[peteeng]

Hi All - made some calls on ALOX heres the breakdown:

al plate at $8/kg $21,600AUD per m3 E70
HE80 at $2.40AUD/kg $5520AUD/m3 E35
EG $5400AUD /m3 E30-35
HE80/ALOX $8100AUD/m3 E100 estimated

I buy alox here for $3.95AUD /kg its 12 grit which is about 1.5 -1.6mm

So CSA-ALOX maybe not too bad for the stiffness. Now looking for Tabular alumina maybe cheaper as less processing...

Peter

[peteeng]

Hi All - I dissected the recipe for the E80 UHPC and figured out that it uses 46% by volume ALOX. So 50/50 is a good bet. Being particles the estimated modulus would be
E concrete 28gpa E alox 300gpa particle efficiency 50%

(0.46*300*0.5)+(0.54*28)= 84GPa of which 80GPa is the quoted stiffness. So I'm happy to be able to replicate that. Now the question is what material to use? More costings and material sources needed.... Peter

[ardenum]

Hi All - I dissected the recipe for the E80 UHPC and figured out that it uses 46% by volume ALOX. So 50/50 is a good bet. Being particles the estimated modulus would be
E concrete 28gpa E alox 300gpa particle efficiency 50%

(0.46*300*0.5)+(0.54*28)= 84GPa of which 80GPa is the quoted stiffness. So I'm happy to be able to replicate that. Now the question is what material to use? More costings and material sources needed.... Peter

How much $ per kg does that end up being?

[peteeng]

Hi Ard - using prior post data------

Hi All - made some calls on ALOX heres the breakdown:

al plate at $8/kg $21,600AUD per m3 E70
HE80 at $2.40AUD/kg $5520AUD/m3 E35
EG $5400AUD /m3 E30-35
HE80/ALOX $8100AUD/m3 E100 estimated

I buy alox here for $3.95AUD /kg its 12 grit which is about 1.5 -1.6mm

So CSA-ALOX maybe not too bad for the stiffness. Now looking for Tabular alumina maybe cheaper as less processing...

Peter

Aluminium plate $8AUD per kg
HE80 CSA $2.40AUD / kg
EG $2.00AUD /kg
HE80/ALox $3.00AUD /kg beware the $/kg its the $/volume that you need to look at.

cheers Peter

[ardenum]

Hi Ard - using prior post data------

Hi All - made some calls on ALOX heres the breakdown:

al plate at $8/kg $21,600AUD per m3 E70
HE80 at $2.40AUD/kg $5520AUD/m3 E35
EG $5400AUD /m3 E30-35
HE80/ALOX $8100AUD/m3 E100 estimated

I buy alox here for $3.95AUD /kg its 12 grit which is about 1.5 -1.6mm

So CSA-ALOX maybe not too bad for the stiffness. Now looking for Tabular alumina maybe cheaper as less processing...

Peter

Aluminium plate $8AUD per kg
HE80 CSA $2.40AUD / kg
EG $2.00AUD /kg
HE80/ALox $3.00AUD /kg beware the $/kg its the $/volume that you need to look at.

cheers Peter

that's some cheap EG, is that a manufacturer price or diy mixture?

[peteeng]

Hi Ard - it could be cheaper if I use beach sand. Its free here. I pay $16/kg for good epoxy. So if its a 10% mix its $1.60AUD for the epoxy and sand is free. So $1.60 for 10kg is $0.16/kg for sand EG, But its not stiff.. Peter

silica sand is 70GPa so
(0.6*70*.5)+(0.4*3.5) = 22GPa not stiff but cheap....

Basalt which is blue metal used for roads and concrete aggregate is about 50% SiO2 so is less stiff then 70GPa. Granite is about 70% plus SiO2 so is stiffer then 70GPa some say as high as 110GPa. Sand is decomposed granite and basalt and as the SiO2 is the hard material in it, its what's left when all the other stuff is dissolved and worn away so is nearly 100% SiO2....

