2D ESSENTIALS

Instructor: Laura Gerold, PE

Catalog #10614113

Class # 22784, 24113, 24136, & 24138

Class Start: January 18, 2012

Class End: May 16, 2012

Tests• Class Average = 87%• Class Scatter

• A, 90-100, 6 people• B, 80-89, 7 people• C, 70-79, 0 people• D, 60-69, 2 people

• Class Problems:• Scaling!• Using a Protractor to Measure Angles• Sketch means to freehand draw, Draw means to use your tools

Course Calendar• Tentative Schedule for the rest of the semester:

• 3/28 – Isometric Sketches (Chapter 3)• 4/4 – Finish Isometric Sketches, Sections Views (Chapter 7)• 4/11 – Section Views• 4/18 – Auxiliary Views (Chapter 8)• 4/25 – Auxiliary Views, Dimensioning (Chapter 10)• 5/2 – Dimensioning• 5/9 – Review for Exam 2• 5/16 – Exam 2

2D Essentials Project• 4/4/12 – 50% Project Plans Due. Turn in what you have

drawn so far and comments will be added to your plans on Post-it notes. Plans at this point should include scale, drawing border, three views. (30 points)

• 5/9/12 – Final Project Due

2D Essentials Project – Scoring Guide

• Project will be scored on the following items:• Drawing Border• Scale• Six Orthographic Standard Views• Auxiliary Views• Section Views• Dimensions• Neatness• Line Types

Orthographic Sketching Refresher• Build an object with your block• Draw the necessary views• Exchange your plan with someone not in your row• With your new plan in hand, build the item drawn by your

classmate• Compare items with your classmate when you have both

finished – did you recreate the item accurately?

1st and 3rd Angle Projections• 1st – Europe (except U.K.), Asia• 3rd – United States, United Kingdom, Canada, Australia• Extra Credit – What other countries use 1st or 3rd Angle

Projections?• Turn in what country and your reference• 5 extra credit points• Due by April 11th

CHAPTER 6 – 2D DRAWING REPRESENTATION

Why Chapter 6 – 2D Representation?• Standard orthographic projections don’t show the

complexities of many shapes that are drawn on plans out in the field, we are going to learn the standard conventions of drawing some complex shapes.

• What objects did you bring to class with “Common Manufactured Features?” What features do they have?

• Let’s learn how to draw these objects . . .

REMOVED VIEWS

A removed view is a complete or partial view removed to another place on the sheet so that it is no longer in direct projection with any other view.

Removed View Using Viewing-Plane Line

Removed View Using View Indicator Arrow

Removed Views• Use removed views when you need to move a view on a

sheet so that it does not follow the standard arrangement.

Standard Arrangement

Removed View

A

NECESSARY VIEWSOne-View Drawing

Two-View Drawing

Three-View Drawing

What are the absolute minimum viewsrequired to completely define an object?

PARTIAL VIEWSA view may not need to be complete but needs to show what is necessary to clearly describe the object. This is called a partial view and is used to save sketchingtime and make the drawing less confusing to read.

You can use a break line to limit the partial view…

OR

Showing Enlarged Details

When adding a detail, draw a circlearound the features that will be included in the detail

Place the detail view on the sheet as you would a removed view. Label successive details with the word DETAIL followed by a letter, as in DETAILA, DETAIL B,

Conventional Breaks

To shorten the view of a long object, you can use break lines…

Using a break to leave out a portion of the part, but allows the scale for the endsto be increased to show the details clearly.

ALIGNMENT OF VIEWS

Always draw views in the “standard” arrangement...

Because CAD makes it easy to move whole views, it istempting to place views where they fit on the screen orplotted sheet and not in the standard arrangement. This is not acceptable.

3D CAD software that generates 2D drawing views asprojections of the 3D object usually has a setting to select from third-angle or first-angle projection. Check your software if you are unsure which projection methods are available.

VISUALIZING AND DRAWING COMPLEX CYLINDRICAL SHAPES

Steps

VISUALIZING AND DRAWING COMPLEX CYLINDRICAL SHAPES

• In this drawing, how many views are necessary?• Which views are repetitive?• Is the centerline required to locate the rounded top?

VISUALIZING AND DRAWING COMPLEX CYLINDRICAL SHAPES

• In this drawing, how many views are necessary?• Which views are repetitive?• What purpose does the centerline serve on this drawing?• How do you locate the hole on views other than the front

view?

VISUALIZING AND DRAWING COMPLEX CYLINDRICAL SHAPES

• In this drawing, how many views are necessary?• Which views are repetitive?• How many lines are used to show the counterbore in the

side and top views?

VISUALIZING AND DRAWING COMPLEX CYLINDRICAL SHAPES

• In this drawing, how many views are necessary?• Which views show the necessary detail?• Where do the lines for the removed portion appear in the

top and side detail?

