TA 101 Think and Analyze Anupam Saxena Associate Professor Mechanical Engineering Compliant and Robotic Systems Lab Indian Institute of Technology Kanpur An for the drawing Comes with practice and with MISTAKES! PULLEY
1 NOS 50 40 80 30 10 24 5 ANUPAM SAXENA TA101 LECTURE XII SECTIONAL AND ASSEMBLY VIEWS
30 2 x 10 15 45 R15 10 50 80 45
10 10 60 BRACKETS 2 NOS 20 20 15 40
ANUPAM SAXENA TA101 LECTURE XII SECTIONAL AND ASSEMBLY VIEWS 170 TA 101 Think and Analyze What does GOD (google) say about sectional views? In section view drawings, hidden line representation is omitted in that part of the view with the section lining. A correct conventional representation of the full section in the
front view omits these hidden lines. In all cases the top view of the drawing is a standard orthographic view complete with visible and hidden lines. Visible object lines take precedence over hidden and centerlines. Hidden lines take precedence over centerlines. Cutting plane lines take precedence over centerlines when locating the cutting plane for the section view. Centerlines are included in the section view, but hidden lines are omitted. Certain features of engineering parts are generally not sectioned even though the cutting plane may pass through them. When the cutting plane passes through the length of supporting ribs, lugs, and other thin parts, the feature is represented without section lines to avoid a misimpression of solidity. In addition to thin structural features, parts not sectioned also
include standard mechanical elements such as shafts, bolts, screws, nuts, rivets, keys, pins, bearings, and gear teeth. The shaft, bolts, and nuts of the assembly are not sectioned even though they are cut by the cutting plane. http://www.tarleton.edu/Faculty/tbarker/105/ Notes_handouts/Sectioning.pdf Okay to hatch because the cutting plane is perpendicular to the rib Impression that the entire object is solid When both a web and ribs are present in section views of cylindrical parts, the alternate sectioning rule applies. When
ribs are present in addition to the web, the usual convention for ribs would result in a view identical to case A. To eliminate this misrepresentation, in this technique, only alternating section lines are shown in the cross-hatching style. Ribs in section - not drawn if parallel to plane because tends to imply greater mass than actual, drawn if rib runs perpendicular to plane, same true for spokes Conventional Practice - sectioning not a physical cut, a
graphic cut - could be different such as ribs not sectioned and spokes not sectioned, also items usually not sectioned: ribs, spokes, bolts, pins, keys http://www.ateneonline.it/bertoline/docenti/IM/IM_ch8.pdf Conventional practices have been established to handle section views of special situations, such as the alignment of holes, ribs, and spokes. 8.41 Ribs, webs, spokes, lugs and other thin features are not section lined when the cutting plane passes parallel to the feature. A rib or web is a thin flat piece that acts as a support. 8.42 Adding sections lines to these figures would give the false impression that the part is thicker than it really is.
http://www.ateneonline.it/bertoline/docenti/IM/IM_ch8.pdf 8.43 Occasionally, section lines are added to a thin feature, so that it is not mistaken or read as an open area. The web could be interpreted as being round (solid) and without ribs. To section line a thin feature, use alternate lines on the feature. 8.44 If the feature is not lost, then the section lines should not be added. Engineering Drawing and Graphic Technology
(Thomas E. French) Page 161: 5: Parts not sectioned Many parts (bolts, pins, shafts) recognized easily by their exterior views than by sections. They may lie in the path of the sectioning plane. Such parts should be left in full view and not sectioned. Otherwise, the drawing will be difficult and confusing to read. 6 A. Spokes not sectioned Even though the section plane passes through two spokes, sectional view must be made without crosshatching the spokes. How does one differentiate between them?
Engineering Drawing and Graphic Technology (Thomas E. French) Page 162: 6 A. Spokes not sectioned Other machine elements treated in this manner are teeth of gears and sprockets, vanes and supporting ribs of cylindrical parts, equally spaced lugs and similar parts. B. Ribs in Section When the cutting plane passes longitudionally through the center of a rib or web, crosshatching of ribs is not performed as if the cutting plane were just in front of them. Ribs crosshatched gives a misleading effect suggesting a cone shape (implies presence of a lot of material)
Engineering Drawing and Graphic Technology (Thomas E. French) Page 162: 6 B. Ribs in Section When the cutting plane cuts a rib transversely (right angle to its length or axis direction), it is always cross hatched. 6C. Lugs in Section A lug (projecting ear, of usually a rectangular cross section) is not crosshatched. Fig. 30: Small lugs (not hatched) treated as spokes or ribs. Large lugs (hatched) treated as the solid base of the part. Pages 161-165: Nice read
Oblique Views Organization of Lectures and Laboratory Assignments Topic Week (No. of Lectures) Lab Intro and Basic Constructions Week 1 (2) Orthographic Projections Week 2 (2)
Lab 9 Auxiliary Projections Week 11 (2) Lab 10 Intersection of lines/planes/solids Intersection and Development Week 12 (2) Lab 11
Week 13 (2) Lab 12 TOTAL 26 12 TA: PROJECTIONS REMAIN PARALLEL IN ALL THREE SENSE OF DEPTH TRUE FEATURES
OBLIQUE ORTHOGRAPHIC ISOMETRIC ANUPAM SAXENA TA101 LECTURE OBLIQUE VIEWS XIII TA: ROTATED OBJECT TWICE TO CAPTURE IT ON THE PLANE OF SCREEN TA: PARALLEL PROJECTORS ARE PERPENDICULAR TO THE SCREEN ISOMETRIC ANUPAM SAXENA
TA101 LECTURE OBLIQUE VIEWS XIII TA: PARALLEL PROJECTORS PERPENDICULAR TO THE PLANE WHICH IS PARALLEL TO ONE OF THE PRINCIPAL PLANES OF THE OBJECT ORTHOGRAPHIC ANUPAM SAXENA TA101 LECTURE OBLIQUE VIEWS XIII
TA: PARALLEL PROJECTORS OBLIQUE (NOT PERPENDICULAR) TO THE PLANE OBLIQUE ANUPAM SAXENA TA101 LECTURE OBLIQUE VIEWS XIII TA: CHOOSE THE FRONTAL PLANE (E.G.; ONE WITH MANY CIRCULAR/COMPLEX FEATURES) TA: TWO OPTIONS: RETAIN THE DEPTH DIMENSION
CAVALIER FORESHORTEN THE DEPTH DIMENSION TO HALF CABINET Depth direction 30 or 45 degrees POSSIBLY THE SIMPLEST AMONGST THE THREE SCHEMES OF DRAWING ANUPAM SAXENA TA101 LECTURE OBLIQUE VIEWS XIII
50 36 30 2 holes 20 80 10 10 40 200
20 100 8 CAVALIER ANUPAM SAXENA TA101 LECTURE XIII CAVILIER VIEW EXAMPLE 80 60
50 35 8 40 4 8 20 30 50
8 8 130 CABINET ANUPAM SAXENA TA101 LECTURE XIII CABINET VIEW EXAMPLE Think and Analyze Until next time...
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