Re: [CAD_CAM_EDM_DRO] About to start building a CNC wood router

>
>
>>Especially since I'm
>>homebuilding my own board. what can I say? I'm a nerd!
>>
>>
>
><grin>
>

Do I sense a little nerd solidarity forming here? :-) Would it help
you to know that I still have a TS1000 with ZX81 motherboard? hehe

>>Anyway...like the subject line says, I am about to start building the
>>machine itself. And, I'm trying to do it on the cheap, while
>>maintaining some level of precision. Unlike metalworking setups, I
>>don't require a level of precision measured out to 10 decimal
>>places...the wood will move more than that with changes in humidity! A
>>few thousandths of an inch would be nice, though. My intention is to
>>build wooden (laminated material) clock parts, so reasonable precision
>>is going to be a priority.
>>
>>
>
>And the size of this project is?
>

Sorry -- I'm still gathering surplus parts, and the final design won't
be completely finished till I have all the parts. Since I'm salvaging
things like motors from printers...my design has to be a little more
flexible than I like.

Anyway, as to size, I've identified need, want, and acceptable
compromise for my first attempt. Here're my thoughts, so far.

Need = just over 4x4" table...my largest clock gear could be cut on a
table this size.

Want = 49x97" table, the exact size of the largest sheet goods I can
easily get in my area...MDF. It's 1" bigger in each dimension, than any
other sheet good.

Acceptable compromise = 12x18" table, which I think is managable for a
first time effort. It gives me a large enough area to cut almost
anything I actually need, and some room to grow, while not requiring
creative solutions to flex over an 8' long active surface. Parts much
larger than this, in the types of woodworking I actually do, do not
usually require the precision available to me on a CNC machine. And,
since I know of nowhere to scavenge steppers of a size that would make
sense for a 4x8' table, the parts are, currently, unavailable to me.

Since this is a wood router, and my intention is to do primarily 2D
parts, my Z axis travel will be quite limited. 2 or 3 inches, maximum.

Of course, as with most plans, changes will undoubtedly be made as I see
creative solutions to my problems, and ways to integrate the scavenged
parts into the design. However, this is as close as I've come to a
final design. I've decided on a moving gantry design, which will span
the 12" dimension of the table. I've also decided on screw drive for
the motion...directly coupled to the stepper shafts. For a small
machine, this sounds managable...for something larger, the design will
have to be refined, significantly. For example, whip on a long lead
screw would be a killer...a rack would be a more appropriate solution.

>>Here's my problem. I live out in a small country town...our primary
>>sources of parts are WalMart, a small local hardware store, and some car
>>parts stores. Thankfully I'm a nerd and had some old HP LASER printers
>>that I could scavenge some steppers from -- 100 oz in. Not huge, but
>>they should be sufficient for a woodworking lathe, and they're of very
>>good quality.
>>
>>
>
>www.herbach.com for herbach and rademan, good quality steppers, but
>low in-oz, little bigger than 100 oz/in, but not bigger than 200 right
>now.
>

Well, I've already got the steppers I'm going to use. Like I said, they
were scavenged from old Laser printers I had around -- 3 minebea
astrosyn steppers, 6 pin. They're mismatched, but since I'm going to be
building the boards anyway, this doesn't present a huge problem.
Largest one is 100 oz-in...a little small, but it should suffice for a
smallish proof-of-concept unit, and I'll build with an eye towards
upgrading the motors later.

>look for electronics goldmine on the web, L298 drivers with heatsink
>for 2 dollars each. Go look at the specs, you will probably want the
>
>

I didn't think the L298 did step translation -- the Allegro 3967 does
translation and drives small loads -- hook up to some power transistors
of appropriate size, and I could drive anything I wanted. It does
microstepping, too...and they give samples! :-)

>them. For the board, if you can do printed circuit boards, you will
>be *very* happy. www.mgchemicals.com has a good PC board kit, most of
>this you can breadboard yourself. I'd recommend the most dense
>negative you can get, period.
>
>

Like I said, I took apart *some* of my LASER printers for motors...I
have an HPLJ-4ML on this machine, and it prints beautifully. A little
transfer paper, and I can easily etch. Of course for a proof-of-concept
board I'll probably just wirewrap it...proof the circuit...and then etch
(or mill?) some boards. Alternatively, I also still have an old pen
plotter -- they do make an acid resist pen!

