With the chocolate project I'd be interested to know how you intend to get around the phase diagram? If memory serves it forms several crystal structures based on cooling rate, and the one you want for eating is also the one with the slowest rate required. You could seed it with a layer of tempered chocolate on the build plate I suppose, but you're asking for trouble with that if you get your heat control wrong not just in the extruder but also in the environment in general...
The only printers I've seen in chocolate either start out with a powder or melt, and both ignore this issue entirely. The product would have a very soft texture and melt on your hand before it found its way to your mouth I think.
My wife and I started a rapid prototyping business 2 years ago, based in Sheffield UK. We've had all kinds to print in that time, from high resolution miniatures for war-gaming to engineering part prototypes and all the way back again for jewellery. Combined with some of the better scanners, there are loads of possibilities.
What we've found so far:
- Loads of people sneer at FDM filament based printers. Mostly because the media has oversold them. But they are great in their application, as long as you just treat them as a tool rather than a replicator. They aren't going to print your final part and they have limited geometries - but they are a nice alternative to CNC for a lot of models.
- SLA resin based machines are really nice. Wider range of geometries, better finishes, and they polish up nicely for finished models too. Their drawback is that for the most part the materials are brittle and get worse over time (crosslinking reaction continues with UV exposure), although new materials are being released that try to address that.
- There is no substitute for holding something in your hands to check it. You have to be very experienced with CAD before you don't need that step, and we've found lots of our customers go through several part revisions with us before taking the next production step.
- As a poster above mentioned, combining printing with investment casting allows you to cheaply make very nice metal parts that would be a pain to make using other methods. With investment casting you just need to be able to get ceramic around the part and away again - slush dipping with ultrasound and job done for anything we've had so far.
- This has allowed us to make finished engineering parts for small batches in aluminium to date, but there is no reason why we couldn't do it in ferrous metals or titanium too.
- We've also done a lot of jewellery castings for people. Very easy to make bespoke gold items, and gem settings from there aren't that hard
-SLS powder sintering is expensive, scary (explosive!) and messy. Also the parts in polymers tend to be hydroscopic so need some coatings as quickly as possible after printing to maintain proper geometry. Avoid if possible!!
I think the real point is that there are a lot of possibilities this tech opens up, especially when you combine it with other methods. Printing is a tool and isn't going to mean you don't need that hammer anymore, but will compliment its presence nicely.
The strangest print we've had to date is probably some body jewellery. The most difficult some LED models (very fine features >0.3mm). The most satisfying would be combined with our scanning, of a flute dug up not so long ago estimated to be 40,000 years old according to the PhD student who brought it in. She plays the flute and wanted a version in silver to find out what it would have sounded like without risking damage. The biggest would probably be some of the parts we've been prototyping for a company in the rail industry. My personal favourite though would be going from hand painted Chinese calligraphy to solid gold pendant.
Also moved to Sheffield as a student and never left. Wonderful place:
- Friendly strangers rather than what you get with southerners, who look at you as if you are mad if you speak to them (I'm from High Wycombe originally so I'm in that southerner bracket!)
- London accessible on 2hr train if you need something bigger/business networking
- Peaks on doorstep
- Regeneration is going nicely and the town centre is nice and has everything you really need
- Central location in the UK easy to get to other places
- Lots of great breweries nearby
- Laid back attitude that comes with the generally nice environment and universities
- Great intermingling of cultures in places
They are even finally doing something about the roads!
There absolutely is a great scene developing over in the US. I have a fairly broad taste in beer, depending on mood and weather I'll order anything from a deep porter to a light pilsner or lambic. For a summer BBQ a beer should be refreshing but should still have lots of flavour - a good lager has both in spades.
Being in the UK I've not had much exposure to the good American brews, but I really enjoyed what I've had from Anchor Steam (good porter) and Goose Island (great hoppy IPA). Would try more if they were available nearby. That said, with the weather going the way it is at the moment I think I'll be enjoying a local bitter this weekend...
" LITERATURE PRIZE: The US Government General Accountability Office, for issuing a report about reports about reports that recommends the preparation of a report about the report about reports about reports.
REFERENCE: "Actions Needed to Evaluate the Impact of Efforts to Estimate Costs of Reports and Studies," US Government General Accountability Office report GAO-12-480R, May 10, 2012. "
Its a shame the guys who did this didn't get a mention: http://www.bbc.co.uk/news/science-environment-18247680
It had a been a subject of great debate a amongst my friends - other stouts not doing this was a point of confusion for a long time! (which of course lead to more testing....)
I'm afraid it does - here the electrons are your gas
Long time lurker, commenting because I know something about this one (doing my PhD in thermoelectrics).
First of all, you _can_ use thermoelectrics to cool things like CPUs or fridges, but don't expect to generate any energy from them when you do it because you need to be putting electricity into the system, essentially carrying the thermal energy with it. You will cool one end and heat the other end. If you've ever heard of a Peltier cooler then you know what I am talking about.
A good background can be found here: http://thermal.ferrotec.com/technology/thermal/thermoelectric-reference-guide/
Second, this is something people have been messing around with the nanostructure of tellurium alloys for ~20 years or so, with the sole purpose of reducing thermal conductivity. The figure of merit for thermoelectrics is ZT = thermopower^2 x electrical conductivity x temperature / thermal conductivity. You can't increase electrical conductivity without reducing thermopower and increasing thermal conductivity (as there is a lattice and an electrical contribution). Thermopower is more or less a function of the number of carriers (lower is better) and their effective mass, so this is difficult to increase without durastic changes in the crystal structure or killing electrical conductivity. This leaves thermal conductivity. If you increase disorder in the material you make it harder for thermal energy to travel through it, which as lead to lots of research on how you manage this without messing up your carrier conduction. These are known as PGEC (phonon glass electron crystal) materials.
Third, there are lots of applications of these (in heating/cooling and power conversion) if they can be made efficient and cheap. Anywhere you have a heat source pretty much. To use the classic car analogy, BMW, Ford, GE (amongst others) are looking at using a thermoelectric module to generate power for the car from the waste heat in the exhaust gases from the engine. This would increase the power of your engine by removing the alternator and also make the car lighter.
The problem is the efficient and cheap part. These kinds of thermoelectrics are based on tellurium, an element about as abundant in the earth's crust as platinum, but to my knowledge isn't specifically mined for. Most other elements involved are toxic heavy metals (Pb, Sb, Bi, etc.)... so these aren't exactly nice things to have around or to make.
This is where oxides come in. Made of lighter, more abundant, less toxic elements they are much cheaper to make (not just sourcing the materials, heath and safety too etc.), and are stable at much higher temperatures. As you know from Carnot, the higher the temperature a heat engine works at the more efficient it becomes; rather than 900 K (600C) you're looking at more like 1300 k (1000C) and upwards. Current high ZT oxides are things like NaxCoO2 and Ca3Co2O6, which have layered structures; one part is great at absorbing thermal energy (due to Na disorder for example) and the other is good at conducting electricity (like the CoO2 portion of NaxCoO2)
The way I see this paper: great proof of concept, PGECs are doing what they say on the tin and this will be great for low T applications. But for high power generation we need something more like the oxides which are cheaper, easier to produce, and work at higher temperatures.
There is never time to do it right, but always time to do it over.