By on Saturday, April 18, 2020 (1599 views)

Lofts

In DeclaraCAD the ThruSections declaration is used to perform a loft as it follows OpenCASCADE naming conventions. As the name implies the "through sections" it lets you create a shape by lofting through several cross sections of the shape. Each child shape will be used as a section of the loft.

Note: Use from declaracad.occ.api import ThruSections as Loft to rename it

To create a loft first create the sections to loft between. Here three circles are created oriented at different positions and heights.

# Created in DeclaraCAD
from declaracad.occ.api import *


enamldef Assembly(Part):
    attr thickness = 0.2
    attr diameter = 3

    Wire:
        color = 'red'
        Circle: c1:
            radius << diameter/2.0
    Wire:
        color = 'red'
        Circle: c2:
            position << (c1.x+3,c1.y,c1.z+5)
            direction = (1,0,0)
            radius << c1.radius*0.5

    Wire:
        color = 'red'
        Circle: c3:
            position << (c1.x+6,c1.y,c1.z+3)
            direction = (0,0,-1)
            radius << c1.radius*0.6

    # For reference    
    Line: xaxis:
        color = 'black'
        direction = (1, 0)
    Line: yaxis:
        color = 'black'
        direction = (0, 1)
    Line: zaxis:
        color = 'black'
        direction = (0, 0, 1)

Loft sections

Next add the cross sections as children of the ThruSections

# Created in DeclaraCAD
from declaracad.occ.api import *


enamldef Assembly(Part):
    attr thickness = 0.2
    attr diameter = 3

    ThruSections:
        material = 'chrome'
        Wire:
            Circle: c1:
                radius << diameter/2.0
        Wire:
            Circle: c2:
                position << (c1.x+3,c1.y,c1.z+5)
                direction = (1,0,0)
                radius << c1.radius*0.5

        Wire:
            Circle: c3:
                position << (c1.x+6,c1.y,c1.z+3)
                direction = (0,0,-1)
                radius << c1.radius*0.6

    # For reference    
    Line: xaxis:
        color = 'black'
        direction = (1, 0)
    Line: yaxis:
        color = 'black'
        direction = (0, 1)
    Line: zaxis:
        color = 'black'
        direction = (0, 0, 1)

Loft thru sections

Since the cross sections used are wires and not faces it creates a hollow surface as shown below.

Loft hollow section

To make it a solid set solid = True which will fill in the sections.

Loft solid section

By default the loft will generate smooth curves between each of the sections. If this is not desired set ruled = True which changes them to straight lines as shown below.

Loft ruled

Example

Lofts can be fused with other shapes to create more complex parts such as this spindle vacuum nozzle.

Loft example