Re: Opinions on $250 cnc machine

>
> Hi John,
>
> I quite agree with the precision. Using 200 step motors run with a

> microstepper can do 800 accurate steps per revolution coupled to a 20tpi
> leadscrew with zero backlash and you have 0.0000625" per step. Even

> microstepping positioning is well under 0.001". Slow traversals though.
>
> For engraving it may not be an issue but engraving away the copper on a
> circuit board and/or drilling holes, the tolerances on the leadscrew

> well cause misplaced pads or holes.
>
> Were I to do it over again (which is probably guaranteed) I would

> thicker rails but in this case the 1/2" size was dictated by what I

> hand. You design looks interesting. Any chance you can post a

> the bottom axis without the metal plate in the way?
>
> Model Engineers Workshop had an article on turbine type air powered
> spindles. I don't believe Dremels have the bearings capable of

> and maintaining accuracy.
>
> John Dammeyer
>
> >
> > Threaded rod is not the best thing but I do wish I could get
> > pics of the detail it will do. It is amazing provided everything
> > fits well on the machine.
> >
> > I'm making a machine that would come Very usable but if one wanted
> > precision rod or screws it would be a simple thing to add those
> > better parts. It's modular. You can see the x-z assembly in it's rough
> > form. Mass -like you said is much better than one might guess.
> > A block of poly is maybe half what aluminum is.
> >
> > There' a "trick" to using this stuff and that "trick" is make it 1.5
> > times as thick as you think it should be.
> >
> > Rigid as can be.
> >
> > I just think it would be great it a person could have a
> > good,reliable,solid, tabletop
> > machine for less than $500 for the whole works.
> >
> > and you can.
> >
> >
> > thanks -John
> >
> >
> >
> >
> >
> >
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