Re: Acme, ball screw or rack for wood router?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "echnidna" <echnidna@y...>
wrote:

> Considering that rack, belt and chain drive will all hold .002 and
> perhaps down to .001, while you only need .010 means that the

expense

> and added complexity of ballscrews isn't warranted. Ballscrews and
> leadscrews really belong in the non dusty environment of

metalworking

I have to hold that tolerance through hundreds or even thousands of
moves. Typically I hold .005 or better after several thousand lines
of code. On any individual move I can hold .0005 or better. Couple
that with it's a 6' wide gantry with dual drive screws, and I am
pleased with the tolerance. The decision to go with long ballscrews
was largely financial; it was what I could get used for a really low
price. The complete set of motors, housings, ballscrews, rails and
mounts for 4 axis cost me less than an evening out at a good
restaurant. Would I go spend thousands on a new set of ballscrews
and rails? No. Since the Z axis of my machine is setup to take
interchangable heads there may come a time I want to do some
precision work though and I am confident my machine would work.

Having never built a belt or chain driven machine I can't attest to
any level of accuracy they will or will not hold. In working with
large CNC punch presses, lathes and mills I never saw one that ran
off belts or chains...maybe it's a marketing thing.

> machines. In the list archives somewhere is a description of a
> commercially made chain drive large gantry router capable of high
> speeds at .002. The manufacturers of this well reputed machine
> eventually went to rack drive, despite comparable accuracy between
> chain and rack. They only changed due to marketplace perceptions

that

> rack was better. That decision was purely a marketing choice.
>
>
>
>
> As for dust extractors, none are technically perfect and some
> ultrafine dust will occur. Not only is this a mechanical nuisance

but

> its also a health hazard, which can be extremely hazardous

depending

> on specific wood species (or resins present in manmade boards).

Have a

> look at any commercial woodshop with the huge inbuilt extractors,

they

> are all dusty to some extent.

I recommend a respirator when working around any tool that creates
fine particles. There are, as you metioned, species of wood that are
dangerous to breath. The issue we were addressing form the question
is one of keeping a level of dust and chips off the moving parts so
as not to cause wear or binding. I clean my machine often (maybe too
often because it makes me feel good) and keep everything lubricated
and as dust free as possible. MDF is a real treat to cut and spreads
a fine mist of nasty particles all over the shop. I have to stop and
clean up often.

The point I was trying to make to the requester is that knowing what
you want to make with your machines should determine the design
approach.

>
>
>
>
> Regards
>
>
> Bob thomas
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "caudlet" <info@t...> wrote:
>
>
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "ddgman2001"

<sheldon@d...>

>
>
> > wrote:
>
>
> > > What is the best drive system for a wood router considering the
>
>
> > dusty
>
>
> > > environment?
>
>
> >
>
>
> > Totally depends on your objectives. I use my wood router to do
>
>
> > complex carving and sign work. Deep carves require several

passes

>
>
> > that have to register pretty close. So in thousands of moves I

have

>
>
> > to be able to hold .010 or better or it will show in the carving

and

>
>
> > take a lot of handwork to clean it up. If on the other hand you

are

>
>
> > cutting out furniture parts and large panels then less tolerance

is

>
>
> > acceptable. You need to select your drive mechanism based on the
>
>
> > finish product you want to turn out.
>
>
> >
>
>
> > I agree with the other members about using rack and pinion or

even

>
>
> > chain drive for lower tolerance applications. Yes, dust is a
> problem
>
>
> > but with adequate dust extraction at the cutting point and proper
>
>
> > shielding of the drive mechanisms and ways, its a problem that

can

> be
>
>
> > solved. They make bellows and way covers that accordian up for

both

>
>
> > the ways and/or the ballscrews themselves. The material is not
> cheap
>
>
> > running 30 to 35 bucks a linear foot but for extreme environments
> its
>
>
> > cheap insurance.
>
>
> >
>
>
> > Giving some thought to where you mount the ways and drive

components

>
>
> > out of the direct path of flying chips will go a long way in
>
>
> > reducing problems.
>
>
> >
>
>
> > As for speed, I found that while it's nice to have rapids that

are

> as
>
>
> > fast as possible the type of cutting (often using .125 or .0625
> bits)
>
>
> > I am doing limits my speeds to 60IPM or less except for large

areas

>
>
> > doing roughing cycles.