2D ESSENTIALSInstructor: Laura Gerold, PECatalog #10614113Class # 22784, 24113, 24136, & 24138Class Start: January 18, 2012Class 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
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 DRAWINGREPRESENTATION
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 VIEWSA removed view is a complete or partial view removed to another place on the sheetso that it is no longer in direct projection with any other view. Removed View Using View Indicator Arrow Removed View Using Viewing-Plane Line
Removed Views• Use removed views when you need to move a view on a sheet so that it does not follow the standard arrangement. A Standard Arrangement Removed View
NECESSARY VIEWSOne-View Drawing What are the absolute minimum views required to completely define an object? Two-View Drawing Three-View Drawing
PARTIAL VIEWSA view may not need to be complete but needs to show what is necessary to clearlydescribe the object. This is called a partial view and is used to save sketchingtime and make the drawing less confusing to read. OR You can use a break line to limit the partial view…
Showing Enlarged Details When adding a detail, draw a circle around the features that will be included in the detailPlace the detail view on thesheet as you would a removedview. Label successive detailswith the word DETAIL followedby a letter, as in DETAILA,DETAIL B,
Conventional BreaksTo 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 VIEWSAlways draw views in the “standard” arrangement... Because CAD makes it easy to move whole views, it is tempting to place views where they fit on the screen or plotted sheet and not in the standard arrangement. This is not acceptable. 3D CAD software that generates 2D drawing views as projections 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 SLICEDCylinders 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 SLICEDIn the diagrams below (page 207), as a group, identify which view is the “lineof sight” with the normal surface shown as a true shape and which viewshows 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 byan ellipse. This ellipse will appear as a circle in the top view, as a straightline in the front view, and as an ellipse in the side view.When a circular shape is shown inclined in another view and projected intothe adjacent view it will appear as an ellipse, even though the shape is acircle. It is not shown as a true shape in any view, but we will learn how todraw 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), butwhen 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 TANGENCIESWhen plane surfaces join a contoured surface, a line is shown ifthey are tangent, but not shown if they intersect. (e – h) As agroup, talk through e-h. Do they make sense to you?
Intersections of CylindersWhen the intersection is small, its When the intersection is larger,curved shape is not plotted it can be approximated byaccurately because it adds little to drawing an arc with the radiusthe sketch or drawing for the time it the same as that of the largetakes. Instead it is shown as a cylinder.straight line.
Intersection and Tangencies GroupProject• 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 ROUNDSA rounded interior corner is called a fillet. A rounded exteriorcorner is called a round. Rounds on a CAD Model of a Design for a Three-Hole Punch Fillets on a CAD Model. (Courtesy of Douglas Wintin.) (Courtesy of Ross Traeholt.)
RUNOUTSSmall curves called runouts are used to representfillets that connect with plane surfaces tangent tocylinders. Runouts from different filleted intersections will appear different owing to the shapes of the horizontal intersecting members.
CONVENTIONAL EDGESThere is a conventional way of showing rounded and filleted edges forthe sake of clarity. Added lines depicting rounded and filleted edges.Rounded and filleted intersections eliminate sharp edges and can make it difficult topresent the shape clearly. Small Y shapes are used where rounded or filletededges 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 opposite parts 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 CONVENTIONS Regular multiview projections are sometimes awkward, confusing, or actually misleading.Revolutions like these arefrequently used in connectionwith sectioning. Revolvedsectional views are calledaligned 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?