Hello I'd be interested in the design choices for the frame, I'm planning on building something similar with ultra high performance concrete and similar hardware I just don't know how to start designing the frame
Hi, thanks for sharing. For beginners that come from computers ambient, it is very useful to learn of the methodology the measure and align at micron level. Thanks.
Can you please show us in great detail how exactly you scraped or sanded the planes for accurate surfaces. Also what is the accuracy and repeatability like of the CNC when milling?
NIce, jetzt musst nur noch den Tisch und das ganze Holzzeug ersetzen, damit das nicht resoniert. Sonst bringt dir ja die Beton CNC nix :-) Grüßle CNCPRINT
1:19 5 microns across the whole surface? I'm pretty baffled by this considering in most builds a super flat surface that is also perpendicular seems like one of the hardest things to achieve.
Please, please follow up with more information on it! I was under the impression that concrete is less than ideal because it is likely to shrink when cured.
Who always tells people concrete machine beds need reinforcement? It's complete nonsense. If you're dead set on using fibers - just clad it in a quasi isotropic carbon fiber laminate. Compound beams from Cf clad polymer concrete test surprisingly good considering the comparably tiny amount of fibers and resin. Thought to be a result of the strengthening of the concrete itself by confinement as well as by taking the tensile loads.
nice! however, epoxi granite machines do not require steel reinforcement. in fact, the epoxy only stabilises the matrix, the stiffness comes from the quartz or granite infill. when properly cast, those pebbles directly contact each other, so the epoxy granite has the stiffness of the granite (which is much highter than the stiffness of the epoxy matrix)
Nice-looking design & machine. I suspect you could have skipped adding fiber to the concrete. There's a nice book on building machine beds with (UHPC) concrete "Maschinenteile aus zementgebundenem Beton" (www.amazon.de/-/en/DIN-V/dp/3410271864) and the author goes over why fibers are mainly helpful in case of catastrophic failure but at that point you have to anyway repair or throw away the machine. The relevant snippet from pages 15-16 (it's in German but it kind of looks like you're in Austria or Switzerland from that landscape?): "Für den Maschinenbauingenieur gilt zu beachten, dass Bewehrung, Stahlfasern, Mikrostahlfasern, Kunststofffasern, Glasfasern, Fasercocktails, Carbongelege oder Nanotubes erst dann richtig wirken, wenn ein Riss im Beton entstanden ist und das Materialverhalten nicht linear wird. Oder wie Prof. Mechterine aus Dresden zu sagen pflegt „Vor dem Riss ist der Bewehrung langweilig“. Durch die mit dem Riss einhergehende Verformungs- und Steifigkeitsänderung ist das Bauteil maschinenbautechnisch zerstört und muss entsorgt werden. Bewehrung und Fasern machen deshalb nur unter sicherheitstechnischen Aspekten Sinn. Wenn ein Gabelstapler die Ecke abfährt, fliegt diese Ecke nicht durch die Halle. Wenn die Maschine vom Kranhaken fällt, muss man nur ein Maschinenteil entsorgen und nicht zwei." So as far as I understand it, if the fibers are doing their magic your machine bed is already under so much stress that it's been deformed beyond its elastic limit and is toast. So, you can save yourself some cash by not using fibers. Commercial concrete machine bed makers also apparently don't use fibers (page 16, same book) "der Hersteller bei seinen Maschinenelementen aus UHPC keine Fasern verwendet. Dem Unternehmer, welcher Maschinenbauteile aus zementgebundenem Beton herstellen will, muss klar sein: Wer der Zugfestigkeit „seines“ Betons nicht vertraut, sollte dieses Material nicht einsetzen. Stahl in Form von Bewehrung, Fasern oder Mikrofasern sind nicht die ideale Hilfe." I know they're using UHPC but I think the lack of fiber benefit would also apply for normal concrete (not sure though). What might make sense would be pre-loading the concrete with tensioning members that go through it so it's biased into its compressive range and external tensile forces would have to be greater to push it out into a state under tension. I think some machine bed makers do that but I don't find an example offhand, so, maybe not. I don't know. But prestressing is used in bridges and other concrete structures.
I wish I could read German as I think that book would answer a lot of my questions! (Thanks for taking the time to make this post it's still very helpful.) I'm currently trying to find more information on the best concrete formula to minimise the corrosion of the embedded steel parts.
@@ContractCAD you could buy the .pdf version (www.beuth.de/en/publication/maschinenteile-aus-zementgebundenem-beton/265421762) then upload to your Google Drive (might have to make an account), open the pdf in Google Docs, do menu Tools -> Translate document, target language English. That works reasonably well although it only did 33/133 pages when I tested it so you might have to chop the book up into 30-page segments. In the various things I've read about UHPC over the past couple of years I don't recall seeing talk of formulas to prevent insert corrosion, so, maybe that's not a big deal (maybe everyone uses stainless steel?), but, I don't really know either. Also, did you see this guy's channel? He seems to be doing a diy hpc mix, no idea how it compares to durcrete's: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-LYpIhXgDufQ.html.
