Sorry for not having the clearest title but what I'm trying to do is cut a circular hole in the side of a cylinder, that was created by lofting 2 circular wires, such that the hole matches the wire that is the top of another cylinder. The "internal cylinder" is highlighted in green in the image below.
This would be simple if I were allowed to subtract the internal cylinder from the solid but I'm restricted to operating on a per-surface basis for this application; I am restricted to using only the points that lie on the surface.
So far, my procedure when working with the large lofted cylinder's outer surface is to
- make an extrusion using the internal cylinder's end and cut it from the surface using a "Part::Cut" where the Base is the lofted surface (the result of a Part.makeLoft using the top and bottom wires where Solid=False, Ruled=True, Closed=False) and the Tool is the Part::Extrusion
- Identify the intersection of the extrusion and the lofted surface using a Part::Section where the Base is the lofted surface and the Tool is the extrusion
- And finally use the intersection as the new end wire for the lofting of the internal cylinder (this is saved and used later when working on the internal cylinder's surface)
A very zoomed view of where the lofted surface and internal cylinder meet is shown below
My guess is that this edge discrepancy is because the lofted surface removes the edges that would constitute the intersection during the cut and thus the large cylinder and internal cylinder don't meet at precisely the same edge.
Is there a better way to got about this process?
How best to cut a hole through a lofted surface such that cut hole matches a perpednicular
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Re: How best to cut a hole through a lofted surface such that cut hole matches a perpednicular
Can you upload the file?
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Re: How best to cut a hole through a lofted surface such that cut hole matches a perpednicular
Sorry, I forgot. Here is part file shown in the post
The hole in question is the one in the negative X space. The hole in the positive X space has a separate issue I'm trying to resolve with the lofting (it's edges follow the same procedure though).Re: How best to cut a hole through a lofted surface such that cut hole matches a perpednicular
Probably the discrepancy is not a "real" discrepancy, maybe it is simple a "rendering artifact".
Take in account, that FreeCAD has two "engines":
This could lead to some discrepancy see:
https://wiki.freecadweb.org/Scenegraph
You could tune something in the View Tab, usually you will find them set as:
But with this simple example
You could see the difference, in the image below.
Note that the object is the same, as both objects are a copy of the same circle, that is stored internally as a "infinite curve", but when visualized it became a "polygonal approximation", as it have to be translated in pixels by Coin3D.
Hope it helps.
Regards
Carlo D.
Take in account, that FreeCAD has two "engines":
- A "modeling engine" OCCT.
- A "visualization engine" Coin3D.
This could lead to some discrepancy see:
https://wiki.freecadweb.org/Scenegraph
You could tune something in the View Tab, usually you will find them set as:
Code: Select all
AngularDeflection = '28.5500 deg'
Deviation = 0.50
But with this simple example
Code: Select all
import Part
from FreeCAD import Vector
circ = Part.makeCircle(100, Vector(0,0,0))
circ1 = circ.copy()
Part.show(circ1, "circle_rough")
FreeCADGui.getDocument('test').getObject('circle_rough').AngularDeflection = '28.5 deg'
FreeCADGui.getDocument('test').getObject('circle_rough').Deviation = 0.50
circ2 = circ.copy()
Part.show(circ1, "circle_fine")
FreeCADGui.getDocument('test').getObject('circle_fine').AngularDeflection = '5.0000 deg'
FreeCADGui.getDocument('test').getObject('circle_fine').Deviation = 0.05
Note that the object is the same, as both objects are a copy of the same circle, that is stored internally as a "infinite curve", but when visualized it became a "polygonal approximation", as it have to be translated in pixels by Coin3D.
Hope it helps.
Regards
Carlo D.
GitHub page: https://github.com/onekk/freecad-doc.
- In deep articles on FreeCAD.
- Learning how to model with scripting.
- Various other stuffs.
Blog: https://okkmkblog.wordpress.com/
- In deep articles on FreeCAD.
- Learning how to model with scripting.
- Various other stuffs.
Blog: https://okkmkblog.wordpress.com/
Re: How best to cut a hole through a lofted surface such that cut hole matches a perpednicular
Can you provide the FreeCAD file?
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Re: How best to cut a hole through a lofted surface such that cut hole matches a perpednicular
I'm doing all this in python so there isn't one (the step file is the only one I generate/save in this process). I can open the step and save it as a FreeCAD file if that helps (I suspect it does not though).
Re: How best to cut a hole through a lofted surface such that cut hole matches a perpednicular
Post the script, so maybe others could investigate and make some tests.
Regards
Carlo D.
Regards
Carlo D.
GitHub page: https://github.com/onekk/freecad-doc.
- In deep articles on FreeCAD.
- Learning how to model with scripting.
- Various other stuffs.
Blog: https://okkmkblog.wordpress.com/
- In deep articles on FreeCAD.
- Learning how to model with scripting.
- Various other stuffs.
Blog: https://okkmkblog.wordpress.com/