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

[Geof]

I found this page which gives a lot of answers that lead me to conclude this is not a technique that can be readily adapted to DIY; considering you first need to make a very precise steel mold and the material cannot be worked after casting.

http://www.itwpolymercastings.com/faqzanite.html


But the materials are not difficult to find:

"Zanite® polymer composite is a blend of pure silicon dioxide ceramic (99.8%) quartz aggregate, specially formulated high strength epoxy resin and selected additives. The natural elliptical shape of quartz is ideal for casting intricate structures."

In fewer words; sand and epoxy.

[lgalla]

Mcgyver and Geof
I have to agree, I cant see a hobyist building an entire machine ofE/G.For us hobbists we can use it for table tops,machine bases and weldment filling.Yes there are commercial machines totally composites, made in molds.
I would hate to think what would happen if a forklift bumped into a 100% polymer machine
Larry

[Geof]

...I would hate to think what would happen if a forklift bumped into a 100% polymer machine Larry

I would hate to think what would happen if a forklift bumped into any machine!!

But I do have a question: You say; "there are commercial machines totally composites", are there really? All I have read refers to machine bases not the full machine.

[walter]

I had never thought of an epoxy granite structure as replacing a steel fabrication, its not strong enough imo, the yield stress is much lower than steel or cast iron irrc and the modulus of elasticity is about 1/6....

Good point.

Then again, folks here don't build metal working CNCs. 90% of these machines are destined for wood, mdf, foam, plastics, aluminium.

I'm into wood machining, and really dislike the idea of steel tubing, welds, drilling. Fastening together 800 lbs of tubing would take months! I even hate the smell of it

I just need the basic rigidity and level- I'll go with (reinforced) concrete type of material.

Thanks for all the replys- you guys are the best!

[greybeard]

Mike - could you revise the link to that story in #23 as your link is only to the picture.Thanks
John

[schrupphobel72]

http://5128.rapidforum.com/topic=110...6&search=beton

try this link. German cnc site. Just look at those pic's. Looks Good

[greybeard]

schrupphobel72 - Your last three images are corelpaint (?) could you make them jpegs so we can enlarge them.
Not sure about the link as I don't read German -it's a forum, I think ?
John

[lgalla]

And now for the bad news, cost.
Lets assume$50/gal for epoxy,10 cents a pound for sand.I will round off to the nearist numbers.
To simplify things we will try 33 1/3 % epoxy/sand.
1cu/ft epoxy=7gallons =70lbs=$350
1cu/ft sand=166lbs=$16.60X2=$33.20
Now we take 1 cuft epoxy and 2cuft sand and have our33%to66% ratio
So the cost for 3cuft=$350.00+33.20=$383.20
Cost per cuft.=$120.00
Weight of 3cuft 402lbs
Cost/sqft=$10.00
Our 3cuft at $383.20 gives us 32sqft one inch thick.
Looking back to post #10 from Episs we are close to the same price and weight
More calculations for my 6'X12'X4" router table.Lets see 72sqft4"thick=280sq ft X$10=$2800.00 Total weight 3080lbs
Larry

[greybeard]

Larry - Why not use a layer of patio paving slabs as the top, epoxied together, then coat that with 1/4"skin(or even less?)
John

[greybeard]

Build a torsion box out of paving slabs ?
John

[schrupphobel72]

attached the pic's from the german site again

[Mcgyver]

Good point.

Then again, folks here don't build metal working CNCs. 90% of these machines are destined for wood, mdf, foam, plastics, aluminium.

thats part of it - different paradigm - no doubt we're visualizing two very different machines! its building metal working cnc's that interest me, I have little interest in wood machines for now. my thoughts were that a heavy weldment, using structural shapes could be filled with E/G and you'd have a chance at a metal working machine, small work envelope but very heavy and rigid. still, from I've been able to learn, its advantage over steel/CI is in vibration dampening, not strength or rigidity.