3D Printing a train station.
September 29, 2017 8:12 AM   Subscribe

3D Printing concrete for Crossrail. Crossrail is a big fancy new rail route through London and surrounding counties. In the process thet're also building a load of lovely new stations. Here's a nice short article about the 3D printing process used to make exciting futury curved concrete panels.
posted by Just this guy, y'know (20 comments total) 20 users marked this as a favorite
 
This is really cool. I'd really like to see these stations once they are completed.
posted by carter at 8:26 AM on September 29, 2017


Amazing looking structures done with a very clever technique. The amount of effort involved in achieving these is exhausting just to contemplate. Perhaps it is a common thing but I am particularly impressed that the architect was so involved in the materials science and creation of the techniques required to more efficiently achieve his design.
posted by bz at 8:51 AM on September 29, 2017 [1 favorite]


Beautiful work, and the engineering behind it is just as cool. This overhang looks like some kind of giant brutalist bicycle part, and I love it.
posted by OverlappingElvis at 8:59 AM on September 29, 2017 [1 favorite]


Live in an older house with a stairway with curved plaster walls, it's not something one perceives most of the time but I think the organic flow is calming, subtly more comfortable. (except when moving furniture, arghh)

The curves probably reduce sound without being explicitly muffling.

Our future robotic builders may enable wonderful architecture that would be prohibitive currently.
posted by sammyo at 9:37 AM on September 29, 2017 [2 favorites]


tl;dr; The molds are printed, not the concrete itself.

They appear to be made by a gigantic CNC machine that extrudes wax into the rough shape of the mold, and then mills out the finer details. Cool stuff (and definitely a time-saver if they're insisting on so many unique molds), but this isn't employing any technologies that weren't already being widely-used in the 1980s.

On the other hand, it's a little surprising that they're going all-out on using thin concrete panels for every interior wall surface. That's gonna be loud, and very difficult to clean.
posted by schmod at 10:28 AM on September 29, 2017 [2 favorites]


That's gonna be loud, and very difficult to clean.

Sweet sweet Brutalism isn't about practicality (as anyone who ever tried to navigate my old community college can attest), its about how it FEELS... harsh and uncaring.

This is good stuff!
posted by The Legit Republic of Blanketsburg at 11:34 AM on September 29, 2017 [12 favorites]


They appear to be made by a gigantic CNC machine that extrudes wax into the rough shape of the mold, and then mills out the finer details. Cool stuff (and definitely a time-saver if they're insisting on so many unique molds), but this isn't employing any technologies that weren't already being widely-used in the 1980s.

On the other hand, it's a little surprising that they're going all-out on using thin concrete panels for every interior wall surface. That's gonna be loud, and very difficult to clean.


Depending on your definition of what is a new technology versus a novel application of a previous one, this isn't employing anything that wasn't being widely-used by the Romans. Yet I think it's fair to say that custom mass production of concrete wax moulds using robotic technology is new. I don't think that any additive manufacturing was being done in scale in the 1980s, but it's not my area of expertise.

I suspect all of the little divots in the downward facing panels above head height are for acoustic purposes; I don't know the state of play on concrete sealants, but I hope there are some good ones. Perhaps they should put a sample outside in an area that taggers frequent and see what happens.
posted by Homeboy Trouble at 11:54 AM on September 29, 2017 [5 favorites]


It's still going to look like brown, cracked, rust-stained ass in 20 years, no matter what shape it is. Exposed concrete starts looking like absolute shit long before it reaches the end of its actual service life. Curved walls look great as a 3D rendering, though. And they will probably amplify sound rather than muffle it; that's why things like band shells are curved—to focus and direct sound so that it appears louder.
posted by Anticipation Of A New Lover's Arrival, The at 12:05 PM on September 29, 2017


Didn't we learn anything from the Space Shuttle tiles?
posted by JoeZydeco at 12:23 PM on September 29, 2017


That's gonna be loud, and very difficult to clean.
Excellent spider habitat though.
posted by Bee'sWing at 12:24 PM on September 29, 2017 [1 favorite]


I was under the impression that the concrete would be covered by metal cladding.
posted by acb at 12:39 PM on September 29, 2017


Excellent spider habitat though, exactly, I have a small catalog of unintended spider habitat images, I know of a house paneled with deep gaps between panels; it's festooned in web and becoming more so by the year.

I am surprised the dimples are regular; sound is disrupted better with irregular patterns, especially when it is directional - I would think the sound would 'flow' up the smooth sides before encountering the dimples.
posted by unearthed at 12:58 PM on September 29, 2017


It appears that this is possibly a first for using hybrid CNC to generate custom moulds for concrete casting (using both more common and established subtractive milling methods as well as the additive 3D printing technique).

