Archive for September 9th, 2013

Makergear M2: Bridge Torture Test

Although I’ve pretty much given up on torture tests, I saw a note about the troubles someone had with Triffid Hunter’s Bridge Torture Test object. I did a bit of tweaking to the OpenSCAD source to shorten the struts and add the pads (which could be done with Slic3r’s Brim settings), but it’s otherwise about the same. The clear span is about 50 mm:

Bridge Torture Test - solid model

Bridge Torture Test – solid model

Using my usual settings, with no special setup, the front looked OK:

Bridge torture test - overview

Bridge torture test – overview

One strand came out rather droopy:

Bridge torture test - front

Bridge torture test – front

The bottom layer of the bridge isn’t as consolidated as it could be:

Bridge torture test - bottom

Bridge torture test – bottom

The overall speed dropped considerably as the Cool setting limited the layer time to 20 seconds; the Bridge settings didn’t apply.

I could probably tighten the bottom strands a bit, but it’s OK for a first pass.

The OpenSCAD source code:

bridge_length = 50;
bridge_angle = 0;
bridge_width = 5;

strut_height = 4;

layer_height = 0.25;
extrusion_width = 0.5;

bridge_recovery_layers = 2 / layer_height;

module foot() {
	rotate([0, 0, 180/4]) cylinder(r=bridge_width * 2, h=layer_height, $fn=4);
}

module strut() {
	rotate([0, 0, 180/4])
	difference() {
		cylinder(r1=bridge_width / 1.5 / cos(45), r2=bridge_width / 2 / cos(45),
			h=strut_height, $fn=4);
		translate([0, 0, -1]) cylinder(r1=(bridge_width / 1.5 - extrusion_width * 2) / cos(45),
			r2=(bridge_width / 2 - extrusion_width * 2) / cos(45), h=10, $fn=4);
	}
}

translate([-bridge_length/2,0,0])
rotate(bridge_angle) {
	translate([00, 0, 0]) foot();
	translate([bridge_length + bridge_width, 0, 0]) foot();

	translate([00, 0, 0]) strut();
	translate([bridge_length + bridge_width, 0, 0]) strut();

	translate([bridge_width / -2, bridge_width / -2, strut_height]) cube([bridge_length + bridge_width * 2, bridge_width, layer_height * bridge_recovery_layers]);

	translate([bridge_length / 2 + bridge_width / 2, 0, strut_height + layer_height * bridge_recovery_layers])
	difference() {
		cylinder(r=bridge_width / 2, h=1, $fn=32);
		cylinder(r=bridge_width / 2 - extrusion_width, h=1.01, $fn=32);
	}
}

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