Alphabet of Lines Object Line: Thick lines about.6mm(.032in) that show the visible edges of an object. Hidden Line: Lines used to show interior detail that is not visible from the outside of the part. Center Line: Lines that define the center of arcs, circles, or symmetrical parts. They are half as thick as an object line. Construction Line: Very lightly drawn lines used as guides to help draw all other lines and shapes properly. Usually erased after being used. Short Break Line: A freehand drawn line that shows where a part is broken to reveal detail behind the part or to shorten a long continuous part. (See example of Long Break Line on the next slide.) Section Lines: Lines are used to define where there is material after a part of the object is cut away.
Alphabet of Lines Cutting Plane Line: A line used to designate where a part has been cut away to see detail. The arrows should point in the direction that you are looking at the cutout. Long Break Lines: Break lines are used to either show detail or as in this case they can be used to shorten very long objects that do not change in detail. Notice that this part is 12” long however we have shortened the drawing with break lines to use our space more efficiently. Dimension Lines: Lines that are used to show distance. Arrows are drawn on the ends to show where the dimension line starts and ends. The actual distance is usually located in the middle of this line to let you know the distance being communicated. Dimension lines are used in conjunction with extension lines to properly dimension objects. Extension Lines: Lines used to show where a dimension starts and stops on an object. Used with dimension lines to properly dimension an object. The line is 1/16” away from the part as to not get confused with the object lines Leader Lines: Leader lines are used to show dimensions of arcs, circles and to help show detail. An arrow head is used to point to the part you are dimensioning and the line comes off the arrow point usually at a 45 degree angle. At the end of this line a horizontal line is drawn with a note at the end telling information about what is being pointed at. How many lines from the previous slide can you identify here?
Alphabet of lines Phantom Lines: Phantom lines are used to identify alternate positions that a part my take up. In this example we are using Phantom lines to show that the door handle may only move 45 degrees from it’s horizontal position. How many lines from the previous 2 slides can you identify here?
Orthographic (Multiview Drawings) Pictorial sketches are great for engineers to explain ideas and communicate what the final part will look like to the customer. Unfortunately, pictorial drawings have some disadvantages. Foreshortened views and distorted features do not allow for accurate prototyping. Many times, for parts to be accurately depicted, you need straight on views of each surface.
Orthographic (Multiview Drawings) In order to obtain these straight line views we have a type of drawing called Orthographic Projection also known as Multiview drawings. Orthographic projection is a way to project a view based on a line of sight that is perpendicular to that view. There are six of these views to any object as shown in the next slide.
Orthographic (Multiview Drawings) ORTHO The arrows represent the line of sight associated with each view. Use the button below to jump between this view and the ortho view on the next page.
Orthographic Principal Views ISO Click to go back to ISO view. Front, Top and Right views are used most often. You can see how other views resemble these three except they are not as clear due to hidden lines. Note how the views are oriented. Each view is adjacent to the other as if they were unfolded from a 3D shape.
Orthographic View Selection Finding the best view of a part can be difficult. Two or more sides may look like the best solution for a front view. On the next slide is a list of characteristics that you should use in choosing your views.
Orthographic View Selection Steps in selecting the front. Most natural position or use. Shows best shape and characteristic contours. Longest dimensions. Fewest hidden lines. Most stable and natural position. Relationship of other views Most contours. Longest side. Least hidden lines. Best natural position.
Orthographic View Selection Longest Dimension Most natural position. No hidden lines. Best shape description.
Orthographic View Selection Numbers Another decision on view selection you need to make is how many views. You usually do not need more than three but you may only need one or two. The following slides will show when to make a decision between one, and two view drawings.
One View Selection Uniform shape. Two views will be identical All dimensions easily shown on one view.
One View Selection It is also possible to have one view drawings of objects that are flat and have even thickness. Gauges and gaskets are two such objects. We have a gauge here on the left.
Two View Selection Symmetrical parts. A third view would be identical to the other views Second view is necessary for depth.
Precedence of Lines In multiple view drawings, many times different line types will take up the same space, therefore, we have line precedence. The following is an explanation of which lines exist over others. Object lines over hidden and center. Hidden over center. Cutting plane lines over center lines. The following slide will show an example.
Precedence of Lines Object lines took precedence over the hidden lines you would see from the hole. The center line in the top view would show the depth of the hole as well as the right side view. An object line here takes precedence over the center line. However we draw short thin lines beyond the object to show there is a center line underneath the object line.
