The best 3D printers fabricate models and parts that are true to design. In other words, models and parts that are a perfect physical representation of the digital model drawn in CAD. To achieve this high degree of dimensional accuracy, printers must produce a very fine edge across the build area. This is how we perceive parts to be high quality or not when we look at them and inspect them.
Of course, multiple variables determine how fine that edge is, and you cannot always rely on the quantitative values manufacturers place on their 3D printers. If we did, every printer on the market would be pinpoint accurate.
When you are shopping for your next printer, consider this: accuracy is the value that determines how close a 3D printed part is to its digital drawing. Precision refers to the repeatability experience of a printer, or how reliable the printing experience is. If you want a consistently good 3D printing experience, you need both.
Technologies and processes
The two most common 3D printer technologies are FFF and SLA.
The most common technology is fused filament fabrication (FFF), also known as fused deposition modelling (FDM). Both technologies are in fact one in the same.
These 3D printers are the lowest cost. They melt a plastic and extrude it layer-by-layer to build up models from nothing. This process is traditionally best suited to low-cost prototyping, but advancements in technology mean this is no longer the case. There’re more variables that can affect the quality of a print with FFF than SLA, but solutions like an enclosed build chamber and heated build plate reduce this.
SLA (stereolithography) 3D printers use a laser to cure resin (liquid plastic) onto the build platform in desired areas.
Unlike with an FFF 3D printed part, parts printed by an SLA 3D printer need to be post-processed with UV light. This cures the resin, causing it to solidify and reach the mechanical properties required for the application. The method of production is cure, peel, raise, with the laser curing the resin layer by layer; the peel mechanism lifting each new layer off the surface; and the raising action allowing new resin to flow under the build platform.
Desktop and large format
3D printers are available in all shapes and sizes to suit any project, but there are two common classes: desktop, and large-format.
Desktop printers do exactly what they say on the tin - they fit on a desktop (or most workspaces) and take up around the same footprint as a large LaserJet printer. Large-format printers are four or five times bigger, enabling you to manufacture models and parts like car bumpers and snowboards in one go.
You’ll find the bigger you go, the rarer photopolymer technologies like SLA and DLP (digital light processing) become. This is because they get very expensive as you scale up. Most large-format 3D printers are of the FFF variety because the technology is cheaper and easier to produce on a large, industrial scale.