materials

Materials

This page documents the clay-side parameters: presets, water % convention, and shrinkage compensation. Hardware-side calibration (SPD→flow, ratio pot) lives on the Calibration page.

Clay presets

The plugin ships three presets in Models/ClayPresets.cs. Selecting one in Settings → Clay Material → Preset overwrites bead diameter, max overhang, bond ratio, density, and the PBR material used in Preview Clay Model.

Preset	Use for	Notes
Porcelain	Fine, smooth surfaces; small parts	Tighter bond ratio, higher subsurface for translucent rendering
Stoneware	General-purpose; default	Mid-range across all parameters
Earthenware	Coarser textures, larger parts	Loosened overhang + bond tolerances

For exact preset values, see Models/ClayPresets.cs in the code repo.

📷 Three side-by-side photos of test prints in each clay type, showing the surface-finish difference.

Water % convention

Water content is recorded as % of dry clay mass, additive:

6% water = 60 g water per 1 kg dry clay

This matches standard pottery practice. Not weight-percent of the wet mix (which would be 6% / (100% + 6%) ≈ 5.66%). The convention is consistent across the lab's mix recipes and the plugin's WaterPercent field.

⚠ The WaterPercent field is recorded only at this writing. The plugin does not yet adjust nozzle / feedrate / SPD recommendations based on water %. Downstream behavior wires in once the lab's water % study produces a defensible curve.

Shrinkage compensation

Clay shrinks during drying and firing. To land at a designed size, the plugin scales the input geometry larger by an inverse factor before slicing:

scale = 1 / (1 − pct / 100)

So a 12% shrinkage compensation scales geometry up by ~13.6%.

Design choices

Choice	Picked
Axis behavior	Uniform XYZ — every axis scales equally
Origin of scale	Footprint centroid on Z=0 — keeps the bottom of the part on the build plate, only the top moves
Drying vs firing	Single combined % — not separated. The user enters one total shrinkage value.

These were chosen as defaults from the offered alternatives (per-axis scaling, scale-about-center, separate drying/firing). Override in code if you need different behavior; rationale is captured in the lab's design notes.

What scales, what doesn't

• The geometry the slicer sees is scaled (in-memory copy)
• The source Rhino object stays at design size — your model file is unchanged
• The toolpath, skirt, build-volume preview, Print Position marker all reflect the scaled geometry — what you see in Rhino is what the robot will print

The status line shows the applied scale, e.g. "scaled +13.6% for 12.0% shrinkage compensation".

📷 Rhino viewport showing a part with shrinkage compensation enabled — original ghost vs scaled solid, status line visible at the bottom.

Build-volume implications

A scaled-up part may overflow the build volume even if the design-size part fits. The pre-slice build-volume check runs after shrinkage scaling, so the warning fires correctly. See Pipeline 3 — Slice for the gate.

Mix-recipe workflow (lab convention)

Step	What
1	Weigh dry clay (g)
2	Compute water mass = dry × (water% / 100)
3	Add water, mix to homogeneity
4	Load ram, log batch ID + water % + clay supplier in the lab study log
5	Print test pattern (e.g. slump cone, vase tower) before committing to the real part

The active study at this writing is the water % study at 6 / 8 / 10 / 12 %; see Lab studies.