Computer Science and CAD Flashcards
(24 cards)
Design
The process of bringing together engineering principles, material resources, and creativity to solve problems
CAD
Computer aided drafting - the use of computer techniques in designing products, esp involving the use of computer graphics
Sketching
A rough freehand drawing used to document, communicate, and refine ideas developed in the ideation phase; Mechanics of sketching: lines and curves, and a bounding box; Why use sketches? creativity, communication, documentation, and should be the first step of any CAD drawing
Hidden lines
Lines that outline surfaces that are not visible in the current view, and are represented with dashed lines
- holes: two hidden lines to represent the depth of the hole
- views should be selected to minimize the use of hidden lines
Tolerance
Allowance for specific variation in the size and geometry of a part; it is impossible to manufacture a part to an exact size or geometry; since variation from the drawing is inevitable the acceptable degree of variation must be specified; large variation may affect the functionality of the part; small variation will affect the cost of the part: requires precise manufacturing and the inspection and the rejection of parts
High Tolerance: more expensive; high quality
Low Tolerance: less expensive; lower quality
Dimension
Help understand a drawing even more, by letting you know the length of the sides, and where the center of the objects are; indicates the length/width or diameter of an object or parts even to indicate the length from a side to the center of a whole; the dimension lines do not touch the actual drawings. Over dimensioning can make the drawing too complicated to understand. R represents the radius, and a zero with a slash represents the diameter. It’s best to keep all dimensions to two sides of the drawings. Place as many dimensions as possible on the most descriptive view (Front). Dimension holes from the center point. If a curve/arc is less than 90 degrees, you dimension in respect to the radius. Extension lines must not cross. Dimensions should also be in between views when possible.
- Problem Identification
What is the problem? What part of the problem do we hope to solve? What is the design criteria? Make a formal problem statement
- Preliminary Ideas
Brainstorm. Make sketches
- Preliminary Design
Select best of preliminary ideas. Combine ideas. Refine sketches. Develop simple computer models. Evaluate the merits of each design.
- Refinement
Look at the most promising ideas from the previous step. Work out the details of each design.
- Analysis
Apply engineering and scientific principles to evaluate the design
- Implementation
Choose best design based on results of the previous steps (refinement and analysis). Documentation. Build a prototype. do thorough testing. Marketing. Production planning
Isometric
designating a method of projection (isometric projection) in which a three-dimensional object is represented by a drawing, having the horizontal edges of the object drawn usually at a 30° angle and all verticals projected perpendicularly from a horizontal base, all lines being drawn to scale.
Center lines
Are used to indicate the center of a hole; they look like a cross hair when you can see the hole; when the hole is shown by hidden lines a dashed dot line represents the center of the hole
Extension lines
Extension lines are thin lines that extend from the object outline or point on the object to a place outside the image area. Extension lines define areas for dimensions
The 6 Steps
- Problem Identification
- Preliminary Ideas
- Preliminary Design
- Refinement
- Analysis
- Implementation
Multi-view Sketching
Represents a 3-D object with a series of 2-D views in contrast to “pictorials” which show all three dimensions in a single view. Also called orthographic projection. Best understood by engineers or technically trained people
Orientation and Placement of Views
The most descriptive view should be selected as the front view. The natural orientation of the part should be preserved if possible. Views must be aligned: Top view above front view; right view to the right of the front view
Parallel Projection
- Preserves the true relationship between features: the geometry is generally not distorted; lines that are parallel on the object are parallel on the drawing
- Parallel projectors: the object is projected onto a projection plane as a shadow is projected where the rays form the light source are parallel; projection from one view to another is accomplished with parallel projection lines
Projection planes vs. Views
- Projection planes: object formed projection lines projected perpendicularly onto a projection plane; planes: horizontal, formal, and profile; each projection plane is perpendicular to adjacent projection planes
- Principal views: the objects is rotated 90 degrees about the horizontal or vertical axis to give six principal views (top, bottom, front, rear, left, and right side); common views: top, front, and right side
Only use Necessary views
- One view drawings: stamped, thin or extruded parts; specify thickness with a note
- Two view drawings: cylindrical parts; show the circular and rectangular view
- Three view drawings: usually sufficient for all other drawings; top, front, and right side view
Fold lines
- represents a 90 degree fold between views
- generally not shown on engineering drawings except when views other than the principle views (auxiliary views) are used
Constructing a New View
- The top and front views of a surface are shown
- the fold line represents a 90 degree fold between the views
- parallel projection lines are perpendicular to the fold line
- a vertical fold line is drawn at an arbitrary distance from the front view
- parallel projection lines are drawn from each vertex
- the common depth between the top and side view is used to locate each vertex on the projection lines
Formal problem statement
- Problem description
- requirements
- limitations
- additional information