Do you want to be a good sketcher? First Slide
Multiview Drawing Another name for orthographic projection is multiview drawing Involves visualization and implementation Ability to see clearly in the mind’s eye an object Process of drawing the object
Multiview Drawing A system that allows you to make a two-dimensional drawing of a three- dimensional object
Viewing Objects A box is formed by six mutually perpendicular planes of projection that are located around the object
Viewing Objects Lines are formed on the planes by projecting the edges of the object onto the planes These images are called “views” There are six views formed by the planes of a box
Viewing Objects Unfolding the box produces an arrangement of the six views
Angles of Projection First-angle projection Used by many European countries Object is projected onto planes from the first angle or quadrant Front view projected to vertical plane Top view projected to horizontal plane Left-side view projected to profile plane
Angles of Projection Third-angle projection Standard for the United States Third quadrant is used for projection Front view projected to vertical plane Top view projected to horizontal plane Right-side view projected to profile plane
Viewing Objects Each view is placed in a constant location relative to the other views Each view must be placed in its correct position Views and features must be aligned
Choosing Views Most commonly used views Front View Top View Right Side View Most descriptive view is typically designated as the Front View
Choosing Views Complex objects require three views to describe its shape Simple objects can be described with two views Ex: Soda Can Thin objects can be described with only one view Depth is given in a note Ex: Erasing Shield
Choosing the Views Objects described in two views Third view would add nothing to the description of the object Carefully select views to describe shape of objects accurately
Curved Surfaces Some curved surfaces do not show as curves in all views CYLINDER FRUSTRUM CONE WHEEL
Object Dimensions All objects have 3 dimensions Height Distance from top to bottom Width Distance from side to side Depth Distance from the front to back
Object Dimensions Front View Shows width & height Top View Shows width & depth Side View Shows height & depth
Drawing Views of Objects Depth can be projected between views by using a 45 ° miter line
Line Types - Visible Edges that can be seen in a given view areVisible or Object lines Visible lines are thick and dark.028” or.7mm F or HB lead
Line Types - Hidden Edges that cannot be seen from a given view are indicated by Hidden lines
Line Types - Hidden Drawing hidden lines.125” (3mm) dashes.0625” (1mm) spaces between dashes Thin:.020” (.5mm) Dark: F or HB lead
Line Types - Hidden Follow rules for hidden line placement Alphabet of Lines Drawings produced with CAD may violate hidden line rules
Line Types – Center Center lines indicate axes of symmetry
Line Types – Center Perpendicular lines for circular objects Small dashes cross at the center point of feature One center line drawn to indicate longitudinal axis of cylinder or hole
Line Types - Center Draw center lines using a series of long and short dashes.125” (3mm) short the center.75”- 1.5” (20mm-40mm) long dash.0625” (1mm) spaces between dashes Thin:.02” (5mm) Long dash extends.125” to.25” beyond feature
Placement of Views Views should be visually balanced within the working space
Steps for Centering a Drawing Draw border and title block using light construction lines Draw diagonal lines from corners of border
Steps for Centering a Drawing Add: Width 5.13 Space 1.50 Depth 2.00 Horizontal 8.63 Height 3.00 Space 1.50 Depth 2.00 Vertical 6.50
Steps for Centering a Drawing Draw a box the size of all views Measure from the center: Half the width Half the height
Steps for Centering a Drawing Draw in views using light construction lines
Adding Details Add holes and features Transfer horizontal and vertical features Use miter line to transfer depth
Straight Edges Edges that are perpendicular to a plane of projection appear as a point 231
Straight Edges Edges that are parallel to a plane of projection appear as lines Edges that are inclined to a plane of projection appear as foreshortened lines
Curved Edges Curved edges project as straight lines on the plane to which they are perpendicular Curved edges project as curved lines on the planes to which they are parallel or inclined
Normal Surfaces Normal surfaces appear as an edge in two opposite principal views, and appear a surface in all other principal views.
Inclined Surfaces Inclined surfaces appear as an edge in two opposite principal views, and appear foreshortened (not true size) in all other principal views.
Oblique Surfaces Oblique surfaces do not appear either as an edge or true size in any principal view.
Intersections & Tangencies Where a curved surface is tangent to a plane surface, no line should be shown where they join
Intersections & Tangencies Where a plane surface intersects a curved surface, an edge is formed
Intersections & Tangencies Where the plane surface is horizontal or vertical, exceptions to these rules may occur