High resolution drawings in FreeCAD

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wandererfan
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Re: High resolution drawings in FreeCAD

Post by wandererfan »

cadmar2021 wrote: Mon Dec 20, 2021 10:11 pm
"Convert geometry to B-spline" - as usual, @chrisb gives excellent advice. OCC projects the parabola in the original sketch as a spline with 15 poles and degree 1.
ribAsParabola.png
ribAsParabola.png (28.44 KiB) Viewed 1597 times
After converting the parabola to a bspline in Sketcher, the projection is a bspline with 3 poles and degree 2, giving a smoother result.
ribAsSpline.png
ribAsSpline.png (18.68 KiB) Viewed 1597 times
Unfortunately there is no mechanism to control how the projection algorithm handles a parabola.

How do you plan on cutting your ribs? Do you use something like a laser cutter?
cadmar2021
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Re: High resolution drawings in FreeCAD

Post by cadmar2021 »

wandererfan wrote: Tue Dec 21, 2021 8:22 pm How do you plan on cutting your ribs? Do you use something like a laser cutter?
Hi wandererfan, yes @chrisb gave me very useful information. This group is fantastic and the response is phenomenal. We're dealing with passionate people here... It's obvious that this topic is of interest to a number of people. After all, what's the use of a sophisticated modelling tool if you can't output precision products.
At the prototype stage, I will be cutting the ribs manually. This first involves the precision fabrication of a template made out of something like 1/8" massonite. I first glue the 1:1 scale printed drawing using epoxy. The epoxy penetrates the paper and the massonite surface and bonds them together in a solid plastic matrix. This prevents the paper edge from messing up during the fabrication process.
The template is then roughly cut near (within 1mm) the drawing outline with a jigsaw. Afterwards, using a sanding paper jig at 90 degrees to the edge of the template, I slowly sand down the edge all the way to the drawing trace while wearing magnifying goggles very close to the surface. The template edge being ground down is slightly inclined (maybe 10 degrees) relative to the horizontal to make sure that the sanding strokes are always downwards from the surface to prevent the paper from rolling back. Afterwards, I use the template as a guide to machine the ribs with a router and a bearing bit. If the drawing trace is precise enough, I can easily attain a precision of 0.05mm.

I now have 2 methods of generating the required prints thanks to all your help. Using FC and other tools such as Octave, Gimp, etc., all my design tool requirements are met.
cadmar2021
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Re: High resolution drawings in FreeCAD

Post by cadmar2021 »

Good day all,

One more question on this topic. To summarize, the best method of generating high resolution drawings is to select a sketch (or multiple sketches) in pretty well any workbench, and export to flattened svg. The resulting svg file can then be opened in a graphics app such as GIMP and imported at the required resolution since it is a vector format.

Here is the weird thing, this only works if the sketch sits on the XY plane (top). There is no way to export in svg from sketches on any other plane.
Does anybody know how to circumvent that problem?
I tried different parameters in the settings, but nothing doing.
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Roy_043
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Re: High resolution drawings in FreeCAD

Post by Roy_043 »

cadmar2021 wrote: Fri Jan 21, 2022 9:45 pm svg from sketches on any other plane
Align the view, create a Draft_Shape2DView from the sketch and export that.
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Re: High resolution drawings in FreeCAD

Post by cadmar2021 »

Thanks Roy_043, almost worked!
Unfortunately, the projection is too segmented.
In the end, I circumvented the problem by selecting the sketches I need converted to SVG and temporarily changed the support plane while I export to SVG. I then flip back the sketches to their original support plane.
The export function should be able to detect which plane the sketch is drawn on.

Thank you all!
domad
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Re: High resolution drawings in FreeCAD

Post by domad »

cadmar2021 wrote: Sat Jan 22, 2022 5:38 pm .....
Hello cadmar2021, greetings to the Community!
I am attaching a file in * .pdf format of the parabolic curve only to offer you a print on your plotter / printer and hear your evaluations.
I will explain later how it was obtained in TechDraw and then exported to * .pdf.
Attachments
Parabola.pdf
(107.48 KiB) Downloaded 31 times
cadmar2021
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Re: High resolution drawings in FreeCAD

Post by cadmar2021 »

Thanks domad, that seems to work, but does it work on sketches drawn on any plane?
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