Epoxy granite or UHPFRC Concrete 5 axis CNC

Dear All,
I am up to a vertical CNC project to one of my friend for 3 months.
This is something serious project.I have designed very big machines before around 140 tons-300 tons and several high tech machines however i dont have any experience with CNC design so far.
I started my engineering carrier as CAM&CNC responsible Which is a plus thing.
I want all of you guys learn what I learn on this path and take any advice or critics which are all welcome.
Now to tell something for a start about this very project which is eating my brain for 3 months day and night.
Material to be machined is marble.
X axis 3 m - Y axis 2 m - Z axis 1 m
Complete welded construction cost without milling head
and 15kW spindle, tool change magazine (14 tons) : 30.000 euro
(X-Y-Z axis drive unit parts, servos, ball screws, bearings, couplings etc are included, sand blasting, painting, flexible cable trays inc.)

Hybrid construction :
for concrete based casting is 7.500 euro cheaper
For epoxy granite casting 5.000 euro cheaper

Y axis bridge (2,5 tons) , Z axis saddle (500 kg) are weld construction while there is a 50% chance to build ram (400 kg) gray cast iron.
(GG40)
X axis column and footings are hybrid (steel embedded concrete).
Each footing is 1.250 kg while %25 is concrete.

I will decide to choose ultra high performance steel fiber reinforced self compacting deairing concrete or epoxy granite for footings and columns.
It seems epoxy granite will be minimum %50 more expensive than the concrete based casting.And disadvantage of epoxy granite is the thermal
expansion is higher than steel while concrete based casting remains similar.

UHPFRC Concrete Mixture:
Concrete+Slag+Basalt or river quarts aggregate 5-10 mm+ fine sand+plasticizer (to reduce water requirement)+160 micron diameter steel fibers+silica fume+water+additive to reove air balloons+shrinkage reducer additive
One of my customer has a basalt mine while another one has a quartz crushing plant. I will receive those for free.

I am going to share the distribution later after some tests.
Coarser agregate result less water requirement however lower flow quality.
The compressive strength goal is to reach min.100 MPa
I am going to use anchored with M20 screws, 40 mm thickness plates embedded on and bottom of the column and footing.
I tried add perspectice screen shots however I keep receiving error.
I will share each axis drive units in the coming days.
I will purchase or do my own fork type 2 axis milling head.
It is goin to be welded conatruction at first and it will be updated gray cast iron casting after seeing the results to have a accurate casting model.
Servo+Cycloid drive (with a ratio 153) for C axis
Direct drive for A axis.
I will ad pics when i get to my computer.

http://www.cnczone.com/forums/attach...d=362900&stc=1

Welded footing with internal ribs : 900 kg (St 37)
(Mass could be reduced by using St52-3)


http://www.cnczone.com/forums/attach...d=362902&stc=1

Hybrid footing : 1.250 kg

http://www.cnczone.com/forums/attach...d=362904&stc=1

X axis horizontal columns are preliminary drawn (only the boundaries) yet in this picture.
There will be 2 horizontol columns fixed onto the footings with special height adjustment mounts.
Y axis bridge, X axis footings, Saddle and Ram welded construction.
Z axis saddle is preliminary design in this picture not the final.
Counter weight cylinders for the ram are not added yet.
Frond and back slide doors are not drawn yet.
Automatic tool change magazine is not drawn yet. (At design stage, rotary type will be chosen over belt type)
Frames for the servos and bearing housings are not drawn yet. These are insignificant details for now.

http://www.cnczone.com/forums/attach...d=362906&stc=1

Preliminary design Hybrid Construction.

That's a pretty impressive-looking design. But if you're planning to cut stone with it, remember to save room in your budget for bellows all around, since the abrasive dust and slurry will get everywhere and destroy your moving parts.

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Originally Posted by awerby

That's a pretty impressive-looking design. But if you're planning to cut stone with it, remember to save room in your budget for bellows all around, since the abrasive dust and slurry will get everywhere and destroy your moving parts.

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Thanks pal, it is a good advice. At the begining I was going to use bellows only for ball screws but i will use wide "U" shape accordion type fabric bellows all over the screw and rails.
Telescopic metal bellows are too expensive and not vital for this design
Metal bellows are good choice for moving table type cnc or moving bridge with long foots.

