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  1. #81
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    Default Re: Large Epoxy Granite Vertical CNC Mill

    Contact the epoxy maker, usually the kind you are working with can be helped with raising to 150 degrees for a few hours which is pretty attainable with the method suggested

    nothing on the expansion, it is what it is, the only thing you could do is keep the temp stable and not let it vary widely, you have re-bar in the casting right?

    What does a 20 degree rise equate to in linear per inch? remember that for each cross- section of the casting epoxy is spaced apart with rock which has a different expansion rate so the overall change in length should be reduced wouldn't it?

    Where in Cali are you? I'm in 1000 oaks



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    Default Re: Large Epoxy Granite Vertical CNC Mill

    Quote Originally Posted by johnh View Post
    you have re-bar in the casting right?
    Right, there is re-bar in it, not a lot that it should bend the whole structure though.

    Quote Originally Posted by johnh View Post
    What does a 20 degree rise equate to in linear per inch? remember that for each cross- section of the casting epoxy is spaced apart with rock which has a different expansion rate so the overall change in length should be reduced wouldn't it?
    Yes, stone has a much lower expansion coefficient, about half of that of steel so overall the expansion is reduced from that of epoxy. I still feel that EG expands more than steel though. Concrete on the other hand expands at the same rate as steel - one lucky accident of nature!

    Expansion of steel is about 1.3 tenth per inch per 20 F. Pure epoxy is 7 tenth and natural granite is 0.9 tenth (1 tenth = 0.0001").

    Quote Originally Posted by johnh View Post
    Where in Cali are you? I'm in 1000 oaks
    San Francisco Bay area



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    Default Re: Large Epoxy Granite Vertical CNC Mill


    The stand is joined using the normal mortise an tenon method. Making tenons is easy, it can be done with a hand saw. Mortises in 4x6 are not so easy to do without a mortising machine. Luckily I have a Sieg mini mill which can be used as a mortiser. Here's one leg being machined.

    Large Epoxy Granite Vertical CNC Mill-jpg

    Here are the four pieces making up one of the sides of the stand.

    Large Epoxy Granite Vertical CNC Mill-b-jpg

    And here is a closeup of the joint. The top hole is where the cross beams are going to plug in.

    Large Epoxy Granite Vertical CNC Mill-c-jpg

    The joints will simply be glued and clamped tight.





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    Default Re: Large Epoxy Granite Vertical CNC Mill

    Haunched tenons.... Nice work!



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    Default Re: Large Epoxy Granite Vertical CNC Mill

    Yes, stone has a much lower expansion coefficient, about half of that of steel so overall the expansion is reduced from that of epoxy. I still feel that EG expands more than steel though.
    If EG is ~85% stone, then it's not going to expand more than steel.

    Gerry

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    Default Re: Large Epoxy Granite Vertical CNC Mill

    Hi Petrus

    Good lord man! This is a workstand for a CNC, not a Glory Box for a wedding!
    OK, like Louie, I am impressed.

    All I did for mine was clean the old second-hand Australian hardwood beams up with a circular saw bench and glue/bolt them together! There may be a few notches here and there, done with the saw bench. (Caution: Aus Hardwood can be as hard as mild steel, so it's not like pine.)
    Then I covered a few sides with 5-ply (glue & screws) to give the whole thing some rigidity. Gave it a coat of Estapol when done. Mine's very solid, so yours should be like a rock!

    Cheers
    Roger



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    Default Re: Large Epoxy Granite Vertical CNC Mill

    make sure to apply some sealing oil after your done to prevent the wood from moving due to moisture content.



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    Default Re: Large Epoxy Granite Vertical CNC Mill

    Id be worried about adding resonance to the build with a wood frame. I am avoiding ALL kinds of wood in my next build. I don't plan on using a single piece of it. it may be inevitable to use some, but i plan to avoid it at all costs.

    Also another problem with wood, is that it expands when wet. if you spill something it might make one leg swell, or something else crazy that might throw off the balance. The quick and dirty... find its permanent home, and stack some cinder blocks (bolted together and gaps filled by resin) and put your mill on top of it.

    Or...coat the HECK out of your wood with something waterproof.



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    Default Re: Large Epoxy Granite Vertical CNC Mill

    I would endorse the idea of sealing/coating, but more for appearance than anything else.
    Moisture absorption ... with pine and MDF maybe. Rather doubtful on well-aged hardwood though.
    Resonance? Mine does NOT resonate, that's for sure. If you build it out of 2x2" pine it might though. The sticks would have a much higher slenderness ratio.

    I did try anchoring a machine (actually a robot) down once with concrete paving slabs. It walked. The hydraulic actuator on the main arm hit resonance...

