My Newest Desktop machine

[microcarve]

Video....

http://www.microcarve.com/zone6/BMmillhead.wmv


Newest BlackMagic machine running prototype milling head.

Mill head is cast & machined urethane block with spindle for 1/4"
bits. Bearings are some I picked up years ago for replacement
in a well pump motor...IIRC.....

The milling head uses a sewing machine motor with cast & machined
pulley. The motor actually runs very cool. The bearing temp ran
at about 100F for this job making a lithophane.

The *Huge* advantage this thing has, is, it doesn't throw dust
into the air, and I'd surely expect it to run a lot quieter if I wasn't
using a homemade coupler for the motor pulley....

...which means dust collection doesn't appear to be a huge problem,
and it could be run in a place where loud noise would be a concern.

I doubt it'd be good for really heavy duty stuff, but that appears
to be more of a limitation with the small sewing motor.

It's run for a total of about 4 hrs with zero glitches.

It's still highly experimental, but it sure looks good and useful right
now....



John

[microcarve]

That's the extent of the mess it all made.

I still need to make a decent set of pulleys to up the speed a bit, but
this carving came out excellent.

If it works this well with the half-fast cobbling together of it, it
has great promise.


John

[Mr.Chips]

Ahhhh Haaaaa

So this is what you've been up to. Looks like a good plan. Urethane for a milling head, is it rigid enough, well your testing will tell. Like the looks of it. Do you think it is rigid enough for cutting wood.

Thanks for the post

Hager

[microcarve]

Hi Hager....and Thanks!



It's been a busy time....

Yep, it's very rigid. I think it'll support a motor maybe 4 times what
a sewing motor is, so that brings it into the 1/2 horse range.

Now that it seems to work so well, I'd like to make one with an ER
collet extension in it. I expect that'd take a few trial & errors, but I
*think* it may work pretty well.

LIke I mentioned before, I tried several new things on this "BlackMagic"
version of the machine. The brass leadscrew I mentioned....

I liked it very much and it's dead simple to make backlash free delrin
nuts. It totally matters not if it's ACME thread. That means anyone could
use an affordable and readily available tap to make nuts as and when
needed.

The drawback to brass is, they're not handled as carefully as I'd like where
they come from. They're not intended as leadscrews so they get banged
around a bit...unless someone is willing to pay $$$ for special ones.
(which BTW....brass is used for leadscrews due to it's nonmagnetic properties.)

Also, for the extra cost of them being brass, it's not worth the extra investment.
What is important....to me anyway...is that a high quality regular/normal
common UNC thread will work every bit as well as any ACME, and it's easy
and cheap to make high quality delrin nuts. So, I need to get some steel
ones.

Only other drawback is they're not multi start, but I want finer pitches for
finer work anyway.








The other thing that's kept me busy was making a means of having the X & Z
assembly on the machines a dead simple drop-in bolt-on single assembly.
That makes adjustment of a machine an easy task here and makes it
easier for someone to do an asembling of one of my machines, or, use
parts for their own design.







Getting back to milling heads & spindles.....Yes I do think it'll cut wood
just fine. Right now it's only geared basically 2:1 so it's puny as far
as any power goes. It's got some weight to it, but not what
a mini mill head is.....so there's some good possibilities.

It is more rigid than I expected, and I have a different motor I'll try
later. It's well within capabilities of the machines components and
power.


John

[Mr.Chips]

I thought when I saw the photos the lead screw looked to be a finer pitch than acme. You say they use brass threaded rod because it is non magnetic, why in non magnetic important? You say the brass threads are nicked up some, then you could run a die over it to clean it up once and for all.

On my first machine I tapped delrin making drive nuts using a piece of 1-10 Acme rod. Put a taper on it and machined three flats turning it into a kind of tap tool, it worked OK but the friction from one nut to another varied. But if you'r making nuts on a regular basis an acme tap is justified.

Could you mold a nut out of urethane, or wouldn't it flow in tight enough against the threads?

It looks like the X/Y bushings are urethane, or is that just the brass bushing holder?

I used my CNC today to cut a couple of 35" birch plywood disks, making a lazy Susan for a friend and one for us. Probably be the last thing I make before we move. Moving to Phoenix around the end of the month so busy packing. One good thing is that the new house has a 3 car garage and an attached workshop, it 8' x 24' long and narrow, no way to get everything in there but a lot of the table top things as it has a built in bench the full 24'. Looking to expand it another 8' out into the patio, but lots of other things to do first. I made do with a 3 car garage here in Tucson for 6 years so more space is a plus. Been thinking about taking my 1st machine apart and making a bench model out of it more like your size.

[microcarve]

These are exceptionally practical machine sizes. Most anything works that
you try without stressing parts & components.....but naturally, the cutting
area is a bit small.

Why do they use brass?....Lots of reasons that are well worth looking up
on google....

But yep, I did and always do run a die down them to smooth and deburr
them. That also has a side benefit of making sure the threads are a bit
more uniform.....you can tiny feel errors in the rolling process.
(Though I'd expect screws that are made for power transmission to be more
carefully made.....)

Like you, I also make taps from the ends of a scrap of ACME.....and with a mill
and lathe on hand, that's pretty easy to do. But, here's a slight problem.
Multi start screws aren't made to any standards like most screws. That means
that each maker of them makes them how they want to. They vary, and one nut
may work perfectly with one makers screw, but then, again, they may not....and
wear excessively.

