Gas station without pumps

2019 July 7

3D slug printing

Filed under: Uncategorized — gasstationwithoutpumps @ 14:39
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I used my Monoprice Delta Mini 3D printer again yesterday, after a long break since the last usage.  My wife wanted a banana-slug charm to hang on her new mustard-yellow purse—she liked the color and size of the 3D-printed slug I had bought her from the UCSC IEEE chapter, but it did not have any easy way to attach it to the purse.

I found the design on Thingiverse by  scanlime, and checked the licensing (CC by 3.0), which only requires attribution, even for commercial uses.

I wanted to add a ring to the slug, so that it could be attached to a keyring.  Unfortunately, the design is only available as an STL file, and I’ve been using OpenSCAD, and I forgot that OpenSCAD has an import option for importing STL files, so I did a crude hack instead:  I made a ring in OpenSCAD, exported it as STL, then placed it in Cura overlapping the slug STL file.  When I sliced the models, the two files were merged producing a single gcode file, that printed as a single object. I think I want to see if I can also use the “include” command and get a properly merged STL file that I can post to Thingiverse.

I printed the model with 0.1mm resolution (finer than the resolution used for the IEEE printing, but I was not trying to produce slugs in sufficient quantity to sell them, so a slower printing to get a smoother surface was fine for me).

The gold slug is the one I bought from the IEEE student chapter, and the green one is the one I printed with the added ring.

The green color is obviously not suitable for banana slugs, but I’ve ordered some gold filament to print the slug properly.

One interesting side effect of slicing two overlapping models is that the exterior wall of each model was preserved, so that there were interior lines in the finished slicing corresponding to the original exterior walls.  This is an interesting, if somewhat awkward, way to get Cura to create specific interior structure, in addition to the generic interior fill patterns that it uses.

I have ordered two different gold filaments: Hatchbox Gold, which is what the IEEE slug was printed with, and CC3D Silk Gold, which should be shinier.  I’ve also ordered some hardware for attaching the slug to the purse (split rings and lobster hook).  I’ll have enough filament to do hundreds of slugs, since it only weighs 6.51g (not that I plan to make more than a handful—one in each color for my wife, and maybe another one for my backpack). The extra shiny gold filament can be used to make costume jewelry for WEST Performing Arts perhaps.  The filament costs a little over 1¢/gram, so the only real cost is the design and printing time.

Incidentally, the photographs were taken using another recent acquisition: a large Shibusa Photo Studio in a Bag, which I got from American Science and Surplus.  I think that the reason they were marked down is that the sides are so warped that they unsnap under the weight of the top.  I managed to make the thing work by using binder clips to insert some MDF pieces to stiffen the sides.  I think that I want to cut a couple of permanent MDF pieces that are exactly the right size and shape to support the top cleanly.  It would probably be best to use a laser cutter, but I’ll probably just use my scroll saw.

UPDATE 2019 July 7: I released the model as

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