My Newest Desktop machine

[atwooddon]

What about 'gunk' build up? I have noticed the bushings on my V90 seem to need a cleaning every once in a while particularly if I am cutting MDF. That dust gets every where and seems to be sticky. Not being negative, just asking questions. I am certainly gonna try this, maybe even today. I can see a new Z axis on my old DIY machine!!!

Don

[microcarve]

No, Be negative....Question everything!



I don't expect any real problems with buildup. Especially
if...which I'd expect in most cases....no lube is needed.

At any rate...McMasters sells felt washers. Those are cheap and can
easily be super glued in place as a wiper system.

I suspect even the $.50 felt from Walmart would work as well.

Questions are good for everyone. May be I'm overlooking something
important. It does look like a good practical idea so far, though. I think it's
gonna work great....

John

[atwooddon]

Well, I can't stand it, I am off to the hobby shop with my collection of printer rods/rails!!! I can see a new Z axis on my old DIY cnc machine by noon... ;-)

Don

Update..... Ok, maybe not by noon, I am back from the hobby shop with brass tubes to fit 2 sizes of rails I have scrounged from old printers. Now, off to the workshop. I think I will use my V90 to cut parallel 'troughs' for the brass tubes to lay in while the ca or epoxy set up. I will use MDF for the Z axis and see how it goes.....

[atwooddon]

John, quick update and some info

i drew up some quick parts for a Z axis using CamBam. I used the V90 to cut parallel troughs just wide enough to accept the brass tubing, slip fit everything together and epoxied the brass tubes in place with the rods holding them parallel. Then clamped everything together and I can't believe how smooth the router mount tray slides on the rails!!! Silky smooth all the way end to end. Wow, thanks John.

Quick info. Just saw in another thread about making anti backlash nuts using acetal and a heated acme rod. cool info, will have to try it. Similar results to your urethane casting approach, perfect fit, zero backlash....

Making Acetal leadscrew nuts the easy way - The Home Shop Machinist & Machinist's Workshop Magazine's BBS

Don

[microcarve]

Thanks for the update Don!



I was gonna ask, but I know sometimes what seems like it'll be
done by noon can mean... noon 4-5 days from now...

They make extra long oilites, but they cost a small fortune. It seems
that whenever extended length bushings/bearings...of whatever sort...can
be used, they tend to be much easier to align and resist any
binding much better.

The brass should work very well for a very long time....


John

[microcarve]

Just a quick note for anyone else thinking about giving
it a try....

Super glue also works very well. It's very thin and soaks into
MDF nice and deep and creates a really solid and permanent
connection. It's one way to do it that's really fast when used
with super glue setting accelerators.

Just be sure to give the tubes a light sanding so that the
surface is slightly roughened and clean.

Carefully done...the tube can't be removed without destroying
it. It's permanent and reliable.

Dead parallel slots/grooves are easily made on a mill using a
common router bit, if one is available (mill).....or with a table saw
just by moving the fence the thickness of the sawblade
with a few passes.


John

[microcarve]

Here's the general idea for ease of visualizing it....

The center slot is an example of some place to maybe glue
a nut in place.

These could be any size or orientation and 3 of them could
make a dead simple machine that's reliable for light duty work.
Very precise work too, with a little care in designing it.


John

[atwooddon]

John, that's exactly the way I did it including the center slot. I used 30 minute epoxy but will try CA next time. The outside frame is setting up right now and then I will mount it on the cnc machine. Am working on the stepper mounts right now. This is SO much better than the cluge I had to start with for the Z axis.

Don

[microcarve]

That's Great to hear!



It makes posting crazy ideas worth the time and trouble when
they're proven useful to someone...

If someone didn't feel the tube would hold well enough...and it
sure will in most cases.. a mating back plate could also easily be
made to lock the tube within a "sandwich" of 2 MDF 'plates'.
Then the tube would be unable to even be torn away with force
from using a larger router.

I'm looking forward to seeing how it works for you.
Maybe you can get a picture or two if you get a chance!



John

[microcarve]

A little off topic but I'm reminded of one of the first little machines
I made about 20 years ago using brass tubes for bearings.

They're used on a somewhat polished 1/4-20 bolt here as the
rollers for a small precise sanding machine.

This was --and is still used for sanding the tiny little metal parts
edges that I showed earlier. It's done literally hundreds of thousands
of those little highly detailed parts for many, many years. I changed
the bearing once as an upgrade.

I'm sure if surface feet was calculated, it's been to the moon and back
probably several times. It's run for 12 hours many days.

Another great thing about it is that I sized it for...I think...a common
20-24" sanding belt. I just take a razor knife and make little slits in
the belt and tear off thin strips. Lasts forever, and you can make different
widths for ultra detailed sanding of corners and edges.

Made from complete trash from a dumpster....