Even my single start ACME varies a bit. I guess it all depends on the machine
operators weekend.....they don't pay enough attention some days....

So, one batch of screws....(I'm small time, so my batches are small....) are
slightly different. Which means making taps more than I'd like. And some are
a little looser and have a little backlash, while some are too tight and need
extra attention and time.

Use of a thread die would make the threads easily more consistent as the
rolled threads can be "corrected" well enough. So there are real advantages
to regular common threaded rods.....like 1/2-13 for example.

It's a little different once you try to reproduce anything in numbers. Making
one of anything works pretty well as you can take a little time to modify
parts as needed, but to make many of them, it's nearly impossible to get the
sort of consistency someone will try to maintain......so as to make parts
interchangeable.....which at these close tolerances is practically impossible
without some very expensive tools & machines.

Do-able....but not easy.....

The bushings are now extended via PVC tubes which makes the travel/gliding
smoother. The ideal position for something like an Oilite bearing/bushing is
a square pattern....meaning if the rails are separated 3", then the bushings
will work best when separated the same 3". Or more.

1" less of travel, but it appears that it moves better and smoother now.
3-4 more machines will decide if that change stays, but I 'm sure it will.

Yes, you can cast nuts directly....and they will work fine for a while.
Well enough to make a "better machine". Heat and friction will
degrade the urethane fairly quickly, so I haven't used them for any
long periods of time on any machine, but they have worked well
when I have made them. They still do need a secondary tapping
of them.


It's a similar problem with polyethylene. The heat and friction
of travel will degrade those quickly too. Best to use a material in
that case that's intended for the job, such as Delrin.

The heat/friction causes a chemical change that makes it possible
for the threads themselves to eventually be pushed right out.
That's happened a few times here. I stay clear of HDPE nuts now.


Interesting questions, Hager!

It's nice you're so observant....

John

John

[microcarve]

Video....

http://www.microcarve.com/zone6/acrylic/acrylic1.wmv

Test cutting acrylic. The cut is made into the handle of one
of my acrylic sanding sticks I make.

I did make one major miscalculation on this one.....that was
setting the zero top of the stock a little too deep for my good
carbide cutter......which did have a tip that was about .004 or so.
Now it's about .020"....

But no problem....I'll just hone it back.

What it did cause to happen though, is the gcode file has a stepover
for the finer tip. With it broken off a bit right from the start, it
was "overwriting" the lines already carved....as the tip was now
wider.

But it still did a very good job. And with very little mess.
It would have been 10x cleaner and finer if I'd judged the situation
a little better. Acrylic is hard and brittle, so trying to plunge right
in to a depth of about .070" right away was a bad thing to do.
The fragile carbide tip wasn't going to handle that, unless I slowed
things down a lot more than the 24ipm.

For a first try with acrylics though, it came out very well.
The bit would....right now....lend itself to larger carvings very
well, so I may just keep it as is and get another for the finer work.

The slower milling head works great for solving the melting problems
some plastics have. It sounds bad because the pulleys are still
mismatched. Easily corrected, but it means disassembling it.
Which, I'll get to after I play around with it a bit more. It's not
going to hurt anything at this point....



John

[microcarve]

Video....

http://www.microcarve.com/zone6/aluminum/aluminum1.wmv


Aluminum cutting. I set Z at about .010 below the top surface so
I could do the thing in a single run for a total depth of about .050"

It ran at 12ipm for about 40 min or so, using one of Curt's 60 degree
carbide cutters....

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

The milling head wanted to do it, but I decided to use the Bosch
first to have a good one to make a comparison with later on. The
mill head still really needs to have those pulleys done....

It's really hard to take pictures of something like this because there's
no way to light it from behind. I used the same gcode file I've been using
also to make comparisons.

I'd give it about an 8 on a 1-10 scale for a first shot at milling
metal. I'd give the machine a solid 10. It's a bad-ass little machine.

It's also running at 24VDC with motors set at 1.5A, so that tells
a little something about how well it works.

Pointless, but fun!


John

[microcarve]

BTW...the line in the picture is from using one of my versions
of microcarve. It's the watermark line that goes away after it
gets registered. I forgot about it when I made this file....

[Drools]

Sorry to ask you to repeat yourself but whta is the torque on the motors you are using with the small router and what drivers are you using?

[microcarve]

This kit from Probotix.....

http://www.probotix.com/index.php?vi...&product_id=88

I got the "ready to run" kit. It costs as much to do all the wiring and gather up all the
extra parts as it does to just let those guys wire it up for me. It's "Plug-n-Play"
at it's most convenient.

[microcarve]

Video....


http://www.microcarve.com/zone6/aluminum/aluminum3.wmv


This cuts much quicker as it's all vectors instead of individual scanlines.

(design made in VCarve Pro.....I wouldn't want to be without it)

It's also proof it takes a bit of trial & error to get the hang of milling
metal.

I chipped the bit when positioning it and sharpened it up by eye.
So it's not as perfect as it should be. I also went a little too deep
at about 60 thou on it, so I ran a second pass to smooth out the
lines.....which is one really nice thing about cnc.....it goes back to
the exact spot to do the second "clean-up" pass.

I wish I hadn't chipped that bit. I think it would've been nearly
perfect.

Lesson learned is ---Practice!....and count on ruining at least one bit
before getting the feel of what's going to happen.

The machine handled it with ease....



John