[peteeng]

Hi Ard - Give them a call and find out!! I have started massaging Milli-M around the 450x225mm table size. I have flicked the separate table and will cast in a grid of thread inserts into the base. Started adding gutters. Current stats are X 22 Y 34 Z 38 N/um.. Happy with that. But Milli is 350kg without drives motors etc. So a few more holes needed.... I'm going to model the 20 vs 25mm rails with cars and bolts as a small model to see the difference... There's been more Covid stuff going on so my holidays are cancelled and I'm home. Will paint the workshop floor and get more Milli done.... Merry Christmas Peter

[ihavenofish]

I did some digging "EPUMENT 140/8 B1 30kg" for 50EUR, No indication whether just the dry mix or together with the epoxy.

I'd expect dry, but, that's not too bad, especially if there was some form of guarantee of result (follow x instructions, use x equipment)

You'd need 3kg epoxy - about 1 gallon / 4L. $100ish. lets say $200usd for 33kg. $6/kg. $3/lb.

Why would you mess around with unproven concrete mixes?

[ardenum]

Why would you mess around with unproven concrete mixes?

Me? it's EG and I'd hardly call it unproven, compared to doing everything by yourself, which could be described as even less proven. Since the company that provides it makes EG beds professionally, I'd be pretty confident with them more so than with me.

On top of that, most proven EG done in the diy community uses sand, I never had any intention of using sand. Maybe metal dust instead of granite dust and maybe basalt rocks up to 8mm, but never regular sand, which is silica.

[ihavenofish]

Me? it's EG and I'd hardly call it unproven, compared to doing everything by yourself, which could be described as even less proven. Since the company that provides it makes EG beds professionally, I'd be pretty confident with them more so than with me.

On top of that, most EG done in the diy community uses sand, I never had any intention of using anything other then granite particles. Maybe metal dust instead of granite and maybe basalt rocks up to 8mm, but never regular sand, which is silica.

sorry, you misread or i misexplained. i meant with a proven premix like the epucrete that isnt too expensive, why would you mess with concrete - csa, etc.

[ardenum]

sorry, you misread or i misexplained. i meant with a proven premix like the epucrete that isnt too expensive, why would you mess with concrete - csa, etc.

That explains it, this thread is peteeng's build thread that sometimes gets hijacked by me and others, he's doing his stuff in CSA.

I'm doing mine in EG, mainly due to the fact that CSA sets like in 20mins, I wont have a big enough container to mix 1000kg of stuff and pour it, so EG in that regard wins for me because I can make it in batches and pour on on top of the other, and while I'm mixing another batch the previous shallow layer has enough time to get rid of bubbles.

In the end it comes down to whether cheap CSA with expensive fillers is cheaper then expensive EG with cheap fillers.

[ihavenofish]

Fast setting concrete (ca mixed with portland is the worst) are extremely exothermic, so they will mess with your precision. for EG they deliberately choose a very slow setting epoxy so it heats up as little as possible. ca and portland sets in as little as 30 seconds and will boil a bucket of water if you dump it in. fun.

so its more than just about the working time.

[peteeng]

Hi All - I have not yet decided the build material. I use "concrete" here to cover CSA, Portland and UHPC

In summary Part of this Milli effort is an exploration of possible materials. I have always aimed at an aluminium replacement so the target E is 70GPa. UHPC is available in Europe with an E=80GPa which is very attractive. And this material is used in high precision machine bases exclusively, it is not sold as a building construction material....This gives me hope that I can replicate that here. I have been using epoxy for over 30 years in industrial applications and yacht structures. So have full understanding that epoxy is a reliable and a known solution. However its E=3GPa so its a struggle to get to 70GPa with low cost fillers. Easy to go out and use carbon fibre if you have the $$$. "concrete" is 30GPa out of the bag (round figure) so its well on the way to 70.... Its not unproven or unreliable if you get the right stuff. Many DIY builds use the wrong epoxy as well but they muddle along and get a machine working...

Another aim is that the cast material be machinable so near nett castings, post cure and finish machining can be done. (Look up Tetrium-S) By the way concrete should be post cured as well. Using mineral fillers usually excludes machining unless you have a wet grinding machine in the shop.... However these days dryish diamond tools may do the job in a router. Something else to explore.

Casting offers opportunities that machining, plate builds, sheet metal builds do not. Especially since the intent is to make many machines. So early 2021 I shall be making sample blocks to figure out max aggregate and fibre ratios with CSA then shall do some modulus testing. I have already done a lot of this development in epoxy, the result of which is the Tetrium stuff but it does not get to 70GPa yet unless I use high modulus minerals (silicon carbide, carborundum) which then is not traditionally machinable. I have a lot of blocks of various materials around here...