    Cheers
    Roger



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    Default Re: Large Epoxy Granite Vertical CNC Mill

    if you made a machine with Aus hardwood it would be very close to aluminum bang two bits of dry old Aus hard wood together it sounds like steel banging on steel

    <img src="https://ivxo1q-dm2305.files.1drv.com/y4mENMmTr_Cabc7pR0FUdB6gtbADq2JbuG4_rGy0eBQvLJx19pTi6TqMUIJN0xgOyDIc0gWoxYhS38HpbSTFGdfaK-o42IOU6jczrhDpfpCOTNGL1X6hvZCbgj0y35gqmq1YGTrWwShYGV-C7lXA2esy0Pi_WfnBSyroDLSGXwce4uSr1U7op7srdi78rispHCa_K4aFlTlJPVkkNWMfgh_Tg?width=60&height=60&cropmode=none" width="60" height="60" />

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    Quote Originally Posted by nateman_doo View Post
    Id be worried about adding resonance to the build with a wood frame. I am avoiding ALL kinds of wood in my next build. I don't plan on using a single piece of it. it may be inevitable to use some, but i plan to avoid it at all costs.

    Also another problem with wood, is that it expands when wet. if you spill something it might make one leg swell, or something else crazy that might throw off the balance. The quick and dirty... find its permanent home, and stack some cinder blocks (bolted together and gaps filled by resin) and put your mill on top of it.

    Or...coat the HECK out of your wood with something waterproof.
    Realistically, wood does not shrink/expand much if at all along thr grain, which is the orientation of the legs. Maybe on the stretchers some, but a little sealant would help. Wood will take in and release moisture no matter how much you seal it short of impregnating with acrylic in a vacuum chamber.

    The end grain is the most susceptible to absorbing moisture and releasing it, which after a few cycles will cause the ends to check and split if not sealed. Tropical hardwoods are most impervious to this though it would be a crime to use them for this purpose. The best for this however IMO would be ipe, a Brazilian sustainable hardwood use mainly for outdoor decks. You can buy up to 6 x 6 and it's rock hard. So much that it has a life expectancy of over 30 years under marine conditions (it's used in many boardwalks for example.) Kills carbide tols however, and all screw holes need to be piloted and countersunk. Looks beautiful with teak oil...



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    Quote Originally Posted by daniellyall View Post
    if you made a machine with Aus hardwood it would be very close to aluminum bang two bits of dry old Aus hard wood together it sounds like steel banging on steel
    LOL in the US we prize these hardwoods for use in acoustic and electric guitars, where that "ring" is a desirable attribute. I'd almost give a finger for some ancient kauri that is salvaged from the bogs. But, I suppose one man's exotic hardwoid is another man's domestuc scrap wood!



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    Default Re: Large Epoxy Granite Vertical CNC Mill

    that stuff is a killer to use had 1 stick of it stuffed to many tools using it makes good fire wood,

    it has a very high amount of silica in it like coconut

    the ipe is pretty much like teak but grows very fast.

    we get a lot of Aus hardwoods in NZ I use it all the time for making wood working benches it make for very good vice material you can bend it around a lot.

    anyway back on to the op`s build

    <img src="https://ivxo1q-dm2305.files.1drv.com/y4mENMmTr_Cabc7pR0FUdB6gtbADq2JbuG4_rGy0eBQvLJx19pTi6TqMUIJN0xgOyDIc0gWoxYhS38HpbSTFGdfaK-o42IOU6jczrhDpfpCOTNGL1X6hvZCbgj0y35gqmq1YGTrWwShYGV-C7lXA2esy0Pi_WfnBSyroDLSGXwce4uSr1U7op7srdi78rispHCa_K4aFlTlJPVkkNWMfgh_Tg?width=60&height=60&cropmode=none" width="60" height="60" />

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  14. #94
    Gold Member daniellyall's Avatar
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    Default Re: Large Epoxy Granite Vertical CNC Mill

    Quote Originally Posted by louieatienza View Post
    LOL in the US we prize these hardwoods for use in acoustic and electric guitars, where that "ring" is a desirable attribute. I'd almost give a finger for some ancient kauri that is salvaged from the bogs. But, I suppose one man's exotic hardwoid is another man's domestuc scrap wood!
    you have to go to china to get it they brought up all the land where it is dug it up stock piled it, and send it over buy the ship load then they sale it back as furniture Aholes they brought out the company that came up with the way to proserive it after its taken out of the ground to

    <img src="https://ivxo1q-dm2305.files.1drv.com/y4mENMmTr_Cabc7pR0FUdB6gtbADq2JbuG4_rGy0eBQvLJx19pTi6TqMUIJN0xgOyDIc0gWoxYhS38HpbSTFGdfaK-o42IOU6jczrhDpfpCOTNGL1X6hvZCbgj0y35gqmq1YGTrWwShYGV-C7lXA2esy0Pi_WfnBSyroDLSGXwce4uSr1U7op7srdi78rispHCa_K4aFlTlJPVkkNWMfgh_Tg?width=60&height=60&cropmode=none" width="60" height="60" />

    Being Disabled is OK CNC is For fuN


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    Default Re: Large Epoxy Granite Vertical CNC Mill

    Quote Originally Posted by louieatienza View Post
    Realistically, wood does not shrink/expand much if at all along thr grain, which is the orientation of the legs. Maybe on the stretchers some, but a little sealant would help. Wood will take in and release moisture no matter how much you seal it short of impregnating with acrylic in a vacuum chamber.

