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Thread: Epoxy-Granite machine bases (was Polymer concrete frame?)

  1. #561
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    Hi, I am filling the base of my R45 style mill with a mix of West marine 105 epoxy , play sand and washed river rock. The sand and rock came from Lowes. The 50 lb sand was real nice and dry and clean. The rock was in a 40 lb bag and was wet and full of dirt and silt. I washed the rock well and spread it out on a couple old towels and let it dry. The sand and rock was about 6 or 7 dollars total. The epoxy was expensive , I bought it locally cause I wanted to play with it that day and was too impatient to wait on mail order. $130 for 1 gal of 105 epoxy and 1 quart of 206 slow hardener. It mixes 1 part hardner to 5 parts epoxy. I did partial fill on a small part of the base underneath where the column sits and the west epoxy mixes very good with the sand and rock. It is very thin and it wets out the filler very easily and goes a long way. Meaning you can make a lot of mixture with a gallon of epoxy. I have my base ready for the final pours now. I put in plumbing for a pressure lube system and made a framework that sits inside the base to keep the epoxy in the area that I want filled and out of the area I dont. Here are a couple pics. I will post more in a couple days of the final product. On the topside of the area I filled it ended up being a little higher than I wanted so I ground it down with a 4.5 inch body grinder about an eighth of an inch. It can be ground but its slow. This stuff really is hard like a flipping rock Ok let me see if the pics load. Dave

    Attached Thumbnails Attached Thumbnails Epoxy-Granite machine bases (was Polymer concrete frame?)-base9-jpeg   Epoxy-Granite machine bases (was Polymer concrete frame?)-base10-jpg  


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    The frame insert is made from 1/4 thick by 4 inch mild steel welded together. It drops down into the base and I drilled and tapped the base for 4 3/8 bolts to secure it. I will use some aluminum tape to seal up a few small gaps while the epoxy hardens. You can see I boxed around the bays where my column attach bolts go so no mix goes in those areas. I want to keep access the that area. I got rid of the original column bolts and now have grade 8 bolts that go in from the bottom. They first go through a 6 inch long by 3/4 thick , 1.5 inch wide steel bar that is secured to the base with two 1/2-13 setscrews tapped through the plate and the base and also a flushhead 3/8 bolt from the top with a nut on the bottom.

    Attached Thumbnails Attached Thumbnails Epoxy-Granite machine bases (was Polymer concrete frame?)-base2-jpg   Epoxy-Granite machine bases (was Polymer concrete frame?)-base4-jpg  


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    I am also filling the bottom 6 inches of the column with the mixture. I have a steel pipe insert in that column attach area on the base , It is for a 1.25 inch dia bolt about 12inches long that will go from the bottom of the base up and through the center lower part of the column which will also have a pipe insert in it. . A 1/4 inch plate on top and bottom and crank down the nut and squeeze the column and base together. Im thinking that along with the filled base and lower column should add a bunch of strength and rigidity to my mill. I also have 1/2 inch pipe inserts that will go in the base where the 4 bolts go through to secure the mill to the bench. I should have the base fill done by thurs night and will post more pics then. Dave



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    Gold Member BobWarfield's Avatar
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    Nice job Dave!

    It will be interesting to see how much difference you can tell after this is completed. It certainly will be heavier!

    After you fill the base and bottom of the column, are you going to button up the mill and give it a try?

    Best,

    BW

    PS It occurs to me there is a vague possibility the weight distribution of the EG on your mill might tweak it a bit in one way or another. It shouldn't, but I would make sure you've got some pretty strong bolts in place in the base to be used as leveling screws before the epoxy gets in the way of that possibility.



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    Great job Davo.



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    Hey Bob, Thanks. I plan on having it back together in about a week or two. I bought it in feb and really hadnt done much work with it, just played around a little before taking it apart. Im doing a few other mods now also that I will detail shortly in the benchtop mill section. I think they might be interesting to some of the square column peoples I will have the base blocked up and level supported on the Y-axis ways when I do the fill pour on it. So it should be all level and square and not tweeked while the epoxy hardens. After it hardens it aint gonna move, flex or do anything. I swear this epoxy concrete mix is just crazy how hard and solid it is. I will weigh the base when its done. It weighed 100 lbs when I started. Ok , Check you all later, Dave



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    Walter,

    Thanks for posting the link. Also good to see some design ideas. I'm vacillating between a more standard design and a monolithic design that is sectioned a bit like Davo's but recessed at least six probably 12 inches in the middle. I want some verticle travel.

    One problem I see is you wan't to eliminate right angles as they will be obvious stress points. You can see that in one of the anocast flat v profiles --\____/--

    Last edited by jsage; 03-20-2007 at 08:28 PM.


