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Sunday, June 1, 2014

Day 279 - Pre-USAMO prints

Today we are firing up our travel Afinia H-Series to get ready for tomorrow's 3D-printing workshop at the USA Math Olympiad award ceremony at the MAA Headquarters in Washington DC. The twelve student champions will each be designing and/or printing a 3D model at the workshop. One student did his homework, learned how to use OpenSCAD in advance, and then emailed me a snowman design he made from scratch. Here is his code:

x = 8.0;

module nose() {
color("orange") scale([3, .5, .5]) sphere(5);
}

module eye() {
color("black") sphere(2.5);
}

module face() {
translate([11, 0, 0]) nose();
translate([x * 1.55, x * .5, x * .5]) eye();
translate([x * 1.55, -x * .5, x * .5]) eye();
}

module body() {
sphere(25);
translate([0, 0, 30]) {
sphere(20);
translate([0, 0, 25]) {
sphere(15);
}
}
}

module arm() {
color([.6, .3, 0, 1]) {
cylinder(20, 1.5, 1.5);
}
}

module snowman()
{
union() {
color([.7, .7, 1, 1]) body();
translate([0, 0, 55]) face();
translate([4, 16, 37.5]) rotate([-135, -45, 0]) arm();
translate([4, -16, 37.5]) rotate([135, -45, 0]) arm();
}
}

translate([0, 0, 16]) intersection() {
color([.7, .7, 1, 1]) translate([-50, -50, -16]) cube([100, 100, 90]);
snowman($fn = 100);
}

I printed this model on the Afinia today, but the arms didn't get supported (maybe they were too small to be detected by the slicing software as needing support?), so they printed as little fuzzy pom-pons instead of looking like proper sticks. I added the following to the OpenSCAD to support the arms with tall truncated cones that can be cut off later:

// add arm support poles
translate([14,-30,0]) cylinder(h=45,r1=3,r2=1);
translate([14,30,0]) cylinder(h=45,r1=3,r2=1);

And here is the result:


Settings: Printed on an Afinia H-Series with super bling Build-Tak and glass build plate. If you look closely at the back of the build plate you can see two of walter's Customizable Platform Clips from Thingiverse holding down the glass build plate. The usual binder clips were too small to fit around the glass build plate so I printed walter's customized clips with the following settings:

  • _platformGap = 7.2 
  • _wallThickness = 1.0 
  • _style = square 
  • _diameter = 2.2 
  • _length = 16

One of the things I like most about the Afinia is its opaque white ABS filament; it looks so smooth and matte, never shiny. Perfect for a snowman!  On the other hand, for something detailed like the Videogame Die all the way back from Day 12 that another of the USAMO students requested, the MakerBot Replicator 2 is the way to go:


Thingiverse link: http://www.thingiverse.com/make:80345

Settings: Printed on a MakerBot Replicator 2 with .3mm/low settings and raft, but NO supports. NOT using supports is key, because supports will fill up the designs on at least two sides of the die and be impossible to remove afterwards.

UPDATE: The student that did his homework turned out to be Joshua Brackensiek from Arizona College Prep-Erie, who got a perfect score on the USAMO this year. He also turned out to be a lovely person and it was a great pleasure meeting him and his mother at the award ceremony.