    The end grain is the most susceptible to absorbing moisture and releasing it, which after a few cycles will cause the ends to check and split if not sealed. Tropical hardwoods are most impervious to this though it would be a crime to use them for this purpose. The best for this however IMO would be ipe, a Brazilian sustainable hardwood use mainly for outdoor decks. You can buy up to 6 x 6 and it's rock hard. So much that it has a life expectancy of over 30 years under marine conditions (it's used in many boardwalks for example.) Kills carbide tols however, and all screw holes need to be piloted and countersunk. Looks beautiful with teak oil...
    I have worked with ipe and other hard woods extensively- built a 20ft x20ft deck. The Atlantic city boardwalk has 100 year old ipe on it... I still won't make my frame from wood. Wood moves bottom line. Even the most extreme examples like ipe move way more than I would want for a machine base.

    Bottomline: Wood absorbs moisture and wood moves



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    Default Re: Large Epoxy Granite Vertical CNC Mill

    > Even the most extreme examples like ipe move way more than I would want for a machine base.
    > Bottomline: Wood absorbs moisture and wood moves
    Forgive me, but I am confused here.

    When I talk about a hardwood machine base, I am talking about a large heavy mobile trolley. My CNC machine sits on top of that, supported at the correct key points. Now, if the wood in the trolley moves, or grows by 10 mm - so what? It's just a table.

    Maybe what I mean by 'a machine base' and what others mean by that are two different things? To be sure, I would NOT use wood in the construction of a CNC - absolutely NOT.

    Louie commented that
    Kills carbide tools however, and all screw holes need to be piloted and countersunk. Looks beautiful with teak oil...
    Oh yes - definitely to both.

    Cheers
    Roger



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    Default Re: Large Epoxy Granite Vertical CNC Mill

    Quote Originally Posted by RCaffin View Post
    > Even the most extreme examples like ipe move way more than I would want for a machine base.
    > Bottomline: Wood absorbs moisture and wood moves
    Forgive me, but I am confused here.

    When I talk about a hardwood machine base, I am talking about a large heavy mobile trolley. My CNC machine sits on top of that, supported at the correct key points. Now, if the wood in the trolley moves, or grows by 10 mm - so what? It's just a table.

    Maybe what I mean by 'a machine base' and what others mean by that are two different things? To be sure, I would NOT use wood in the construction of a CNC - absolutely NOT.

    Louie commented that
    Kills carbide tools however, and all screw holes need to be piloted and countersunk. Looks beautiful with teak oil...
    Oh yes - definitely to both.

    Cheers
    Roger
    I get your point and let's not detour too much from this inspiring build. Using wood for a "trolley" is not the same as a machine base. Anyway, I appreciate the craftsmanship even if I would go this route.



  18. #98
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    Default Re: Large Epoxy Granite Vertical CNC Mill

    its his build. if he wants to use wood, he will. I still enjoy the build. I just won't use wood in my build.



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    Default Re: Large Epoxy Granite Vertical CNC Mill

    Quote Originally Posted by gt40 View Post
    I have worked with ipe and other hard woods extensively- built a 20ft x20ft deck. The Atlantic city boardwalk has 100 year old ipe on it... I still won't make my frame from wood. Wood moves bottom line. Even the most extreme examples like ipe move way more than I would want for a machine base.

    Bottomline: Wood absorbs moisture and wood moves
    I never advocated it's use; just mentioning that if I DID have to use wood, that's what I'd use. We don't always get to use what's ideal, though we use what's available or what we know of.

    Heck, steel moves, epoxy granite moves, cast iron moves... Polycarbonate absorbs moisture, but it doesn't stop us from using it for shields and enclosure windows.

    As to the AC boardwalk, it did have 100 year old ipe. Superstorm Sandy took care of that. Many of the boards were found over a quarter mile away, in ironically newly built housing.



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    Default Re: Large Epoxy Granite Vertical CNC Mill

    I like the attitude in the last comment by louieatienza. All material have shortcomings and we design around their limitations. This stand is just that: something for the mill to sit on so it doesn't sit on the floor with me bent over it. If it changes shape and the six contact points are no longer co-planar I will shim them. If it does not stay level in the beginning I will add shims under the legs until it does. After a while wood dries and stabilizes and California is not exactly a wet environment. The base is so think that it will probably not deform even if the contact points move. Ad far as stability and precision are concerned there are much more consequential issues to worry about...



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