But, it wasn't about being cheap....it's the "Right" thing for the job.


John

[microcarve]

If anyone cares for the latest A4 microcarve made, i will be running it will the following setup:

Probotix parallel RF-isolated breakout to their bi-polar stepper choppers.

With an Intel d425kt mini ATX as the computer running Ubuntu 10.04 for EMC2.

This should allow me to fit everything under the machine and run a headless machine controlled via remote desktop after its all setup.

I'll probably tuck a drawer under it with a mouse and keyboard if the network setup gives me issues.

after all you can't hide work like that under a ton of ugly wires and stuff.

Well, I'm certainly interested...

Hopefully, this machine will be to John on Monday. They pack
really nicely now. It's about a 40 lb box.

Some parts got here today to start on another one....

The weathers getting nicer. That's always helpful.


John

[atwooddon]

Well, I finally got around to taking a picture of the new Z axis mount I threw together using brass tubing and some rails I had scrounged from old printers. The rails are only about 3/8" but over this small span, they are very rigid. The mount is on my old original DIY cnc machine I put together a few years ago. I am surprised at out rigid and smooth it operates compared to the original Z axis. The two pix below are the side/back view trying to show the way the brass tubes and rails go thru back of the router mount and a front view.

John showed a drawing of this approach a few posts ago. It was super easy to make using my V90 machine. The sliding on the rails is silky smooth and no matter how much pressure I put on one side of it trying to cause racking, it did not show any signs of that.

Don

[jig123]

John,
Like so many others, I have finished going through all of this thread. Fantastic!

I've been dreaming of a CNC machine for years and am really interested in your Microcarve A4 machines. They look great.

A couple of questions that I haven't seen answered so far.

What is the workspace clearance in the Z direction between top of table base to bottom of Z-axis mount (when z-axis is at min/max limits)?
I notice you frequently have a vise on the table base/bed in your pictures.
I notice that it looks like the z-axis has several mounting holes to mount to the gantry axis. And since the normal z-axis has about 4" of travel, I'm curious about what mounting options there are and determining the min/max clearance over the table bed for different mounting positions/offsets.

I have several uses in mind of such a machine:
- pcb milling (where I would have the workpiece flat on the table base); z-axis range is not a real issue as long as the bit can reach the table, which shouldn't be a problem I think.
- misc workpiece milling/drilling/etc (where I might have the workpiece in a vise. Depending on what I'm milling/drilling/etc, might want full z-axis range, but from a vise "offset" in z-axis.
- possible future plastic extruder (where I would either form a workpiece on the table bed, or have a heated platform sitting on the table bed. Here I would want max z-axis to allow maximum forming volume space.

Given the above, I'd like to be able to change the "offset" of the z-axis to account for the different workpiece "base" height to retain full range of the z-axis.

Also, in an older post you mentioned that the z-axis could be changed to support a larger range, such as 5-6". I'd be interested in how stable the gantry is for such enlarged ranges. Do you see any meaningful deflection (twisting of the rails) at extreme z-axis positions. Would the gantry side supports need to be raised/extended also to accommodate the extended z-axis range? If you don't think the gantry sides need to be extended for a 5-6" z-axis, how much could the z-axis be extended before you would need to do so?

I think in an older post you mentioned using a larger (than Bosch colt) router. What would you expect reasonable weight/load limits to be for what could be mounted on the z-axis carriage and still have stable positioning?
I'm considering what might happen if someone tried a 12" z-axis with a relatively heavy router and possible some sort of quick change tool holder at maximum deflection and was trying to mill fine pcb traces. What might reasonable repeatable tolerances be? (Would deflection or stiffness/stability become an issue due to the relatively long z-axis lever arm? Would the gantry axis rails need to be space further apart for more stability?)

Thanks again for sharing all this tremendous experience and the photos. I can't wait to see what comes next!

JohnG

[microcarve]

Thanks JohnG!


Lots of questions, so forgive me...and ask again if I don't
answer completely....

The Z clearance is determined by what height of work material
can move under the bottom of the bridge slide block that the Z is
bolted to. So it's limited to a max of about 4"....as the bridge is fixed.

I say "about" because the expendable MDF table is 3/4" thick. It could be
replaced by a thinner fixture to gain most of that thickness.

It's my opinion that in most cases it's always better to bring the work closer
to the bottom of the Z when possible. An extended bit is a lever and will
act as such. The shorter the bit and the closer to the Z bottom, the finer
the work should be. And by "finer", I mean the tiniest little bit can help
with something like PCB milling. ANY stability that can be gained...no matter
how minute...can only be of benefit.

A very long extended Z wouldn't be of any real help except to raise the router
higher --due to the limits of the slide block clearance.

A machine like this could easily be made to take advantage of an extended
travel Z, but the length of the extension will still cause leverage and could
become too much at, say, 6" or more. Which would limit it to lighter duty
work.

