
it to push a bit at that speed. :)
[...]
>My Z-axis weights perhaps 3 - 4lb plus the dremel. The 0.0003" was an
>average of several backlash measurement tests. There is no hardware
>backlash elimination.
That is great performance then.
--
Cheers, Gene
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
Education is the process of casting false pearls before real swine.
-- Irwin Edman
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