Previously, the fillet started at a fixed value, tailored at 20° pressure
angle, a fillet radius of 0.375 and a dedendum of 1.25. With PR #8184
those values became user-adjustable and thus the assumptions of the
original code are not fullfilled any more. This resulted in significant
artefacts, especially for higher pressure angles or smaller dedendums as
commonly found in splines.
This commit actually calculates the junction between fillet and involute
so that the tangents of the both curves match.
The mathematical approach is described in source code comments.
The change in the fillet calculation also affects compatibility with
files generated by earlier versions of FreeCAD. Those changes are way
below 0.1% per tooth, however the earlier test required absolute equality
down to the micron. This was relaxed and also changed to a relative, per
tooth, tolerance.
There is one particular case where the new algorithm performs slightly
worse, though. That is when the fillet radius is too large to the
dedendum, i.e. resulting in a single arc instead of two fillets, and
effectively cannibalizes some of the clearance. This happens with internal
gears having less than 25 teeth. At about 15 teeth it becomes visible
that the fillet is not 100% tanget any more. However, as such a low
number of teeth is highly unusual for internal gears and the effect,
although noticeable, is minor, the overall benefits of the new algorithm
outweighs the drawbacks. And now with the fillet radius being adjustable
it is easy to fix, too.
The technical reason is that the tangency is calculated correctly, but
the fillet circle is displaced aferwards to avoid an overlap of the two
fillets. For the new fillet position, the tangents do not align any more.
This little script has proven to be a vauable debugging aid, so it got
some love. All the new properties from #8184 can now be set, together
with the option to generate internal gears.
The original implementation always took 150% of the addendum/dedendum
difference as fillet radius. For a standard full-depth system this
results in a normalized value 0f 0.375, which is pretty close to the 0.38
definded by the basic ISO rack. However, when using much shorter teeth as
e.g. required for a splined shaft, the fillet becomes way too large.
In addition, I don't understand the approximation to calculate the
distance between the gear's center and the top of the fillet yet. It was
only refactored to allow the custom fillet radii, but it retuns the same
values as the original implementation.
However, with high pressure angles, up to 45° used for splines, this
approximation comes to its limits.
Exposing the addednum and dedendum coefficients as properties allows to
change the tooth length above and below the pitch circle. This makes it
possible to use the profile beyond standard full-depth systems, e.g. for
stub tooths and most importantly: involute splined shafts and hubs.
Gear objets created with earlier versions automatically get the
additional properties on document restore. Its values match the hard-
coded values used in earlier versions.
There is a change when creating *new* internal gear profiles, though:
Previously, an addendum coefficient of 0.6 was used, presumably to reduce
the tip length beyond the base circle in order to avoid a non-involute
edge. This method is one proposal from the "Handbook of Gear Design" by
Gitin M. Maitra, as referenced in the original source code comments.
However, Maitra also states that this reduction of the anual gear's tip
in turn requires an enlagement of the mating gear of 1.25 instead of the
ordinary 1.0. And it is only required for a low numer of teeth and/or the
mating gear being quite large (less than 10 teeth in difference, to avoid
interferences).
Because those additional requirements and conditions have not been
implemented, the previously used values have been incomplete anyway. Thus
I decided to not implemented this special case and use the standard
values of 1.0/1.25 for newly created external and internal gears alike.
Internal gears need special care for other kind of interference anyway
and the newly exposed properties now allow to do so.
There is no entry in the task panel for those advanced properties yet.
This is a pure refactor, without any change in visibile functionality.
However, the new structure allows easy addition of new properties without
breaking existing documents.
The goal of this refactor is to get rid of gear-specific knowledge from
the implementation and argument list. This is to remove the duplicate
definition of addenddum and dedendum that was hidden there.
This is in preparation for new features, to ensure we don't break
existing documents created with FreeCAD-0.20.
The fixtures have been created with the official mac build of
FreeCAD-0.20.1 using mostly default parametrization -- only the number
of teeth has been reduced in order to keep the file size low.
* Replacing the static_cast with a dynamic_cast in 668adaacdf is a regression because it cannot be guaranteed that the linked object is a sketch.
In fact it can also be a shape binder which is explicitly allowed.
Forum: https://forum.freecadweb.org/viewtopic.php?f=19&t=74939
* Move initialization of some variables into the if-statement
- the error can also occur when the mode it not UpToFace (ToFirst or ToLast)
- also add note when Reversed checkbox is enabled since this is no obvious (as discussed in the forum)
- also some whitespace unification and include sorting
* QApplication::setFallbackSessionManagementEnabled has been removed
* QString::medRef() has been removed. Use QString::mid() again.
* QTextStream::setCodec has been removed
* Use operator QVariant of the QFont class to make code Qt5 and Qt6 compatible
* Signature of QTreeWidget::mimeData() has changed in Qt6. Remove TreeWidget::mimeData() because it doesn't change the implementation
* QLayout::setMargin() is deprecated in Qt5 and has been removed in Qt6. Use QLayout::setContentsMargins()
* QDateTime::toTime_t() is deprecated in Qt5 and has been removed in Qt6. Use QDateTime::toSecsSinceEpoch()
* QDesktopWidget is deprecated in Qt5 and has been removed in Qt6. Use QScreen
Removes the BUILD_QT5 flag and adds a new FREECAD_QT_VERSION option,
which can be set to either "Auto" (default), 5, or 6. Auto detects which
version of Qt is installed on the system and chooses it. If both version
are installed, Qt5 is used.
Note that this DOES NOT implement compiling against Qt6, it only adds
the necessary cMake infrastructure to begin work on the source code
changes that will be required.
- as discussed in https://github.com/FreeCAD/FreeCAD/pull/7642 the backwards compatibility for deprecated holes was already lost since FC 0.19
- this PR removes the deprecated types and transform holes created with FC 0.19 or 0.20 to the corresponding countersinks/counterbores.
- also add Counterdrill for translations
