[castinite]

When Milltronics started, I designed a cast polymer base for their small miller. I then designed bases for some of thier other bed mills. We also supplied an epoxy grout to allow them to attach the machine bed to the base quickly and accurately. After I sold my company the new owner overcharged and lost the business.

[veteq]

Would a UHPC (ultra high performance concrete) be a good material for a hobby machine base?
It is easy to use since there is no vibration neccesary.
Ant idea`s on this?
[ame=http://www.youtube.com/watch?v=ftopsaGUZzs]Production of UHPC-Elements (English) using Ultra High Performance Concrete - YouTube[/ame]

[rocketflier]

Would a UHPC (ultra high performance concrete) be a good material for a hobby machine base?
It is easy to use since there is no vibration neccesary.
Ant idea`s on this?
Production of UHPC-Elements (English) using Ultra High Performance Concrete - YouTube

[ame=http://www.youtube.com/watch?v=naRoDinbbdc&feature=related]Concrete countertops: Using superplasticizer to increase workability without decreasing strength - YouTube[/ame]

[the4thseal]

where do you get thins stuff.I am in the USA

[veteq]

But why dont we all use this stuff to build a machine, what are the pro`s and con`s? I found a website that stated that the mechanical performance is the same or better as EG. What would be the problem, creep, the water?

[lgalla]

uhpc can cost 10 times more than regular concrete.I may cost as much as EG but may be easier to use I doubt this is a material you can get at Home Depot
Larry
http://www.dhs.gov/xlibrary/assets/u...ialization.pdf

[the4thseal]

i would not expect to find it a home cheapo but i can not find a source for the additive.

[JohnMcNamara]

Hi All

Hi performance concrete.

Clearly a great material for building thin shells and slender bridges.

And (possibly) machine bases as the video shows? were the machine bases in the video destined to be part of high performance CNC machines or were they for a use where less accuracy is required? Maybe materials handling or bases for pumping or processing machinery? The video did not make this clear.

Even ordinary concrete has always been strong enough to build machinery frames ; it is let down by susceptibility to expansion due to moisture, long term shrinkage and cracking and micro-cracking. Not a serious problem as it is known and the design engineer allows for it when building say a reinforced bridge; but totally unsuitable for a precision machine tool where micron accuracy is required.

Before getting excited about high performance concrete technology I would like to see detailed specifications. It has to perform physically at least equally to Epoxy/Aggregate before it is worthy of consideration.

Can any forum member post a link to a site that gives that detail?

Cheers
John

[lgalla]

characteristics


value



density

< 2.500 kg/m³



ultimate pressure strength

> 100 [MPa]



ultimate tensile strength in bending(acc. to recipe)

up to 25,00 [MPa]



young´s modulus

≈ 45.000 [MPa]



water absorption in weight

1 - 2 [Mass %]



fire behaviour

class A1

[JohnMcNamara]

Hi Lgalla

From your post:
"water absorption in weight 1 - 2 [Mass %]"

I can only assume it expands.
It is a pity they do not quote a figure.

Without an accurate number it is a No Go zone.

Cheers
John

[lgalla]

more links
Durcrete GmbH

[lgalla]

one more
http://people.ce.gatech.edu/~kk92/uhpc.pdf

[lgalla]

homag uses UHPC


durcrete: examples for machine beds

[JohnMcNamara]

Hi All

Having downloaded all the brochures. I was not able to get a number for the effect of one or two percent water absorption as mentioned in their specification. I did notice that they forbid the use of kiln dried aggregates in the mix?

As most CNC machines use coolant this is not a small issue.

Cheers
John

[alex_ku]

John, What about to cover it with few layers of epoxy based paint(or just epoxy). You'll get couple mm of protection layer.

[JohnMcNamara]

Hi Alex

Yes that would work for a time, however any sort of membrane just sits there waiting to be broken; and what about all the bolt holes and cast is steel fittings? If a tiny crack forms around one or two the membrane defence line is broken.

What is the first life (purchased from new) of a machine? maybe 10 years.... A long time for water to seep in even through a pinhole.

We don't actually know if water does expand High performance concrete but if it does no thanks. Epoxy/aggregate will do fine.

I do wish the makers would publish and confirm that it is not affected by water (and or Oil); or if it is by how much?

Cheers
John

[alex_ku]

Hi All

Here is my first part, fresh, from oven (1hour at ~80C)
First made epoxy-granite part . - YouTube

Mix
.7l of 5-8mm
.6l of 1mm
.5l of 0.1mm
it made 2 liters of mix.
epoxy 20% by volume. (hardener is 1:10)
The consistence of mix is quite dry. Snowball holds form perfectly.

Hand drill mixer do the job very well.

Vibration table almost do nothing(visually). Probably neet to dramaticaly increase a vibration level. And i think that mix should be moister to use vibration.

We will se it in next part

PS: sorry for my english. :tired:

[alex_ku]

Now I'v found one more negative side of part - it air conductive. So, it will suck water oil and so on.
So, definitely should be more epoxy.

[rybov]

Hi Alex,

Like you I am experimenting to find a good formulation and construction process for EG. I am no expert.

From my experimentation I think you could improve your formulation by having more sizes in the aggregate. The smaller sizes is suppose to fill the crack inbetween the bigger ones. You have a big jump in size from 1mm to 5-8mm.

Regarding the usefulness of vibration, I use the exact same vibration motor as you for my experimentation and find vibration an important part of construction to eliminate air bubbles and spread the EG evenly. My vibration table uses four springs to isolate the vibration plate. Maybe a lot of the vibration power from the enigne is lost in the tire you use. If it is not the vibration table, it certainly could be the visocity of the EG mix. What epoxy are you using?

Best regards
Jacob

[alex_ku]

Hi Jacob,

Thanks for comment. I'll try one more size(marble flour) in my next part (the column).
About vibrator - its my mistake. At begin i'v set it to minimal vibration level and found int quite enough. But it's not. So i'v change the setup to 50% of maximum vibration on both sides of vibrator, connect it to triangle. Now i feel the changes

We will see.

Best regards,
Alex