Precision CNC With Epoxy Granite

Epoxy granite is an overlooked material when it comes to making home CNC builds. As far as time and money goes, when you add in all the equipment it comes out cheaper than an aluminum casting set-up. Epoxy granite has mechanical properties better than cast iron, increased dimensional stability, better vibration damping, and looks awesome when done right. Also, you can cast precision surfaces and threaded holes into your design, which is pretty cool.

In these two videos by [Jørgen Hegner] we get to watch him and a friend make a matching set of precision CNC machines. It’s built in a similar style to other nice builds we’ve featured. This way of making it needs a bigger footprint than a gantry mill and can’t be built as large. However, it solves a lot of mechanical issues and squaring with the gantry design while not being as difficult to get right as a box or knee mill.

After casting they machined the material embedded in the granite to mount the ways. The ways are linear bearings and ball screws. Expensive, but as the footage shows, very accurate.  The rest of the machine is assembled and tuned. Then it gets installed in a home made 80/20 enclosure. We really like the LCD panel that’s incorporated into the front shield of the machine. They really went all out with the CNC control panel. It looks like they can do anything from jog the axis to monitor and control the water cooling for the spindle.

It appears that all the precision work is put to good use as there are some shots at the end of video two of a beautiful clock CNC’d on this machine. Videos after the break.

28 thoughts on “Precision CNC With Epoxy Granite

  1. This answers the question of “What could I do if I had all the time, equipment, knowledge and experience in the world, and had the patience to put something together properly?”

    They’re making their own castings and embedding them before machining (which takes confidence), to avoid unmeasurably small thermal fluctuations with welded structures (in the comments of vid #2).


    1. But still not perfect. See how the mould stayed glued on the base. I would be surprised these guys forgot to apply wax before molding the epoxy-granite mix. Then what happened ?? How to avoid the ugly mould spots ??

  2. Absolutely fantastic build, and the clock is simply wonderful!

    But with my luck, if I had put a control panel anywhere chips could possibly fall down onto it, it would short out in a week.

    Honestly can’t wait to see more from these guys!

  3. I’m really interested in the new CNC machine they mentioned at the end of the second video. Really want to know what that one’s going to be like. If it’s an improvement over this one it should be amazing.

  4. This is really awesome; I also haven’t heard yet about epoxy granite, sounds interesting.
    I just wonder which radiation / Radon levels one has to expect, granite as material seems to show some variation depending on source location.

    Has anyone ever tinkered with it yet? I wonder about 3d printing negative forms in PLA…

    1. It’s pretty common in high speed high precision industrial CNC machines. Just ckeck out any company that makes circuit board drills/routers. To keep them stable at extreme axis acceleration (>40ms^-2) and get position errors down to less than 10um they make a big block of cast granite (usually several tons heavy, depending on how many spindles are running in parallel in that machine) that fixes the rails for the X and Y axis directly. (I did an internship at Posalux years ago)

    2. The members of have been tinkering with epoxy granite for at least a decade, they’ve researched and covered pretty much everything there is on the subject. I can’t say any of them were standing around with geiger counters, but I don’t think any of them reported getting lymphoma either.

  5. These guys clearly have access to a REALLY nice shop to begin with which causes me to wonder at 3:25 of the first video why they milled the axis for the rails and the ball screw. As soon as I saw it I thought I’d probably have ground them. They appear to be doing the milling on a knee mill. While you can “swing” in the head (in another life I got really good at it with tons of practice) the bed still isn’t going to be able to churn out as precision results as would grinding. It would have taken a little more time, but saved them some of the headache of adjusting the rails if they ground a shoulder to register the location of the rails (which appear to be ground). Still amazing to watch those guys work and as said before, Damn that is one beautiful clock.

    1. I have a ProLIGHT PLM2000. Intelitek discontinued the 2000 quite a while back but kept producing the PLM1000 and the enclosed Benchman version. Both of those used stepper motors and Windows control software was written for them. The servo motor PLM2000 is stuck using the old DOS software. :( I finally managed to get someone at Moog Animatics to excavate some technical info and software from their archives for the 5000 series servo controllers which Light Machines used in the PLM2000. Posted on dropbox here

      Hopefully someone can use that to put support for the PLM2000 into modern CNC software like Linux CNC. Light Machines and Intelitek didn’t come near to fully utilizing the capabilities of the Animatics controller.

      What helps the ProLIGHT mills hold their value is they beat every new mill currently available in their size class on load capacity and speed. They can handle a 100 pound working load and the 2000 (dunno about the 1000) has traverse speeds up to 100 inches per second. To get something new with that kind of capability, it will cost a lot and will be larger. 5000, 1000 and 40K+ spindles were available, but the super high speed wasn’t an option on the 1000.

      If you’re looking to buy a PLM1000 mill, or PLT3000 lathe, make sure to get both the huge, black electronics box AND the ISA or (of course it’s better) PCI card plus all the connecting cables. If you do not get the interface card, you can buy one from Intelitek, at a price higher than what it’ll cost you to replace all the electronics with new stuff that runs with non-proprietary software.

      The PLM2000 is self-contained, all electronics in the ‘backpack’ box on the back of the column. Only requires 115VAC power and one RS232C connection to a control PC.

      1. Intelitek’s current small CNC machines are all (like most other companies still in the business) Sherline machines only good for doing tiny stuff. Light Machines built their mills and lathes with the capability to be used in light industrial, laboratory and educational fields – with the education not just on the basics of CNC operation but for learning about designing decently large things to be made by CNC machines.

        With a Sherline CNC, students can learn about CNC but they can’t do much about verifying a designing for manufacturing project, unless it can be done as a (very small) scale model.

  6. Bigger one, made with smaller tools:

    I met the guy quite a long time ago (he is dead now), very skilled (professional machinist) but he intend to build the mill with only a small hobby desktop mill (BF20) and lathe (9×20 kind).
    He succeed quite well as his mill was able to mill steel easily.
    He has used clever way to overcome limited machining capacity: prepare mild steel rail support on the mill with notched design for supporting the rail, then finish with a hand scrapper and a machinist level (0.05mm/m sensitivity).

    The main limit with epoxy/granit is that you cannot make thin walled part like casting iron, minimum reliable size is around 50mm. Less than that and it can fracture under stress or deform.
    You also need big curing enclosure to maintain high curing temperature (depend on expoy used, but most high perf are high curing temperature), good mixer system. So it’s not a zero tool thing…

  7. nice clock but agree the location of the control panels is er, strange given how far brass chips can travel. Likewise the orientation of the upper profiled rails..

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