cut surface

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sket
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cut surface

Postby sket » Sun May 25, 2014 8:03 am

Hi all, i need to cut a surface, i try to find tutorial and topic in the forum but nothing.
Someone can inform me the way to do this?
Attachments
test.fcstd
(7.76 KiB) Downloaded 83 times
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quick61
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Re: cut surface

Postby quick61 » Sun May 25, 2014 3:13 pm

sket wrote:Hi all, i need to cut a surface, i try to find tutorial and topic in the forum but nothing.
Someone can inform me the way to do this?
You don't give very much information here. But either way you want to go, I don't think your going to get the results your wanting with what you have. This is because your 2 surfaces have no thickness. Visually, it may look like they do, but that's only because you can't show "nothing", but mathematically, they are only 2 dimensional objects and you need at least the object doing the cutting to be 3 dimensional when making this type of cut.

Now, FreeCAD can cut faces when they are both on the same plane, but when they are at an angle like your example, there is a cut made, but you do not get the result you might hope for.

Mark
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jmaustpc
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Re: cut surface

Postby jmaustpc » Sun May 25, 2014 3:30 pm

Part WB boolean operations can sometimes work in simple cases with surfaces, but you very quickly get failures when things start to get at all complicated. You can use a 3d shape (e.g. a Part Cube) for a tool to cut a Part Plane. But your curved faces will not work even if I modify your tool sketch to make the tool a 3d block rather than just a face.

However as Mark said, if you can first make both these faces into 3d solids then the Part cut will work.

There has at times been some talk of writing a surfaces WB for FreeCAD but nothing has come of that yet.

So if the end result of why you are modelling this surface is to make a solid, then make the solid first and probably use 3d solid tools and the Part wb cut.

Jim
jmaustpc
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Re: cut surface

Postby jmaustpc » Sun May 25, 2014 3:36 pm

Another round about way to get the result that would probably work is

change you sketches to closed profiles, so that you have two 3d solids and not surfaces
then do the boolean cut in the Part WB

then change to the Draft Workbench, and select "downgrade" on the result of the above
then select all the downgraded faces that you don't want and delete or hide them, ....you would then be just left with the surface you asked for..

Jim
looo
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Re: cut surface

Postby looo » Sun May 25, 2014 4:15 pm

another way:

1: make a fusion of the two objects
2: select the needed face and enter this command to duplicate it:
Part.show(Gui.Selection.getSelectionEx()[0].SubObjects[0])
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NormandC
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Re: cut surface

Postby NormandC » Sun May 25, 2014 4:22 pm

Guys, have you noticed that sket used Part Design Pads to create the surfaces? sket must use 0.13.1828. Just try to edit one of the pads, it will throw an error.

sket: the purpose of the Part Design workbench is to create solids. Making surfaces is not allowed anymore in the current v0.14 development version which is almost ready to be released as the new stable. To extrude surfaces you should use Part Extrude.

A surface trim tool sure would be nice.

An alternative way at the moment would be to use the Part Section tool to create an intersection edge on the upright surface, then use Shape Builder to create vertical edges then make a face of this.

looo, your solution is good as well and less of a hassle. Though it's a pity that all these alternatives don't create a parametric surface.
Attachments
FC_Section_of_2_surfaces.png
FC_Section_of_2_surfaces.png (26.51 KiB) Viewed 5227 times
jmaustpc
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Re: cut surface

Postby jmaustpc » Sun May 25, 2014 5:28 pm

I assumed that the vertical surface is wanted to be cut off at the horizontal surface so that all the material of the vertical surface that protrudes above the horizontal surface is removed? Is that what you are trying to achieve?

I had previously tried simple copies and they did not work, however after Norm's post I thought I would try Part Extrusions from the sketches. It works if you change the horizontal sketch so that it is a profile for a solid that fully encloses all the material to be removed from the vertical surface, and then Part extrude both sketches and use a cut.

like this
test(2)3.fcstd
(12.44 KiB) Downloaded 51 times
You would save a lot of confusion if you would post your Help about FreeCAD data.....when you first post a question.

Like this

OS: Ubuntu 12.04.4 LTS
Platform: 64-bit
Version: 0.14.3638 (Git)
Branch: master
Hash: 940f7e69ba0a0d1c34a910b58ef96f4e551fda07
Python version: 2.7.3
Qt version: 4.8.2
Coin version: 3.1.3
SoQt version: 1.5.0
OCC version: 6.7.1
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sket
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Re: cut surface

Postby sket » Mon May 26, 2014 11:13 am

thanks guys for all the suggestion, but i've tried many and many ways (pad or extrude) to achieve the part that i want and nothing.
now i begin the project with another cad, i think to draw what i want but it will be not refine as i hope to do with freecad.
when i finish show here the result and to understand if possible to create with freecad.

thanks.
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bejant
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Re: cut surface

Postby bejant » Tue May 27, 2014 2:22 pm

normandc wrote:A surface trim tool sure would be nice.
Would this be a good candidate for a feature request in Mantis?
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NormandC
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Re: cut surface

Postby NormandC » Tue May 27, 2014 10:14 pm

Absolutely! :)

But jriegel may prefer to wait for a Surface Design workbench, which he's mentioned as planned.

Still, it doesn't hurt to put it on Mantis.