>also for some things, like the z axis, you may want to go to linear
>bearings. www.mcmaster.com you can get 1/2 inch ceramic bearings
>(need to be lubricated, but tolerate dust a bit better than linear
>ball bearings) for under 10 dollars each.
>

My current intention is to use rollerblade bearings, some of which are
built with a dust shield. I've salvaged some beautiful, if a bit short
(just under 12") rails from the LASER printers which I thought would
work very well indeed. HP designed good products...

Would these ceramic bearings be any better than a homebrew linear
bearing? This is the basic design I'm intending to use...simple, and
from the looks of it, quite robust.
http://www.rudijanke.de/Home/Projekte/CNC-Frase/CNC-Frase_Mechanik/hauptteil_cnc-frase_mechanik.html

>>lead screw and the anti-backlash nut. The only threaded rod I can get
>>in this town is allthread, which is 60 degree standard screw thread.
>>
>>
>
>Ick...
>

Tell me about it...but in its defense it is cheap, commonly available,
and seems reasonably consistent. Being rolled, I would expect
consistency between adjacent threads, but I may be wrong. It wouldn't
be the first time.

I'd still prefer ACME threads, and am pursuing this...hopefully I won't
have to make the 100 mile trip to Dallas (TX) just for threaded rod, though.

>Acme Rod is surprisingly inexpensive. Enco has a sale on it, IIRC....
>www.use-enco.com. Available in 3 and 6 foot lengths, but you're
>likely to pay a bit more for shipping if you get the 6 foot length.
>Nuts are more expensive than not, but the inexpensive plain variety
>can be turned down. (Hint: turn it down on the shaft to make it
>centered),
>
>
>
>>Not the best for transferring loads. Is this going to cause me trouble
>>in the future? I mean, I know it'll work, but will it work well enough,
>>and for a sufficiently long time? Should I just bite the bullet and
>>mail order some acme threaded rod? Where can you get it? My background
>>is not in machining, so I don't know the parts sources!
>>
>>
>
>You don't have a lathe? Access to one? Drill press I hope....
>

I have a very well equipped woodworking shop, with most power tools
including more than a few special purpose ones. Almost any kind of saw
you can think of, drill press, 36" bed lathe, etc... Tools aren't my
problem...skill is my problem. Or, lack thereof. ;-) My interest in
CNC is the level of precision that can be had...far better precision
than I can manage by hand.

>>And, the anti-backlash nut. Obviously nothing like this is going to be
>>
>>
>>Simply tapping "some" material should
>>not provide greater precision than a storebought nut...or would it?
>>
>>
>
>Might, but an Acme thread is an expensive tap.
>

There's a local place, believe it or not, that carries all sorts of
taps. They don't know what an ACME thread is, but they carry the taps!
Not the rod, screw, nuts, etc..but yes to the taps! And, besides, if
I was to use a plastic material, I could just use a short offcut of the
threaded rod itself, as a tap. I've done it before!

>>I appreciate any help or insight you can provide...
>>
>>
>
>Some of this is possibly OT for this list, so please contact me
>directly if you need more information. All these places do ship by
>UPS, and even in a major metropolitan area, you'd be surprised about
>what you can't find, and how expensive it is otherwise.
>

I can't see how it'd be OT...it pertains, directly, to the design and
construction of a CNC machine. Admittedly low end...but a CNC machine,
which is right in line with this list's charter.

If you want to contact me off list, though, just hit reply to sender.

-- Chuck Knight