Category:3D printing (resin)

Modern 3D resin printers use a tank of special UV resin that is cured hard by a brief exposure to ultraviolet light.

Early resin printers would aim crossed lasers harden resin in a tank and cost tens of thousands of pounds.

The more recent and more affordable resin printers leverage the LCD screen technology developed for mobile phones and tablets.

New-generation resin printers

Modern units typically consist of a base containing a microcontroller and a source of ultraviolet light, with an LCD screen embedded in the top surface. Temporarily fixed on top of this screen is a shallow removable resin tank whose base is a thin sheet of flexible clear plastic non-stick film ("FEP").

To print, a stepping motor lowers a 'print bed into the resin and onto the surface of the clear plastic film, then raises it a twentieth of a millimetre, sucking a thin (~0.05mm) layer of resin into the gap between the print bed and the film. The LCD screen then displays an image of the desired shape as a pattern of clear pixels, the UV lightsource switches on (for about eight seconds), and a layer of resin in this shape hardens onto the print bed. The UV lamp switches off, the print bed raises enough to wrench the layer of exposed resin away from the FEP film, and then lowers again, to a twentieth of a millimetre higher then its previous position. The process then repeats, over and over again, progressively building up the model out of the sequence of exposed images.

Once the model has finished being printed, it is prised from the print bed, washed to remove its coating of uncured resin goo, and "finished" (typically the removal of any additional supports needed to create the model). At this point the model feels slightly damp, and is soft enough can be marked with a thumbnail. To finish it off, the whole print is then exposed to more UV light, either using an ultraviolet lamp, or by placing it in strong direct sunlight. The result is a print with a hard plastic finish.

Advantages

Resin printers typically produce much finer, higher-resolution prints than extrusion printers, with layers typically having a thickness (z axis resolution) of ~0.05 mm, and a pixel resolution (x and y axis resolution) of 0.05 mm for most models, and ~0.11 mm (about a ninth of a millimetre) for the entry-level AnyCubic Photon Zero. They are typically used for making small-high quality prints

Resin printers expose a complete layer in one go, exposing for maybe ten seconds without needing a print head to draw anything. This means that for small parts, it can sometimes be possible to produce perhaps ten or twenty small prints, arranged side by side on the print bed, in the same time that it would take to produce just one.

Mechanically, a resin printer is simpler than an extrusion printer, with the only moving part being the print bed, and the motor and screwthread that raises and lowers it. Once the print bed's default height has been set by spacing it form the film with a sheet of paper and tightening its mounting screws, there's nothing else to calibrate, unlike extrusion printers that have to move their print heads on the x, y and z axes, and which tend to need careful calibration and recalibration.

Disadvantages

The UV-sensitive resin used by these printers in inherently chemically unstable, and is toxic until cured. It is also very "gloopy" and tends to get everywhere. Users are supposed to wear gloves and avoid getting the liquid resin onto their hands, as repeated exposure can lead to sensitisation and subsequent allergic reactions.

The print comes out of the printer “sticky”, covered in a layer of wet resin that needs to be washed off (usually with some form of alcohol), and the print then needs a final exposure to UV light to permanent cure it properly, so there’s a bit more hassle involved.

Where filament printers can often be upgraded part by part, (often with parts printed on the printer itself) resin printers tend not to be so upgradable, their print size and resolution being limited primarily by the size and resolution of the LCD screen. It can often be difficult to see what's going on for the first hour or so of a print, as the print bed and resin tank walls typically block the user's view until the bed is higher than the tank walls. While it's theoretically possible to build large resin printers, the requirement for the exposure screen and tank to be as long and wide as the print means that very large resin printers, with very large tanks, are likely to be "industrial" (whereas an extrusion printer simply requires a conventional print head and motors attached to longer axis-bars).

Marketplace

Originally prohibitively expensive, entry-level machines can now (as of 2021) be had at the £100 mark, before you add the cost of the resin. Larger, faster machines with larger print areas and higher resolution (0.05 * 0.05 * 0.05 mm) tend to start at around £200.