Assembly Materials as Tags

Assembly Materials as Tags#

CadQuery 2.6.1+ supports cq.Material objects for assembly parts. Use these as material tags for cleaner separation between part identity (name) and material assignment.

Basic Usage#

Assign materials to assembly parts, then use material_tags="assembly_materials":

import cadquery as cq
from cad_to_dagmc import CadToDagmc

sphere = cq.Workplane().sphere(5)
small_sphere = cq.Workplane().moveTo(10, 0).sphere(2)

assembly = cq.Assembly()
assembly.add(sphere, name="large_sphere", material=cq.Material("tungsten"))
assembly.add(small_sphere, name="small_sphere", material=cq.Material("steel"))

model = CadToDagmc()
model.add_cadquery_object(
    cadquery_object=assembly,
    material_tags="assembly_materials"  # Use Material objects as tags
)
model.export_dagmc_h5m_file(min_mesh_size=0.5, max_mesh_size=1.0e6)

This creates volumes tagged with mat:tungsten and mat:steel.

When to Use Assembly Materials#

Use Case	Recommendation
Part names describe geometry	Use `assembly_materials`
Part names describe materials	Use `assembly_names`
Multiple parts, same material	Use `assembly_materials`
Need CadQuery < 2.6.1	Use `assembly_names` or manual

Example: Names vs Materials#

import cadquery as cq
from cad_to_dagmc import CadToDagmc

assembly = cq.Assembly()

# Name describes geometry, material describes composition
assembly.add(
    cq.Workplane().sphere(5),
    name="inner_shield",           # Geometric description
    material=cq.Material("tungsten")  # Material composition
)
assembly.add(
    cq.Workplane().sphere(10).cut(cq.Workplane().sphere(5)),
    name="outer_shield",           # Geometric description
    material=cq.Material("tungsten")  # Same material!
)
assembly.add(
    cq.Workplane().box(30, 30, 30),
    name="coolant_channel",
    material=cq.Material("water")
)

model = CadToDagmc()
model.add_cadquery_object(assembly, material_tags="assembly_materials")

print(model.material_tags)
# Output: ['tungsten', 'tungsten', 'water']

Multiple Parts, Same Material#

The material tag is reused for parts with the same material:

import cadquery as cq
from cad_to_dagmc import CadToDagmc

assembly = cq.Assembly()

# Multiple fuel pins, all tungsten
for i in range(5):
    assembly.add(
        cq.Workplane().moveTo(i * 3, 0).cylinder(10, 0.5),
        name=f"fuel_pin_{i}",
        material=cq.Material("tungsten")  # All share same material
    )

model = CadToDagmc()
model.add_cadquery_object(assembly, material_tags="assembly_materials")
# All 5 volumes tagged with "tungsten"

Requirements and Errors#

Warning

CadQuery version: This feature requires CadQuery > 2.6.1.

All parts need materials: Every part must have a material assigned, or you’ll get an error:

assembly.add(sphere, name="sphere")  # No material!
model.add_cadquery_object(assembly, material_tags="assembly_materials")
# ValueError: Part 'sphere' has no material assigned

Check your CadQuery version:

import cadquery
print(cadquery.__version__)

Comparison with Assembly Names#

Feature	`assembly_names`	`assembly_materials`
Tag source	`name="..."`	`material=cq.Material("...")`
CadQuery version	Any	> 2.6.1
Unnamed parts	Gets UUID	Error
Same tag for multiple parts	Must use same name	Use same Material