5 axis cnc router for marble engraving? Machine structure is unqique, Why design this kind of frame? To reduce vibration?

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Originally Posted by falacncrouter

5 axis cnc router for marble engraving? Machine structure is unqique, Why design this kind of frame? To reduce vibration?

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When I visited his workshop I saw several CNC routerd with half meter Z axis. Standard cnc routers, spindle mounted on a plate moving up and down. He told me he is goin to buy a new cnc router, with a price of 30.000 euro. He asked me if i can do 3 axis cnc router like he had.
I told him this is something garbage, I can make better CNC for him with a lower price and better quality and skills as a wedding gift.
He will pay the costs ofcourse :))
5 axis cnc with automatic tool change and he will not require manual saw machine anymore. (800 mm diameter saw) to be mounted on milling head)
Sawing, cutting, finishing could be made in a single CNC.
i didnt like the routers structure because it wasnt rigid enough, will eventually result in bearing failures and low surface quality due to excess vibration. I decided to make my Y axis and Z axis box in box design.
Y axis cross bridge is symetrical construction to have the Ram located in the center of gravity. This bridge has 2 colums, I could have design the bridge only 1 colon but there will be banana effect on the ram.
Symmetric double column bridge will have good thermal expansion distribution.

Ammazing project. Hope you can keep posting pictures once you start the build.

One major advantage of Epoxy Granite is that it is dimensionally stable. Cement based concretes shrink fo years. Is the ultra high performance steel fiber reinforced self compacting deairing concrete somehow formulated to prevent shrinkage?

The aisadvantage of Epoxy Granite will be mixing and compacting the large volumes you will need.

You know of this build?
https://www.youtube.com/watch?v=bqGzbKFMhSg
Mark

Quote:

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Originally Posted by RotarySMP

Ammazing project. Hope you can keep posting pictures once you start the build.

One major advantage of Epoxy Granite is that it is dimensionally stable. Cement based concretes shrink fo years. Is the ultra high performance steel fiber reinforced self compacting deairing concrete somehow formulated to prevent shrinkage?

The aisadvantage of Epoxy Granite will be mixing and compacting the large volumes you will need.

You know of this build?
https://www.youtube.com/watch?v=bqGzbKFMhSg
Mark

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Good comment . I will watch the video and make a comment.
Both casting creeps. Concrete based tend to more creep.
Shrinkage reducer additives come to aid.I will see how good can both be.
My second engineering carrier was at a company dealing with fiber composite castings for automative industry.. epoxy based polyrster based castings creep so bad if they are properly cured and in excess quantity of epoxy.when i was a junior mech engineer i got a project for manufaturing tractor hood made of polyester casting. Everythink was good after casting but when the products shipped after 1 month none of them was big enoug to cover motor because of excessive shrinkage. 😂😂

Quote:

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Originally Posted by RotarySMP

Ammazing project. Hope you can keep posting pictures once you start the build.

One major advantage of Epoxy Granite is that it is dimensionally stable. Cement based concretes shrink fo years. Is the ultra high performance steel fiber reinforced self compacting deairing concrete somehow formulated to prevent shrinkage?

The aisadvantage of Epoxy Granite will be mixing and compacting the large volumes you will need.

You know of this build?
https://www.youtube.com/watch?v=bqGzbKFMhSg
Mark

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Yes I know this build. Thanks very much for the video.This is cement based casting with very good flow quality (aggregate less then 8 or max 10mm) and packing density thnx to plasticizer anf silica fume.this is exactly what my footings and x axis horizontal columns.But there is a small chance that these guys might use glass fibers instead of steel.This is all about the stregth of casting and dynamic loads on these columns..If you use glass fiber you cant get higher compressive stregth than 15.000 PSI.
I will check their website and tell you guys about their process.I hope i can find somethink english i dont understand german.

