Composite quartz countertop base


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Thread: Composite quartz countertop base

  1. #1
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    Thumbs up Composite quartz countertop base

    Hi everybody,

    I've been lurking and reading for several months now getting inspired by awesome builds and trying to figure out how (and what) exactly I should build (I don't need a machine, I WANT one). anyways I just found out about the whole EG machine building scene and had an interesting thought I would like to bounce off you guys.

    I used to work in a large factory manufacturing high grade quartz composite kitchen countertops - essentially 7% polyester resin and 93% quartz sands, the precise recipe is very similar to the EG recipes iv'e found online. The mix is then compressed with a huge industrial vibration press under a vacuum and cured for several hours in a low temp kiln. I still have access to the plant and to quite a large amount of left over slabs which I thought of using as a base for a mill i have in mind.

    The slabs are 30mm thick and ground and polished to a mirror finish so are extremely even and flat, they are extremely heavy (around 50kg a square meter) and they can be glued together with special epoxy glues which last a lifetime, the slabs would break before the glue does.

    I was thinking of coming up with some kind of very simple design and have the slabs machined (stone cnc/water cut) to accept some linear rails (directly bolted on to the surface of the cured 'stone' as opposed to set in the material pre-curing) and building some kind of construction around the rails - i'm guessing this thing would way around 200 kg for a box sized 600X600mm as in the attached concept drawings:




    The rails are HIWIN 20mm, ballscrew drives and large steppers, but those are just the parts i happened to have handy in the cad program, i'm more interested in what you guys think of the idea of bolting the linear rails directly to the quartz surfaces and gluing them all together in some kind of box (would be great to have a lid closing the whole thing so it doesn't disturb me planning my next weird build as it churns out parts)

    Any feedback would be greatly appreciated!
    Jon

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    Attached Thumbnails Attached Thumbnails Composite quartz countertop base-2-jpg   Composite quartz countertop base-1-jpg  


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    Default Re: Composite quartz countertop base

    the design you have is relatively floppy when you consider the money you have to spend on ball screws and linear rails compared to the cost of the (relatively, it sounds like) free engineered stone.

    i would double up up the base and the vertical slabs, but perhaps not the entire surface area. maybe epoxy two slabs together for the full height, and twice the width of the Z and Y axis. also. the triangular sides, a single sheet for those is probably fine if you can ensure the joints are sufficiently rigidly held together. you don't want an epoxy joint to start cracking at the edge over time.

    a double thickness around the open perimeter would be good because the stress will be highest around the perimeter of the open section. so maybe add another 4 inch wide strip of material around the open face of the whole thing.

    another point.. the way you have the system designed, you might as well double the distance between the Z and Y axis rails.



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    Default Re: Composite quartz countertop base

    Besides beefing it up as Eldon mentioned, the weak point is the base to back connection. The stiffness of that joint will make a break a machine design no matter how small. You can get away with a lesser joint there for a non contacting Z axis like a plasma, laser 3D printing etc. Machining of any type will need a solid joint.
    Even with the gussets, the back plate can flex. Different material may work out better for you, but given that the stuff is free, you can always build a different frame for your components later if you do not achieve the results that you want.

    Lee


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    Default Re: Composite quartz countertop base

    Thanks for the feedback!

    the gluing of the slabs was defiantly a weak spot in that plan, I was thinking of maybe beefing it up by combing the ready polished slabs with the more traditional EG method (since I also still have access to an unlimited supply of epoxy...)

    1 - have the the X/Y and Z slabs machined to accept my linear guides & ballscrew supports
    2 - align the surface slabs to each other and glue them together
    3 - flip over, build a wooden frame around them and fill with EG and some rebar
    4 - after curing flip over, make sure everything is still aligned (why wouldnt it be?) - hopefully no scraping or sanding of any sort will be needed
    5 - bolt everything together

    any thoughts about this? I could basically swap out the quartz base slabs for steel or aluminium i suppose..
    what about preforming stage 5 in my plan straight after stage 3 - having it all bolted together and aligned and only then building the frame around it and casting the EG - could make for an easier (and lighter) build at the cost of a slightly more complicated casting process. could have the bolt heads from the rails protruding into the epoxy that way so they are deep in the epoxy cast.


    Composite quartz countertop base-1-jpg
    Composite quartz countertop base-3-jpgComposite quartz countertop base-4-jpg



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    Default Re: Composite quartz countertop base

    the engineered stone might be both stiffer and higher dampening than any epoxy granite you can make, not by much but on the order of 10%. you could leave your structure hollow. doing such gives room for you to put the Y and Z axis servo or stepper inside the column.

    maybe make the plates where the rails bolt to, make those two thicknesses bolted and glued together, this will help if you insist on placing the rails close together, in the middle of the plate. i would put the rails as far away from each other as you can. for the z axis, they should be as far away from each other as the distance from the spindle to the rail, this is so that the forces on the spindle are not multiplied, and the slop in the bearings will not be multiplied.

    save weight by leaving it all hollow. if you need more dampening, fill it with sand.

    filling it with epoxy granite might double the stiffness, at the cost of a lot of weight. calculate the moment of inertia for your system and compare the two, solid vs hollow.. then look at the weight...



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