Chamfer and Loft not good

[SvenGoord]

Why is chamfer not straight? What to fix? Fillet does not 3d print good I need chamfer inside and outside

loft-01.FCStd

(283.86 KiB) Downloaded 36 times

OS: Linux Mint 19.1 (X-Cinnamon/cinnamon)
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.16966 (Git) AppImage
Build type: Release
Branch: master
Hash: fbafd698aefeae2dbb5a711647346b9cac7794e9
Python version: 3.7.1
Qt version: 5.6.2
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)

[kisolre]

Not sure what your question is. Why do you need that chamfer to print the model? This should be printed upside down of how you modeled it. You dont need those bridges. If you need 45deg overhangs you can sketch a triangle and additive sweep that along the internal edge. But you dont need that. Could you give some more info what is the final goal?

[SvenGoord]

Thank you, the file was just an example of wavy line inside lofts. My reel part is printed like you show but watch https://www.youtube.com/watch?v=XTvBOGgx48I for why not fillets.

[bejant]

Not sure what your question is.

Along the inside flat faces I would expect the Chamfers to be straight, but they aren't:

Screenshot from 2019-06-20 11-35-05.png (47.22 KiB) Viewed 1372 times

I don't know why...

OS: Ubuntu 18.04.2 LTS
Word size of OS: 32-bit
Word size of FreeCAD: 32-bit
Version: 0.18.1.
Build type: Release
Python version: 3.6.7
Qt version: 5.9.5
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)

[kisolre]

Along the inside flat faces I would expect the Chamfers to be straight, but they aren't:

Since there was no screenshot I did not notice that. It realy looks not correct.
Changing the rounding radius for the substractive loft came to this:
.

LoftRoundingProblem.JPG (103.65 KiB) Viewed 1364 times

.
Which looks wrong since both sketches have the same number and type of edges. But looks a little like where the chamfer bends.
I tried sweeping a sketch to create a chamfer. This does not look correct but the edges are straight. Not sure how OCC creates chamfers.
.

SketchSweepChamfer.JPG (84.96 KiB) Viewed 1364 times

.
Then I tried creating a sketch mapped to OCC chamfer - not luck because the face is not flat:
.

ChamferNonPlanarFace.JPG (109.03 KiB) Viewed 1364 times

.
So there is definitely something problematic here but what I cant figure out.

[chrisb]

I think the deviations are due to the vertical draft and the resulting trapezoidal vertical ends. The chamfer cannot have everywhere the same section geometry and OCC seems to perform some tricky calculations to create a chamfer after all.

The phenomenon vanishes as soon as all arcs share the same center (and not the same radius). This makes the lines going from base to top rectangular to the chamfered line:

[bejant]

A different work flow using the Thickness Tool instead of Subtractive Loft, and subsequently applying the Chamfer, does seem to produce the result SvenGoord wants: Aargh - Strike that - the image is of the wrong Body. Even so, using the Thickness Tool does still seem to produce a better result.

20190620b.png (16.14 KiB) Viewed 1329 times

The file is attached, but I did fork body-chamfer into two different histories:

20190620a.png (151.31 KiB) Viewed 1329 times

(Yikes - that Dependency Graph image is ginormous!)

20190620c-thickness.FCStd

(480.28 KiB) Downloaded 30 times

OS: Ubuntu 18.04.2 LTS
Word size of OS: 32-bit
Word size of FreeCAD: 32-bit
Version: 0.18.1.
Build type: Release
Python version: 3.6.7
Qt version: 5.9.5
Coin version: 4.0.0a
OCC version: 7.3.0
Locale: English/UnitedStates (en_US)

[bejant]

I tried sweeping a sketch to create a chamfer. This does not look correct but the edges are straight.

I did too, using the smaller Sketch of the inside as the Sweep Path, and got the same result as shown in your subsequent image - the slope along each inside curve isn't constant as the Chamfer travels though the curve. So, I wonder why Fillet produces a different footprint (straight along the inside face) than Chamfer.

[papyblaise]

Hello
You know , when you use Loft , it creat B-spline not strait lines , maybee the problem is that
A best solution : you use "Shell" tool , instead of addloft and soustractloft , it ll'be better

[bejant]

when you use Loft , it creat B-spline

Yes, but doing a Subtractive Sweep instead, then a Chamfer, still doesn't result in straight edges...