My Newest Desktop machine

[dertsap]

its funny the variance in mdf , it probably varies country to country , the stuff I use is cleaner looking
I bought a cheap dresser a while back (made in china) and the corner broke , the mdf was made with everything and was probably 30 % recycled news print , on the outside it looked pretty good with the laminates covering it but the core is a pos

[microcarve]

Very true.....I'd expect there to be some fairly extreme variations form
place to place.

I used to have a very bad opinion of MDF. But all I had was some pieces
I'd set aside from a demolition project.

I kept seeing mention of "MDF cnc machines" about 10 years ago.
I thought that was an insanely bad idea.....but I went a bought a piece
just to look at.

I got Lucky....rare, but it does happen....
It was a high quality shelf....as I wasn't about to invest in a full sheet
of potentially crappy material.

(Sometimes I suspect the shelves are better quality for the job expected
of them)

Anyways, that shelf I made my first experimental machine from
was impressively work-able to cause me to build another...and another....and...


I've been after the "perfect" design for awhile. My understanding of what
that means is, the design is "perfect" when there's nothing to add and nothing
to take away. It's *Right*.

A well made MDF machine can be expected to handle hard use and perform
as well as a metal one. It's simply not a wet-use machine. But coolants aren't
exactly good for the common router used on a home-built, DIY, "cheap machine"
anyway.....

Getting the right bits does allow for a bit of aluminum milling, but that's...IMO...
still a job for the right machine. An iron mill, or a very expensive machine intended
for the job.

I used to hate MDF. Now I think it's great stuff. But design and assembly
makes or breaks it's usefulness.


John

[microcarve]

link to gcode file.....

http://www.microcarve.com/zone2/mills/endmills.zip



John

[microcarve]

Someone may notice that some of the pictures are cut backwards.

(Some I flip before posting so they match the picture....)

That's because I'm using an older Mach3 profile from a machine that
was set up to cut these sort of small designs into negative mold cavities.
With these lithophanes, it doesn't really matter. I'm just using the profile to
test the machines for now.


John

[microcarve]

The fact that this works so well is actually pretty amazing...

A picture is internally converted into a greyscale image.

That means there are 256 possible assigned heights to each
pixel in an image.

So, say, as in this case, I limit my max depth of cut to .023"

That's .023 divided by 256.

Seems impossible.....but it works just fine....

Most times the weight of a Z axis & router will keep everything pre-loaded
downwards, so that helps.

I do use finer pitch screws on the machines. The cut area is relatively small
so there's no need for quicker rapids that come with multi-start screws.
The resolution is finer too.

This would very work well with common threaded rod. But the sort that comes
from the hardware store has a zinc coating.....which will destroy a delrin or
homemade plastic nut in a short time. The zinc has pits and high spots all
over the screw.....

There is a type that can be bought that's called "oil-finish" that has no zinc
coating. That'll work better for a cheap home built machine.

Most everyone already knows that, but I mention it for the new guys who
are just getting started. Lots of little details like that can make a big difference
in machine performance...


John

[Mr.Chips]

Hi John,

You have some really nice pictures posted there. I have Microcarve but am still finishing up my dust collection system so I have used it very sporadically.

I would really appreciate it if you would note the depth, stepover, and bit size/type you use. I find I have to run one several times to get the desired effect. And seeing your numbers it would help in establishing a better feel for the outcome.

What is that material you are using and if you are making Litho's why are you using such a thick block?

Keep the good work coming.

Hager

[microcarve]

Thanks Hager!



The bit is a home made one. It takes a little trial & error to
make one that works well. That's done by using 2 Dremels
and sharpening a broken off drill bit or some 1/8" scrap
of tool steel, to a point. Then grinding a "D" profile on the
end of it.

...Look up "D bits" on google...

There are also places to buy them, but I forget where...

