Thread solids invalid

Thread solids are not valid, and consequently fail boolean operations.

>>> import cqparts
>>> thread = cqparts.types.threads.iso_262.ISO262Thread().make(5)
>>> thread.val().wrapped.isValid()
False

solids can be cleaned up using the method(s) described here, but they’re not always successful.

slight variations initially yield an unclosed solid, but are fixed with sewShape(), for example

>>> import cqparts
>>> thread = cqparts.types.threads.iso_262.ISO262Thread(pitch=0.7).make(3)
>>> thread.val().wrapped.isValid()
True

Exception

code modified to crash more gracefully by raising:

SolidValidityError: created thread solid cannot be made watertight

[fragmuffin]

This bug is making thread-building completely unmanageable. It’s making building a very painful and error-prone experience… the presence of thread faces makes cqparts very unstable.

Mitigated by Simplifying to Cylinder

For the time being, I’ve converted the base Thread type to a Part so I can exploit the _simple=True flag, which causes the make_simple() method to build the part’s .local_obj as opposed to .make(). (see f1e98fe)

In other words, by default, threads are not generated. Instead they are replaced with a cylinder with the thread’s average radius (outer + inner) / 2.

Workaround

If you’d like to play with real threads, you can turn off default simplification with any of…

import cqparts
from cqparts.display import display
from cqparts.params import Boolean
from cqparts.fasteners.base import FastenerMalePart
from cqparts.solidtypes.threads import base

# --- an individual part
screw = FastenerMalePart()
screw.thread._simple = False
display(screw)

# --- all threads by default
base.Thread._simple.default = False
# you'll have to re-define the thread type, because the default thread
# was instantiated before the above change was made
screw = FastenerMalePart(
    thread=('iso262', {
        'diameter': 3.0,
        'pitch': 0.7,
    }),
)
display(screw)

# --- all threads by default (by environment variable)
# because the above way is messy... you can set an environment variable:
#       CQPARTS_COMPLEX_THREADS=yes
display(FastenerMalePart())  # default of _simple is False at import time

none of the above methods are permanent, please keep this in mind if you’re planning a future-proofed script.

Fix Delay

I also won’t have time to fix this for the initial release… but it’s very high on the priorities list after v0.2

[fragmuffin]

Task

• remove warning about this fault from cqparts_fasteners README.rst