[turpija]

I, as many of you around here have build a simple cnc, then another more advanced, then i saw how it could be improved, and decided i have to build yet another cnc

So, wishes first
hiwin linear rails
chinese ballscrews
stepper motors from previous cnc
pretty ordinary stuff, except, main construction will be epoxy granite woohoo !

simply amazing stuff that is, epoxy-granite mix, and after too much looking at other people projects i warmed up solidworks and start building

too cut story short, this is what design i'm satisfied with looks like


beside epoxy mix, metal parts embedded in it would be aluminum pieces, cause i can easily cut em on my cnc

almost forgot ... dimensions

working envelope would be something about 200x250x100mm and according to solidworks model it will be little over 100kg in weight !! seems robust enough

just a short overview and i'll upload some more images soon

[shedbob]

I like you design.I am hoping to build a machine of similar size so your design is of
interest to me.It looks well proportioned and should be very stiff.Portals look
to be the best design for eg because of their closed loop design.Your bridge is nice
and deep which should prevent bending under its own weight and the small travels should
improve stiffness even more.Is there a reason for only 100mm of z travel?When you
could easily lengthen the columns and/or reduce the depth of bridge to get 200mm/250mm
without increasing weight or reducing stiffness much.
What materials are you planning to machine?
What size rails are you planning on using?

I see an increasing number of router builds using poured and gravity leveled epoxy
for railmounting.Maybe this is a possible rail mounting option.But I do have
doubts about this methods precison and overall effect on machine stifness.A few links
to machines using this method.

BUILD LOG: A sufficiently strong machine

BUILD LOG: Quite an Unusual one - Page 13

In case you havent see them already these are imo the two best pdfs on eg and machine
construction.

Rapid machine tool design.A thesis on design and construction of an eg portal.Bostomatic
BD12 year 1998.Has much general info on eg its properties,use,design with etc.

DSpace@MIT: Rapid machine tool design

German Castillo's thesis on developing and testing of an epoxy granite for machine tool use.
In French.

http://www.cnczone.com/forums/epoxy-...frame-104.html
See post 3606.

Together these two thesis answer many(but far from all) of the often asked questions asked
about eg and machine construction.

I hope you find some of the above helpful.This is a very interesting project.I will be
watching with great interest.Thank you for posting it.Good luck with its construction.

[turpija]

Thanks for interesting links !

to answer your questions ...
100mm of Z travel is more than i need, and i like how it looks in proportions, style at first place

here are rails for X and Y, still need to get for Z axis, but will be the same size, 20mm, hiwin in this case


and here are other components

stepper motors are quite small, but should be sufficient (if not, easy upgrade)
ballscrew are 12x4mm

so, let's continue (or start actually) the process

here is basic shape of mould for lower part


after some thinking how to solve the problem of "attaching" aluminum pieces firmly into epoxy this is what i've come up with
pretty simple, and with some of loctite in thread just to make sure, it's not coming apart ever


this is all assembled
there is not reason to save on bolts, so i used plenty


base will be 100mm at thickest places


and around 70mm at thinest


next is exciting part of mixing epoxy to total of around 40kg of mix for this bad boy ...

[turpija]

pouring, or actually, shoveling the epoxy mix


here you see the tools i've use to compact it between all those gaps ...


...done


here you can roughly see the size of stones, scale is in mm


and fast forward it to interesting part ...


you can see some mdf pieces stuck to aluminum, cause i didn't properly closed all the holes, and epoxy found it's way out ...
but still, it turned out pretty great

did a quick test and weight it, it turns out this bad boy is solid 42kg ... will make a stable base for sure

[RotarySMP]

Good start. I have also been collecting rails, ballscrews etc for a little E/G emill of about this size.

[Hydropower]

Nice!

Skickat från min GT-I9300 via Tapatalk

[jefersonbmx]

Nice job!

You milled with another CNC the aluminum parts after made the EG block?

[aarggh]

What a fascinating build, and great results!

I've long toyed with the idea of an epoxy build and yours looks ideal.

cheers, Ian

[turpija]

yes, good old cnc did the job of surfacing the alu pieces

[turpija]

epoxy-ing is not done yet ... so let's prepare mold for top piece ...

you know the drill ...


some assembly required ...


done


paint ...


screw ...


mix ...


done ...


demold ...


test fit ....

[CaptainVee]

Thanks for the detailed pics, really nice to be able to follow this process closely!
You make it look easy

Could you share what mix you are using? It seems to be a mix of say 5 mm pebbles and sand and (estimate) 7%-10 or so epoxy?

[RotarySMP]

Fantastic work you are doing there.

[CaptainVee]

Seem like 50% granite < 5mm., 40% sand and 10% very fine sand. Need people who know german to verify.

Awsome reading, thanks for sharing!
The "very fine sand" is ground sand, translated directly as "rock flour"

[BjornskiNL]

Die Trockenmischung besteht aus 50% Split mit einer maximalen Korngröße von 5mm, 40% Sand mit einer Korngröße von 0,2 bis 0,63mm und 10% Steinmehl mit einer Korngröße von 0,0063 bis 0,02 mm.
The (Trockenmischung) dry mix mixture consists of 50% maximum grain size (Korngröße) of 5mm, 40% grain size between 0.2 till 0.63mm and 10% rock dust or fine sand grain size between 0.0063 till 0.02mm.

Die Mischung wurde so gewählt um eine maximale Dichte mit so wenig wie möglich Lufteinschlüssen zu erhalten.
The mixture is chosen in such way to maximize density and avoid as less as possible air intrapment.

Very nice project by the way

[CaptainVee]

I was wondering:

Did you take any provisions for the possibility that the ganty's feet did not come out plumb?

And offcourse, would like to see more pics of the finished system

[crazydiamond]

[QUOTE]

Such a nice process I'm learning a lot from:

I found that there're many ways about the mix and your mix seem very smooth.

Here's my 2 cents about what I've found:

From Tobias Merten and Michale Gunther's research on page 12, 5.1.3.1
http://www.technikerschule-noerdling...N%DCRNBERG.pdf

Seem like 50% granite < 5mm., 40% sand and 10% very fine sand. Need people who know german to verify.

Ahh yes Tobias Merten.. He's got some videos on the tube. Really impressive machine, actually quite a similar design.

https://www.youtube.com/watch?v=fDiEi2bOXgs

Looking awesome by the way! Keep the updates coming

[turpija]

feet were not flat right from the mold but it got cnced flat ...

but i have another issue, as it turns out my cnc is not straight enough for my liking ...

here is some testing, and at this configuration i need 2,5kg to slide this plate along rails ...



hopefully i'll get it within acceptable tolerance and continue the build

[turpija]

it's all about function, but it has to look pretty

time to decorate it a little bit ...







made a table ...



did some assembly ...



and made motor mounts ...

[turpija]

if you see this on your table, you've made a wrong step somewhere along the line

pretty tricky to get it back in, but now i know balls circulate in three separate circles, 16 of them in each ... how would i knew that otherwise :P

and one more discovery about nut ... you can't cut threads in mounting holes, well actually, you can't redrill and enlarge them ... pretty hard material

[RCaffin]

Relax!
Nothing that can't be solved with a credit card.

I have disassembled a zero-backlash ball screw once, to get hypothetical gunge out, but I did it over a very big plastic tub, to catch all the balls. Eh - cleaned it all up, regreased the balls, reassembled, and it goes fine - within specs.

The secrets are: don't lose any balls, and grease is great for keeping the balls in position while you fiddle.

Cheers
Roger