Epoxy concrete CNC milling machine

3-Axis CNC milling machine with solid epoxy concrete cast.

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Our selfmade CNC machine;
Epoxy granite , 3 axis, with housing.

We want to upgrade some components when we can afford it, like the 2KW spindel, 3NM stepper and we want to add another axis, quality guiding rails and sleds.. and so on.
Here are some steps on how we made everything in the last 1,5 years.
And a Solidworks Photoview 360 movie with my 3D Model CNC mill.

CAD-Files for the machine (more will follow):

My heavy epoxy granite CNC mill and some Details about the progress building it. This is my first CNC machine project.

Step one, the making of the mold;

Plywood mold with silicon sealing o n the inside makes nice round corners on the molded part corners.

Bolts with threads as inserts for the guide screws on the right position!

Some granite plates to support the casting mold and to make everything as plain as possible.

Good portion of wax on the inside, so the board can be opened up easy.

Insert guidance pipes for mounting the CNC bridge to the CNC base part with bolts.

Clamping down the plywood form, the curing epoxy gets quite hot, this did bend our first mold so our base surface was uneven and we had to repair this.

And everything is ready for casting

Step two, mixing the epoxy and some different sized rock, preferably basalt. Our casting is greenish because we mix everything we could find in different grain size; 17mm basalt rock, 12mm marble, 6mm quartz rock and sand.

We took 18% - 20% from the weight of the stones to measure the amount of the epoxy. It was a rather wet mixture and good to pour without many bubbles. This was also important for us because we had no shaker for this +200kg mold.

We closed the mold in the middle when we reached the level but the epoxy came through the small gabs of the not sealed cover.

Step three, opening the mold is easy and fun as long as the boards do not stick to any bad waxed areas.

Then, these main parts (machine base and the bridge) are screwed together with 6 tread bolds. A perfect alignment is very important and a bit tricky, especially without proper measurement tools.

The X 6 Y axis guiding rails where mounted afterwards. They have to be aligned, and orientated to each other, starting with the X axis linear guides.

The rails have to be straightened during the mounting process.

Our epoxy granite surface was not perfect straight and we had no better option to level the surface with tinfoil underneath the linear guides. It may not be perfect, but it worked for us, temporarily. We may catch up on timing the surfaces by face-grinding.

Parallel to the making of the machine, we have made a 3D model with Solidworks. This is a rendering from The machine base:

Next step was to make the Z axis and X plate out of aluminium. At first, we made it out of plywood, than we milled and drilled the aluminium parts. It worked, but in the end of this process, the plywood construction got weaker and we just could replace it with the aluminium in time.

Here are some milling operations with the plywood construction. We gained a lot of milling, machining modeling and G-coding experience during this work. We got a sense about you much strength each part of the machine can handle and where the weak points where. At this time it was the plywood Z construction.

Here are some Photoview render pictures from my 3D Model coming up on grabcad soon:

CNC Mill Epoxy Granite.jpg

CNC Base and bridge mineral cast.

JPEG Image - 1.55 MB - 12/15/2016 at 17:59


CNC mill epoxy granit base 1.SLDASM

epox concrete CNC base CAD

sldasm - 10.93 MB - 01/21/2017 at 01:47


JPEG Image - 25.67 kB - 02/12/2017 at 12:15



epoxy concrete CNC base 3D model

Standard Tesselated Geometry - 605.16 kB - 01/21/2017 at 01:47



cutting the boards

JPEG Image - 1.54 MB - 12/13/2016 at 16:43


View all 11 files

  • 2 × Linear guides DIN 645 900mm 23mm x 22mm x 900mm
  • 2 × Linear guides DIN 645 600mm 23mm x 22mm x 600mm
  • 2 × Linear guides DIN 645 400mm 23mm x 22mm x 400mm
  • 4 × 20kg Resinpal 2401 + 5000 g Härter - 90 Minuten High Qualitiy Epoxy for the CNC bridge. 20% Epoxy and 80 % rock and sand.
  • 1 × Ball Screw Drive 600mm 16mm /Pitch 5mm /600mm

View all 14 components

  • Stainless Steel Housing, welding

    3D Meister07/26/2017 at 11:32 0 comments

    Here is another step where i weld some stainless steel for machine stand and the housing. My first time ever, welding something. These bars are for the drawer rails under the machine.  3 Drawers will be installed, on the left side for collecting the cooling water and separating dirt from milling. The middle drawer of all kind of important stuff and the right side for electronics, pneumatic and connections, vacuum and air.

