Multi-section Sweep

[CONNOR MORENO]

Hi all,

I'm having some difficulty understanding how to use the multi-section sweep (using the multisection flag on workplane.sweep). As an exercise, I'm trying to create a sweep whose cross-sectional shape alternates between circles and squares along a path of a half revolution of a circle. I thought perhaps the following script would work

import cadquery as cq
import numpy as np

n = 5
phi = np.linspace(0, np.pi, num = n)
rad = 5
pts = []
j = 0

for i in phi:
pt = (rad*np.cos(i), rad*np.sin(i))
pts += [pt]

rotation = (0.0, np.rad2deg(i), 0.0)

if i == phi[0]:
sweep = cq.Workplane("XZ").transformed(rotate = rotation, offset = pt)
else:
sweep = sweep.copyWorkplane(cq.Workplane("XZ")
).transformed(rotate = rotation, offset = pt)

if (j % 2) == 0:
sweep = sweep.circle(1)
else:
sweep = sweep.rect(1, 1)

j += 1

path = cq.Workplane("XY").spline(pts)
sweep = sweep.sweep(path, multisection = True)
cq.exporters.export(sweep, 'sweep.step')

but running gives the following error

Traceback (most recent call last):

File "/home/camoreno/Documents/ParametricStellarator/sweep_test.py", line 35, in <module>

sweep = sweep.sweep(path, multisection = True)

File "/home/camoreno/miniforge/lib/python3.9/site-packages/cadquery/cq.py", line 3161, in sweep

r = self._sweep(

File "/home/camoreno/miniforge/lib/python3.9/site-packages/cadquery/cq.py", line 3732, in _sweep

thisObj = Solid.sweep_multi(sections, p, makeSolid, isFrenet, mode)

File "/home/camoreno/miniforge/lib/python3.9/site-packages/cadquery/occ_impl/shapes.py", line 3234, in sweep_multi

builder.Build()

OCP.Standard.Standard_ConstructionError: BRepFill :: profiles are inconsistent

I'm having trouble finding documentation for the multi-section sweep and I'm certain I'm using it incorrectly. Any help would be greatly appreciated and please let me know if I can provide additional information/explanation.

Thanks!

Connor

[CONNOR MORENO]

Was able to get it to work with the following script. Turns out I was misplacing the cross-sectional profiles such that they didn't coincide with the defined path.

import cadquery as cq
import numpy as np

n = 5
phi = np.linspace(0, np.pi, num = n)
rad = 5
pts = []
j = 0

for i in phi:
pt = (rad*np.cos(i), rad*np.sin(i))
pts += [pt]
rotation = (0.0, np.rad2deg(i), 0.0)

if i == phi[0]:

sweep = cq.Workplane("XZ", origin = pt).transformed(rotate = rotation)
else:
sweep = sweep.copyWorkplane(cq.Workplane("XZ", origin = pt)
).transformed(rotate = rotation)

if (j % 2) == 0:
sweep = sweep.circle(1)
else:
sweep = sweep.rect(1, 1)

j += 1

path = cq.Workplane("XY").spline(pts)
sweep = sweep.sweep(path, multisection = True)
cq.exporters.export(sweep, 'sweep.step')

For anyone viewing this from the future who is also confused about how to use this feature, what you want to do is the following:

• Define cross-sectional profiles of the shape you want to sweep. Put them all on the same stack in a manner similar to what's done in the script above.
  
• Define the path you want to sweep along
• Ensure the profiles coincide with the path, meaning the path passes inside of the profile

At least, that's my understanding of how it works. Hope this helps!

Connor

[CONNOR MORENO]

Here are some images of the shape created from the script above as a reference