darn you , .....
there you go testing ideas again! at the rate you are going (and the rate which im building a machine) there will be nothing left for the rest of us to test
slow down and let the rest of us (and by us i mean ME) catch up
you will have already figured it all out
you come up with some pretty cool ideas microcarve, lookin good!
"witty comment"
Hello John,
Reinforcing the lower axis rail mounts huh, how about doing the same to the upper one where it fits into the side MDF pieces, it would give additional rigidity of the Z. Or would that be over kill, LOL?
Glad to be able to check your progress out again, moved from Tucson to a suburb of Phoenix AZ and it took a week to get access to the internet again..
Hager
John,
Interesting and clever concept! Did you have to hold or clamp down the MDF while the urethane cured to prevent curling? What's the shore hardness of the resin you are using?
Seems like a lot of work in strips that size but I could really see a use for rail mounts cast directly into your large MDF side panels. Keep up the inventiveness!
Dave
Hi Hager!
So you got moved and are settling in....
It took me a few years to do the "settling in" part.
(In fact, 6 years later, I'm still at it....
The top is already about as reinforced as it can get. It's
a multi-layered, easily assembled, arrangement of a thick urethane
plate for the rails themselves....and an outer aluminum plate for the
motors to bolt to. The MDF side is sandwiched between the two.
Practically a bulletproof situation as far as the top axis goes.
I doubt it could get better, outside of steel & welding....
Reinforcing an MDF part may seem a little extreme, but it makes for
a serious improvement. One main reason is, as most of us know, a machine
get re-assembled many times. MDF is some great stuff and is so dimensionally
stable....(I've run a few machines for years with no adjusting at all to them....)
but besides it's "can't get it wet" drawback, it has one more....
Compressibility. So doing any repeated reassembling of it will cause any necessarily
tight fitting parts to become a little loose. Then it gets adjusted a little tighter,
but too many tightenings means it'll compress a tiny bit and get out of whack.
Nothing against the MDF....even a 1/4" aluminum extrusion will deform if it
get's repeatedly loosened and re-tightened several times.
But by reinforcing with the urethane, the urethane permeates into the MDF.
Becoming a permanent part of the assembly/part. It doesn't have near the
compressibility the MDF allows for such a thing as a press fit of a round rail.
So the assembly is actually *Much* more rigid, tighter, and reliable for the
long term.
It does add a whole nother element of work into the mix though, but it's
a reasonably inexpensive thing to do that does make a huge improvement.
Why not just make the whole part of urethane? Well, urethane is expensive
material. But I'm trying both techniques to see where and when it's a good
idea to take the extra time to do so.
I think for the rail supports I showed in the previous pictures, I will just
make the whole thing from urethane. It's rock solid and will last practically
forever. Problem free. But there are other places to use the same idea.
Nuts can be cast directly into place on parts that may be too large to
economically use a lot of expensive urethane resins.
Lots of places to use it. Finally getting around to trying it to see how
useful it may be has been a good idea. I've thought about it for years
but never actually took time to give it a go....
John
Yup, letting it impregnate into the MDF really makes for a good application and you get the best of both materials. Good thoughts John.
Can't wait to see the next refinement, such an interesting and stimulating thread.
Hager
Hi Dave,Originally Posted by dpgoldberg
I may have just asnwered a few of those questions....
The resin is about a 75D or so, IIRC. The trick to getting the resin
in the cavity is pretty simple. Just wax the heck out of the surface
it's set on and it'll release easily.
(the weights to hold it down flat can be seen in the pictures.....)
The resin begins to heat up and thicken after about 60 seconds
of mixing, so the process has to move along fast. By the time
it fills the cavity, it's beginning to set. So it doesn't run out
and get everywhere....which is something someone does not
want to happen.....it'll be the stickiest mess ever recorded
in that guy's shop/house/apartment....
It does take a bit of trial & error to get the procedure down, which
is one of the drawbacks of using those expensive resins. But after
getting a bit familiar with them, they are pretty predictable to use.
As I mentioned, I've thought about it for a long time, but never got
around to actually trying it. It was worth the time to see how well
it'd work.
I tried before to seal the MDF edges with it. That works very well.