Quote:

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Originally Posted by Halbmond

Good comment . I will watch the video and make a comment.
Both casting creeps. Concrete based tend to more creep.
Shrinkage reducer additives come to aid.I will see how good can both be.
My second engineering carrier was at a company dealing with fiber composite castings for automative industry.. epoxy based polyrster based castings creep so bad if they are properly cured and in excess quantity of epoxy.when i was a junior mech engineer i got a project for manufaturing tractor hood made of polyester casting. Everythink was good after casting but when the products shipped after 1 month none of them was big enoug to cover motor because of excessive shrinkage. ����

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Aren't you mixing up polyester resin (which shrinks badly) with epoxy (which is more stable after curing). An optimal 8% epoxy mix is very dry and needs significant, tuned vibration to compact. Optimised epoxy granite is very stable though, which is why it is typically choosen for machine tools. Along with its damping.
Mark

Quote:

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Originally Posted by RotarySMP

Aren't you mixing up polyester resin (which shrinks badly) with epoxy (which is more stable after curing). An optimal 8% epoxy mix is very dry and needs significant, tuned vibration to compact. Optimised epoxy granite is very stanble though, which is why it is typically choosen for machine tools. Along with its damping.
Mark

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Yea you are correct about polyester resin and epoxy difference.
Agreed. If total mass is too much like this project, cost differs significantly.
Almost 10 tons of epoxy granite casting cost and cement based casting for the same weight is very different. Around 3k euros.
Polymer casting mixture, has simple and easy to find ingredients.
Only gravels, sand and epoxy. Very simple combination.
May be fiber additives for higher strength capacity.
epoxy casting will remain as an option .May be a couple of the footings will be epoxy while the others ultra performance cement.So we can make a comparison before the next upgraded project.

Are you designing based on compressive strength, and not youngs modulus? Normally strength is pretty irrelevant to tool frames, other than certain features like not wanting threaded anchors to pull out. The machining loads are orders of magnitude below the allowables, as you design for stiffness. There is little need for fibers in an epoxy granite frame, they'll just make compacting harder. You should be able to acheive 50 GPa youngs modulus with a reasonable Fuller curve approximation of aggregates and 8% epoxy. What is the youngs modulus of the UHPFRC Concrete?
Mark

Quote:

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Originally Posted by RotarySMP

Are you designing based on compressive strength, and not youngs modulus? Normally strength is pretty irrelevant to tool frames, other than certain features like not wanting threaded anchors to pull out. The machining loads are orders of magnitude below the allowables, as you design for stiffness. There is little need for fibers in an epoxy granite frame, they'll just make compacting harder. You should be able to acheive 50 GPa youngs modulus with a reasonable Fuller curve approximation of aggregates and 8% epoxy. What is the youngs modulus of the UHPFRC Concrete?
Mark

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Thanks for the comment.
The young modulus to be reached 35-50 Mpa.It is easier to reach high young modulus and stregth values for polymer concrete casting rather than cement based castings

Quote:

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Originally Posted by RotarySMP

Are you designing based on compressive strength, and not youngs modulus? Normally strength is pretty irrelevant to tool frames, other than certain features like not wanting threaded anchors to pull out. The machining loads are orders of magnitude below the allowables, as you design for stiffness. There is little need for fibers in an epoxy granite frame, they'll just make compacting harder. You should be able to acheive 50 GPa youngs modulus with a reasonable Fuller curve approximation of aggregates and 8% epoxy. What is the youngs modulus of the UHPFRC Concrete?
Mark

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http://durcrete.de/wp-content/uploads/2017/02/Nanodur-Compound-5941_2017_1_GB.pdf

http://durcrete.de/wp-content/uploads/2015/06/downloads-durfill_Prospekt_E_0615.pdf

Do you have any information on the shrinkage of those products. I didn't see anything in those broshures.

Do you have the provisions to vibrate a ton of epoxy granite in a mould?
Mark

You should do a long term test for creep with different post curing. Some polymer concrete maybe ok for routers.


The Raw material cost 1x
Labour cost in casting and mould prep 10x
Geometric alignment and assembly cost 50-100x

Quote:

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Originally Posted by RotarySMP

Do you have any information on the shrinkage of those products. I didn't see anything in those broshures.

Do you have the provisions to vibrate a ton of epoxy granite in a mould?
Mark

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I dont have any info or feedback about the durfill and nanodour or similar type cement based casting shrinkage quantities at the moment.
And no idea how effective Shrinkage reducers (one of the main additives) are.

It's interesting to watch how different people approach similar situations as far as it's goes by. For instance, there are different way to handle concrete connections, like http://hardman-de.com that brings invitational method of keeping it together. I mean, it's not that suitable for private usage, but still looks interesting. As for me, if you adding an extra floor to garage, you better stick with bricks and do it in old style way. Cheaper and actually should be staying for a while.