@perspectivex Thanks again. This page has some info regarding corrosion www.cement.org/learn/concrete-technology/durability/corrosion-of-embedded-materials. Sadly, further reading looks to be in the form of paid-for technical docs and regulations. I'd like to cast 'ground flat stock' in place (levelled on a surface plate) to act as the foundation for the linear rails (this should mean I can avoid milling them and go straight to lapping or scraping). Flat stock is mild steel and using stainless screws to anchor into the concrete will supply one of the corrosion triggers mentioned in the link above. I think it's got a lot of potential but I don't want to see my machine bubbling rust around the critical rail foundations in a few years time. Maybe something as simple as chemically blackening it would help? (Again, there is a paid document from my link that goes into suitable treatments.) I'll either end up just going for it and seeing what the future brings or opting for epoxy instead. Or (and this is how comments like this help get the brain working!).. I could look at a hybrid system of a concrete base with the steel foundations anchored and set in epoxy.
@@ContractCAD As that page mentions, "reinforcing steel does not corrode in the majority of concrete elements and structures. However, corrosion can occur when the passive layer is destroyed. The destruction of the passive layer occurs when the alkalinity of the concrete is reduced or when the chloride concentration in concrete is increased to a certain level. ...steel’s natural tendency is to undergo corrosion reactions, the alkaline environment of concrete (pH of 12 to 13) provides steel with corrosion protection. At the high pH, a thin oxide layer forms on the steel and prevents metal atoms from dissolving. This passive film does not actually stop corrosion; it reduces the corrosion rate to an insignificant level. For steel in concrete, the passive corrosion rate is typically 0.1 µm per year. Without the passive film, the steel would corrode at rates at least 1,000 times higher ...intrusion of chloride ions, present in deicing salts and seawater, into reinforced concrete can cause steel corrosion if oxygen and moisture are also available to sustain the reaction." I think maybe for concrete machine beds after the concrete cures since you normally coat it with a sealing paint or two component epoxy (as mentioned in that German book...UHPC needs protection from coolants) the steel inside is going to be frozen in time regarding corrosion. Like I said, I don't know for sure, but that's how I read that article and think of applying it to the case of steel inserts inside a concrete machine bed. Also I wonder if casting the flat stock in place on a known flat surface is enough...the concrete will shrink for a month or so (again what I read for UHPC in that book) and I wonder if it does not shrink perfectly isometrically if it can start to twist or otherwise pick up the flat stock from the surface plate while it cures. Maybe if the flat stock were non-permanently glued to the flat surface? but then also you might 'burn in' stresses that as soon as you release everything from the flat surface it moves. Don't know. Just musing. oh, also I think you could just cast pockets into the concrete where you want to later add inserts and then add the inserts with epoxy, which would anyway seal them. In some tests in the UHPC book, test pulling inserts put in with certain epoxies caused the UHPC to fail and tear out around the socket before the epoxy interfaces failed.
@ perspectivex thanks. The book you are referring to "Bernhard Sagmeister - Maschinenteile aus zementgebundenem Beton" can be partly accessed via google books. The title sounded very interesting and relevant, but I have to agree with the bad reviews the book got on amazon. I am sorry to say, it seems like an (expensive) advertisement for Nanodur Concrete containing very little (half) knowledge on fiber reinforced concrete. It is an experimental fact that fibers improve the overall structural strength (compressive strength, splitting tensile strength, the flexural strength) and threaded anchor strength ( doi.org/10.1016/j.jestch.2019.01.003 doi.org/10.1016/j.jobe.2020.101842 ). The reasons behind why this behaviour is observed and models that explain the behaviour might be subject of discussion. For example, the first (peer reviewed) publication above reasons "the reinforcement provided by fibers can work at both a micro and macro levels. At a micro level fibers arrest the development of micro cracks. The ability of the fiber to control micro cracking growth depends mainly on the number of fibers. Whereas at a macro level, fibers control crack opening and increasing the energy absorption capacity of the composite. Hence, a higher number of fibers in the matrix leads to a higher probability of a micro crack being intercepted by a fiber leading to higher compressive strengths as can be seen in Fig. 4 where a sharp increase in the compressive strength is observed as fiber percentage increase from 0.0 to 0.6. Whereas at a macro level, the mode of failure will be enhanced due to the great amount of energy that consumed by fibers and due to postponing the formation of the first major crack in the matrix." Having said that, there is no reason why one should not experiment without fibers if the extra strength is not needed or the budget is constrained. hope this points you guys in the right direction - happy tinkering!
awesome idea: just two things: 1-make a video about milling capabilities and 2-make several video tutorials building one from scratch... you will boost your channel!!!!
