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

[walter]

WilliamD already started some testing:

http://www.cnczone.com/forums/showthread.php?t=33434

My first "pour" will be in about 2 weeks...

Shopmaninc epoxy is on it's way, and I found local suppliers of Zeeospheres and ground silica sand - all I need is a chunk of steel (reinforcement).

Edit: Black carbon thing will also be needed (for added sportiness)
Well, it may take longer than 2 weeks..

[Zumba]

Hey Walter, did you end up buying the 635 Thin Epoxy? I will probably pick up the 1/2 gallon and 32 oz hardener set for 34 bux.

How much are the Zeeospheres running you? what are you using for large aggregate?

[martinw]

Originally Posted by walter Edit: Black carbon thing will also be needed (for added sportiness) Well, it may take longer than 2 weeks..

Dear Walter,

Aesthetics tend to. Much higher price as well.

Best wishes

Martin

[walter]

Agreed Martin. Good looks cost money.

Zumba,
I will skip the "large" aggregate this time (to speed up the whole process). The article on top of this page (EDIT: the article in post 541) says the "sand only" performance is about the same. I just need to see some results.

Yes, I went with slow 635 kit from shopmaninc.

Don't know the pricing on quartz sand/zeeospheres. Suppliers are 90 min away- I'll just go for it.

The sand is 40-250 microns, 50 lbs bags.

Zeeospheres- that is a novelty to me, I just have to have it...
Same with Monarch 800 black carbon pigment. Thanks to Larry for all the info, you guys rock!

[Armstrong]

I have not tried it, but I have heard about it many times.

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[lgalla]

Walter the carbon black is extremely black and fluffy.Opening a bag carefully would create a large black cloud.I am sure you do not want a 25lb bag it would last a lifetime.Try to get a sample.An alternative source for carbon black or lampblack is art supply retailers.Glad you posted on Zeeospheres.That showed what I had been trying to explain about advantages of micro fillers properties.
Any of the products I have recomended I have used over the years and obtained good results for my purpose.Good luck with the 635.
Larry

[Zumba]

What would be a suitable substitute for zeeospheres? Preferably something cheap and easy to find?

[BobWarfield]

FYI, I did a design sketch for an epoxy granite table for a gantry-style milling machine:

Pour Frame with Sub-Frame:



Threaded Inserts:



Inserts installed in pour frame:



Poured Epoxy-Granite Table:



More details about how all of this works and could be built is available on my web site:

http://www.thewarfields.com/cnccookbook/CCEGGantry.html

Epoxy granite is quite an intriguing material. If professional quality results can be attained in a home shop, e.g. smooth finishes and 0.001" accuracy, it seems quite tractable to build very impressive machines in a relatively modest shop.

I look forward to seeing more "pour experiments" before diving in myself.

Best,

BW

PS Anyone here have a good recommendation for reasonably priced FEA software? This sort of thing cries out for it.

[davo727]

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

[davo727]

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.

[davo727]

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

[BobWarfield]

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.