Lots of after-sanding involved, but it does work very nicely.
I just wish the stuff didn't cost so much. I'd use it for a lot more
things.
John
LOL!darn you , .....
there you go testing ideas again! at the rate you are going (and the rate which im building a machine) there will be nothing left for the rest of us to test
slow down and let the rest of us (and by us i mean ME) catch up
you will have already figured it all out
you come up with some pretty cool ideas microcarve, lookin good!
Thanks .xXACEXx....
There's more to come....
Here's one in progress right now.
I've began to take a new approach to the final finishing/painting
of them. Inspired mostly from seeing how they do fancy $$$ car
restorations on TV....
Usually, I'd wait til the end to do all the final sanding and sealing.
But, I noticed how when they do something like build a cool
motorcycle or restore some nice automobile, it looks like crap
throughtout the process....until the final sanding and painting.
So...now, I add a few coats of sealer here & there as I work.
Mostly just wood glue and water brushed on. If I were to wait
until the end, It'd have to dry a long time before sanding and
painting. But doing it as I go adds more coats and makes it
all easier in the end.
It looks bad, but the final finishing is where the end result
matters. If those cool cars and bikes look as good as they do
in the end, well, it'll work as well for MDF machines...
The new urethane bars/elements can be seen in the pictures.
They're rock solid and as stable as possible. Nothing will ever
go wrong with them.
John
There's a point where...after lots of experience with these things....
you can tell a really good machine from one that needs extra work.
Get things sliding well and you have a good one. The rest is just
tedious details and aligning & squaring.
With the fixed bridge design, if the holes are where they should be,
exactly.....aligning and squaring is easy.
I'm playing around with the idea of getting the major assemblies
and main parts in place and selling the machine to be completed
by someone else. I could sell them very cheaply if someone
were willing to do something like purchase the leadscrew and
couplings and do the final sanding and painting of a machine.
A sort of half & half type of deal where the machine is available
much like seen in the picture. Pretty much guaranteed to work
correctly once someone else does the time consuming
painting and final adjusting.
I don't know if that'd be of interest to anyone, but it can be
sensible to both save a good bit of $$$ and still have ended
up completing a DIY project to one's own standards.
For example, at this stage, I can sell that one for $225.
Pret-ty cheap for what this machine can and will be in the end.....
Just thought I'd mention it. It's just an idea at this point. Anybody
finds that of any interest, just send me a PM or preferably an email....
John
You've gone back to curved surfaces? I thought you changed to straight surfaces so users could easily bolt on strengthening rails, enclosures, e-chain racks etc.
And I think your price is too cheap, for sustainability of a business/product model you would probably need a higher price to allow for production costs, labour, etc etc.
As far as the cost of the urethane goes, have you considered using a filler material? If you use one of the commercial (machinable) fillers it reduces your resin costs and will also help with that short 60 seconds pot life problem as the filler will slow the thermoset down a bit. You could even try some MDF dust as filler after running it through a mesh first to remove larger particles. You can run quite a high filler percentage while still retaining most of the structural properties of the urethane.
There are still 4-5 of the more rounded design that were never
completed, so I can sell those off for dirt cheap. I may go to the more
squared edges like the larger machine, but I'm not sure just yet.
Once I get my web site in order, I'll have a few different sizes, and
they may have the same cosmetic look to them, or the small one
could stay like it is now. At any rate, the MDF frame itself can also be
offered in several different configurations.....such as extra deep for
machining holes in enclosures and.....a 4th axis....which actually lends
itself very well to the rigidity of the smaller fixed bridge machine design.
The MDF frame is the cheap & easy part, easily swapped out for another
as needed. One could even hang on a wall and work just as well....
This is a type of design that lends itself very well to various bolt on, add-ons.
The larger one I showed is a pretty good sized machine and I still want to have a
smaller one. The 12 x 10 x 4 model takes up a bit of space and it could be a bit
too large for someone with limited space. It also has a presence and feel
of some sort of heavy machine.
Yep, they are way too cheap for now. It'd be good to get a dozen or
so out and in use to serve as examples of just how useful a small machine
it really is. It's hard to convey in pictures....and the needed examples take
time that I need to devote to parts making for now. If I sell a handful
off at basically cost, then maybe some examples could come from those
machine owners.....which may help others decide if they could use one.
