Epoxy/Granite VMC Build - many questions - could help others with similar plans

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Thread: Epoxy/Granite VMC Build - many questions - could help others with similar plans

  1. #1
    Join Date
    Mar 2017

    Default Epoxy/Granite VMC Build - many questions - could help others with similar plans

    Hello guys,

    i am planning to build an VMC-Style Milling machine with Epoxy/Granite which should weight about 1000-1500kg (maybe more). Here an example how the construction should look:

    I have done my workshop floor with epoxy resin, so i have a bit experience with it, but i have not use any filler like granite (just chips for the look), so i have couple of questions, but i just want to say, that i have read the last 3-4 days about epoxy granit and was searching for an good mix and of course i looked for information in the big Epoxy-Granit thread here in the forum.

    So, here my questions:

    A1. Is the Pot Life of the epoxy resin (epoxy+hardener) same long when its mixed with Granite or any other filler at 10/1 ? (example: 1000 kg granite mix + 100 kg epoxy).

    I know that, there more quantity of epoxy resin you mix, the shorter becomes the pot life, but how does it work when its mixed with filler? I am just thinking about the heat the epoxy+hardener produces after its mixed, but i think it should react completly different when 90% of the total volume is Filler.

    A2. How to calculate the exact amount of Epoxy?:
    I was thinking to calculate the exact amount of epoxy i need for the mix by filling the mould with the Granite (or any other filler i use, but i have over 3000kg of Granite stones in my garden, which i could crush and use it for the mix). Then, i would take the granite out and weight it. After that i should know exactly how much Epoxy-resin i need, or am i wrong ?

    A3. How to fill the mould with the E/G mix (filling in layers?) ?: Currently, i dont know how the pot life reacts when mixing with filler, but here my idea: After i know the amount of Granit and Epoxy i need, i would put the granit in couple containers, so that i can use an one 30kg Epoxy-Resin-Set for each Granit-container, because 30kg is largest/common Epoxy-resin-set which i can buy.

    So, here the progress for
    OPTION Nr. 1:
    1. Mixing the Epoxy and Hardener,
    2. Filling one Granit-container with the Epoxy/hardener and mix it for couple of minutes
    3. Filling the Epoxy/Granite mix into the mould
    4. Installing an "concrete vibrator" (that kind of: http://www.airtoolequipment.com/513/...ors-rental.jpg) and keep it there until the mould is filled (moving to different points and pulling up the vibrator to each layer)
    5. Next layer

    Problems with this idea
    : Each layer/mix has to have an large volume if i want to fill the mould as soon as possible (lets say 20% of the total mould volume so about 200kg if the total weight of the base should be 1000kg), so it will be problematic to lift that amount (alone, but could use an engine-lift or use an Concrete mixer which will stand next to the mould).

    I have an idea how to solve that problem (quiet logic ):
    OPTION Nr. 2:
    1. Filling 90% of the mould volume with the Granit-mix
    2. Mix one 30kg-Epoxy-Set
    3. Fill the mould with one ready mixed Epoxy-set
    4. Installing the vibrator and mixing with a mixing-stirrer
    4. Mix the next 30kg-Epoxy-Set ,fill the mould and continue it until the mould is filled

    Option Nr.2 should be the way to go, because i can save a lot of time, but i would need someone who will permanently mix with the stirrer and move the Vibrator to different points.
    With this progress, i could be ready within 30-60minues and have a lot less work which results in less stress .

    A4. Is it possible to not fill the mould in overhead-position?
    All moulds i have seen for Mill-builds got filled in overhead-position, with installed and aligned "flat-steel?" (for sure not the right word for it, sorry) for the linear guide rails on the bottom. That is for sure the best way to go, but it becomes problematic if you want to fill an mould which will later weight at least 1000kg.
    In my case, i can not fill the mould in overhead-position, because i see big problems to turn the base later and also its just to risky. One fail, and the base will brake and of course i also risk to loose some parts of my body.

