CadQuery Assemblies

CadQuery Assemblies#

CadQuery assemblies provide a structured way to organize multi-part geometry. They offer special features for automatic material tagging based on part names or materials.

Basic Assembly#

Create an assembly and add parts:

import cadquery as cq
from cad_to_dagmc import CadToDagmc

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

# Create assembly
assembly = cq.Assembly()
assembly.add(sphere)
assembly.add(small_sphere)

# Convert with manual tags
model = CadToDagmc()
model.add_cadquery_object(cadquery_object=assembly, material_tags=["mat1", "mat2"])
model.export_dagmc_h5m_file(min_mesh_size=0.5, max_mesh_size=1.0e6)

Using Assembly Names as Material Tags#

Name your assembly parts and use those names automatically as material tags:

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="tungsten")      # Name becomes material tag
assembly.add(small_sphere, name="steel")   # Name becomes material tag

model = CadToDagmc()
model.add_cadquery_object(
    cadquery_object=assembly,
    material_tags="assembly_names"  # Use part names as tags
)
model.export_dagmc_h5m_file(min_mesh_size=0.5, max_mesh_size=1.0e6)

Note

Parts without explicit names will receive auto-generated UUIDs as material tags. Always name your parts to ensure meaningful material tags.

Using Assembly Materials as Tags#

CadQuery 2.6.1+ supports cq.Material objects. Use these for material tagging:

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="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)

Warning

This feature requires CadQuery > 2.6.1. All parts in the assembly must have materials assigned, or a ValueError will be raised.

Assemblies with Mesh Parameters#

Assemblies work well with per-volume mesh sizing using the set_size parameter:

import cadquery as cq
from cad_to_dagmc import CadToDagmc

# Create boxes with different intended mesh resolutions
coarse_box = cq.Workplane().box(1, 1, 2)
fine_box = cq.Workplane().moveTo(1, 0.5).box(1, 1, 1.5)
default_box = cq.Workplane().moveTo(2, 1).box(1, 1, 1)

assembly = cq.Assembly()
assembly.add(coarse_box, name="coarse")
assembly.add(fine_box, name="fine")
assembly.add(default_box, name="default")

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

# Use material tag names in set_size
model.export_dagmc_h5m_file(
    filename="different_resolution_meshes.h5m",
    min_mesh_size=0.01,
    max_mesh_size=10,
    set_size={
        "coarse": 0.9,  # Coarse mesh for this material
        "fine": 0.1,    # Fine mesh for this material
        # "default" not specified - uses global min/max
    },
)

Nested Assemblies#

cad_to_dagmc handles nested (hierarchical) assemblies automatically:

import cadquery as cq
from cad_to_dagmc import CadToDagmc

# Create sub-assemblies
fuel_assembly = cq.Assembly()
fuel_assembly.add(cq.Workplane().cylinder(10, 1), name="fuel_pin_1")
fuel_assembly.add(cq.Workplane().moveTo(3, 0).cylinder(10, 1), name="fuel_pin_2")

coolant = cq.Workplane().box(20, 20, 12)

# Create main assembly with nested assembly
main_assembly = cq.Assembly()
main_assembly.add(fuel_assembly, name="fuel")  # Nested assembly
main_assembly.add(coolant, name="coolant")

model = CadToDagmc()
model.add_cadquery_object(main_assembly, material_tags="assembly_names")
model.export_dagmc_h5m_file()

The nested assembly’s leaf solids are extracted and tagged appropriately.

Assembly Tagging Options Comparison#

Option	Source	Example	Notes
Manual list	Explicit	`["mat1", "mat2"]`	Order must match volumes
`"assembly_names"`	Part names	Uses `name="..."`	Auto UUIDs for unnamed parts
`"assembly_materials"`	Material objects	Uses `material=cq.Material("...")`	Requires CadQuery > 2.6.1

CadQuery Assemblies

Contents