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Lecture 03

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Orthographic, Multi-view Projections

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Lab

Load SolidWorks & Test SolidWorksSee link on Materials page for 2015 version

Copy & run the “workarounds” from your desktop

Takes about 1 hour (if nothing else running)Test Installation by starting Tutorials

Re-install (repair installation) if necessary

May only be used from Campus IP addresses M, W, F: 1:00 – 5:30 PM IER 308/310 for help Can VPN into SDSM&T to run from off-campus site

Computer Lab work starts Thursday! Lab project will require teamwork, so start to

form 4 - 5 person teams:Sit in teams by table pods for class (share e-mail)Share texts by table pods when doing HW / Labs

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Assignments

Lab 01: Due 24 SEPOpen SolidWorks, Open the TutorialsPerform the Introduction to SolidWorks (~ 1 hr)Print the model, staple & turn in with a cover page

HW 3: Due in One Week Turn in the following on EP with a cover sheet

Sketch the symbol for a third angle projectionComplete HO 5.5 and HO 5.6 on the photocopiesDraw the following Projects (p.152) two per page:

# 3, 4, 16, and 22 (note: numbers are below object)

Draw the following Projects (p.154) two per page: # 6, and 11 (note: numbers are below object)

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Orthographic Projection

a system of drawing views of an object using perpendicular projectors from the object to a plane of projection

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Projection of an Object

A projection is a single view of an object Imagine tracing the image of an object on a sheet of glass with a pen If the projection rays are perpendicular to the glass, the view is orthographic

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The Glass Box

To get to a Multi-view drawing: Imagine encasing the object within a glass box and tracing the outline on each face Note that there are 90o between each adjacent face

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Unfolding the Glass box

To locate the six standard views Imagine that the walls of the box are hinged and unfold

the views outward around the front view.

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Standard Views - (3rd Angle)

Unfolding the box flat locates the projections Each of the six views aligns with the adjacent views

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Locating Side Views An alternative position for a side view is to rotate it and align it with the top

view Note that there is still a 90o fold between the top and side view in the alternative

position

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Projection Systems

Third Angle Projection: Is the arrangement of standard views used in

the U.S., Canada, and Mexico. For this system, imagine the planes of glass

being between the viewer and the object - so one traces the outline, then opens planes flat.

First Angle Projection: Is the arrangement of standard views used in

the E.U., and most Asian countries. For this system, imagine that the object is

between the viewer and the plane of glass - so one draws around the object edges like a template, then opens the planes out flat.

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First Angle Projection

For 1st Angle projections then: The right side view is located left of the front view, The top view is located below the front view, … etc.

To distinguish between projection systems, a standard symbol is used

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Symbols for 1st & 3rd Angle Projection

The symbol is a simple front & right side view of a truncated cone The front of the cone is always viewed head-on (target-like)

So for 1st Angle projections, the profile view is located to the left, …and for the 3rd Angle projections, the profile is on the right

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Transferring Dimensions

The depth of a projection should be the same in both the Top and Side views One method to keep the depth proportional is to

measure from a parallel reference (like the folding line), and transfer the distance to the vertices from one view to the other.

Folding lines are considered a form of construction line

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Transferring Dimensions - Miter Lines

Dimensions can also be projected across a miter line - a four step process that does not require measurements…

1. Draw a miter line at 45 degrees, located at a convenient distance to produce the desired view.

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Transferring Dimensions - Miter Lines

2. Sketch light lines projecting depth locations for points to the miter line…

…and then down into the side view

(as shown).

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Transferring Dimensions - Miter Lines

3. Project additional points…

surface by surface…

and project the corresponding surfaces

from the adjacent view… to locate each intersection

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Transferring Dimensions - Miter Lines

4. Then draw the view by connecting the ‘dots” – each vertex of a surface projection

and a miter line projection – using visible lines.

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Hidden Lines

are similar to the visible lines of a drawing, but have a different pattern

are used to show the intersections of surfaces that are not directly visible from the direction of sight

each view in a drawing shows the entire object (including hidden & center lines) as seen from that viewing direction

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Conventions for Hidden Lines

Hidden lines shouldjoin neatly with visiblelines except when itcauses a visible lineto be extended. Whentwo different lines jointo form a single line, leave a gap on the lessimportant line.

Hidden lines shouldjoin neatly to form “T”or “L” shaped inter-sections.

Hidden lines shouldjump visible lines thatthey do not intersect.It is permissible for ahidden line to cross avisible line.

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More Conventions for Hidden Lines

Stagger the dashes on closely spaced parallel hidden lines.

Hidden line dashes should intersect neatly at clear corners, as in the bottom of this drilled hole.

Intersecting hidden lines should form neat corners, as in this countersunk hole.

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Conventions for Curved Hidden Lines

Curved hidden lines should not extend a visible curve in the same direction. Leave a gap on the hidden line so that you can easily see where the visible line ends.

Curved hidden lines dashes should extend to the point of tangency. Don’t end with a gap at the point of tangency. It makes it hard to see the location.

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Choice of View

orient the object so that the front view shows the shape of the object most clearly (fewest hidden lines)

chose front view so that it has a large number of normal surfaces.

show the object in the usual or operating position

show the right side view & top views unless other views are better (fewer hidden lines)

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Necessary Views

A sketch or drawing should only contain the views needed to clearly and completely describe the object. Choose the views that show the shape most clearly,

have the fewest hidden lines, and show the object in a usual, stable, or operating position.

One view drawingof a shim (thin, flat)

One view drawingof a connecting rod

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Remember the part in the Glass Box?

IF DRAWING ALL SIX STANDARD VIEWS … … we imagined unfolding the walls of the hinged glass

box outward around the front view …

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Remember the part in the Glass Box?

… but we don’t need all six standard views! Which of the views below are necessary?

XX

X

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Partial Views

When the entire view is not necessary to show the object clearly you can use a partial view. Use a break line to limit the partial view as shown in (a), (b),

and (d) below. For symmetrical parts, you can draw a half-view on one side

of the centerline as shown in (c).

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Right & Left Hand Parts

Many parts are used in pairs where opposite parts are mirror-images of one another. A left-hand part is not just a right hand part turned around. It has to be manufactured differently from a right hand part. In order to save time, a single drawing can be used for both a left and right handed part by noting on the drawing such as:

“LH PART SHOWN, RH OPPOSITE”.

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Summary

The six standard views are often thought of as being produced from an unfolded glass box.

Distances can be transferred or projected from one view to another.

Only the views necessary to fully describe the object should be drawn.

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Summary: Necessary Views

Show only the views needed to fully define the shape of the object.

Choose the views which show the shapes of the features clearly.

The right side view is preferred to the left side view if they show the object equally well; the top view is preferred to the bottom view if they show the object equally well.

Showing only the necessary views saves time, makes the drawing less cluttered, and makes it easier to interpret.