I havent' found the various fillers to be of any real use. Aluminum fillers only
add to the cost and don't do much --if anything, for the quality of the parts.
Cheaper fillers only cause different problems. The obvious MDF flour has to be
specially treated with ovens or it's natural moisture content can cause
severe foaming at worst, or unpredictable inconsistencies at best. Time and
extra tools make usefulness of fillers too cost prohibitive....at least for now.
There are a fair bit of "gotcha's" involved with working with urethanes. Besides
the expense. But I started out 20 years ago with "tooling plastics" so I got
most of the hard lessons out of the way a long time ago. Still, surprises can
and do happen. It's a genuine heart breaker to have a $200 mix fail on you.
All within 2 minutes.....
But yes, they will eventually have to cost more. They're time consuming
to make and there's no real way to cut out a lot of that time....at least
without some large and expensive production machines.
John
A couple of pictures of a full sized Milwaukee router mounted on the
larger machine.
It works fine, but I think a router that big is a bit overkill. Trim routers
such as the Bosch Colt, Ridgid, PC, or DeWalt will be ideal. If a heavier
full sized router were actually "needed" on a small machine, I'd increase
the top rail sizes. But the trim routers are plenty powerful enough.
It's a good sized machine that's hard to show in pictures, so a picture
with the full size router may give a better idea.....
John
There are two new small routers coming out soon, a porter cable and a dewalt. Both are the same basic router, since they're now the same company.
Delta Machinery|Porter Cable Product Details for 1.25 HP Max Torque Compact Router - Model # 450
Gerry
UCCNC 2017 Screenset
[URL]http://www.thecncwoodworker.com/2017.html[/URL]
Mach3 2010 Screenset
[URL]http://www.thecncwoodworker.com/2010.html[/URL]
JointCAM - CNC Dovetails & Box Joints
[URL]http://www.g-forcecnc.com/jointcam.html[/URL]
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Hi microcarve
Thank you for this great tread! You do nice and simple machines!!!
I have one question!
I have some experience with urethane resins (some time ago I've made some resin toys, soldiers and other miniatures) and had an idea to use it in cnc homebuilding, and now just discover your topic here on cnczone
What do you use as a forms for your urethane castings? is it a rubber forms or something other? And have you ever try to cast some complicated details spindle mount for e.g.
Best regards
Dmitry from far away Russia
Hi Dmitry,
Yes rubber molds/forms work very well. I haven't made any spindle mounts
myself....but only because I can't make them any better than the guy
I buy them from....
MCPi - Nicknacks
Oooops! He's sold them all! Well, it's an excellent example of one anyway....
I'm glad I got one before they were all gone. So now I'll refer anyone to either
Probotix or K2CNC for any tool holders/spindle mounts they need for my
machines. I don't provide them with my machines. There are too many
choices in routers for me to make them myself. And....I can't make them at
a better price.
John
Also Dmitry,
For simple geometric shapes, any container made from Polyethylene...which
is the type of plastic common milk jugs are made from, also work very well.
The clearer plastics may not work as they're usually made from a
type of plastic the resin will stick to. Polyethylene is usually....here anyway...
a translucent plastic. Spray paint can tops and aspirin bottles are a great
source of free molds.
It's always best to test any container before casting a large volume.
John
Thank you John for your prompt reply
I've just finished my first homemade cnc from aluminum, it was really a challenge to do it on my kitchen without mill and late
So I was thinking about casting some parts from urethane, I think ill do it on my next project.
And yes I have already found tool holders you've been using in your machines so I decided that my initial thoughts about casting such complicated parts was right and I can give it a try
Thanks again
Dmitry
You are very welcome Dmitry...
With the experience you already have casting urethane, it should be
easy for you.
John
Well, here she is all painted up nicely...
Still need to make the leadscrews and a few other little details
Sure looks a lot different with the paint job.
John
Last edited by microcarve; 10-21-2010 at 04:48 PM.
Looking GOOD! I haven't near that far on mine yet!
Art
AKA Country Bubba (Older Than Dirt)
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