Curt sells a good bit for litho's & picture carving....

http://www.cnctoybox.org/store/page27.html

The 20 degree bit has a tiny .010" flat at the end. I have
one I plan to hone to about .005" or so with a fine diamond
hone....as the stuff you see is very small at about 1" width or
height....

My stepover for these tiny lithophanes has been .004" for the
last 2.

Cut depth has been .023"


I resize them first thing so they fit on the scrap block of urethane
that I've been cutting them into.

It's a material I got from...

http://www.alumilite.com/Category.cf...sting%20Resins

All you need is the "regular" alumilite. It's a bone color and is a nice
hard material. It takes about 15 minutes to cast a block to machine
very high detail into.

My scrap block I've been using was then sliced on my bandsaw.
Reason is....it's easy to hold the larger block in the vise. If I screw
up, then I just mill it flat and start again....

Like I've mentioned, this urethane doesn't melt like most plastics
someone might ordinarily use. It's a thermoset plastic.

Also, a homemade bit works very well with it, due to the fact that
the material has no "grain" to it. The bit can be somewhat crude
and still perform great....but a good "bought" bit works much better.

It takes a little practice to get the idea of what to look for in a
picture to cut. Hardly any are ideal.....though lithophanes are easy,
as there's no real concern about common problems...such as dark hair
being recessed...like there is in the common picture carving.

It does take some trial & error, but it's pretty easy once you learn
what to look for.


John

[Mongkol]

John,
Have you ever engrave on the stone? I found this machine on youtube.
It can engrave the image which you need on the stone.
I think it's challenging for you.
[nomedia="http://www.youtube.com/watch?v=fy7xMITGyy8&feature=player_embedded"]YouTube- ‪CNC G-10 engraves photos into stone‬‎[/nomedia]

Here's the original website.
http://www.acmetek.biz/g10.html

Mongkol

[microcarve]

An example of a bad choice to carve. But it has more to do with
my crude home made bit and/or run-out in the router/home made adapter.

Lighting and the brushed surfaces in the picture are hard to translate.

I think I could do 2x better with more care and attention to setup....
with the correct cutting tools...



John

[microcarve]

Hi Mongkol

I've seen that before....

I have some scraps of marble around here somewhere, so maybe
if I get time I'll see if I can make it work.

I've also seen where someone carved into glass. Which was very interesting.
They used a diamond ball bit....but the Z axis was offset to an angle, so the
axis of the spinning ball tip wasn't straight upright. The ball, rotating at the angle was
efficiently removing the glass. But, they were keeping it cool with water or
some other coolant to prevent ruining the diamond bit.

Later, I may try making some sort of pan to allow for using a spray bottle for
doing some stuff that needs a bit of coolant. The thick coating of paint should
protect the MDF sides of the machine well enough if it's wiped off at the end
of an occasional wet job.

One of the first plans I have is to make some sort of low profile bolt-on vise/jig
attachment. The one I have works great, but it's big & not too pretty. Lots
of easily interchangable table fixtures are possible. Lots of ideas here....

http://www.visionengravers.com/produ...sories.html#wh

Great links!!!


John

[microcarve]

When I was cleaning out my shop a month ago, I threw
away a bunch of these things before I realized.....


Luckily I saved a few of them...

[Mr.Chips]

That's exactly why I never throw anything away, just ask my wife. LOL:rainfro:

Thanks for posting what won't work so well, this is as valuable as success.

Hager

[microcarve]

Yep, I *Knew*....as soon as I threw that stuff away, I'd need
it.

I also think that showing what doesn't work is every bit as important
as what does. That's what can really save someone some $$$....knowing
what NOT to do....

(Only took me one time of touching that pretty red hot burner on the stove)

[microcarve]

My original hand operated cnc machine.....1992...

It made tons of molds & dies for metal embossing. It'd even do 3D
stuff with a little extra setup time...

Hand carved from the alumilite urethane I mentioned.


John

[microcarve]

Site glass built into the side of my small metal router.

