About radii and sizing

Hi,

I have a question relating to shapes within OpenSCAD defined by radii and rendering with respect to the 3D printer nozzle.

If I specify a cylinder with radius 5.0mm, is that radius point placed at the centre of the printer nozzle?

Would this mean that a cylinder representing the interior of an object will actually print with a size of (2 * radius) - line width. Which for my aforementioned example would be (2 * 5.0mm) - 0.5mm = 9.5mm (for a 0.5mm line width)?

Regards,
Neil Darlow

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I try to write with consideration for all nationalities. Please let me know if something is unclear.
Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.

Depends on your slicer, and whether you're creating a 10mm diameter "rod" or 10mm diameter "hole".

Slic3r is notoriously bad at making internal holes the right size (for me anyway) but external dimensions do tend to be correct.

Apparently Skeinforge doesn't suffer from this but I haven't tried it yet - I've chosen so far to adjust my hole clearance sizes accordingly to compensate.

Slicers inset the outlines and outset the inlines by half the filament width. What they tend to get wrong is the flow rate of outlines has to be less than infill to get them the same width.

Holes also come out undersized for reasons I explain here: [hydraraptor.blogspot.co.uk]

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[www.hydraraptor.blogspot.com]