[peteeng]

Morning all - Gantry Alignment stuff

https://www.machinedesign.com/market...ght-and-narrow

https://pinpointlaser.com/articles/s...ment-for-less/

Peter

I made an error in the prior posts. Granite can't be higher stiffness then 70GPa if the main constituent is SiO2. But if the rest 30% stuff is a very high stiffness material then it can be higher then 70GPa... Granite stiffness is published from 50-100GPa.. Using mechanical tests its hard to determine E in this sort of material. Acoustic testing is the best method...

[jackjr-123]

I don't think Nanodur E80 uses alumina/ALOX. Their "datasheet" talks about heat-treated stones.

Anyway if you want to do some experiments with that stuff I could send you some samples. But not many kgs obviously.

[peteeng]

Hi Jack - I spoke to the manufacturer of the "stones" and they said it was calcinated alumina. Look it up.. Australia produces huge amounts of alumina products so I'm sure I can find it here. The Alox grit blasting material is readily available (which is ground up alumina), tabulated should be cheaper so I'm looking for that...Peter

[jackjr-123]

Durigid "stones" look very different than calcinated alumina:

[pippin88]

I'm interested in how you go with ALOX / CSA mix (need a catchy brand name to hide what it is - ausidur?)

I wouldn't mind if it's more $/kg than epoxy granite. We should be looking at $/stiffness

If it is 2-3x stiffer than EG then less is needed and $/kg is misleading.

A solution that can be mixed in a standard cement mixer and poured easily has great advantage. Many epoxy granite machines have just used large blocks - lots of material not doing that much. Seems harder to get epoxy granite to work in complex forms.
Also if you don't have to wash and dry all the aggregate...!

[pippin88]

Durcrete are using multiple size aggregates.

https://www.youtube.com/watch?v=tjEp...ature=emb_logo

[pippin88]

"Nanodur Concrete E80 a class of its own
The secret of this unique international development is the exchange of natural stone with the industrially enhanced aggregate durigid. It is submitted to fire at over 1,400 °C and solidified in a sintering process. The result: the modulus of elasticity is significantly increased, along with the abrasion resistance of the hardened concrete. This technique likewise allows ease of casting, enables production without solvents, and maintains the self-compacting properties of the mixture. Durcrete markets the new material under the product name Nanodur E80 concrete. The cold-hardening casting is highly resistant to deformation and unbending and sets new standards for mineral-cast materials."

https://www.bvv.cz/msv/aktuality/new...eds-reduction/

[peteeng]

Hi Jack - Yes agreed on colour but the supplier says its equivalent. You can get brown ALOX and white ALOX as well. Suppliers of this sort of stuff have to have proprietary product and have to make it appear complex so as to slow down various parties doing it. It can be very simple. Its part of my job to make stuff and its the marketing dept that writes lots of that copy...

brown alox 95% AlO2 white 99% AlO2 same for our purposes

Pippin - The Bluey CSA is a graded mix already. If you add coarse aggregate or fibres it just improves stiffness if the additive is stiffer. Peter

[ardenum]

Many epoxy granite machines have just used large blocks - lots of material not doing that much. Seems harder to get epoxy granite to work in complex forms.

I can assure you that it's doing it's job of damping. Usually to replace a solid cast iron wall, you need 3 times the thickness in EG. On top of that comes the fact that EG has a minimum wall thickness requirement depending on particle size you used. If you take all that into consideration instead of a cast part that has walls and casting holes, you end up with a pure solid piece.

EG is slightly better at damping vibrations in terms of per /kg and not per /volume, so an EG part weighting the same as cast iron will dampen vibrations better(granted it's properly designed) but that part will have a way bigger volume.

[peteeng]

Hi Pippin - DIYers make simple block forms because the mould is then simple. Most times simple is best. Ramf and other commercial composite machine builders make very complex moulds. They use UHPC or EG as these forms would not be possible in cast iron. These forms include the wiring and services ducts that can't be done in a CI mould. Or shapes that would warp severely in CI like the machine Mactec put up a little while ago with thick and arced thin sections. EG is easy to do in complex forms just requires the effort to make the mould.

