Comment on 3D printing a house
isleepinahammock@lemmy.blahaj.zone 1 week agoThat would be a lot of waste plastic.
I wouldn’t think so. This may be one of the few cases where recycling plastic is actually practical. Recycling plastic is normally a big problem because it’s a very dirty supply stream. Plastic products often have multiple types of plastic laminated together, often include plastic labeling, etc. Even if you make a plastic consumer good out of a reusable thermoplastic, recycling is still impractical. Plus the main contaminants - food remains, react chemically at the temperatures necessary to remelt the plastic.
But this? You would be printing out huge slabs of solid plastic. Imagine big blocks and slabs of plastic 3"-12" thick. They could be made entirely of a single type of plastic. You use a thermoplastic, one that can be melted and reused repeatedly. Make them with no dyes and a chemistry optimized for maximum recyclability.
The printer prints out big plastic forms. Then the forms are injection-filled with concrete. Workers then pry or chip off the plastic forms and collect the debris for recycling. At the recycling plant, the pieces are given a basic cleaning, but the contaminants are almost entirely bits of concrete. Plastic melts at a temperature far far below the melting or decomposition point of any of concrete’s components. Concrete dust can simply be filtered out from the stream of molten plastic.
And that is a lot of plastic on one job. But because of that, builders would actually be incentivized to recycle it. You’re talking potentially thousands of dollars worth of plastic sitting there.
This wouldn’t be a practical replacement for regular rectangular concrete formwork. If you just want straight vertical walls and floors, since you have to tear-down the dorms afterwards, this isn’t going to be competitive with regular formwork. But what if you want to live in a curvy house? What if you want a more flowing space with continuously varying arches, curves, and vaults? This kind of almost organic home form is not within the budget of the average person. The forms required are just too complex. For this type of organic modern architecture, I could see 3D printing plastic forms being a practical option.
You’re right, it would require a lot of plastic. But existing concrete forms also require a lot of material. We’re just able to reuse the forms many times.
Problem is that plastics do not recycle too well. Every time you melt plastic it degrades. That means you always need new plastic and some gets lost. If you want to use recycled plastic you have to add virgin plastic every time. Also printing such thick plastic will take a long time. I don’t think it scales. If you want concrete forms, then generic preforms made from wood are way more practical.
isleepinahammock@lemmy.blahaj.zone 1 week ago
Eh, some can be recycled up to ten times. And it’s not like you can use plywood forms infinitely either. Those break down after 10-20 uses as well on average. And, just like plastic, every time you reuse plywood molds some of the material gets lost. Some gets damaged when prying the forms off. Plywood sheets get cut down to the shape of the next job. Etc.
And again, I’m imagining this primarily where plywood forms are not practical without very skilled and intricate work. Imagine a home built like this. The cost would be completely impractical for normal residential budgets. But printed forms and injected concrete? Maybe.
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Yes but plywood is made of wood. A renewable resource. Also I must be int but nobody needs these kinds of houses and we don’t need them to be easily manufacturable. Tbh they look incredibly impractical. We need to build a lot of practical houses. If someone wants a house like this they probably have the means to get it handmade.
TonyOstrich@lemmy.zip 1 week ago
There are plastics that can be made from renewable materials as well. Not that I’m advocating for 3D printed houses, I think that is a terrible idea, but not for any of the arguments made here.