Very small radius - manufacturing / visualization?

[-andrew-]

Hi all,

 

I am creating some parts for 3d printing.

 

One is basically an 8 inch diameter plastic disk, extruded about 1/4 inch.

 

I have no idea, in manufacturing terms, what happens at the edges when manufactured. It looks realistic if I create, for example a 1/100 radius on the whole thing.

 

But... I know that creates a lot of geometry, probably solely for the purpose of visualization.

 

So:

 

1) Do I have to actually model the edges with the tiny radii to get it to look realistic in renders?

 

2) If not... what's the best practice for simulating this?

 

Thanks,

Andrew

[setz]

Hi Andrew,

 

Depends on the resolution of the printer.  FDM (ABS,PLA) will give every corner a 1/100" radius, desired or not, so no small radiuses required in the model.   In addition, FDM models almost always require sanding or coating, and edges will be knocked down even more during the finishing of the part.

 

UV solidified resin printers like Objet's or Form Labs' will be 4-5X more finely resolved and will clearly show hard edges or low res facetting.  Models for these types of printers require more accurate radiuses and much higher resolutions in the conversion to STL or OBJ, similar to rendered images which, as you point out, also require high definition and small details including very small edge rounds to look realistic.

 

In my work I keep a low-res, unrounded version for drawings and hidden line renders and a high-res fully rounded version for printing and rendering.

[-andrew-]

Thanks!

[etroxel]

Setz is right on. I've 3d printed with an Objet and a Makerbot Replicator II. The Objet will print sharp edges, and sanding is not required on resin models so they will stay sharp (and "sharp" is a relative term—they aren't knife sharp). It wouldn't be necessary to bevel or round your edges for printing on the Makerbot. If you want knocked down edges in the final model, do a test print on the machine you're going to use in the end so you can determine this before doing your real objects.