Creating drainage holes

After 3D printing hollowed-out parts, we will need to drain or remove all trapped powder/resin during the postprocessing phase. That’s why we need to include drainage holes in our design phase. The diameter of the drainage holes depends on the 3D printing technology we are utilizing as well as the viscosity of the material we are 3D printing with. For example, if you are using a laser-based resin printer (SLA), your resins are generally more viscous, compared to resins for DLP printer resins. Certain resins can also be used for both DLP and SLA printers. The more viscous a resin is, the larger the diameter of the drainage hole needs to be.

Table 4.1 shows two resins from different sources with varying viscosity. According to the manufacturer, the second resin is compatible with both SLA and DLP printers:

Resin	Viscosity @ 25 deg. C
Prusa Orange...