Glossary
Every term here is used with exactly this meaning throughout the course. Where CAD packages disagree on a word, the Onshape sense is the one given.
Modelling
- Parametric CADtaught here
- A modelling approach where the file stores the ordered operations that build the shape, plus the numbers driving them. Editing a number replays the operations and rebuilds the part.
- Featuretaught here
- One operation in that list — an extrude, a revolve, a fillet, a variable. Features are editable after the fact and execute in order.
- Feature tree / historytaught here
- The ordered list of features. It is the program that produces the part, and reading it top to bottom should describe how the part is made.
- Part Studiotaught here
- Onshape name for the modelling environment. One Part Studio can contain several parts that share a coordinate system and variables — the right place to model things that must fit each other.
- Sketchtaught here
- Flat 2D geometry on a plane or face, used as the profile for a 3D feature.
- Meshtaught here
- A shape stored as a set of triangles, with no record of how it was designed. STL files are meshes; they are an output, never a source of truth.
Sketching
- Degree of freedomtaught here
- An unknown the sketch solver has not yet been told. Each sketch point carries two — an x and a y. A line segment starts with four.
- Constrainttaught here
- A geometric rule between sketch entities: coincident, horizontal, tangent, equal, concentric, symmetric. Removes degrees of freedom without naming a number.
- Dimensiontaught here
- A numeric value applied to sketch geometry. Also removes degrees of freedom — the difference from a constraint is that it fixes a size rather than a relationship.
- Fully definedtaught here
- Zero degrees of freedom remaining. The sketch has exactly one possible shape and nothing in it can be dragged. Onshape draws it black rather than blue.
- Over-definedtaught here
- More constraints and dimensions than the geometry has freedom for, usually because the same fact was stated twice or two facts conflict.
- Origin / datumtaught here
- The permanent point and three planes every document starts with. The most durable thing to anchor geometry to, because no edit can delete them.
Features
- Extrudetaught here
- Push a flat profile along a straight line to make or remove material. The default verb of solid modelling.
- Revolvetaught here
- Spin a profile around an axis to make anything round.
- Boolean operationtaught here
- What a feature does with its result: new part, add to an existing one, remove from it, or keep only the intersection.
- Fillettaught here
- A rounded edge, applied as a feature. Structural in loaded inside corners; an overhang problem on downward-facing edges.
- Chamfertaught here
- An angled cut edge. Self-supporting when printed, which is why it is the right choice on any edge facing the build plate.
- Through alltaught here
- A depth option meaning "as far as there is material", rather than a typed number. Keeps a hole a hole when the part gets thicker.
Intent and parameters
- Design intenttaught here
- The relationships a model encodes about what must stay true — which dimensions move together, what each feature is measured from. Lives in your references and constraints, not in comments.
- Variabletaught here
- A named value usable in any dimension field, written #name in Onshape. Turns a repeated number into a single stated fact about the design.
- Configurationtaught here
- A mechanism for generating variants of one model — sizes, options — without duplicating the Part Studio.
- Fragile referencetaught here
- A dependency on a face or edge that a later edit can rename or destroy, causing downstream features to fail. The usual cause of a red feature tree.
Printing
- FDM / FFFtaught here
- Fused deposition modelling — the layer-by-layer molten filament process almost every desktop printer uses. Every design rule in this course follows from it.
- Overhangtaught here
- A surface leaning out over nothing, measured as an angle from vertical. Beyond roughly 45° it needs support.
- Bridgetaught here
- A flat span printed across open air between two supported ends. Clean under about 5 mm; sagging beyond that.
- Anisotropytaught here
- The fact that a printed part is weaker between layers than within them. The reason print orientation is a design decision.
- Elephant's foottaught here
- The bulge at the bottom of a print where the squashed first layers spread. A small chamfer on the bottom edges makes it irrelevant.
- Extrusion widthtaught here
- How wide a bead of plastic the nozzle lays down — close to, but not identical to, the nozzle diameter. Walls should be whole multiples of it.
- Tolerancetaught here
- How much a dimension is permitted to vary from nominal. A property of the process, not something you choose.
- Clearancetaught here
- The gap deliberately designed between two mating parts, quoted per side. A diameter needs twice the per-side value.
- Press / slip / free fittaught here
- Assembles with force and stays; assembles by hand and holds; moves freely. Roughly increasing clearance, with the actual values measured from your own printer.