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Resin printing explained: how MSLA printers work

Resin printing6 min readUpdated: 10/2026

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A resin printer does not build parts from melted plastic but from liquid synthetic resin. Light cures the resin layer by layer. This produces much finer detail than filament printing, for example for miniatures, jewellery or dental models. In return, the work around it is more involved: washing, curing and careful handling of the resin are always part of it.

You will find all resin printers in the wiki with build volume, resolution and price in the overview of resin printers.

How a resin printer works

Most devices for hobby and small business use work inverted: the build platform dips into a vat of resin from above. The vat has a transparent bottom made of film. Light shines through this bottom from below, and exactly the thin layer of resin between platform and film cures. Then the platform lifts by one layer thickness and the next layer follows. The part therefore grows upside down, downwards.

Curing is done with light of usually 405 nm wavelength, that is visible violet just above the UV range. Formlabs calls 405 nm the wavelength usually used for curing resin. Typical layer heights are 0.025 to 0.05 mm.

SLA, DLP and MSLA

ProcessHow the light reaches the resinTypical for
SLAA laser traces the cross-section of each layerprofessional devices
DLPA projector exposes the whole layer at oncesome professional and dental devices
MSLA (LCD)An LED panel lights up, and an LCD screen in front lets only the cross-section throughalmost all hobby devices

With MSLA (masked SLA), a black-and-white screen serves as a mask. Because the whole layer is exposed at the same time, each layer cures in a few seconds. Monochrome LCDs let more light through than colour displays and shorten exposure to as little as one to two seconds per layer in some cases.

What 8K, 12K and 16K mean

The number roughly describes the pixels along the long side of the display. More pixels on the same area mean smaller pixels and therefore finer possible detail. The pixel size in micrometres (µm) is therefore more meaningful. An example: the Elegoo Saturn 4 Ultra 16K has 15,120 x 6,230 pixels on a 10-inch display, and one pixel measures 14 x 19 µm.

Two caveats apply: pixel size is only a theoretical lower limit, and real details are usually much coarser. And a large display with the same K number has larger pixels than a small one. On large devices such as the Anycubic Photon Mono M7 Max, the pixel size is therefore 46 µm.

How a print proceeds

  1. Slicing: In the slicer (for example Chitubox, Lychee or the manufacturer’s software) you orient the model, add supports and cut it into layers. Hollow models need drain holes, otherwise liquid resin stays trapped inside.
  2. Printing: Shake the resin, pour it into the vat, start the print. Many manufacturers recommend a room temperature of at least 20 °C, which is why some devices heat the vat.
  3. Washing: The part comes out of the printer covered in liquid resin and is cleaned in isopropanol or, for water-washable resin, in water.
  4. Drying: The part must be completely dry before curing.
  5. Curing: Under UV light the part reaches its final strength. Formlabs recommends removing the supports only afterwards.

Exactly how washing and curing work is explained under Washing and curing. Before you start, please read Safety in resin printing. If a print does not adhere, sticks to the film or has holes, the resin printing troubleshooting guide helps.

What print time depends on

Because each layer is exposed as a whole, a full build plate takes hardly any longer than a single part. What matters is the number of layers, that is the height of the model divided by the layer thickness. If you print many small parts, you therefore fill the plate instead of printing them individually. A thicker layer saves a lot of time on tall models but costs detail.

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