Sunday, January 3, 2010

There's a Skeinforge Setting for That...

I'll share a couple bits of wisdom from trying to do a 3d print of a HO scale model building. (BTW, the prettier pictures are here.)

Keith's Electronics Blog reminded me that if there's a printing problem, there's usually a Skeinforge setting to fix it. The picture shows the front face for the store. I've inset this behind my nice arches, so I didn't think it would be as visible as the main building facade. So, I tried seeing whether I could print an adequate building part without spending a couple hours on gesso, spackle, or other fillers.

The top blank shows the initial attempt. Note the diagonal striping from the fill, and also note that it has a strong washboard texture. This doesn't look so hot (even from a distance), and if I was seriously building this model, I'd be scratchbuilding the building face from plastic strip.

The diagonal stripes are the worst part, but I remembered that Skeinforge has a setting to specify the fill pattern - the angle of the initial fill lines, and the amount to rotate the fill on each layer. Making the stripes either vertical or horizontal would help make the piece look more realistic, because then it might be passed off as the outlines of wood. I tried changing the initial fill angle to 0 (then to 90 degrees when I realized the stripes came out horizontally.) The vertical strips look better; they might be wood detail, but the curves at the end of each fill pass spoil the illusion.

On the third one, I made two changes: first, Keith's blog suggested playing with the Carve setting's "Extrusion Width over Thickness". This controls the thickness of each layer, and determines how much the stream of plastic get squished into place. By changing this value from 1.9 to 1.5, the occasional gaps between the extruded plastic disappears, and the surface starts looking more like a flat surface with board texture. Second, I added some "trim pieces" to the top and bottom to cover where the fill path curved back. This final piece looks much more realistic (except that the "trim" over the window has a gap because it's 4.5 extrusions wide; reducing that size a bit would get rid of that gap.

The third building face still isn't suitable for close-up viewing, but it looks decent at a distance and in shadow. With this print, I'm starting to believe I could use the Makerbot to build HO buildings.

Friday, January 1, 2010

Now it's getting hard to figure out where to put the entries. The post had more on the model, so check my railroad blog for details on printing a model of a 1920's drive-in market, and more photos of my progress.