$fn = 50;
pip_radius = 1.5;
pip_spacing = 14/3; 
difference() {
	minkowski() {
		cube(14, true);
		sphere(1);
	}
	interval = [
		-pip_spacing, 
		0, 
		pip_spacing
	];
	dim = [-8, 8];
	for (d = dim) {
		for (pi = interval) {
			for (pj = interval) {
				translate([d, pi, pj])
					sphere(pip_radius);	
				translate([pi, d, pj])
					sphere(pip_radius);	
				translate([pi, pj, d])
					sphere(pip_radius);	
			}
		}
	}
}