I am interested to see what you find. There are simply too many FDM printers out there, 90% of which only can output a quality print after many weeks of tweaking, installing a bunch of upgrades.
For those not versed, here are the basic (Okay, this gew more as I typed) run down and pro's and con's of each technology.
SLA: "Stereolithography"
This is actually a very old technology. Basically, you take a ultraviolet curable resin and fire a UV laser at it. Wherever the laser hits, the UV resin hardens. Accuracy is determined by the accuracy of the actual laser. (Both ability to zero in on a location, and focus size). The layer size is set by moving the printing platform up or down exposing a new layer of uncured resin. New innovations in this industry include using an oxygen permeable barrier to help speed up cure time, and speed up printing. Most early model home machines use UV lasers from Bluray players, which work, but are much slower than industrial models.
Pros:
-Can be very fast.
-Can make very detailed models.
-Great at making a master model for building a mold to cast in other materials.
-Short learning curve, commercial models require very little spin-up time before printing.
Cons:
-Because Resin is sensitive to UV light, it will break down over time. Unless treated, the part won't last more than a few years.
-Build area is typically very small
-More expensive than FDM, the resin used for many commercial models is proprietary.
-Depending on the model geometry, you may need support material which has to be cut away afterwards.
-If you only occasionally use the machine it can be a major pain to clean and maintain.
FDM: "Fused Deposition Modeling"
As
tehfailsafe mentioned, this is basically a glorified hot glue gun. You have the "hot-end" which is little more than a heating element wrapped around a tube with a small opening. Accuracy is determined by the size of the opening, precision of the placement of the head. Layer lines are almost always present and the printer must wait for the layer below to cool before depositing a new layer. That limits the print speed, and causes layer lines. Each layer is basically a small round piece of plastic, and doesn't merge with the layer below. The layer lines typically don't sand away easily, requiring you to coat the print with another material to smooth it out.
Pros:
-Once you optimize your machine and learn all the tricks you can make amazing stuff on the cheap.
-Printers can be very cheap, mostly due to the fact that most are evolutions of a open-source design, and the fact that the market is saturated.
-Actual part costs can also be very cheap, again mostly due to the market driving down the cost of materials.
-Printed parts are made with real plastic. PLA or ABS. PLA is more common. PLA melts at a lower temperature, and isn't' quite as strong as ABS. ABS however is very strong, it is what Legos and most electronic device enclosures are made from.
-Can make functional moving parts, however resolution and strength of the print is limited.
-Many different materials are available commercially.
Cons:
-Many part geometries require support materials, which must be cut away. However some printers can print using dissolvable support materials.
-Dimensional accuracy suffers greatly depending on the part design, size, and printer accuracy.
-Layers can delaminate, parts are weaker along the layer lines.
-There are simply so many models out there it can be very difficult to figure out what model to buy. Buyer's remorse is common. Often leading to said buyer saying "I think I design a better one". This leads to many upgrade kits, and new designs. This pushed the technology in a better direction, but is also the cause of said market saturation.
-Most home models have a huge learning curve, you have to basically figure out exactly what settings make a good print on your machine through lots of trial and error.
-Print bed size limits the size of parts that can be built.
SLS: "Selective Laser Sintering"
This is my prefered method of 3D printing. It uses a laser to melt a layer of plastic or metal powder together. This technology is only just barely starting to enter the home-printer market. This is the technology that Shapeways uses in most of their prints, and is the technology you see often on the news related to NASA or formula one using 3D printing to make some new part design. Dimensional accuracy is very high with SLS parts as the un-melted powder helps hold the part and keep it from warping. The un-melted powder also means no support materials is required for most part designs. Plastic parts are typically made in Polyamide plastic, in other words Nylon. Nylon is used somewhere nearly every complex product you can imagine, from tent canvas to electrical connectors. Parts have a sandstone like finish, small layer lines are visible but easily sanded smooth.
Pros:
-Fused material is very strong in all directions, and flexible.
-Can make metal components
-Good for making mold master models
-Nearly unlimited part geometry.
-Very high accuracy
-Many different materials can be used. (Although not on the same machine)
-Polyamide parts are flexible, allowing for snap fits and parts that need to bend.
-Very thin walls and detail possible.
-Parts will last for many years without deterioration.
-Can make very small, and very large parts.
-Can make parts with captive links, such as chains or meshed gears.
Cons:
-No real options for at-home printing. You need to order parts from a 3D printing shop.
-Expensive when compared to FDM printing.
Polyjet
Another "not at home" technology. Polyjet is sort of like a glorified inkjet printer. It prints one tiny layer of resin at a time. It can make insanely detailed models, such as tiny details like skin texture on a character model. The resin can be strong, but isn't stable over a long period of time. This technology actually has the most potential to become super cheap at-home, as the actual print heads and control technology are not much different than your cheap home inkjet printer. This is still a highly limited market as the technology is still limited by licensing and patents.
Pros:
-Very detailed models, with high dimensional accuracy
-Lots of different plastic-like and rubber-like materials available.
-Can print both rubber and plastic into the same part, making highly flexible parts.
-Can make very small, or very large parts
Cons:
-Resin materials have limits as far as long term stability.
-No real options for at-home printing, (Need to wait for the patents to expire)
-Support material required, but dissolvable options are available.