  • The Bridge

    Sixtus02/26/2017 at 19:44 0 comments

    Was casted right after the Machine Base and Finished in September 2015

  • CNC Machine Base

    Sixtus02/26/2017 at 19:42 0 comments

    The Machine Base was Finished in August 2015

  • The Housing

    Sixtus02/26/2017 at 19:40 0 comments

    Stainless Steel Housing is fully CAD designed, The Frame was finished in August 2016.

View all 4 project logs

Enjoy this project?



detimew139 wrote 05/20/2021 at 05:50 point

what a pleasure to watch and read this idea  you are doing wonderful job I like the idea you can see some more similar ideas here

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Matt Bennett wrote 02/06/2021 at 12:22 point

This is indeed very impressive.  Well done to all involved!  I think I'm about to embark on a granite CNC build of my own and all passive learning and the opportunity to build upon other people's knowledge is invaluable.  Thank you for sharing and I'm sure I'll be documenting my build if and when it moves from CAD to reality.

I'm going to give some feedback on your build.  You will know much of what I'm about to write (and more!) because of your experience so this might be of little help to you (the author) but might assist other readers considering this route.  My background of nearly 35 years has been in precision manufacturing and CNC.  I've ran high profile machine shops and even part-owned one previously.  I have a lot of experience to draw upon in design and precision manufacturing (assembly, hand finishing & inspection/calibration) but I'm not a know-it-all.

1.  You learned the hard way that granite worktop isn't flat.  So, if you want an engineered flat surface, start with an engineered flat surface.  Granite inspection tables or surface plates aren't massively expensive. Second-hand ones are available and they remain a sellable asset long after the build is finished.  Get what you can afford and base your design off the limitations of its work area.  A used table may have pits or scratches that you'll need to fill and polish back but this isn't difficult and can be done with the same epoxy you're about to cast the granite with.

2.  Don't mould against wooden panels for critical surfaces (ie where you're mounting guide rails).   Aluminium tooling plate would be better.  Google "MIC 6" or "5083 cast tooling plate".  It's likely though that you'll still have to stiffen these to prevent the weight of the 'concrete' from distorting it while casting.. unless you went crazy with the thickness, only have a light pour of concrete over the top, or if you could lay it face down on that granite table we just bought :)  Stiffness can be added quite cheaply by screwing good quality aluminium extrusion on the back.

There is a cheaper way than using alum tooling plate and to use wood.  It's possible to 'float' plywood on a bed of resin.  Smoothly apply mould release to the face of the granite table, pour resin over the face of the table and drop the plywood on.  Add any stiffness reinforcement (alum box section etc) to the back of the plywood first and you'll find that you can accurately transfer the smoothness and flatness of the granite table onto a (now very rigid) piece of ply.  The disadvantages are; time, mess, the risk of permanently bonding plywood to our new granite table (even with copious use of mould release, don't underestimate the amount of sheer force it takes to break this bond!) and of course wood is always moving.  I've used this technique and I recommend you start with small test pieces to prove you can do it.

Another option would have been to cast flat steel bars in place to carry the rails.  At least the steel faces can be worked to very high accuracy, even by hand, once the the concrete has set (if necessary).  I'm going this way with my build and intend to use "ground flat stock".  I'm hoping I can support it so that it doesn't distort while casting then I won't have to work the faces at all (to achieve the accuracy I'm aiming for anyway) but at least the option is there.

My final thoughts are just regarding the bulk of the machine.  We can see it's huge and massively heavy and currently it's complete overkill while coupled with C7 accuracy ball screws and that spindle.  You do however have the foundations to go on and upgrade it into a really accurate mill.  Getting it running is to be applauded and it's all yours to upgrade and improve over time - a route many people should take even if they're aiming for high accuracy and rigidity in their first build and I'm sure you've have had that in mind from day one.  But for the benefit of others, I'll say this; if all you want to do is push a 6mm cutter thru' aluminium, you probably don't need half a ton of granite to support that kind of cutting force.  If you have a cutter diameter, material and spindle in mind, concentrate on designing your frame around that, with the components to (even eventually) achieve the accuracy you're looking for.  Chances are there will be a number of CNC builds on youtube these days that'll come close to matching your requirements that you can take as inspiration.  In all credit to the author, most of my online research is coming from videos and build logs that are just a few years old at best, so there's been an explosion of information and ideas released in the last couple of years that he didn't have access to.  (Obviously not all information is good information but I'm finding it interesting to dissect all builds right now regardless.)

Looks like a long post.  I hope I haven't bored or offended anyone.

- Matt

PS.  Those slideway covers are beautiful :)

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Jacob.R.Jennings wrote 06/23/2019 at 19:26 point

Awesome project. What's the total volume of epoxy granite? How much does it weigh?

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David H Haffner Sr wrote 01/10/2017 at 13:59 point

Very cool project!

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3D Meister wrote 01/18/2017 at 15:51 point

Thank you

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