OpenSCAD创建螺旋形结构物体
OpenSCAD不仅可以快速创建立方体、圆锥体、球体、椭球体、多边形体等，还可以通过编程、循环等特性来创建螺旋体，如常见的螺栓、螺孔等，如下图所示：
下面给出建模的代码：
module screw(type = 2, r1 = 15, r2 = 20, n = 7, h = 100, t = 8)
{
linear_extrude(height = h, twist = 360*t/n, convexity = t)
difference() {
circle(r2);
for (i = [0:n-1]) {
if (type == 1) rotate(i*360/n) polygon([
[ 2*r2, 0 ],
[ r2, 0 ],
[ r1*cos(180/n), r1*sin(180/n) ],
[ r2*cos(360/n), r2*sin(360/n) ],
[ 2*r2*cos(360/n), 2*r2*sin(360/n) ],
]);
if (type == 2) rotate(i*360/n) polygon([
[ 2*r2, 0 ],
[ r2, 0 ],
[ r1*cos(90/n), r1*sin(90/n) ],
[ r1*cos(180/n), r1*sin(180/n) ],
[ r2*cos(270/n), r2*sin(270/n) ],
[ 2*r2*cos(270/n), 2*r2*sin(270/n) ],
]);
}
}
}
module nut(type = 2, r1 = 16, r2 = 21, r3 = 30, s = 6, n = 7, h = 100/5, t = 8/5)
{
difference() {
cylinder($fn = s, r = r3, h = h);
translate([ 0, 0, -h/2 ]) screw(type, r1, r2, n, h*2, t*2);
}
}
module spring(r1 = 100, r2 = 10, h = 100, hr = 12)
{
stepsize = 1/16;
module segment(i1, i2) {
alpha1 = i1 * 360*r2/hr;
alpha2 = i2 * 360*r2/hr;
len1 = sin(acos(i1*2-1))*r2;
len2 = sin(acos(i2*2-1))*r2;
if (len1 < 0.01)
polygon([
[ cos(alpha1)*r1, sin(alpha1)*r1 ],
[ cos(alpha2)*(r1-len2), sin(alpha2)*(r1-len2) ],
[ cos(alpha2)*(r1+len2), sin(alpha2)*(r1+len2) ]
]);
if (len2 < 0.01)
polygon([
[ cos(alpha1)*(r1+len1), sin(alpha1)*(r1+len1) ],
[ cos(alpha1)*(r1-len1), sin(alpha1)*(r1-len1) ],
[ cos(alpha2)*r1, sin(alpha2)*r1 ],
]);
if (len1 >= 0.01 && len2 >= 0.01)
polygon([
[ cos(alpha1)*(r1+len1), sin(alpha1)*(r1+len1) ],
[ cos(alpha1)*(r1-len1), sin(alpha1)*(r1-len1) ],
[ cos(alpha2)*(r1-len2), sin(alpha2)*(r1-len2) ],
[ cos(alpha2)*(r1+len2), sin(alpha2)*(r1+len2) ]
]);
}
linear_extrude(height = 100, twist = 180*h/hr,
$fn = (hr/r2)/stepsize, convexity = 5) {
for (i = [ stepsize : stepsize : 1+stepsize/2 ])
segment(i-stepsize, min(i, 1));
}
}
translate([ -30, 0, 0 ])
screw();
translate([ 30, 0, 0 ])
nut();
spring();
上面的几何体生成代码使用了module来进行几何对象的封装，这是新的OpenSCAD非常有用的一个特征。可以把零部件定义为一个Module，然后在使用时重复引用即可，非常便于创建具有大量的规则几何形状的物体。