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Mass properties

The mass, volume, surface area, centre of mass and moments of inertia of the parts you select, or of the whole design, as Onshape and SOLIDWORKS report them.

  • Mass properties AdvancedPart Studio toolbar, at the right
What other CAD programs call it
SchoolCADOnshapeFusionSOLIDWORKS
Mass propertiesMass propertiesPropertiesMass Properties

Mass properties tells you how heavy a part is and where its weight sits: its mass, volume and surface area, its centre of mass, and its moments of inertia (how hard it is to spin round each axis). It works like Mass properties in Onshape and Mass Properties in SOLIDWORKS (Evaluate tab), with the same names and units, so the numbers mean the same thing when you move on to them.

Mass properties is in the Advanced tool set, in the Measure ▾ menu on the toolbar. In Standard, find it with Search tools (` or Alt+C).

How to use it#

  1. Choose each part's material first (right-click the part in the Parts list): the mass comes from the material's density.
  2. Click Mass properties. With nothing selected, it shows the whole design.
  3. Click a part to see only that part, or Shift-click several parts to add them up.
  4. The centre of mass is marked on the model with the black and white symbol used on engineering drawings.
  5. Click Copy values to paste the numbers into your folio.

What it shows#

ValueWhat it means
MassHow heavy it is, in grams or kilograms, from the volume and the material's density.
VolumeHow much material, in cm³.
Surface areaThe area of every face added up, in cm²: how much there is to paint, oil or sand.
Centre of massThe point where the weight balances, in mm from the origin (X, Y, Z).
Lxx, Lyy, LzzThe moments of inertia about lines through the centre of mass, along X, Y and Z, in g·mm² (SOLIDWORKS' units). A bigger number is harder to start or stop spinning.
Px, Py, PzThe principal moments: the smallest and largest moments of inertia, whichever way the part is turned.

Tips#

  • To check whether a design tips over, use Measure: it shows how far it can tilt before it falls.
  • A part with no material is weighed as water (1000 kg/m³), and the panel says so.
  • Curved faces are made of many small flat ones, so the numbers can be a little different from Onshape's or SOLIDWORKS' exact ones (usually less than 1%).