[ardenum]

Pete,

Hahaha. I thought the same thing after I designed it. Welding nightmare.

Regarding UHPC, is the precision grout you recommended not a type of UHPC? I would also like to know if there are ways to optimize the casting, so I don't just end up with a solid block for a casting. Can I do webbing or pockets in some areas? If I can reduce some of the weight without affecting the performance, that would be great. Currently my casting weight estimate is at approximately 2.5 Tons. One of the concerns I have is that I don't think I am capable of mixing that quantity of material in a short period of time, if needed.

I'd very much urge you too drop the router frame, you're spending a lot of $$ might as well get something that isn't mediocre, routers aren't very stiff. UHPC is also $300-500 per ton. look at lukahr build thread, he posted a full UHPC recipe from durcrete.

here's a video, the slides are in english and say the same thing the guy says, he's from the company durcrete that makes 2 kinds of UHPC E40 and E80.

https://www.youtube.com/watch?v=au3eD3ZmAvI

[peteeng]

Hi All - For the engineering grout I pay $1200 AUD per tonne or $2646 AUD per m3 (thats a 20kg bag price). For aluminium I pay $9000 AUD per tonne and $24300 per m3.... HE80AG gets E=40GPa out of the bag. I spoke to Durcrete and they won't supply the high modulus additive outside of europe. But durcrete publishes the chinese suppliers name. So I emailed them and they were helpful but dealt in tonnages but they put me back to a german lab so I emailed them and corresponded with the techs there. They concluded that the additive is Alox and its pointless sending alox from europe to Oz. So I researched alox and Australia is one of the major producers of alox so I dug around and found some here. Its a common grit for grit blasting. Now The E80 is the compressive modulus and all the info I can find shows the tensile modulus to be very poor. I tried to make modulus test coupons for the alox but failed...

So I have given up trying to make a high modulus concrete with good all round properties. So E=40GPa it is, out of the bag easy peasy.... In the UHPC video he mentions shrinkage which is the first time this is mentioned from this mob. That's because of the Portland component, Find a 100% CSA grout/concrete and zero shrinkage small growth is minimal.... As a material 2100kg/m3 and E=40GPa its quite good... Peter

[ardenum]

In the UHPC video he mentions shrinkage which is the first time this is mentioned from this mob. That's because of the Portland component, Find a 100% CSA grout/concrete and zero shrinkage small growth is minimal.... As a material 2100kg/m3 and E=40GPa its quite good... Peter

I'm actually thinking of experimenting and using a full CSA in the durcrete recipe instead of their portland/csa mix, will see how that works out, you know with all the additives i.e superplasticizer etc.

So the E80 is alox huh? they mention something about a special superhard blend of rocks called durigid(one site calls it bauxite)

growth? how much of it? maybe that's why they add portland to counteract this?

[peteeng]

Hi Ard et al - Wherever you are there will be a commercial CSA mix for non shrink grouting. The chemistry in these things is complex and you can muck around with it forever and unless your a concrete chemist never know where you are. Durigid is ALOX. Std concrete is about 2100kg.m3 alox is really dense and get you to 3100kg/m3. Its grinding wheel stuff. Can't drill it unless you use diamond bits. So inserts are essential. The attached image is a cast that should be E80 via the formula. But that's compression modulus. So talk to your local concrete guys they will know what you are talking about and will have a solution sorted. They use portland because its cheap, they add CSA to counteract portlands shrinkage. HE80 shrinkage is 170ustrain thats 170/1e6*1000=0.17mm per metre. or 0.02% This is less then epoxy at about 0.1 to 0.5%... Peter

look for a class C grout

sikagrout 212 grows 0.02% sika is available anywhere on the planet....
flowset 690
quikcrete 0.2% shrink still less then epoxy its a portland csa mix. Peter there's heaps out there

https://www.homedepot.com/p/Quikrete...8500/100318529 $34usd per 50lb bag from Home Depot just looked this is from Guam open till 11pm !! get some now...

go with sika always a good brand- peter

[ChipsBFlyin]

Ardenum,

Thanks for the links to the videos on designing with UHPC. I'll look over the build thread and the videos and comment when I process everything. I am limited on space, so the raised gantry is the most compact option so far. I checked out the lukahr build. His set up is similar to the Haas UMC mills, these mills have been known to deflect when fully extended on the Y axis, resulting in tapered parts.

Can be seen here, starts @ 14:00-16:50

https://www.youtube.com/watch?v=YRncPJZeo0E


Pete,

I think I misunderstood you. I thought you said, you the QUIKRETE® Non-Shrink Precision Grout (No. 1585-00) was not suitable for material? Looks like I can get the Sika 212 grout near me.