Made by Verrrry slightly doming one end of an acrylic rod about
1" long. Then scribing crosshairs on the other side.

Very good for having a specific point to align a router to.

Invaluable IMO....


John

[Mr.Chips]

Site glass built into the side, I would think it would be top mounted to focus on the material, or am I missing something?

I'm just finishing up my 2nd machine a movable gantry with 48" x 36" work area. But almost everything I have been playing with is quite small usually under 3".

My 1st machine is a fixed gantry 25" x 25", it was the easiest and most rigid to build with the tools I had at that time. But sure takes up a lot of space. It uses 215 OZ/IN steppers. Have been thinking on recycling it into CNC No. 3 one about the size of yours, have the steppers and electronics and plenty of 1 start 10 acme thread and I could cut all the pieces on No. 2. Make it a movable gantry, I was thinking about a Jegro (SP) design, that way you could take it anywhere clamp it down and start cutting, but not made up my mind yet.

Anyway thinkin's cheap, LOL

Hager

[microcarve]

The site glass(es)...there's one on top too...

are for marking multiple X or Y origins on the fly. Sort of like a movable
home switch might be.
They're pretty accurate with the very fine cross-hairs scribed on them
when I want to mark a temporary zero/home position.

Wow!...Nice work you do!



I think your little portable machine sounds like a good idea.
It'd be easy to take it anywhere and carve designs into material
that would be too big, otherwise. That could work on stone
as well. Maybe put some suction cups on it to lock it in place...


John

[microcarve]

Sometimes the forces of the universe want to give us a good shafting.

Sometimes you have to put holes in the end of MDF.

Same thing????


Nah...just kidding....

Done this way....I won't say it's the 100% *Right* way, but I will say it's
a *Good* way....

A solid, stable, long term connection can be made.

This thing from Harbor Freight is on sale nearly always. It'll guide
your bit to make a nice hole in the right place. And holes in the right
place are a joy...

You can see in the picture it has a little notch mark to line up
where you want the hole.

I use 1" Delrin for the nut. There are little bought ones to be had,
but they're not a wide and solid 1".

(btw....the delrin nut isn't drilled/tapped yet in my picture....)

If the nut hole is a little tight, it can be rounded out a touch with
sandpaper wrapped around a stick of dowel rod.

This is very, very strong and with a 1" deep tapping in the delrin nut,
it won't strip without trying to purposely do that.

Reason for this in my design, is, the motor bolts don't allow for
the threaded rod tensioning done on the rear of the machine.

And it looks good when done carefully....


The Harbor Freight thing is a worthwhile thing to have on hand.

http://www.harborfreight.com/self-ce...jig-41345.html


John

[Mr.Chips]

OK, I'm 70 and a little slow but eventually figured it out, LOL.

MDF will not hold a thread if screwed into it through the side, it will split 99% of the time. To eliminate this you drill a hole to fit the delrin plug an inch or so from the edge then drill and tap the delrin to fit the bolt say 1/4 20 then drill a hole in from the edge a little larger than the 1/4" bolt the bolt, then the bolt can be screwed into the Delrin "nut" without risk of splitting the MDF.

Excellent idea.

In wood work we use hardwood dowels for the same purpose. Threading into the end grain of anything is not a secure method. If we don't want it to show on the outside the hole is not drilled completely through. In this application you might want to use 2 bolts/nuts, because the delrin has a larger contact surface than just one square nut, a judgement call, LOL.

An alternative method if you don't have any delrin is to cut a slotted hole just large enough for a square nut and use it instead of the delrin.

Hager

[microcarve]

Yep, that's the idea....

http://www.rockler.com/product.cfm?page=367&Max=999

They're pretty common, but I need the larger contact area the 1"
delrin provides. Mostly for looks, but also to avoid needing to use
2 skinny ones that are easy to get and inexpensive enough.

Just drilling a single hole is pretty fault tolerant.