funnel.js

var extrude = require('extrude-by-path')
var matScale = require('gl-mat4/scale')
var toStl = require('serialize-stl')

function createCirclePath (r, fn) {
  var circle = []
  for (var i = 0; i <= fn; i++) {
    var theta = Math.PI*2/fn*i
    circle.push([r * Math.cos(theta), r * Math.sin(theta), 0, theta + 0.15])
  }
  return circle
}

function createFunnel (opts) {
  opts = opts || {}
  var fn = opts.resolution || 40
  var bh = opts.bellHeight || 6
  var slope = opts.slope || 0.7
  var sl = opts.spoutLength || 2
  var r = opts.radius || 5.5
  var t = opts.thickness || 0.3
  return extrude({
    positions: [
      [0,0],[-slope*bh,bh],[-slope*bh,bh+sl],
      [-slope*bh-t,bh+sl],[-slope*bh-t,bh-t],[-t,0]
    ],
    edges: [[0,1],[1,2],[2,3],[3,4],[4,5],[5,0]],
    path: createCirclePath(r, fn),
    closed: true,
    caps: false
  })
}

function scale (mesh, vec) {
  for (let vert of mesh.positions) {
    matScale(vert, vert, vec)
  }
  return mesh
}

var mesh = createFunnel()
scale(mesh, [ 5, 5, 5 ])
var stl = toStl(mesh.cells, mesh.positions)
process.stdout.write(stl)