The A4 is a compromise between more travel and a smaller/tighter built
machine to get as much travel/cutting area, and still have in mind doing
very detailed work like PCB milling. It's as large as it should be, but not
so big as to make the highly detailed work any problem.

I've mentioned a few times that I've come to see these type of machines
as "specialty" machines. Much like a sawblade....the main question is
what does someone need it to cut. There's a better design/configuration
for most jobs. The larger a machine gets....and still is an inexpensive machine...
the more it becomes a "general purpose machine". Else it needs much more
expensive parts and design to do highly precise work.

So, the extended Z's aren't much, if any, benefit. The one the machine uses
is intended for the Bosch sized trim routers and handles it easily.

Maybe for plastic extruding, it could work if the assembly wasn't
too heavy and an extension plate was bolted to the Z, but that'd
still limit it to the reach of the extruder head...because of the slide
clearance.

That said...once someone has the machine, it's not a lot of trouble
to make extended height sides that could make plastic extruding
practical...as there aren't any sideways forces that cause problems
with the extended travel.

The machine just bolts together easily, and different sides would be
easy to swap out whenever needed.

I wouldn't think the total weight of the extruder heads was much
more than the Bosch. So it could be a practical thing to do.

I'd love to finally see it done. Others have mentioned using those
heads on a machine like this for a long time now....



John

[microcarve]

Well, I finally got around to taking a picture of the new Z axis mount I threw together using brass tubing and some rails I had scrounged from old printers. The rails are only about 3/8" but over this small span, they are very rigid. The mount is on my old original DIY cnc machine I put together a few years ago. I am surprised at out rigid and smooth it operates compared to the original Z axis. The two pix below are the side/back view trying to show the way the brass tubes and rails go thru back of the router mount and a front view.

John showed a drawing of this approach a few posts ago. It was super easy to make using my V90 machine. The sliding on the rails is silky smooth and no matter how much pressure I put on one side of it trying to cause racking, it did not show any signs of that.

Don

Thanks for the pictures Don!



That looks very well made and should last a good long time.

Very, Very Nice!


John

[atwooddon]

Thanks John

One of the primary reasons I tried your brass tube approach is I needed to 'fix' the Z axis on this machine because it is going to my step son (Richard) so he can try his hand at CNC 'stuff'. Of our 4 sons and 1 daughter, Richard is the creative one. He has always been into things like glass blowing, metal sculptures, etc. During a conversation a few weeks ago, he expressed some interest in CNC and I showed him some rudimentary stuff on my systems. He didn't say much but called later and asked if he could use my 'old' system. Well, I couldn't give it too him the way it was configured since the Z axis was so problematic. So that gave me a good excuse to build a new axis which is working great. It turned it loose on a 3 hour job yesterday afternoon with a lot of Z axis movement and it performed just fine.

Long story short, the machine is going to a new home (at least for a while). Now, I have already started collecting items for a small machine very similar to your A4. It will be a rail/brass tube fixed gantry assembly with about a 12x18 bed.

You are right, these are 'specialty' machines for smaller, precise work. My larger machine is fine for normal things, but my guess is the smaller machine will get more work......

Don

[microcarve]

They do hold up really-really well for a long time. I haven't
broken one out of several experiments, but I do keep in mind
there are limitations....like no milling metal parts...

I've had a couple machines that were intended to be "ultra cheap"
strictly hobby/learning/craft machines that I never finished, but I
may go ahead and make one to see if there'd be any interest in
something like a $229 machine. It'd be strictly a kit, so it wouldn't be
pre test fitted like all my other machines.

Here's a picture of how strong a super glue bond can be. On an
older Z axis I used to make from urethane. Those are the old concrete
blocks that used to have some weight to them....not the fluffy ones
they make now-a-days...

http://www.microcarve.com/zone12/test2.jpg


John

[microcarve]

Another machine almost finished...just some end plates left
to tap.

This one is one of the earlier smaller versions I was making with
a cutting space of about 9 x 8 x 3.

I'll sell this one off for $375 + shipping. That'll buy some more
materials for another A4 machine. Anyone interested can write
me at john at microcarve.com

Not much more to go with this one. It only has a single coat
of paint, but it's good enough or someone can add another.
They get dinged a tiny bit with all the test fitting of parts....


John

[microcarve]

End plates in place....

Getting shinier by the minute...


John

[vtx1029]

What's the cutting size of the A4 vs this one? and price?

Have you ever had the MDF powder coated? I do powercoating for fun and was thinking I may want to powder the frame if I got one of your machines. I've never coated MDF but I'm sure it wouldn't be that much different from coating any other non conductive material.

What size steppers do you recommend. I would also like to cut aluminum to some point so I'm assuming the stronger the better?

Sorry if I ask dumb questions. I'm still trying to figure out the whole CNC gig.