Spatial Visualization and Onshape CAD Fundamentals

Comprehensive vocabulary flashcards covering spatial visualization concepts (isometric sketches, coded plans, orthographic projections, 3D rotations, reflections) and Onshape CAD techniques (sketch constraints, loop closures, extrusions, dimension types, and drawing standards).

Isometric Sketches

Sketches made as if viewing down the diagonal of a cube, where hidden features and individual cubes are not outlined.

Isometric Axes

The coordinate axes used in isometric sketching, which are all separated by exactly $120^\text{ degrees}$.

Coded Plans

Plan view drawings where the numbers define the height of the building at that specific location.

Isometric Sketch Construction

The sketching process that begins by drawing the corner of the object nearest to you.

Orthographic Drawings

Two-dimensional engineering drawings where squares appear undistorted as squares, typically presenting standard views of an object.

Hidden Lines

Lines represented as dashed lines in orthographic drawings to display interior or obscured features.

Inclined Surfaces

Slanted surfaces on an object that appear as an angled line in exactly one orthographic view.

Centerlines

Reference lines shown as crossing lines in the circular view of a curved surface in orthographic projections.

Standard Orthographic Views

The three standard projection views typically included in orthographic drawings: top, front, and right side.

Rotational Direction Convention

The standard angular coordinate convention where rotations in the clockwise direction are defined as negative.

Equivalent y-axis Rotation

Two negative rotations about the y-axis, which produce the exact same final orientation as two positive rotations about the y-axis.

Reflection Across a Plane

A spatial transformation that produces a second object that is a mirror image of the first object, which cannot generally be achieved solely by rotations.

Multi-Axis Rotation Contact

The kinematic condition in which only a single point on an object remains in contact with the coordinate axes when rotated about two or more axes.

Rotational Reflection Condition

The condition where a reflection can be achieved through rotation, requiring that the object is symmetric and the rotation axis is the intersection of the plane of symmetry with the plane of reflection.

Non-Commutative Rotations

The principle that rotating in 3D is order-dependent; a positive X rotation followed by a positive Z rotation is not equivalent to a positive Z rotation followed by a positive X rotation.

Right-Hand Rule

A directional convention for rotation where pointing the thumb of the right hand down the axis of rotation causes the fingers to curl in the direction of the rotation.

Planes of Symmetry

Theoretical planes that divide an object into two halves that are exact mirror images of each other.

Closed-Loop Shape

A continuous geometric boundary required for extrusion that requires a minimum of $3$ straight lines to construct.

Double Nested Loop

A sketch containing an internal closed boundary completely within an outer closed boundary, forming a valid closed-loop profile in CAD.

Crossing Sketch Geometry

An improper closed loop containing intersecting lines extending past corners that can be repaired into a proper closed loop using the trim option in Onshape.

Gap Sketch Geometry

An improper closed-loop sketch failure caused by lines that fail to meet at endpoints, leaving an open profile.

Negative Extrusion

A 3D modeling CAD extrusion feature that cuts or removes material from an existing model.

Horizontal Constraint

A geometric constraint in Onshape that only requires a single line to be selected to align it horizontally.

Full Circle Constraint Best Practice

The standard dimensioning practice of constraining a complete circle using its diameter and center point.

Driving Dimension

The active parametric dimension controlling sketch geometry (shown on the left); modifying it directly changes the rectangle's height from $1.5\text{ inches}$ to $2.0\text{ inches}$.

Driven Dimension

A reference dimension (shown on the right) determined by other geometry and driving dimensions that cannot be directly edited to alter model geometry.

Drawing Update Associativity

The CAD feature whereby drawings automatically link to and reflect changes in the part file without needing to recreate the drawing from scratch.

Baseline Dimensioning

A dimensioning style where multiple parallel dimensions (such as $1.00$, $2.00$, and $3.00$) originate and reference from a single common datum or edge.

Hidden Line Dimensioning Rule

A drafting convention specifying that dimensions should not be attached directly to hidden lines.

Positive Cylinder Dimensioning Rule

The dimensioning rule stating that a positive cylinder (rod) should be dimensioned in the view where its side profile appears as a rectangle.

Negative Cylinder Dimensioning Rule

The dimensioning rule stating that a negative cylinder (hole) should be dimensioned in the view where it appears as a circle.