OpenJsCad/gearsdemo.html

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<!DOCTYPE html>
<html><head>
<script src="lightgl.js"></script>
<script src="csg.js"></script>
<script src="openjscad.js"></script>
<style>
body {
font: 14px/20px 'Helvetica Neue Light', HelveticaNeue-Light, 'Helvetica Neue', Helvetica, Arial, sans-serif;
max-width: 820px;
margin: 0 auto;
padding: 10px;
}
pre, code, textarea {
font: 12px/20px Monaco, monospace;
border: 1px solid #CCC;
border-radius: 3px;
background: #F9F9F9;
padding: 0 3px;
color: #555;
}
pre, textarea {
padding: 10px;
width: 100%;
}
textarea {
height: 200px;
}
textarea:focus {
outline: none;
}
canvas { cursor: move; }
</style>
<link rel="stylesheet" href="openjscad.css" type="text/css">
<script>
var gProcessor=null;
// Show all exceptions to the user:
OpenJsCad.AlertUserOfUncaughtExceptions();
function onload()
{
gProcessor = new OpenJsCad.Processor(document.getElementById("viewer"));
updateSolid();
}
function updateSolid()
{
gProcessor.setJsCad(document.getElementById('code').value);
}
</script>
<title>OpenJsCad demo: involute gears</title>
</head>
<body onload="onload()">
<h1>OpenJsCad demo: involute gears</h1>
<div id="viewer"></div>
<h2>Source code</h2>
Below is the OpenJsCad script for this demo. To build your own models, create a .jscad script
and use the <a href="processfile.html"><b>OpenJsCad parser</b></a>. For more information see the
<a href="index.html">OpenJsCad documentation</a>.
<br><br>
<textarea id="code">
// Here we define the user editable parameters:
function getParameterDefinitions() {
return [
{ name: 'numTeeth', caption: 'Number of teeth:', type: 'int', default: 10 },
{ name: 'circularPitch', caption: 'Circular pitch:', type: 'float', default: 5 },
{ name: 'pressureAngle', caption: 'Pressure angle:', type: 'float', default: 20 },
{ name: 'clearance', caption: 'Clearance:', type: 'float', default: 0 },
{ name: 'thickness', caption: 'Thickness:', type: 'float', default: 5 },
{ name: 'centerholeradius', caption: 'Radius of center hole (0 for no hole):', type: 'float', default: 2 },
];
}
// Main entry point; here we construct our solid:
function main(params)
{
var gear = involuteGear(
params.numTeeth,
params.circularPitch,
params.pressureAngle,
params.clearance,
params.thickness
);
if(params.centerholeradius > 0)
{
var centerhole = CSG.cylinder({start: [0,0,-params.thickness], end: [0,0,params.thickness], radius: params.centerholeradius, resolution: 16});
gear = gear.subtract(centerhole);
}
return gear;
}
/*
For gear terminology see:
http://www.astronomiainumbria.org/advanced_internet_files/meccanica/easyweb.easynet.co.uk/_chrish/geardata.htm
Algorithm based on:
http://www.cartertools.com/involute.html
circularPitch: The distance between adjacent teeth measured at the pitch circle
*/
function involuteGear(numTeeth, circularPitch, pressureAngle, clearance, thickness)
{
// default values:
if(arguments.length < 3) pressureAngle = 20;
if(arguments.length < 4) clearance = 0;
if(arguments.length < 4) thickness = 1;
var addendum = circularPitch / Math.PI;
var dedendum = addendum + clearance;
// radiuses of the 4 circles:
var pitchRadius = numTeeth * circularPitch / (2 * Math.PI);
var baseRadius = pitchRadius * Math.cos(Math.PI * pressureAngle / 180);
var outerRadius = pitchRadius + addendum;
var rootRadius = pitchRadius - dedendum;
var maxtanlength = Math.sqrt(outerRadius*outerRadius - baseRadius*baseRadius);
var maxangle = maxtanlength / baseRadius;
var tl_at_pitchcircle = Math.sqrt(pitchRadius*pitchRadius - baseRadius*baseRadius);
var angle_at_pitchcircle = tl_at_pitchcircle / baseRadius;
var diffangle = angle_at_pitchcircle - Math.atan(angle_at_pitchcircle);
var angularToothWidthAtBase = Math.PI / numTeeth + 2*diffangle;
// build a single 2d tooth in the 'points' array:
var resolution = 5;
var points = [new CSG.Vector2D(0,0)];
for(var i = 0; i <= resolution; i++)
{
// first side of the tooth:
var angle = maxangle * i / resolution;
var tanlength = angle * baseRadius;
var radvector = CSG.Vector2D.fromAngle(angle);
var tanvector = radvector.normal();
var p = radvector.times(baseRadius).plus(tanvector.times(tanlength));
points[i+1] = p;
// opposite side of the tooth:
radvector = CSG.Vector2D.fromAngle(angularToothWidthAtBase - angle);
tanvector = radvector.normal().negated();
p = radvector.times(baseRadius).plus(tanvector.times(tanlength));
points[2 * resolution + 2 - i] = p;
}
// create the polygon and extrude into 3D:
var tooth3d = new CSG.Polygon2D(points).extrude({offset: [0, 0, thickness]});
var allteeth = new CSG();
for(var i = 0; i < numTeeth; i++)
{
var angle = i*360/numTeeth;
var rotatedtooth = tooth3d.rotateZ(angle);
allteeth = allteeth.unionForNonIntersecting(rotatedtooth);
}
// build the root circle:
points = [];
var toothAngle = 2 * Math.PI / numTeeth;
var toothCenterAngle = 0.5 * angularToothWidthAtBase;
for(var i = 0; i < numTeeth; i++)
{
var angle = toothCenterAngle + i * toothAngle;
var p = CSG.Vector2D.fromAngle(angle).times(rootRadius);
points.push(p);
}
// create the polygon and extrude into 3D:
var rootcircle = new CSG.Polygon2D(points).extrude({offset: [0, 0, thickness]});
var result = rootcircle.union(allteeth);
// center at origin:
result = result.translate([0, 0, -thickness/2]);
return result;
}
</textarea><br>
<input type="submit" value="Update" onclick="updateSolid(); return false;">
<br><br>
</body>
</html>