There is a lot of marketing wank in the article -- this isn't 3D-printed concrete and there isn't any underlying technology here that isn't already established or at least proven out in the industry. But as others upthread have already said, it's the combination of techniques that have delivered a heretofore-impossible aesthetic and structural effect, and that's pretty cool.

There are some significant gaps in the description of the process that I'm having a difficult time puzzling out. Having given interviews to journalists on similar topics myself, I'm inclined to believe the gaps are due to signal loss between the fabricators/designers and the journalist.

Anyway, if you have to melt the mould to get the cast piece out, you're destroying the mould in the process. Sure, you can retain the wax material and re-use it for the next piece, but the cost of the mould isn't in the material, it's in the time it takes to shape it correctly. So they would actually have to form 36000 moulds (one for each panel) across 1400 different types.

This radically changes the time required for the project and if the numbers mentioned in the article are otherwise accurate, kinda kills any CBA against the traditional method. That is, 36000 moulds * 2.5 hours prep time = 90,000 hours vs 1400 moulds * 16 hours = 22,400 hours. Of course you would probably recover the cost delta due to fewer human hours required by the new method (if, indeed, cost/time was even a factor valued by the customer).

I think it's more likely that what was 3D printed were the 1400 positive master moulds (from which 36,000 disposable negative moulds were made with traditional wax casting techniques). Having given multiple technical interviews to non-technical journalists myself, I'd bet dollars to donuts that the elision of this step in the process was due to signal loss between the fabricator/designer and the journalist.

All of this said, I still get super excited to see people rigorously experimenting with materials and technique to do cool and unprecedented stuff -- and this is pretty cool stuff!
posted by turbowombat at 1:41 PM on September 29, 2017 [7 favorites]


Ian Visits isn’t a journalist, he’s a blogger who visits stuff. I’m sure he’d gladly accept any clarifications or suggestions for improvement.
posted by grahamparks at 3:32 PM on September 29, 2017 [1 favorite]


Looks like it might be possible to 'print' normal concrete (the site's English makes understanding it a bit fraught but it sounds like the real deal).

"pure water and cement based 3D Printer Concrete"

This cuts out the middleman altogether, although with "printer volume of ... 60x40x40 cm" is a bit limited, but early days.
posted by unearthed at 5:06 PM on September 29, 2017


It's been possible to print concrete for a while but for structural panels all the seams between layers are weak points.
posted by Mitheral at 8:13 PM on September 29, 2017 [1 favorite]


Does the Washington metro look like rust-stained ass after 40 years? I've only seen it in pictures, but the concrete seems to have held up.

It's amazing how tube-y these stations look. The tube stations' white panels on curved walls, and brightly coloured beams and pipes are there to hide and/or dress up decades-old brick and iron infrastructure. Here, though, it's an aesthetic look.
posted by Pruitt-Igoe at 11:33 PM on September 29, 2017 [1 favorite]


this isn't employing anything that wasn't being widely-used by the Romans

Well the water-powered CNC mills weren't quite as precise, and the human calculators ran a bit slower. Tricky to compute all those movements with Roman numerals, no zero, no calculus, and precious little trigonometry. They had fantastic geometry though! All the forms you can describe with a compass and straight-edge.
posted by Nelson at 1:30 AM on September 30, 2017


Why "brown, cracked, rust-stained ass"?

It's not exposed to external weather, GRC shouldn't crack if the GR is specified properly and hopefully tanking should keep water out. (Concrete doesn't rust in the absence of water. )
posted by Kiwi at 8:51 AM on September 30, 2017 [1 favorite]


The DC Metro stations need to be washed periodically. It doesn't always get done, but it looks OK when they do it. They've given up on a few stations, and have just painted them (which looks awful). A few stations have also had water-incursion issues, which has damaged the concrete panels -- I don't really know what they're going to be able to do to clean those up.

All of the stations with concrete arches have sound-damping panels installed in at least some of the coffers.

However, the DC Metro was explicitly designed to be cavernous and "earthy" -- the concrete has a rougher texture, and warmer color. Indirect lighting and earth-toned accents in the stations help to add to this effect (while also adding a 60s vibe that not everybody loves).

Additionally, the Metro stations were designed with "floating" platforms that keep passengers a few feet away from the walls, which has been a remarkably effective means to prevent vandalism. Corridors and passageways in DC have much more "traditional" designs with poured concrete walls, tile, and metal ceiling tiles, but also tend to have similar design features to keep people away from the wall surfaces themselves.

The other striking feature of London's design is the amount of empty space behind the concrete walls. While this undoubtedly makes it easier to route utilities, and replace the walls/ceilings in the future, underground construction is so unfathomably expensive that it's surprising to see the architects willing to sacrifice interior space like that.

tl;dr; It sure seems like subway tile would have been fine.
posted by schmod at 7:11 AM on October 2, 2017 [1 favorite]


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