    So, here my idea:
    Prepare and prefit an top plate with aligned parts, like e.g. flat steel for the linear rails (60x60 flat steel, precise grinded, with an edge on one side), and plates for the ball screw bearing housing, etc. .
    The top plate will have for example, couple 10cm wholes (e.g. on each corner) which are closed with plexi-glas. The corners of the top-plate and the corners of the side-parts of the mould will have 45° cutted corners, so the top plate will fit perfectly into the mould, but the problem here is that i could not align the top plate anymore (just thinking how to solve that).
    The top plate will have mounted many "hole screws?" (again, dont know the right word for that, sorry), where i can fill more epoxy-resin into it, also to get an better surface finish)
    For pressing the top plate into the mould i thought to use steel plates with nuts mounted to the corvers of the side-plates and between them and press the top-plate into the mould by screwing, so i could still make some alignements.

    So, here the progress (all gaps inside the mould are closed with silicon (dryed) also the 45° surface of the side plate and top plate (not dryed) :
    1. Lay down the plate on the mould plate.
    2. Slowly pressing the top plate into the mould by screwing and permanently checking the level with an precise 0,02mm/m water-balance leveler.
    3. Permanently checking the level of the E/G mix by watching through the plexi-glas
    4. Pressing as long as its possible and until i will see not changes anymore.
    5. If needed, pressing some epoxy-resin through the "hole screws".
    6. Again, trying to screw the plate more tight.

    From starting to to finish, the mould will be heated through infrared heater, to get an better surface finish and to get less bubbles through better viscosity of the epoxy (more fluid). Also i will mount flat steel around the mould and weld or screw it together (in layers, e.g. every 15cm), because i fear a bit that the mould will move/expand when pressing the top plate into the mould.

    A5: Using an "Concrete-vibrator":
    What happend with the smallest pieces of granite or any other filler like sand? Will it move down to the bottom due to the vibration ? If that happend, could i solve the problem through mixing first, and using the vibrator after the top plate is mounted ?

    A6: E/G for Z-Column and Spindle+Motor housing:
    Is it an good idea to use E/G for the Z-Column and the Spindle+Motor housing ? For the alignment of the Z-Column i would use the same technique as this guy has used: Check out this video (alignemnt at 02:20 min):
    The Spindle+Motor (belt-drive) is just an idea, but i am wondering if the vibrations while milling, would make some micro-cracks to the E/G Spindle housing?

    A7: High-quality Concrete vs. E/G:
    An strong high quality concrete mix would be a lot cheaper than E/G, and of course a lot easier to make, due to the long Pot-life and ready mix from some company (like that guy did - check part one of his videos: ).
    I just wondering if the difference (vibration damping, etc) is such big. I read a lot about E/G and also some Analyses like that one: http://annals.fih.upt.ro/pdf-full/20...-2012-2-13.pdf , but is the advantage of E/G to concrete or steel such big in practise ?

    Okay guys, thats all for now. I hope you can help me out and give me some Tipps. That could also help others with similar plans for building an Large/Heavy VMC-style mill.
    I will of course make some documentation about the project, as soon as i will start with it (with HQ pictures and maybe some videos). Currently i am learning Solidworks, while trying to draw the the Project, so it could take some time until i start.

    Thanks in advance !


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  2. #2
    Join Date
    Sep 2012

    Default Re: Epoxy/Granite VMC Build - many questions - could help others with similar plans

    A1. Pot life mixed with filler is long. I didnt see any exotherm

    A2. Measure volume of mould convert to mass using 2200kg/m3 epoxy granit s.g then resin/aggregate 12%/88%

    A3 mix in electric concrete mixer. Pre mix and grade and dry all aggregates. Drying sand can takes weeks in the sun! Mix as big batches as you can.

    Option nr1 ok
    Option nr 2 wont work. It takes alot of mixing. It is not runny at all its like dough at 10-12%.

    Cast bolt inserts into place and close to flat surfaces in mould. Then hand scrape them after to spec. Needs precision strait edge.

    Concrete vibrator is good idea. Use slowest hardner you can get.

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Epoxy/Granite VMC Build - many questions - could help others with similar plans

Epoxy/Granite VMC Build - many questions - could help others with similar plans