Better description of $fa, $fs and $fn and the relationship with printing resolution. [$15]

[ivoknutsel]

The documentation describes $fa, $fs and $fn from an angular and OpenSCAD internal viewpoint.

I'd like to know how to optimize $fa, $fs and $fn for printing in an optimal resolution as described by 3D printhouses like Ponoko and Shapeways.

OpenSCAD (thankfully) doesn't use explicit units (mm or inches) but it would be nice if the description says something about that as well.

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There is a $15 open bounty on this issue. Add to the bounty at Bountysource.

[nophead]

You can convert $fa and $fs to $fn. I.e. the number of sides the circle
has. The error due to faceting is then r * (1 - cos(pi/$fn)).

On 31 May 2013 09:12, ivoknutsel notifications@github.com wrote:

The documentation describes $fa, $fs and $fn from an angular and OpenSCAD
internal viewpoint.

I'd like to know how to optimize $fa, $fs and $fn for printing in an
optimal resolution as described by 3D printhouses like Ponoko and Shapeways.

OpenSCAD (thankfully) doesn't use explicit units (mm or inches) but it
would be nice if the description says something about that as well.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/378
.

[ivoknutsel]

I'd like to have a better description of the optimal usage of $fa, $fs and $fn in preparing models for SLS printing by Shapeways, Ponoko etc and FDM printing on Ultimakers and Makerbots etc.

[torwag]

Hi,

there was a discussion on this mailing list with a similar request. More or
less a feature request to render an object like it would come out of a
certain 3D printer model.
You can make things even more difficult if you take into account that
certain printing technologies have different resolution for x, y and z
directions. Furthermore, one could take the minimum feature size into
account.
All this is unfortunately, not trivial and hence nobody came up with a
solution.

Well, one suggestion was that the printer is part of the CAM process and
OpenSCAD as CAD-tool should not take care of it at all. That is,
draw/design as accurate as it can be and do not take care of any
fabrication requirements. It should be the sole responsible of the
designer to take care of it.
I tend to agree with that, but have two points which let me wish for
something within OpenSCAD:

1. I know that other tools, e.g. PCB design software have DRC (Desgin rule
   checks) to point towards possible glitches which a designer might have not
   notice otherwise. Minimum distances for example or (in case of 3D printing)
   possible unwanted unions (or the lack of it) due to feature size and given
   distances, etc.
2. As in my case and in yours, CAD and CAM are physically separated (in my
   case across the building, in yours maybe across some continents ;) ). Thus,
   there is a urgent need to check the design within OpenSCAD itself. I
   believe for the same reasons other software tools have DRC checks in place,
   allowing to check against manufacture given rules.

Hence, I would like to see a feature in OpenScad which allows me to define
certain design rule checks and once started, points me to certain
problematic regions which do not fulfil those checks.

As for now I work mostly with $fs, and set it rather small during design
(until the rendering of an increasing complex design gets to slow). Finally
I set $fs to the printers feature size to get a first idea how it might
look and do a bit tweaking here and there.

All the best

Torsten

On 21 July 2013 10:05, ivoknutsel notifications@github.com wrote:

I'd like to have a better description of the optimal usage of $fa, $fs and
$fn in preparing models for SLS printing by Shapeways, Ponoko etc and FDM
printing on Ultimakers and Makerbots etc.

—
Reply to this email directly or view it on GitHubhttps://github.com//issues/378#issuecomment-21306661
.

[ivoknutsel]

DRC is a nice way of looking at the issue, it actually works well in Eagle. I'm not sure if DRC should be part of the CAD tool or part of the CAM tool.

On the short term i'd like to have better documentation of the settings with some examples and rule-of -thumb's. This is an ungrateful job so i'm trying to set a small bounty on the issue (if bountysource would stop borking).

In the longer term I'd like to be able to code my own checks in OpenSCAD, things like echo-ing the surface and volume of an objects, the number of distinct objects in the file and maybe clearances between objects.

The Shapeways founding office is actually only some 70 km from here. Plan you order just right and you can pick it up on one of the tour-the-factory days.

[ccverg]

@ivoknutsel Bountysource should be all good now :)

[gustavorps]

Bountysource decided to update their Terms of Service:

2.13 Bounty Time-Out.
If no Solution is accepted within two years after a Bounty is posted, then the Bounty will be withdrawn and the amount posted for the Bounty will be retained by Bountysource. For Bounties posted before June 30, 2018, the Backer may redeploy their Bounty to a new Issue by contacting support@bountysource.com before July 1, 2020. If the Backer does not redeploy their Bounty by the deadline, the Bounty will be withdrawn and the amount posted for the Bounty will be retained by Bountysource.

https://www.bountysource.com/issues/378317-better-description-of-fa-fs-and-fn-and-the-relationship-with-printing-resolution

[t-paul]

They retracted that already. We still need to watch what happens and maybe discuss a way out. But right now the risk for losing the existing bounties in 2 weeks is gone.

https://twitter.com/Bountysource/status/1273406549252177920