Hollowing and drain holes

Before you start

This picks up where Your first print leaves off: a printer and resin chosen, and a model on the plate, placed and oriented the way you will print it. Hollow before you add supports, so they go on the final shape. The drainage check slices the plate, so it uses the layer height set for the printer and resin. The numbers below are starting points for one model. Your printer’s and resin maker’s instructions come first.

Hollow is tool 3 and Drain holes is tool 4. Hollow works on the selected models, or on every model on the plate when none is selected.

Hollow the model

1. Open Hollow and choose a mode. Inside grows the wall inward and leaves the outside as imported. Outside builds a mould around the model. Through is Inside with the floor open, so uncured resin drains onto the plate (handle it as your resin’s SDS says, see “Uncured resin and the SDS” below). Use Through only for a model that stands on the plate: where a model narrows below its cavity, the opening can stop short of the plate.
2. Set Wall. The default is 2 mm. The lowest value the panel accepts is 0.15 mm, the thinnest wall the lattice can resolve.
3. Leave Precision at 0.5 unless the cavity looks coarse. It sets how smooth the cavity is, and the line under it shows the lattice in millimetres. It is not the layer height.
4. Press Hollow. A progress bar shows the run, and Cancel stops it.

When it finishes, the panel shows Hollowed and Resin saved in ml. Make solid again undoes it. A wall thicker than the model leaves no cavity, and the model comes back unchanged.

Add infill

Infill is off by default, and the cavity is left empty. Switch it on to fill the cavity with an open lattice, and pick a pattern:

Pattern	Shape	Direction it carries
Hive	hexagonal tubes standing on the plate	vertically only
Grid	square tubes standing on the plate	vertically only
Scaffold	struts along all three axes	in all three directions

Hollowing saves resin, and infill gives some of it back. Neither makes a part fit for load-bearing or safety-critical use. The defaults are Hive, a 5 mm Cell and 15% Density, and the panel states the wall thickness that comes to. All three patterns are open networks, because a closed cell would trap resin. Outside mode ignores infill.

Keep the wall solid where it is thin

A thin spar or spike can print hollow and snap. In Hollow, click the model where the wall must stay solid and Encrust drops a blocker there (Blocker size, 4 mm by default). Alt-click a blocker to remove it. Place blockers before you press Hollow. Outside mode ignores them.

Place drain holes

Open Drain holes. A click on the model cuts a hole at once, hollow or not. Alt-click a hole to remove it.

• Hole size: 3 mm by default.
• Depth: 3 mm by default, measured from the surface inward. On a hollowed model Encrust deepens a hole until it is through the wall, so the depth you type is a minimum there. On a solid model the hole is exactly as deep as typed.
• Taper: 1 is a cylinder, lower values make a cone.

For a long path, switch Holes to Channel. Each click adds a point, and the channel runs as a tube of the hole size under all of them, open at its two ends only. Press Dig the channel. Digging a channel on a model that is already hollow makes the shell stale: press Hollow again.

Check for trapped resin

Trapped resin is uncured resin sealed in a cavity with no way out. A part printed that way comes off the printer with that resin still liquid inside. Treat the part as holding uncured resin and follow the SDS section below.

Press Check drainage. Encrust slices the plate, follows the air through the layers and reports every pocket that never reaches the plate, the edge of the layers or the top of the part. It counts the holes and channels you cut, an infill cell that seals itself and a blocker that walled a cavity off. Pockets under 5 mm³ are not reported.

The result is either “Nothing is trapped: the resin can get out of every model on the plate”, or Trapped (a count) and Resin held (in ml), with a marker in the viewport on each pocket, sized to what it holds.

Press Drill a hole into each. Each hole goes in at the lowest point of its pocket, from the nearest surface and deep enough to reach it, using the hole size and taper you set. Press Check drainage again to confirm.

Uncured resin and the SDS

Handling, protective equipment, cleaning and disposal of uncured resin are set out in your resin maker’s safety data sheet (SDS). Read it, and follow it. Disposal follows your local rules for hazardous waste: never down the drain, never uncured resin in household waste.

If something goes wrong

The Hollow button is greyed out

The panel says why: there is nothing visible on the plate to hollow.

A note says the cavity was cut on a coarser lattice

The model needed more memory than the budget allows. The run finished, with a coarser cavity than Precision asked for.

“The numbers have moved since. Hollow again to catch up.”

You changed a setting or rescaled the model after hollowing. The wall scales with the model, so press Hollow again.

The check reports a pocket you think is open

A passage narrower than the 0.1 mm grid the check uses reads as closed. The cost is a hole you didn’t need.