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    I have seen some posts suggesting a frame to pour in the E/G.If done this way E/G does not self level enough to be a pricision surface or plate.To acheive a precision epoxy surface plate,you would fill the frame withE/G to within 1/16 of the top of the frame.The final pour or pours are unfilled TT epoxy which must run over the edge of the frame to accomplish the precision plate.With inserts the usual method is to attach the inserts to the bottom of a mold and pour around the inserts.The problem with this method is the mold determines the surface accuracy.The raw epoxy,over the edge can acheive flatness to a few thou.
    Larry



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    Igalla,

    Here's what I'm talking about. The orange is the e/p the black is non water catalyzed concrete.

    The milling base could be a secondary cast or somehow adjusted on mounted blocks. The critical part would be the upper sides which should be level.


    Obviously this is very rough concept.

    Mike.

    I used a 5 inch thickness Side height 1' 6". Outer dimensions are approx 5 x 10'. At $60 per cubic foot the e/p part costs approx $2,900? basic.
    (If rhino is giving me the correct volume)

    Attached Thumbnails Attached Thumbnails Epoxy-Granite machine bases (was Polymer concrete frame?)-monolithic-jpg  
    Last edited by jsage; 03-21-2007 at 12:03 AM.


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    Mike very ambitious project and very heavy.12k for E/G tons of mula.Deserves experementation before taking the plunge.Hope you have read early posts on epoxy surface plates.
    Any cheaper products to Zeeospheres?No.Zeospheres I beleive have a Mohs hardness of7or 8 which is similar to granites hardness.
    Thanks for the posts
    Larry



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    Igalla,

    I just wanted to see what a given design would cost. Assuming basic dimensions without regard to price. Of course I made 3 math errors. I think I have right now. 3k would be out of my price range. However, if you could build the mold right it would be pretty simple and serve my needs.

    Haven't done any volume calcs in ages. Converting to cubic inches. Tried to do it in my head ; ) I think I need a beer, I have the concrete fuzzies.

    Just the top would weigh 7,800 pounds. Where's Zumba when I need him.

    Rhino volume 84,273 i set general measure of inches. 1 cubic foot 1,728 cu. 160 lbs each cu. 48.77 cf.

    Zeospheres look good.

    Last edited by jsage; 03-21-2007 at 12:30 AM.


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    Mike you got my attention on the beer idea.
    After reading so many posts and good info a beer may help to clear the head of E/G and get a good nites sleep.The machine I need would cost $120,000.Hopfully we can roll our own for $15K
    Larry



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    Here's to beers and smooth sailing on that goal.



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    Mike you posted and edited while I was a-postin.7,800lbs!!I thought I was krazy at 3600ibs.Your forklift must be higher capicidy than mine.In reality a good comercial machine[5X10]weights 10,000lbs in welded steel.3600or7800lbs in E/G should blow away the commercial machines at 20% the cost.
    Larry



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    Larry,

    well i felt like i was trying to turn a steel design into e/p. thought i'd take a steel-less tack. No caps b/c beer in other hand. Side height 1'7"7/8, quick draft.

    A lot of mixin and shakin. I did just buy a mixer, still would be a challenge.

    : )

    mike



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    Mike
    I am of the group of steel framed enhansed with E/G with surface plate of epoxy.With 30 years of fool'lin around with epoxy and mold'in,I am not capable of cast'in a total E/G machine.Molds cost 5 to 10 times the part cost and designing in steel and E/G can be cost effective and very accurate.
    Larry



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    Quote Originally Posted by lgalla View Post
    The machine I need would cost $120,000. Hopfully we can roll our own for $15K
    Sounds like a lot of work.. But I think it's worth the shot.



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    Curiousity Speaking,

    Put down beer. What degree of precision does everybody need to accomplish their primary goal.

    For me, right now I could use anything w/i 1/16th or better. Of course, I'd like to work harder materials including metals. I won't argue that good dampening will give me longer longevity for my effort. I'd like a fourth axis for greater 3d capability or semi 3d capability.

    Who wants to offer up.

    Larry, to post below, I'm wit u. One must fully consider before committing. Or being committed (%



    Best,

    Mike.



  19. #579
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    Since posting in this thread I tend to keep my head down and look at the concrete sidewalk and curbs checking for cracks and trying to determine the aggreate used.I look at landscaped gardens and wonder where they got the cool aggregates.Is this a sign ofE/G addiction?Any one else have the problem?
    Larry



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    Mike at that accuracy,1/16 many would say you don't need E/G and bishop wiscarvers and a light steel frame would be sufficent.To me a light duty frame could be +or-1/16.Repatibilty is the issue here.We want our cuts to be the same everytime.A light frame will distort whenever it wants to.Solid vibration damping design is a benefit even for low accuracy.
    Larry



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Epoxy-Granite machine bases (was Polymer concrete frame?)

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Epoxy-Granite machine bases (was Polymer concrete frame?)