My Newest Desktop machine

[microcarve]

Hi All,

Some pictures of my latest small desktop sized machine...

Painted & almost finished...







It has a small cutting area of about 9 x 8 with 3" Z travel.



All set up & ready for a first cut with a driver kit from Probotix....




Bosch trim router with tool holder from http://www.mcpii.com/Nicknacks.html




Cutting bits for fine work from http://www.cnctoybox.org/store/page27.html




Small vise bolted to the expendable replaceable MDF table...




My wifes design as a first test cut....




Perfect cut...













Like I mentioned, this is a pretty small design that I plan to use
for small molds & die-sets for jewelry designs mostly. It'd work
great for pcb work as well.

It's carefully built to have no backlash or "play" in it. It's such a solid,
little simple design that I'm even considering making more of them
to sell. It should be a fairly cheap machine to reproduce....


John

[HereinCS]

Congrats. That looks great. Only question I have is that you have the y axis so far back that aren't you wasting lots of cutting area?

[microcarve]

Thanks!...

No wasted cutting area, but there's a bit of a trade off involved.

The overhang of the router brings it very close to dead center. But the
Z axis plate is drilled for several different tool holders....including all
that are offered from Probotix, and many of the K2CNC tool holders.

Those were the the places that offered the most choices in tool holders,
so there's a pretty wide range of routers that will fit correctly. The overhang
of them will vary a tiny bit.

The table is done so that another layer can be bolted to it. That extra
layer could be shifted forward or backward and it'd also extend over the
ends of the machine. Basically meaning it'd accommodate a very long piece
of stock....though cutting it would still be limited to the 8" or so of max front/back
travel.

I did put a 1.75 Hp Milwaukee on it, but I think that's near the limits of reasonable
weight. Trim routers will handle most everything just fine.


John

[microcarve]

A couple of videos if anyone is interested....

http://www.microcarve.com/zonesmall/BBot1.wmv

http://www.microcarve.com/zonesmall/BBot2.wmv

Something is all-of-a-sudden weird with my camera, so the
quality isn't what I wish it was....

John

[microcarve]

Adding T-Nuts to fixture layers....

Multiple cheap, expendable layers are easy-easy to make.

Just do a 3 step drilling using a 1/8" bit first. Drill from the front.

From the back, drill down about 1/8" into the MDF using a 7/8"
spade type wood bit.....to make the t-nut countersunk into the surface.

From the back....for 1/4-20 t-nuts....drill a 5/16" hole on through.

Pull the t-nuts into place. Don't hammer them.

As shown in the pictures...













links....

http://www.microcarve.com/zonesmall/bot024.jpg

http://www.microcarve.com/zonesmall/bot026.jpg

http://www.microcarve.com/zonesmall/bot027.jpg

http://www.microcarve.com/zonesmall/bot028.jpg

http://www.microcarve.com/zonesmall/bot030.jpg

http://www.microcarve.com/zonesmall/bot037.jpg

http://www.microcarve.com/zonesmall/bot039.jpg

http://www.microcarve.com/zonesmall/bot041.jpg

http://www.microcarve.com/zonesmall/bot042.jpg

Nice clean easily replaced fixtures/jigs....

Cheap too!

[Arquibaldo]

Dear John (microcarve):

Congratulations on a beautiful, well built machine...

Would you be willing to disclose a little more about this router:

.size of the guiding rods
.type of linear bearings
.size and type of the screws and nuts
.anti-backlash measures used
.material used for the frame - it looks like .75" thick MDF, but
your beautiful paint job makes me not sure...

Thanks a lot for your attention

Nelson

[microcarve]

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

[microcarve]

Pictures of the machine before it was painted....









Pictures of the first prototype for the design.....








The green one was the original to test the concept. It's a little
small at about a 6" x 7" cutting area. The designed looked to be
good for scaling up a bit, and 9" x 8"....though still a bit small, is
a very useful cutting area, Especially so with the rigidity and
smoothness of the machine.

I think it could even go a few inches bigger, but I'll try that
a little later. This is a "just right" size for a desktop machine.

The green paint was a PITA to do and chips a little too easily.
It was carefully sanded and sealed with Zinsser shellac. It's
a white sealer that seals really well, dries fast, and is easy to
apply. But when the green enamal top coating is bumped...
and it'll get bumped.....it chips, and the white undercoat shows.
Very irritating after all that work....

The hammertones are thick are durable.

So far, anyway.....


John

[UUU]

It's on of those designs that follows the rule "if it looks right it is right". And it does look right.

My milling machine is different in every way. But it has it's front-to-back stepper motor round at the back, rather than at the front. This is really nice, as it's easier to sheild from debris and you can get at the working table more easily. Have you thought of mounting yours at the back?

[microcarve]

Thanks Very Much!



I have mounted the motors at the rear before on other designs. The
problem with doing it on this one is that the motor can get easily damaged
if the machine gets bumped into a wall. This one will likely sit on a workbench
due to the design of it.

I have done that damage before on a different design. It gave the choice of
mounting either in the front or rear. So, this one was intentionally designed
to only go together one way. It could be easily shipped and assembled by
anyone with minimal tools.

Most of my motors I normally use have the dual shafts at both ends of the motor.
I like those because I can put these little knobs on them....


http://www.radioshack.com/product/in...ductId=2102830

...to allow for very fine positioning by hand. Easier than trying to jog a few
thousandths....

But I accidentally bumped a machine with motors at the rear once and
cracked off the knob and slightly bent the shaft. The motor was still
Ok, but I was amazed at how easily damaged it was just by an accidental
shifting into the wall. It didn't take much.....

Another thing I like about this design is that it's so easy to lift up and vaccum
completely underneath it. I had one design that had a bottom "pan" in it and there
were places that were hard to get cleaned. All the debris is really easy to clean
up with this one.

Thanks for the compliment!


John

[microcarve]

Here's a couple of pictures of just how much abuse the Oilite
bearing and Thomson shafting combination will tolerate....

Cutting Z axis parts from urethane castings.....





A huge MDF machine that made many-many parts for a few years.
36" x 36" cutting area. Fixed bridge design mainly to see how well it could
work. 6 foot long, 1.5" Thomson precision shafting.

It worked great with 1/2-10 (supported) Acme and 300 oz motors.
Gecko G203V's at 60 VDC.

I replaced it with a different gantry design when I got a deal on
some Hiwin rails. Just to save space really, though. This one worked
fine.....but I wouldn't recommend the huge design.





Oilites have been really reliable and stable...and easily maintained.
Though very rarely necessary.

Cheap too...


John

[ger21]

You really need to invest in some dust collection.