LC DCG flashcards
LC DCG · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Chain thin line
- A long-dash short-dash line used for centre lines, pitch circles and planes of symmetry. It is drawn as thin as a dimension line and extends slightly beyond the feature it marks.
- Hidden detail line
- A short-dashed line of medium thickness showing an edge that is not visible in the current view. Omit hidden detail where it clutters the drawing and a section view would communicate better.
- First-angle projection symbol
- The truncated-cone symbol with the small circle on the right of the front view and the two-circle end view placed on the left. It signals that the plan is drawn below the elevation.
- Third-angle projection layout
- The plan sits above the elevation and each end view appears on the side from which the observer looks. The truncated-cone symbol then shows the small circle on the left and the end view on the right.
- Scale ratio formula
- Scale equals drawing length divided by real length. A 1:20 reduction means a 2000 mm wall is drawn 100 mm long; an enlargement such as 2:1 doubles the drawn size.
- Title block contents
- The boxed panel giving drawing title, drawing number, scale, projection symbol, material, date, and the names or initials of the draughtsperson and checker. It is normally placed bottom right.
- Reference dimension
- A dimension shown in brackets that repeats information already given elsewhere. It is for reference only and is not used for manufacture or inspection.
- Section hatching convention
- Cut material is hatched with evenly spaced thin lines at 45 degrees. Adjacent parts are hatched in opposite directions, and standard parts cut lengthwise are left unhatched.
- Ground line
- The line XY on a descriptive geometry sheet separating plan from elevation. Heights measured above it in elevation equal true heights above the horizontal plane.
- True length of a line
- Found by constructing a right triangle whose base is the plan length and whose height is the difference in heights between the ends; the hypotenuse is the true length.
- Edge view of a plane
- The projection in which a plane surface collapses to a single line. It is obtained by viewing in a direction parallel to the plane, and it is the key step towards true shape.
- True shape auxiliary view
- An auxiliary view projected at right angles to the edge view of a surface. Because the line of sight is then perpendicular to the plane, the surface appears undistorted.
- Horizontal and vertical traces
- The lines where a plane meets the horizontal and vertical reference planes. Both traces intersect the ground line at the same point.
- Ratio division in projection
- Parallel projection preserves ratios along a straight line, so a point dividing a line 2:3 in space divides it 2:3 in plan, elevation and every auxiliary view.
- Line meeting a plane
- Use an auxiliary cutting plane containing the line, find where its trace crosses the plan of the line, then project that intersection point to the elevation.
- Angle between two planes
- Measured between the edge views of the planes, or between two lines drawn perpendicular to their common line of intersection in a view showing that line true length.
- Fully constrained sketch
- A CAD sketch in which every degree of freedom has been removed by dimensions and geometric constraints. It changes colour and no longer drags, so downstream features stay predictable.
- Feature history tree
- The ordered list of sketches and features that builds a parametric part. Editing an early entry rebuilds all later features, so the order of construction matters.
- Boolean difference
- A solid modelling operation that subtracts one body from another to create a cut or cavity. Union adds material and intersection keeps only the shared volume.
- STEP file
- A neutral exchange format carrying boundary-representation geometry and some product data. It transfers shape between CAD systems but discards the parametric feature history.
- STL mesh format
- A triangulated surface description used for 3D printing. It has no units, features or material data, so the exporting system must fix scale before output.
- Associative drawing views
- Orthographic, section and detail views generated from a 3D model remain linked to it, so a model change propagates to the views and their dimensions on rebuild.
- Exploded assembly view
- A pictorial view in which components are drawn separated along a common axis or leader lines in assembly order, each identified by a balloon number and a parts table entry.
- Design brief versus specification
- The brief states the problem and intended user in prose; the specification converts it into measurable constraints that must be met and ranked considerations used to compare concepts.
- Weighted decision matrix
- A table scoring each concept against weighted criteria. Multiply each score by its weight, sum the products, and select the highest total provided every constraint is satisfied.
- Anthropometric percentiles
- Body measurement ranges expressed as 5th, 50th or 95th percentile. Use the 5th percentile for reach and the 95th for clearance, quoting male and female data separately.
- Evidence-based evaluation
- Judging the outcome against the brief using measured test results, dimensions and costs, and marking each constraint as met or not met rather than offering opinion.
- Isometric ellipse axes
- A circle drawn isometrically becomes an ellipse with major axis about 1.22 times the diameter and minor axis about 0.71 times the diameter, oriented perpendicular to the relevant axis.
- Cabinet oblique projection
- An oblique drawing with the front face true shape and receding edges at 45 degrees drawn at half scale, which reduces the apparent distortion of cavalier oblique.
- Vanishing point
- The point on the horizon where parallel receding edges appear to converge in perspective. One-point views have one such point, two-point views have two.
- Cosine rule
- a squared equals b squared plus c squared minus 2bc cos A. Apply it when two sides and the included angle, or all three sides, are known.
- Sine rule
- a over sin A equals b over sin B equals c over sin C, and the ratio also equals twice the circumradius. Use it with a side and its opposite angle.