Hi Nelson,
Thank You...
I think it's a pretty good design. It's a very rugged and durable little
machine. I've always liked the fixed bridge design for the extra rigidity
it provides. The only thing is has against it, is the small cutting area. But
this one was intended to be a small machine anyway. Not everyone has
space for larger machines. It's very portable and easily enclosed for use
in places like apartments where many people live....
The rails are 5/8" Thomson linear shafting. They're very nice precision
rails that don't flex at the relatively short lengths....14" for the bridge/gantry,
and 16" for the front to back axis....
(depending on how it's set up in software and positioned in an enclosure,
someone may call either axis X or Y...)
It uses common inexpensive Oilite bearings. The fact that they're
"cheap" is really just a plus, as they're ideal for these sort of small
machines. I've used them for many years in many sizes of machines,
including MDF , plastic and all metal machines. They will push dust
and debris away and act as self cleaning bearings. Easily cleaned
if need ever be.
The lead-screws are 3/8-12 Acme, with Delrin nuts. With the Probotix
driver setup shown, at 1/4 stepping, the machine will move at 80IPM,
though it's really intended to go around 30-40IPM max for tiny, precise
carving work.
It is an MDF frame. It's designed so the MDF frame holds the working
parts in place. At these small sizes, the MDF thickness...at 3/4" is
enough to provide very strong and reliable rigidity. The rails are held
in place using 3/4" black HDPE and cast urethane blocks. They won't
flex at all, and the combination of materials practically cancels any
transfer of vibration and resonances. Meaning it'll do very precise
and highly accurate work.
The painting is several layers of Rustoleum Hammertone paint.
It's taken a lot of trial & error to finally figure out that the easiest
way to get a good durable and inexpensive finish, is to be very patient
and let it dry for several days.
The hammertone type paints give it a thicker, but stickier coating
pretty easily without too much "running" of the paint between coats.
The extra thickness makes a glossy heavier coating, but the stuff
has to dry a lot longer than the Krylon paints I normally use.
So I have to give it 3-4 days to completely dry. It's well worth the
extra waiting, because the finish ends up very durable and similar
to powder coating.
I didn't even bother sealing it like I normally do, because the extra
thickness of those hammertone paints sealed the edges well enough
on their own.
It's a very nice little desktop machine. I think it's probably capable
of some very fine PCB work...though I don't do pcb's myself.
It's strong and rigid enough that it may do some light aluminum milling
too.
The key thing is that all the parts are very, very strong and rigid at these
relatively small sizes.
The only hard part to building it is that all the holes must be bored
and drilled in *exact* right places to be as smooth and accurate
as it is. There's no 'slop' at all in the machine.
It has some nice weight to it at around 40 lbs. It should fit well on
most workbenches...it's 19" high, 19" wide and 24" deep with these
smaller nema 23 motors attached.
These motors don't have the extra shaft on the outside...which I
wish they did. I like to put handles on them for hand positioning
everything sometimes.
John