Ortographic representation Flra Hajdu B 406 hajdflsze hu

Ortographic representation Flóra Hajdu B 406 hajdfl@sze. hu

Content • Theory of shape description • Ortographic representation • First angle projection • Third angle projection • Reference arrows layout • Mirrored ortographic representation • Construction of orthographic drawings • Auxiliary views 2021. 10. 29. Hajdu Flóra

Theory of shape description • In technical drawings various projection methods are used to represent objects • Projection is a method of representing visually a 3 D object on a 2 D drawing paper • Orthographic projection is obtained by means of parallel orthogonal projections and result in flat, 2 D views systematically positioned relative to each other 2021. 10. 29. Hajdu Flóra

Orthographic representation • To show the object completely 6 views in the directions a, b, c, d, e and f may not be necessary Direction of observation 2021. 10. 29. Designati on of view View in direction View from a Front A b Top B c Left C d Right D e Bottom E f Back F Hajdu Flóra

Orthographic representation • The most informative view of the object to be presented is normally chosen as principal view (front) • This view usually shows the object in the functioning, manufacturing or mounting position • The position of the other views relative to the principal view in the drawing depends on the projection method • In practice not all views are needed • When views other than the principal view are necessary they should be selected in order to: • Limit the number of views and sections to the minimum necessary to fully represent the object without ambiguity • Avoid unnecessary repetition of detail 2021. 10. 29. Hajdu Flóra

Methods of representation Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design Orthographic representation First angle projection 2021. 10. 29. Third angle projection Hajdu Flóra Reference arrows layout Mirrored orthographic representation

First angle projection • The object appears between the observer and the coordinate viewing planes on which the object is orthogonally projected • The position of the various views relative to the principal view are rotated or positioned so that they lie on the same plane on which the front view is projected • Therefore: • • • 2021. 10. 29. view from above – underneath view from below – above view from left – right view from right – left view from rear – right or left Hajdu Flóra

First angle projection 2021. 10. 29. Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design Hajdu Flóra

Third angle projection • The object appears behind the coordinate viewing planes on which the object is orthogonally projected • On each projection plane the object is represented as if it is seen orthogonally from in front each plane • The position of the various views relative to the principal view are rotated or positioned so that they lie on the same plane on which the front view is projected • Therefore: • view from above – above • view from below – underneath • view from left – left • view from right – right • view from rear – right or left 2021. 10. 29. Hajdu Flóra

Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design Third angle projection 2021. 10. 29. Hajdu Flóra

Reference arrows layout • Permits the various views to be freely positioned • With exception of the principal view each view is identified by a letter • A lowercase letter on the principal view and where required on one of the side views indicates the direction of observation of the other views • Views are identified by the corresponding capital letter placed immediately above the view on the left • Whatever the direction of the observer the capital letters identifying the views whould always be positioned to be read from the direction from which the drawing is normally viewed 2021. 10. 29. Hajdu Flóra

Reference arrows layout 2021. 10. 29. Hajdu Flóra Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design

Mirrored Orthographic Representation • Method preferred for use in construction drawings • The object is a reproduction of the image in a mirror (face up) positioned parallel to the horizontal planes of the object Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design 2021. 10. 29. Hajdu Flóra

Arrangement and construction of views 1. 2. 3. 4. 5. 6. 2021. 10. 29. Decide on the views to be drawn and the scale to be used Make a sketch of the space required for each of the views, showing these views in correct location (simple rectangle) Put on the overall drawing seizes for each views Decide upon space left between views Select the drawing sheet that best accomodates the overall size of the drawing with suitable open space around the views Measure the drawing space remaining after all border lines and title block are in place Hajdu Flóra Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&De sign

Use a milter line (deflector) • Provides a fast and accurate method of constructing the third view once 2 views are established Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design 2021. 10. 29. Hajdu Flóra

Drawing of different shapes • All surfaces parallel to the viewing planes and all edges and lines visible • Hidden surfaces and edges • Inclined surfaces • Circular features • Oblique surfaces 2021. 10. 29. Hajdu Flóra

All surfaces and lines parallel to the viewing planes and all edges and lines visible • Surface will show as a surface on one view and a line on other views • The lengths of these lineas are the same as the lines shown on the surface view 2021. 10. 29. Hajdu Flóra

Hidden lines and edges • Many features (holes) cannot be seen when viewed from the outside the piece • These hidden edges are shown with hidden lines (evenly spaced dashes) • Normally required on the drawing to show their true shape of the object • They should be omitted when not required to preserve the clarity of the drawing 2021. 10. 29. Hajdu Flóra

Inclined surfaces • When a surface is inclined or sloped in only one direction • Seen as a distorted surface in 2 views (foreshortened length) • Appears as a line on the third view (true length seen only this view) • When an inclined surface has important features that must be shown clearly and without distorsion an auxiliary view must be used 2021. 10. 29. Hajdu Flóra

Oblique surfaces • When sloped so that is not perpendicular to any of 3 viewing planes it will appear as a surface in all views but never in its true shape (foreshortened length) • If a true view is required for this surface 2 auxiliary views need to be drawn 2021. 10. 29. Hajdu Flóra

Circular features • Circular feature appears circular in one view only • No line is used to show where a curved surface joins a flat surface • Center line: thin broken line of long and dashes spaced alternately • Locate • Center points axes of cylindrical parts • Axes of symmetry 2021. 10. 29. Hajdu Flóra

Auxiliary views • Many machine parts have surfaces that are not perpendicular or at right angles to the planes of projection (sloping or inclined surfaces) • In regular ortographic views such surfaces appear to be distorted and their true shape is not shown • When an inclined surface has important characteristics that should be shown clearly and without distorsion an auxiliary view is used • Then the drawing completely and clearly explains the shape of the object 2021. 10. 29. Hajdu Flóra

Auxiliary views • In many cases the auxiliary view will explain one of the regular views • One of the regular orthographic views will have a line representing the edge of the inclined surface • The auxiliary view is projected from this edge line at right angles and is drawn parallel to the edge line Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design 2021. 10. 29. Hajdu Flóra

Auxiliary views • Only the true-shape feature on the views need to be drawn • The auxiliary view shows only the true shape and detail of the inclined surface or features a partial auxiliary view is all that necessary 2021. 10. 29. Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design Hajdu Flóra

Construction of auxiliary views scan Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design 2021. 10. 29. Hajdu Flóra

Construction of auxiliary views scan 2021. 10. 29. Hajdu Flóra Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design

Multi-auxiliary view drawings Some objects have more than 1 surface not perpendicular to the plane of projection An auxiliary view may be required for each surface Depends upon the amount and type of detail lying on these surfaces Some objects require a secondary auxiliary view to show the true shape of the surface or feature • The surface or feature is usually oblique (inclined) to the principal planes of projection • • scan 2021. 10. 29. Hajdu Flóra Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design

Multi-auxiliary view drawings scan 2021. 10. 29. Hajdu Flóra Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design

Secondary auxiliary view scan 2021. 10. 29. Hajdu Flóra Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design

Revolved views • when the true size and shape of inclined surface do not in a drawing • Auxiliary view • Keep using the regular reference planes while imagining that the object has been revolved scan 2021. 10. 29. Hajdu Flóra Source: C. Jensen, J. D. Helsel, D. R. Short: Engineering Drawing&Design

Summary • Ortographic representation • First angle projection • Third angle projection • Reference arrows layout • Construction of orthographic drawings • Auxiliary projection Next week: Dimensioning

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