add option to create fillets

[looooo]

fillets instead of undercut and at the top of the teeth would be a nice addition.

[looooo]

ref.: https://forum.freecadweb.org/viewtopic.php?f=22&t=49562

[looooo]

using pyocct as long as there is no freecad function for this:

import numpy as np
import FreeCAD as App
import Part
from OCC.Core import ChFi2d
from OCC import Core

api = ChFi2d.ChFi2d_FilletAPI()

def fillet_between_edges(edge_1, edge_2, radius):
    # asuming edges are in a plane
    # extracting vertices
    p1 = np.array([*edge_1.valueAt(edge_1.FirstParameter)])
    p2 = np.array([*edge_1.valueAt(edge_1.LastParameter)])
    p3 = np.array([*edge_2.valueAt(edge_2.FirstParameter)])
    p4 = np.array([*edge_2.valueAt(edge_2.LastParameter)])
    t1 = p2 - p1
    t2 = p4 - p3
    n = np.cross(t1, t2)
    pln = Core.gp.gp_Pln(Core.gp.gp_Pnt(*p1), Core.gp.gp_Dir(*n))
    occ_e1 = Core.TopoDS.topods_Edge(Part.__toPythonOCC__(edge_1))
    occ_e2 = Core.TopoDS.topods_Edge(Part.__toPythonOCC__(edge_2))
    api.Init(occ_e1, occ_e2, pln)
    if api.Perform(radius) > 0:
    	occ_p0 = Core.gp.gp_Pnt(0,0,0)
    	occ_arc = api.Result(occ_p0, occ_e1, occ_e2)
    	return Part.Wire([Part.__fromPythonOCC__(occ_e1),
                      Part.__fromPythonOCC__(occ_arc),
                      Part.__fromPythonOCC__(occ_e2)])
    else:
    	return Part.Shape

def test():
    App.newDocument()
    radius = 0.1
    p0 = App.Vector(1,0,0)
    p1 = App.Vector(2,0.5,0)
    p2 = App.Vector(1,1,0)
    p3 = App.Vector(1,0,0)
    e1 = Part.LineSegment(p1, p0).toShape()
    e2 = Part.LineSegment(p3, p2).toShape()
    Part.show(e1)
    Part.show(e2)
    Part.show(fillet_between_edges(e1, e2, radius))

test()
FreeCAD.Console.PrintMessage(npt.Coord())

[looooo]

this is now possible with this branch;
https://github.com/looooo/freecad.gears/tree/megagrants

parameters:

• head_fillet
• foot_fillet

Both have no dimension and are used to compute the fillet radius by multiplying with the module.

[rockstorm101]

First of all thanks for the workbench. This is great. I've been testing it and this tip/root radius (which is how it is called in the standards usually) is the first feature I was missing. Looking forward to see it implemented. Thanks again.

[jbaehr]

I just tried it on the develop branch. cool stuff!

I've one addition/enhancement to propose: What do you think about two additional (hidden?) computed properties max_{head,root}_fillet, with the maximum possible value for the fillet? The radius may not be larger than half the traverse-length of the bottom/top land, but this value again depends on profile shift, number of teeth, clearance/head, maybe more.
This would allow to use e.g. =min(clearance, max_root_fillet) as value for the root_fillet.

[jbaehr]

... tip/root radius (which is how it is called in the standards usually)

Which standard are you referring to? ISO 1122-1:1998 "Vocabulary of gear terms" (publicly available as Indian Standard 2458:2001) calls what FCGear calls "root_fillet" just "fillet" and there is no equivalent for the tip defined.

In addition, there is at least a Japanese and an American standard out there, too. In the technical docs from QTC Gears, which symbol names are used within FCGear, different standards are compared. The document itself uses both terms, "Tip/Root Radius" and "root fillet".

Unless you're making a gear cutter, the tip radius/fillet is barely mentioned. Instead, some chamfer at the tip, called "semi topping" seems way more popular.

[rockstorm101]

... tip/root radius (which is how it is called in the standards usually)

Which standard are you referring to? ISO 1122-1:1998 "Vocabulary of gear terms" (publicly available as Indian Standard 2458:2001) calls what FCGear calls "root_fillet" just "fillet" and there is no equivalent for the tip defined.

Well, good point, thank you for questioning that. I'm used to that terminology at work because that's how it is called on the KISSsoft software. However, I went ahead and actually had a look at some standards I had at hand (DIN 3972, ISO 868 and DIN 1825) and there doesn't seem to be a consistent name for these. The root/fillet/radius seems to agree but the one at tooth tip is not even mentioned. Thinking about it one might wrongly assume root/tip radius to be half of the root/tip diameter so it is probably better to name those something less misleading.

In addition, there is at least a Japanese and an American standard out there, too. In the technical docs from QTC Gears, which symbol names are used within FCGear, different standards are compared. The document itself uses both terms, "Tip/Root Radius" and "root fillet".

Unless you're making a gear cutter, the tip radius/fillet is barely mentioned. Instead, some chamfer at the tip, called "semi topping" seems way more popular.

Totally agree, tip radius (or tip fillet or whatever) is rare in "traditional" gear manufacturing), only defined when topping cutting tools have such a radius at the root of the cutting tool. A chamfer/relief is (in what I've seen so far) more common.