CYLINDERS WHEN SLICED

Cylinders are often machined to form plane or other types of surfaces.

Normal surfaces appear true shape in the view where the line of sight is perpendicular to the surface. In the two other views that normal surface appears on edge. The back half remains unchanged.

CYLINDERS WHEN SLICED

In the diagrams below (page 207), as a group, identify which view is the “line of sight” with the normal surface shown as a true shape and which view shows the normal surface as an edge.

Plotting Curves by Hand• Step 1: Break up the

curves into several points and locate them in the adjacent view

• Step 2: Project the points along the projection lines into the top view from the front view. Transfer the depth from the side view, using the back surface as a reference plane.

• Step 3: Draw the curve through the points.

CYLINDERS AND ELLIPSESIf a cylinder is cut by an inclined plane, the inclined surface is bounded by an ellipse. This ellipse will appear as a circle in the top view, as a straight line in the front view, and as an ellipse in the side view.

When a circular shape is shown inclined in another view and projected into the adjacent view it will appear as an ellipse, even though the shape is a circle. It is not shown as a true shape in any view, but we will learn how to draw auxiliary views to show the true shape in a couple of weeks.

Cylinder Group Project• As a group, draw the necessary views of a cylindrical

shape (can use shapes that you brought, or a shape that I give you).

• Present your drawings.

INTERSECTIONS AND TANGENCIESWhere a curved surface is tangent to a plane surface no line is drawn (a), but when it intersects a plane surface (b), a definite edge is formed.

When curves join each other or planes smoothly (tangent) a line is not drawn to show where they come together (c). If a combination of curves creates a vertical surface (d), the vertical surface is shown as a line.

INTERSECTIONS AND TANGENCIES

When plane surfaces join a contoured surface, a line is shown if they are tangent, but not shown if they intersect. (e – h) As a group, talk through e-h. Do they make sense to you?

Intersections of Cylinders

When the intersection is small, its curved shape is not plotted accurately because it adds little to the sketch or drawing for the time it takes. Instead it is shown as astraight line.

When the intersection is larger, it can be approximated by drawing an arc with the radius the same as that of the large cylinder.

Intersection and Tangencies Group Project

• Draw the necessary views of an item with intersection or tangencies. Use an item that a group member brought in or one that I have.

• Talk through your views and show the class.• What was difficult about drawing/visualizing this object?

FILLETS AND ROUNDS

A rounded interior corner is called a fillet. A rounded exterior corner is called a round.

(Courtesy of Ross Traeholt.)(Courtesy of Douglas Wintin.)

Rounds on a CAD Model of a Design for a Three-Hole PunchFillets on a CAD Model.

RUNOUTSSmall curves called runouts are used to represent fillets that connect with plane surfaces tangent to cylinders.

Runouts from different filleted intersections will appear different owing to the shapes of the horizontal intersectingmembers.

CONVENTIONAL EDGESThere is a conventional way of showing rounded and filleted edges for the sake of clarity. Added lines depicting rounded and filleted edges.

Rounded and filleted intersections eliminate sharp edges and can make it difficult to present the shape clearly. Small Y shapes are used where rounded or filleted edges meet a rough surface.

Fillets, Rounds, Runouts Group Project

• Select an item in your group (from your items or one of my items) that has fillets or rounds and apply the conventions as you draw the necessary views.

• Present your drawings• Any problems?

RIGHT-HAND AND LEFT-HAND PARTS

Often, parts function in pairs of similar opposite parts, but oppositeparts can rarely be exactly alike.

On sketches and drawings a left-hand part is noted as LH, and a right-hand part as RH.

REVOLUTION CONVENTIONSRegular multiview projections are sometimes awkward, confusing, or actually misleading.

Revolutions like these are frequently used in connection with sectioning. Revolved sectional views are called aligned sections.

REVOLUTION CONVENTIONS• As a group, think about items in your household, at work,

that you saw on the way to class that would be best represented in a drawing by using revolution conventions

• Will you need to use revolution conventions on your project?

• Report your thoughts to the group

Common Hole Features Shown in Orthographic Views

Apply Hole Representation Conventions to Sketches

• As a group, draw necessary views with Hole Representation Conventions. Use my blocks, regular blocks, one of your items.

• Present results.

Common Features Shown in Orthographic Views

Common Features Shown in Orthographic Views Continued…

Putting in all together . . . • As a group, pick an item that has the most “common

features” on it from items brought in, something you can find in the room, or something in my stash.

• Draw the necessary views and label the “common features.”

What’s Next?• Chapter 3 – Orthographic Sketching

Questions?• On one of your sketches, answer the following two

questions:• What was the most useful thing that you learned today?• What do you still have questions about?

Homework

Finish Reading Chapter 3 (3.5 – end)

Chapter 6 Review Questions: 1, 2, 3, 4

Chapter 6 Exercises: 6.1 (1), 6.2, 6.4, 6.14