Another thing the DIY don't do is test their resulting material so they really don't know what they have. But their machines work so they are happy. You can spend a lot of time preparing, tamping and settling a 200g sample to get a fantastic mix but it won't scale to a 200kg pour.

Merry Christmas to you all out there in the machine tool design and build multi-verse. Thanks for all the input you have provided in 2020 its been a huge pleasure and a smallish pain....I look forward to 2021 and yuall, keep making stuff. Peter

By the way citric acid is used as a retarder in CSA not sure if it upsets its mechanical properties. ....

[peteeng]

Hi All - Milli-M is dressed for Christmas. Ho Ho Ho Peter

[peteeng]

Hi Ard - The TDS for Epument says its a 3 component system. So my guess its epoxy, hardener and aggregate.. Peter

[ardenum]

Hi Ard - The TDS for Epument says its a 3 component system. So my guess its epoxy, hardener and aggregate.. Peter

The price I found is an obscure third party price listing that doesn't specify it, http://ezentrumbilder3.de/rg/pdf/Preisliste-DE.pdf

Rampf does not respond to my emails, I called them too, and they forwarded me to writing an email, so there's that.

[jackjr-123]

The price I found is an obscure third party price listing that doesn't specify it, http://ezentrumbilder3.de/rg/pdf/Preisliste-DE.pdf

Rampf does not respond to my emails, I called them too, and they forwarded me to writing an email, so there's that.

I purchased my EG from Rampf. They are indeed very slow to answer email... Price is about 3€/kg for Epument 140/8. Price list attached.

[ihavenofish]

I purchased my EG from Rampf. They are indeed very slow to answer email... Price is about 3€/kg for Epument 140/8. Price list attached.

that doesnt include epoxy correct?

[jackjr-123]

It includes everything. It's already expensive enough. It's sold in 25kg buckets with aggregate and epoxy. Ratio is 22.5/2.5kg if I recall well.

[ihavenofish]

Ahh, ok. so thats very reasonable. $1.60 usd per lb.

[jackjr-123]

Hi All - I have not yet decided the build material. I use "concrete" here to cover CSA, Portland and UHPC

In summary Part of this Milli effort is an exploration of possible materials. I have always aimed at an aluminium replacement so the target E is 70GPa. UHPC is available in Europe with an E=80GPa which is very attractive. And this material is used in high precision machine bases exclusively, it is not sold as a building construction material...

You're talking about Durcrete/Nanodur right? I've talked with them, and I think the main challenge for the hobbyist is heat-treating the casting to 80°C for 48 hours for quick stabilisation. Otherwise you wait 1 year...
Their special stones to achieve the 80GPa modulus are also very expensive...

[catahoula]

Slightly off-topic but anyone have a good source for cheap, low viscosity casting epoxy in the US? Seems that along with everything else epoxy has gotten more expensive, I'm mostly finding it for $150usd per gallon, yikes.

[ihavenofish]

i just googled epoxy and see stuff in the $50 per gallon range. no idea if its of usable quality. seems to target the people that make resin and wood table tops.

[ardenum]

I purchased my EG from Rampf. They are indeed very slow to answer email... Price is about 3€/kg for Epument 140/8. Price list attached.

Many thanks! Do you have a build thread by the way?

[peteeng]

Hi Jack - The E80 material is the Durcrete material. I don't think its a must to heat treat it and I don't think you have to wait a year to stabilize it. If you want 80GPa you have to pay a price. Everything needs heat treat, steel, alum, epoxy, concrete if you want the best properties... Peter

[spumco]

Slightly off-topic but anyone have a good source for cheap, low viscosity casting epoxy in the US? Seems that along with everything else epoxy has gotten more expensive, I'm mostly finding it for $150usd per gallon, yikes.

I just bought a 1.5g kit of this stuff for $90:

https://www.theepoxyresinstore.com/p...ve-epoxy-resin

It's pretty thin, even as cold as it is here right now (35 Freedom Units). At 65F it's probably about like milk, maybe not 'water' like they claim but it's really low viscosity for epoxy. Cured Shore D of 88 I think, but check the 'comparison' page on the site and it has some - but not all - of the specifications you'd be interested in.

I'm on the fence between this (plus alum oxide filler, plus fibers) or CSA with fibers. Cost isn't an issue with the small volume I need, but I'm thinking I'm going to go with CSA and use this to make some iron powder-filled shim paste as it has such a long open time for alignment.

If my basalt fibers ever arrive I'll do some unscientific tests with this stuff and CSA and see how they both behave with various fillers, temps, etc.

-Ralph