don't forget the upcoming photocuring printers. i can't remember the name of any of them at the moment but the basic idea is that you take a resin that cures under UV, you point a projector downward at a tub of the stuff, and you slowly raise/lower whatever it is you need to raise or lower to form a solid object.
basically the practical method behind additive manufacturing is to take a material that transitions between phases of matter (solid, liquid, gas, plasma), and bring from a non-solid to a solid in a controlled, compounding matter. this differs significantly from subtractive manufacturing in that you usually take a big old brick of solid stuff and hack away at it until it looks like you want it to. one was invented by cavemen. THE OTHER BY MEN AND WOMEN OF THE MODERN SPACE AGE
Resin is 15x the cost of ABS, I looked at building one.
The printers costs similar, but the resin costs will kill you.
completely different error profile, scale and purpose. resin photocuring has the potential to model additive photolithography. you're unlikely to want to make a safety cone with it (and you would have some definite trouble doing so anyway since you're relying on a chemical reaction that may or may not be malleable in terms of color), but you might want to make a the exoskeleton of a tiny robotic swarming bee.
the root of empiricism is trying to gain some understanding of the (inevitably stochastic) mechanisms behind physical processes, and then (or if you still don't quite get it) measuring until you have a reasonable approximation of the distributions on the inputs and a reasonable approximation of the process. as i've been pointing out incessantly, the mechanisms behind additive printing are completely analogous to those of subtractive printing with substantially different inputs.
It's no more accurate than any other as it's all similar systems. It's just a Prusa or Mendel in a fancy box with better documentation and all the bugs worked out.
only in my wildest dreams. a few bugs are worked out such that you can print a traffic cone when you unwrap the box (or at least you may be able to). anyway, as i also have said incessantly, error analysis and correction is all incremental. a bridgeport is just a sherline in a fancy 3-ton box (this is not an exaggeration). but the weight of a bridgeport is essential to reduce specific kinds of error and produce the kinds of extremely high tolerance parts that power the increasingly efficient internal combustion engines and composite molding tooling that the modern world is made out of.
Cheaper ones have smaller print sizes, and depending on model, more or less tinkering required to make quality prints. Some also require special filament, which is normal filament, just wrapped in a fancy overpriced package.
what is filament? it's wire made out polymer? what's the composition of that polymer? what is the typical shape is the extrusion? what is the tolerance of the bounding diameter of the filament? the word fancy hides the details that drive the incremental improvements that need to be made to achieve that incrementally higher accuracy and precision that may be boring to some, but is extremely important in empirical science.
here's an example: the composite parts in a reprap designed machine are often made on other FDM machines to relatively low tolerances and necessarily lower material properties (FDM is not yet very good at making hard dense objects). makerbot inc invested in injection molding tooling to create denser, harder and higher precision composite components that fulfill more or less the same functionality. they invested in a casting mold for aluminum plates to make low thermal resistance platforms that can be machined flat (but of course they don't do that part, sigh. this is, btw, a very definite bug) and have relatively uniform thermal expansion properties. it's not fanciness. it's engineering. (well, i guess if you consider engineering nothing but fanciness you are wrong but only misguided -- there is nothing fancy about engineering. it is a horrid slog of tiny incremental changes, and it's also tedious and hard).
anyway, the point is, the difference between expensive manufactured things or expensive tools and cheap things/tools is all in accuracy and precision, either in manufacturing or some sense of error. there are some things that are completely cosmetic, but it's actually much rarer than you might think. fun example: the difference between a louis vuitton monogrammed hangbag manufactured to specification and the much more common cheap knockoff is the following:
grade and source of leather (softness, thickness, uniformity of grain, lack of polymer or composite filler)
panels are cut, aligned and sewed according to strict specification:
seams must meet strength requirements
distance between threads within tolerance
not a single symbol can be cut off every symbol is at least some distance alpha of the edge of every panel once sewedyes, it's a handbag, and machine-formed polyester will often fulfill the same functionality for a while, but vuitton bags are the kind of thing that are designed and manufactured expressly to be preservable and usable after sitting in peat moss for thousands of years, while loosely sewed polyester will last about as long as it takes for me to get it to it and mangle it in one of my crazy experiments.
i insist a lot of things, but i particularly insist that we respect the incrementalism of manufacturing on this board. this is a forum centered on exotic electromechanical switch designs for computer keyboards. incremental changes matter here. on this forum, fanciness matters.