MWE_occ_cut_spiral

import netgen.occ as occ
from netgen.webgui import Draw as GeoDraw
import numpy as np
import ngsolve as ng
from ngsolve.webgui import Draw

tube_axes        = occ.Axes(occ.Pnt(0,0,0), occ.Z)
tube_radius      = 10
spiral_spacing   = 2.1
spiral_width     = 5
spiral_thickness = 0.8

revs             = 2.02 # NOT okay
#revs             = 2.01 # Okay

angle            = revs*2*np.pi
L                = revs*(spiral_thickness + spiral_spacing) + spiral_thickness

cyl1 = occ.Cylinder(tube_axes, tube_radius, L).faces[0]
cyl2 = occ.Cylinder(tube_axes, tube_radius + spiral_width, L).faces[0]

seg1 = occ.Segment(occ.Pnt(0, 0), occ.Pnt(angle, L-spiral_thickness))
seg2 = occ.Segment(occ.Pnt(angle, L-spiral_thickness), occ.Pnt(angle, L))
seg3 = occ.Segment(occ.Pnt(angle, L), occ.Pnt(0, spiral_thickness))
seg4 = occ.Segment(occ.Pnt(0, spiral_thickness), occ.Pnt(0, 0))

arc1 = occ.Edge(seg1, cyl1)
arc2 = occ.Edge(seg2, cyl1)
arc3 = occ.Edge(seg3, cyl1)
arc4 = occ.Edge(seg4, cyl1)
arc5 = occ.Edge(seg1, cyl2)
arc6 = occ.Edge(seg2, cyl2)
arc7 = occ.Edge(seg3, cyl2)
arc8 = occ.Edge(seg4, cyl2)

wire1 = occ.Wire([arc1, arc2, arc3, arc4])
wire2 = occ.Wire([arc5, arc6, arc7, arc8])

spiral = occ.ThruSections([wire1, wire2])

geo = occ.OCCGeometry(spiral)

cut = occ.Box(occ.Pnt(tube_radius + 0.5*spiral_width, 1, -1), occ.Pnt(tube_radius + spiral_width+1, 2, L+1))
cut_spiral = spiral - cut

GeoDraw(cut_spiral)