SOLIDWORKS Bridge

{
 "id": "cswa-10-community-mirrored-block",
 "title": "Community: a stepped block - one quarter, mirrored about Front Plane (features) and Right Plane (bodies); a boss mirrored about an offset plane",
 "source": "community: built for the bridge's benchmark (no exam publishes it); the key is derived analytically in `derivation`",
 "official": false,
 "units": "MMGS",
 "origin": "symmetric about Front Plane (z = 0) and Right Plane (x = 0), standing on Top Plane (y = 0)",
 "material": {
  "name": "AISI 1020",
  "densityKgM3": 7900
 },
 "expected": {
  "massG": 722.912919,
  "volumeMm3": 91507.964474,
  "centerOfMassMm": [
   -0.082395,
   16.02733,
   0.0
  ],
  "tolerancePct": 0.1
 },
 "keyBasis": "derived analytically (derivation): four copies of the quarter profile (steps 60 x 10, 40 x 15, 20 x 15; area 1500 mm\u00b2, centroid y 15.5) 15 deep, and two \u00d88 x 15 bosses on the top face at x = -15 and (mirrored about x = -5) x = +5. Exact: held to 0.1 %",
 "exercises": [
  "mirror.features.plane",
  "mirror.bodies.plane",
  "mirror.features.offset",
  "sketch.line",
  "sketch.face.top.positive"
 ],
 "derivation": [
  [
   "A_q",
   "60*10 + 40*15 + 20*15"
  ],
  [
   "Ybar_q",
   "(60*10*5 + 40*15*17.5 + 20*15*32.5)/A_q"
  ],
  [
   "V_block",
   "4*A_q*15"
  ],
  [
   "V_boss",
   "pi*4**2*15"
  ],
  [
   "volumeMm3",
   "V_block + 2*V_boss"
  ],
  [
   "massG",
   "volumeMm3*7.9e-3"
  ],
  [
   "centerOfMassMm",
   "[V_boss*(-15 + 5)/volumeMm3, (V_block*Ybar_q + 2*V_boss*(40 + 15/2))/volumeMm3, 0.0]"
  ]
 ],
 "needsOps": [],
 "script": [
  {
   "op": "new_part"
  },
  {
   "op": "sketch",
   "plane": "Front Plane",
   "entities": [
    {
     "polyline": {
      "points": [
       [
        0,
        0
       ],
       [
        60,
        0
       ],
       [
        60,
        10
       ],
       [
        40,
        10
       ],
       [
        40,
        25
       ],
       [
        20,
        25
       ],
       [
        20,
        40
       ],
       [
        0,
        40
       ]
      ],
      "close": true
     }
    }
   ]
  },
  {
   "op": "extrude",
   "depthMm": 15
  },
  {
   "op": "mirror",
   "features": "last",
   "plane": "Front Plane"
  },
  {
   "op": "mirror",
   "features": "all",
   "plane": "Right Plane"
  },
  {
   "op": "sketch_circle",
   "face": {
    "atPointMm": [
     0,
     40,
     0
    ]
   },
   "centerMm": [
    -15,
    0
   ],
   "radiusMm": 4
  },
  {
   "op": "extrude",
   "depthMm": 15
  },
  {
   "op": "mirror",
   "features": "last",
   "plane": {
    "offsetFrom": "Right Plane",
    "offsetMm": -5
   }
  },
  {
   "op": "set_material",
   "name": "AISI 1020",
   "densityKgM3": 7900
  }
 ]
}