Surface Modeling: how to trim surface ?

[Cekuhnen]

i am trying to figure out the surface modeling abilities in FreeCAD and encounter multiple trim related issues with being unable to trim surfaces with surfaces


i made a test test scene with multiple bodies and here is a DL link: https://drive.google.com/file/d/1UEWA_s ... sp=sharing

Screen Shot 2021-07-18 at 3.51.36 PM.png (82.38 KiB) Viewed 2073 times

curves WB
Trim A Face feature:
has a planar/2D trim based on an existing sketch
cannot trim a surface with a surface to my knowledge - lacks the tool to generate the intersection curve
Example:

Screen Shot 2021-07-18 at 4.17.47 PM.png (90.64 KiB) Viewed 2073 times

further the trim face tool has issues in my case : after trim the top face of revolve body is gone

Screen Shot 2021-07-18 at 4.27.27 PM.png (57.42 KiB) Viewed 2073 times

Screen Shot 2021-07-18 at 4.27.36 PM.png (45.38 KiB) Viewed 2073 times

part WB
Join Feature:
can remove interior geometry of two pipe like intersecting surfaces
but this does not work with a closed surface being intersected with a plane/open surface
this makes sense this is about connecting closed shapes!
Example: extrusion is cut right - all other surface keep the surface I want to actually remove

Screen Shot 2021-07-18 at 3.52.33 PM.png (94.27 KiB) Viewed 2073 times

OS: macOS 10.16
Word size of OS: 64-bit
Word size of FreeCAD: 64-bit
Version: 0.19.24276 (Git)
Build type: Release
Branch: (HEAD detached at 0.19.1)
Hash: a88db11e0a908f6e38f92bfc5187b13ebe470438
Python version: 3.8.8
Qt version: 5.12.9
Coin version: 4.0.0
OCC version: 7.4.0
Locale: C/Default (C)

[Cekuhnen]

Part WB
Slice hels splitting but it consumes the slice tool

Screen Shot 2021-07-18 at 4.47.59 PM.png (110.59 KiB) Viewed 2050 times

However I can get this to model but only by using slice hiding unwanted sliced parts rebuilding the slice surfaces so i could trim them with the just created sliced edges

slice trim.png (110.19 KiB) Viewed 2054 times

i attached the file

[Cekuhnen]

for those interested this is a pretty interesting process doing surfacing:

https://www.youtube.com/watch?v=OFQGYXiCwBQ

It makes use of the Create Part command - creating a new part based on selected faces
Only downside is that this breaks the parametric link

[Forthman]

To make the model parametric, why not use the "Join Curves" tool in the Curves workbench rather than the
"Shape Builder" tool to create the wires from the BooleanFragments object ?

[chrisb]

for those interested this is a pretty interesting process doing surfacing:

You should add where to look at, the video is 25 minutes long. I have only watched the first 5 minutes and wasn't really delighted. Much stirring around with the mouse. Looks rather like "this is how I work" and not "this is how you can/should work".

[Cekuhnen]

why not use the "Join Curves" tool in the Curves workbench

How would this work with the surfaces to trim?
You mean after the booleanFragments command?

This design is simple enough to do it with the face trim command or model with part design WB too.

Screen Shot 2021-07-19 at 7.36.45 AM.png (76.08 KiB) Viewed 1908 times

Going back to my model is boolean fragment the best way to trim / split all the objects?

Screen Shot 2021-07-18 at 3.51.36 PM-1.png (82.38 KiB) Viewed 1906 times

I have not found any reference for how to trim surfaces with surfaces or find the intersection curves needed for trimming.

.
.
.

add where to look at, the video is 25 minutes long

Min 11:28 he adds a datum plane with out showing a body from PartDesign WB - I am curious how he did that

Min 14:42 the boolean fragment

MIn 15:05 Shape Builder

[Cekuhnen]

Here is another good video

Min 0:44

So the Mixed Curve command generates the intersection of two planar curves - this is wonderful to know

Screen Shot 2021-07-19 at 7.45.09 AM.png (175.97 KiB) Viewed 1904 times

[Forthman]

I don't use the surface functions very often so I can't give you any instructions, just a few "tricks" I've tried that work easily.

using the "Join Curves" tool often gives good results, and the edges can come from any kind of object.

a small example file to "see" how parametric it is.
by modifying the 3 sketches, the shape of "Ruled_Surface" adapts

ruled surface.FCStd

(121.04 KiB) Downloaded 25 times

[Cekuhnen]

Ah I see you - You build new faces from it.


Here is a classic problem with with the planar trim approach
it cuts through the whole cylinder

Screen Shot 2021-07-19 at 10.43.20 AM.png (72.8 KiB) Viewed 1843 times

Ideally it would be super if you could mark keep and remove faces

Maybe that is why in the end the user decided to go with the shape builder even while it is breaking the parametric flow

Screen Shot 2021-07-19 at 10.44.25 AM.png (75.69 KiB) Viewed 1843 times

[Cekuhnen]

I don't use the surface functions very often so I can't give you any instructions, just a few "tricks" I've tried that work easily.

using the "Join Curves" tool often gives good results, and the edges can come from any kind of object.

a small example file to "see" how parametric it is.
by modifying the 3 sketches, the shape of "Ruled_Surface" adapts

ruled surface.FCStd

I got it to work - somewhat
mix of Part WB slice apart and Curve WB Trim Face
and a lot of cross referencing

Screen Shot 2021-07-19 at 12.26.58 PM.png (230.42 KiB) Viewed 1817 times

.
.
.
when adjusting a sketch things can easily fall apart
like trim a face not updating right

Screen Shot 2021-07-19 at 12.37.38 PM.png (81.49 KiB) Viewed 1806 times

.
.
.

or not - odd - tried ti video record a sketcher issue flipping a constraint sketch
the issue was a now show and also trim a face updated right ?! confused ...
here is a screen recording
https://drive.google.com/file/d/1HXLi1m ... RRJNB/view


I attached the file if you want to look at it






would be killer if FC would have a make solid from surrounding surfaces