I'm back at my commercial work so this will slow down. Got to get YaG built so I can make those complex forms.....Cheers Peter

[peteeng]

Hi Pippin & others - I worked through the Durcrete video and they made some maths errors. Plus I've never thought that grading works. Firstly grading apparently works because the concrete people want to use the largest stones possible because these are the cheapest stones, you can see the gaps so its logical to try to fill them. The smaller the stones the more grinding and grading has been done so the cost goes up. In the case of spherical particles hexagonal close pack or square pack gives you a solid ratio of 74%. In the case of the video if the inside dimension of the container is not a module of 40mm then you can't achieve a close pack arrangement so the efficiency is low. In the video they got 50% solid which is expected. Silica sand achieves 57-60% solid by itself. This is an industry accepted number for cartage, they work on 1500kg/m3 bulk density. The video bottle test they got 54% and I think they could have done better. In their last shot with the balls and sand they incorrectly calculate the solid ratio. 0.31/0.72=43% water ie 57% solid. They could have achieve this by filling with sand directly and wetting correctly. Now the cartage bulk density for alox is 2400/3900= 62% solid.

Anyone trying to make aggregate at greater then 65% solid ie chasing the theoretical 74% and some claim 90% plus solid are chasing straws. In the perfect spherical or elliptoidal world where we can fit smaller and smaller bits into smaller and smaller spatial quanta its fine on paper but viscosity, friction, rough particles, segregation, gravity and many other factors keep the actual figures around 65% best solid. So use a small particle that is much smaller then the thickness of the part you are making and its simpler and just as good as "graded" systems....

Some people put forward the small particle, more surface area theory with the addage that more surface area equals more resin,. This is totally incorrect. It comes down to the volume ratios of the constituents, no surface area involved. Most EG DIYers do not add enough resin to fully wet out the mix so they have porosity which is fine in the application. The water balance test is an easy and useful exercise for those interested in EG graded or not graded systems. Peter

[pippin88]

I can assure you that it's doing it's job of damping. Usually to replace a solid cast iron wall, you need 3 times the thickness in EG. On top of that comes the fact that EG has a minimum wall thickness requirement depending on particle size you used. If you take all that into consideration instead of a cast part that has walls and casting holes, you end up with a pure solid piece.

EG is slightly better at damping vibrations in terms of per /kg and not per /volume, so an EG part weighting the same as cast iron will dampen vibrations better(granted it's properly designed) but that part will have a way bigger volume.

I understand all those principles.

But if weight (and material volume cost) is any consideration (both are certainly important for the hobbyist) then a solid piece is not optimal.

See attached picture. Forces / simulation setup identical on all.

Solid 400mm thick = 883kg, 24micron deflection
Solid 200mm thick = 441kg, 179micron deflection
Hollowed out with diagrid = 446kg, 66micron

(These are simple examples but the principle remains - use mass where is helps).

[peteeng]

Hi Pippin - A better description is to use "geometric inertia" where its needed, sometimes mass and inertia are not related.... if you are comparing different materials with different densities... What FE are you modelling in?? Peter

[ardenum]

I understand all those principles.

But if weight (and material volume cost) is any consideration (both are certainly important for the hobbyist) then a solid piece is not optimal.

See attached picture. Forces / simulation setup identical on all.

Solid 400mm thick = 883kg, 24micron deflection
Solid 200mm thick = 441kg, 179micron deflection
Hollowed out with diagrid = 446kg, 66micron

(These are simple examples but the principle remains - use mass where is helps).

If you were to optimize an EG structure to reduce weight but keep the properties beneficial, I argue that, the added cost for a complex mold would probably offset any gains you'd get from smaller EG volume. EG optimizing is done slightly differently. The universal way of doing eg. criss cross in your example is not the proper way to do it(I do realize it's just an example). You do it for your specific electro-mechanical setup. Here's an example.


I would not want to be the one to design(or make) a mold for something like that.