Design glossary
Plain definitions of the CAD, mechanical, and manufacturing terms used in the Design handbook.
Look up unfamiliar terms here as you work through the lessons. The linked guides show the term in a complete example.
CAD
| Term | Meaning |
|---|---|
| CAD | Computer-aided design: software for accurate drawings and models |
| Document | An Onshape project that holds your tabs and design history and can be shared with teammates |
| Part Studio | A tab in which sketches and features define one or more parts |
| Sketch | Geometry drawn on a plane or other supported reference |
| Origin | The fixed reference point where the model's axes meet |
| Plane | A flat reference surface |
| Constraint | A relationship such as parallel, equal, or coincident |
| Dimension | A value that controls or reports a size, angle, or distance |
| Construction geometry | Lines or curves used to line things up, without becoming edges of the shape you extrude |
| Feature | A modeling operation, such as Extrude, Hole, or Fillet |
| Extrude | Extend a flat region into a solid, or use it to add or remove material |
| Revolve | Turn a profile around an axis to create or modify geometry |
| Fillet | A rounded transition between faces or edges |
| Chamfer | A bevel that replaces an edge |
| Pattern | Repeated geometry or features arranged by a rule |
| Mirror | Reflected geometry about a line or plane |
| Parameter | An input controlling the model, such as depth or diameter |
| Variable | A named value used in dimensions or other expressions |
| Configuration | A selectable variant of one model |
| Derived | A feature that brings reference geometry from another Part Studio or document |
| Suppress | Temporarily turn off a feature or exclude a part instance from an assembly without deleting it |
| Rollback | Temporarily return the feature list to an earlier point for inspection or editing |
| FeatureScript | Onshape's language for defining custom CAD features |
Start with Onshape, Sketches, and Modeling features.
Assemblies
| Term | Meaning |
|---|---|
| Part | One modeled solid object |
| Instance | One use of a part or subassembly in an Assembly |
| Subassembly | An assembly used inside another assembly |
| Mate | A relationship defining permitted movement between instances |
| Mate connector | A reference point and axis directions used to place and connect parts |
| Degree of freedom | An independent way a part can move |
| Translation | Movement without rotation |
| Fastened mate | A mate that permits no relative movement |
| Revolute mate | Lets two parts turn relative to each other about one shared axis |
| Slider mate | Lets a part slide along one axis without turning |
| Interference | Overlapping solid geometry between parts |
| Pose | Where something is and which way it faces |
| Envelope | The space reserved for a component, object, or movement |
| Datum | A reference face, axis, point, or plane used to locate geometry |
| BOM | Bill of materials: a list of parts and quantities |
Use Assemblies and Moving assemblies to practice these relationships.
Mechanics
| Term | Meaning |
|---|---|
| Force | A push or pull, measured in newtons |
| Torque | A force's turning effect about an axis, measured in newton-meters |
| Center of mass | The point used to represent an object's mass distribution for many calculations |
| Stiffness | Resistance to deflection under load |
| Strength | How much load a part can take before permanent bending, cracking, or another kind of failure |
| Load path | The route by which forces pass through a structure |
| Radial | Perpendicular to an axis |
| Axial | Along an axis |
| Shaft | A component that commonly transmits rotation and torque |
| Live axle | An arrangement in which the shaft turns with the driven mechanism |
| Dead axle | An arrangement in which the axle stays fixed and the mechanism rotates around it |
| Bearing race | An inner or outer ring that the bearing’s balls or rollers run against |
| Retention | Features or hardware that keep a part from sliding or falling out of place |
| Reduction | A transmission ratio that lowers output speed and increases ideal torque |
| Pitch | A repeating spacing; its exact meaning depends on teeth, chain links, or screw threads |
| Module | A metric measure of gear tooth size |
| Backlash | Clearance between mating transmission features that allows some lost motion on reversal |
| Stroke | The usable travel of a linear mechanism |
| Rigging | The route and attachment of a lift's cable, belt, or chain |
| Coupler | A link joining other moving links, or a component connecting shafts, depending on context |
Use Forces and motion, Transmission layouts, and Slides and lifts.
Making parts
| Term | Meaning |
|---|---|
| Nominal dimension | The stated target size |
| Tolerance | Permitted variation from a stated dimension |
| Clearance | Space between mating features |
| Interference fit | A fit in which mating size ranges deliberately overlap |
| Kerf | The width removed by a cutting process |
| CNC | Computer numerical control of a machine's movement |
| Counterbore | A larger cylindrical recess around a hole |
| Countersink | A conical recess around a hole |
| Tapped hole | A hole containing an internal screw thread |
| Grip | The stack clamped between a fastener's head and nut or threaded component |
| Preload | Tension established in a fastener by tightening |
| Creep | Gradual deformation under sustained load |
| Perimeter | An outer wall path in a filament print |
| Infill | The internal pattern of a print |
| Support | Temporary printing material beneath geometry that needs it |
| STEP | A common exchange format for CAD geometry |
| DXF | A drawing exchange format often used for flat cutting profiles |
| STL | A triangular surface mesh commonly used for printing |
| CSV | A plain-text table format, useful for exporting a BOM |
| Version | A named point saved in an Onshape document’s history |
| Revision | A name or number that identifies a design change or an approved set of parts and files |
Use Tolerances and fit, Fastened joints, and Drawings and exports.