[peteeng]

Hi CBF - just putting product ideas out there for Ard and others. The Sika212 is the better product. Peter

edit - this doc says E>20Gpa for Sikagrout212, to improve modulus add 3-5mm blue metal or similiar a good % of blue metal will get it to 40GPa. Do test mix to determine most gravel you can add. If you use large chunks of blue metal (20-25mm) you can place the gravel in the mould and pour the grout over it. it will flow down and around the metal. I'd probably mix small gravel in and pour. Some call it pea gravel. Don't use smooth stones you want rough stones to grip the grout better. Peter

[ChipsBFlyin]

Pete,

So the Sika 212 is suitable for machine bases? If so I guess I'll get myself some bags, make a mold and try to cast something. How would one go about mixing large quantities of this? I can rent a cement mixer that can process 5 cubic feet, but it looks like I need at least 20 cubit feet. Do I just send a pallet of my Sika212 mix to my local cement depot and tell them to mix it in a truck and deliver it to me? haha

[peteeng]

Hi CBF - If you ask Sika they will say "we don't know". Thats what Bluey said when I spoke to the tech guys here. But its similiar product to european and US builders that make "concrete" bases. You have about 30mins of flowability so you mix 10kg and pour mix 10kg and pour etc until done. If you have a cement mixer then make a bag or 2 at a time... Peter

re bases - I'm planning on making bases, gantries and saddles from it. I can get the Sika212 from my local hardware so strat with 1 bag 20kg $31 AUD. plus get some colouring. Yellow or orange is good....Peter

[ChipsBFlyin]

Pete,

Please excuse my ignorance with cement. I thought it was like silicone, once that thin film starts to form over it, you can no longer lay more silicone on top of it.

I was looking at these frames for some ideas.

[peteeng]

Hi CBF - The Hermle is a mineral cast base. Hermle have built there own mineral casting division to cease their hot casting and bring cold casting in-house The others are cast iron. The windows in the cast iron are actually the bosses that support the inner mould so they can make hollow parts. You can do the same with grout. I'll start to call it grout vs concrete as the makers call it engineering grout or precision grout (PG) vs concrete. Peter

[ChipsBFlyin]

Pete,


I spent some time looking at some bases and this is what I came up with for my mineral casting. Still needs some revision and a little weight loss? Its at around 3 tons

[ardenum]

Pete,


I spent some time looking at some bases and this is what I came up with for my mineral casting. Still needs some revision and a little weight loss? Its at around 3 tons

actually it looks all right gemometrically...don't wanna bust your...but 3 tons would cost around $20,000 to make, unless you meant UHPC

[peteeng]

Morning CbF - Are you up for such a beast? You can rib the walls and reduce say to 50-60% of the weight. I expect you mean UHPC not epoxy granite.... It has a pit, are you thinking 5 axis or do you need to do deep parts? Peter

[ChipsBFlyin]

Ardenum,

I plan on making it from precision grout. I am going to play around with some of the Sika 212 grout Pete mentioned in a few post ago, before I attempt to cast this beast.

Pete,

I think so, but I am going to experiment with smaller castings first. I checked with the local dump and they said it would cost me about $500 to dispose of it this monster, so I am adding that into my calculations in case it fails. I don't plan on 5 axis, I only want it for 3 axis, maybe 4 axis.

The pit was for the chip pan, but I have changed the design. I know its starting to get a bit complex, but I have some experience in mold making, so I don't think I am out of my reach yet.

[peteeng]

Hi CBF - Then to make things simpler subdivide "THE Beast" into 3 parts or 4. Then they can be taken to the tip or to a machinist easier. On assembly they can be "set" with epoxy and pulled apart in future. Its a totally over the top serious machine bed now your gantry and Z axis are out of proportion. Cast your gantry as well even your saddle and Z axis.... Your in a new stratosphere now... Peter

It won't fail you've done enough homework to make it happen. Think BIG live LARGE....

[ChipsBFlyin]

Pete,

I think I can only afford to make it in one piece. Making it in multiple pieces would add to the cost significantly because I would need a lot of machining for the mating surfaces.

I thought about making one of these attachments as my first casting project. Its a portable mill, so then I can then use it to grind my own machine Y axis rail mounts, scrape if needed. Taking the casting to a shop is quite expensive. The cheapest quote I got was $4,729. For milling and drill/tap rail mount holes.


I have the tools needed to do inspection after I attempt to grind the casting.

[peteeng]

Hi CBF - Yep usually have to make a machine to make "the" machine. Keep at it Peter a mining company I do stuff for has a portable mill like that.

but what I meant by set the surfaces is to make it so it self assembles but the final machining is done like you planned. ie the sub-assembly surfaces do not have to be that accurate, the accuracy is acheived at the final assembly level. Being epoxy set the connections become precision fitted for future dissembly/assembly. But if the weight and logistics is not a big deal then one piece is the way to go.

[ChipsBFlyin]

How would the joints look? I'm a bit confused, I don't understand how can you assemble two surfaces together that are not flat and not introduce stress into the structure?

A picture or a link would be very helpful.

Should I be adding rebar inside my castings?

[peteeng]

Hi CBF - There are several threads showing how to use epoxy to "set" a connection on a machine. eg the column to the base. The faying surfaces are brought together with screws and nipped. The surfaces that are important are brought to their intended position or orientation. This means the connection may have a 0.5mm or 3mm or varying gap. The gap is filled with epoxy (before assembly wax one side of the connection) this cures and creates a firm, zero stressed connection. Then the bolts can be done up tight if the connection needs to be preloaded. I'll have a dig around for an example. In yachting we call it wet shimming. Been wet shimming masts to decks, fittings to decks for decades. Much better then mechanical shims. I used some epoxy putty to shim my saddle in the Brevis thread. Slightly different but same principle. Peter

https://www.cnczone.com/forums/diy-c...ml#post2469586 #428

[ChipsBFlyin]

If I was to cast this in multiple pieces, I would not want it to come part after. So I should use a paste epoxy instead of a liquid epxoy right? I'll research the subject a bit more