Re: Energy requirements of additive manufacturing?
Christian Siefkes
Erik wrote:
> Setting up, maintaining and decommissioning an entire production line
> should be included if it is product specific. Per product this might
> not be much, but considering that there are instances of production
> lines for the vast amounts of products that exist, it is an enormous
> environmental burden. Instead, flexible production machines can be
> used for many different product categories. Granted, you would need a
> machine per neighbourhood for an alternative to be feasible to the
> general public. Yet this is entirely within the realm of possibility.
I agree, but such a distributed production infrastructure (which is indeed
essential for physical peer production in my view) does not necessarily have
to be based on additive fabrication. The Fab Labs are pursuing a similar
approach, using (for the time being) mainly subtractive CNC machines.
Molding & casting infrastructure can be distributed to some
degree, too--there are even small-scale injection molding machines that
might be suitable for localized production, e.g. the X-Ject
<http://www.backyardengineer.com/products3.html>. Of course, molding and
casting can never be as personalized and on-demand as additive or
subtractive manufacturing because of the need to first make molds/patterns.
> For products that are 'made to order' by a local machine, there is an
> almost certain demand for it. So, products that are produced on
> demand for someone, are products that someone actually wants.
True, but that's also possible with subtractive manufacturing. And I would
suppose that semi-decentralized molding and casting can reach a good deal of
on-demand production too, though, of course, with much less personalization
(which for most products probably won't occur anyway).
> Disposal of products should be taken into account. While we cannot
> claim yet that RepRap products are more eco-friendly in disposal
> (unless you print in biodegradable PLA or CAPA (from disposable milk-
> bottles), there certainly is big potential for making cradle to cradle
> products. You can close the cycle of your material flows by recycling
> products that you don't use any more. Normal disposal results in
> transportation and processing of domestic waste, which has its
> environmental costs. In the RepRap scenario there would be less
> disposal because 'waste equals food'.
True, but that's true for thermoplastic plastics in general, regardless of
the type of processing.
> RepRap and other additive production processes use
> material efficiently, it only adds material where needed. In contrast
> to subtractive machining which removes material until the desired
> shape is achieved. Stock material needs to be bigger than the desired
> object and planning is needed to use material efficiently.
That's true.
> Production of RepRap machines, by contrast is very efficient. It
> consists of two types of parts: parts that can efficiently be made
> centrally and products that should be made in a dense, distributed
> network.
[...]
> RepRap has to potential to use this hybrid model in
> foreseeable time.
I agree that such a hybrid model makes sense (though it differs from RepRaps
claims about self-reproducibility).
> Even when limited to thermodynamics of production in
> a RepRap compared to injection moulding, RepRap might eventually win.
> Consider that heating the thermoplastics costs at least as much as the
> specific heat times the amount of material used. This is the
> theoretical minimum. Recovery of heat (e.g. heating the house, which
> RepRap currently does) could even make this energy 100% efficiently
> used during two seasons. Injection moulding often involves use of
> cooling channels through which a coolant will flow after injection.
> This is to speed up the process and quickly make the mould available
> for the next product. It's an art in itself to cool as quickly as
> possible, but I would think that cooling costs energy. The only
> exception is if a heat exchanger were used and heat is useful
> somewhere else in the factory, but I would be positively surprised if
> this were the case in most manufacturing plants. Still, in a RepRap,
> cooling is often passive (just by convection) or at most involves a
> ca. 1 Watt fan. Motion of the RepRap could be minimal if the moving
> mass is minimised.
You're right, looking at it like that makes the energy requirements of
fabbers look pretty good.
> (B.t.w. Christian, I'll be looking into your book on peer production
> after I finished this post!)
:-) That's been more about the social side of organizing production, but I'm
busying myself with the technical side now as well--both are important.
Best regards
Christian
--
|-------- Dr. Christian Siefkes --------- chri...@siefkes.net ---------
| Homepage: http://www.siefkes.net/ | Blog: http://www.keimform.de/
| Better Bayesian Analysis: | Peer Production Everywhere:
| http://bart-project.com/ | http://peerconomy.org/wiki/
|------------------------------------------ OpenPGP Key ID: 0x346452D8 --
We act for material gain, but also for psychological well-being and
gratification, and for social connectedness. There is nothing new or
earth-shattering about this, except perhaps to some economists.
-- Yochai Benkler, The Wealth of Networks
Erik
Thanks for your reply.
> claims about self-reproducibility).
develop fully-replication machines. We think it is okay (arguably even
desirable) to have assembly assisted by a human. We think it's fine to
have a machine that depends on us, since if it's valuable, we will
have a reason to make more of them. Adrian Bowyer speaks of this as a
symbiosis between RepRap and the most powerful species on the planet.
If we want this decentralised production capability, this is a way to
get there. Similarly, RepRap allows a degree of self-replication that
is practical. We want to be able to replicate the things that convey a
lot of thinking and still need to be 'dynamic'. This way, changes can
be made and shared (digitally) and duplication of effort is reduced.
Still, everyone is able to test it in a real world environment. It is
not important to be able to manufacture nuts and bolts, though.
Everyone is able to acquire those, and those will not become cheaper
than through mass produced for a long time. So the things that are
standardized and do not inhibit innovation are okay. We are effective
when we can focus on the things that matter. As an example, for
someone who does complex calculations, in a spreadsheet, it is
important to be able to add custom formulae (change functionality),
but we don't want to write everything from scratch, including the
spreadsheet software. That is why you have a toolkit or programming
environment and an API. So parts of the system are standardized
(having columns with addresses A-Z and rows 1..n) and some are
extended.
But now I'm drifting a bit off topic. We were discussing eco-
friendliness of local versus mass manufacturing.
Erik
> | Better Bayesian Analysis: | Peer Production Everywhere:
> | http://bart-project.com/ | http://peerconomy.org/wiki/
> |------------------------------------------ OpenPGP Key ID: 0x346452D8 --
> We act for material gain, but also for psychological well-being and
> gratification, and for social connectedness. There is nothing new or
> earth-shattering about this, except perhaps to some economists.
> -- Yochai Benkler, The Wealth of Networks
>
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