31372 - Computer-Aided Drawing L

Course Unit Page

SDGs

This teaching activity contributes to the achievement of the Sustainable Development Goals of the UN 2030 Agenda.

Industry, innovation and infrastructure

Academic Year 2020/2021

Learning outcomes

The course aims to provide the necessary basis for understanding the main features of the most modern Computer Aided Design (CAD) programs and for the correct use of such programs in the area of Technical Design. The course consists of a first part dedicated to guaranteeing students the learning of the basic rudiments of the Industrial Technical Drawing. In the second part of the course the topics of computer aided design are discussed and the main methodologies used in modeling, modification, coordinate transformation and visualization of curves, surfaces and solids are described.

Course contents

CAD TOOLS

Architecture of a CAD (Computer Aided Design) system. Hardware: computer, dynamic memory (RAM), mass memory (hard disk), flexible disks, CD-ROM. Data input: keyboard, mouse, digitizing tablets, scanner. Data output: vector and raster-scan display devices, hard-copy devices (plotters, dot-matrix printers, ink-jet printers, lasers). Software: interface with the operator, definition and elaboration of the model, image generation (rendering), database management, applications, utilities. Advantages and limits of CAD.

RASTER AND VECTORIAL GRAPHICS

Notes on raster and vector graphics with particular attention to use in CAD systems.

USE OF A CAD SYSTEM
The graphic primitives, initial design settings, data entry mode, object selection mode, object modification commands, display possibilities, support for pointing, layer use, block usage, dimensioning of a drawing, texts, headings and squaring, raster images, backgrounds, use of paper space, problems concerning printing, simple graphic primitives, complex graphic primitives, drawing of a relief, blocks with attributes.

ELEMENTARY GEOMETRIC CONSTRUCTION
Bisection of a segment, of an arc, of an angle. Perpendicular to a segment (to a line) from an assigned point: external, belonging to it (central or end). Parallel to a given line (at a given distance, for a given external point). Operations related to angles. Trisection of the right angle and the flat angle. Division of a segment in equal parts. Tangents to a circumference from an external or belonging point. Radius of given radius tangent to a straight line in a point. Internal and external tangents to two circles. Circumference for three points, straight lines and circumferences with arcs of assigned radius. Regular polygons: triangle, square, pentagon, hexagon and octagon with assigned side or circumscribed circumference. Construction of a polygon with any number of sides note the circumscribed side or circumference. Flat curves (ellipse, parabola, hyperbola, oval, ovolo, involute of circumference). Study and comparison of the SNAPPING and OBJECT SNAPPING systems present in the CAD system.

THE ORTHOGONAL PROJECTION METHOD
Representation by orthogonal projection on two orthogonal planes of points, lines, planes. Conditions of belonging of point and line, line and plane, point and plane. Conditions of coplanarity, incidence and parallelism between lines; of parallelism between planes. The third projection plane: determination of the third projection of points, lines, planes, curves. Orthogonal projection of plane and solid figures. Criteria relating to the identification and representation of lines in sight and not.

TRUE FORM OF FLAT SURFACES
Generality. Rollover method. Point reversals, straight lines, segments, plane figures lying on planes perpendicular to the main projection planes.

Geometric primitives in MODEL SPACE and PAPER SPACE.

ASSONOMETRIC PROJECTIONS OBLIQUE, ORTHOGONAL AND PROSPECTS
Reduction factors. Unified oblique axonometry (cavaliera; UNI 4819). Parallel orthogonal perspective or orthogonal axonometry. Unified isometric axonometry (UNI 4819). Axonometric representation of flat surfaces, prisms, pyramids; exact and approximate representations of circumferences, curves and solids of revolution. The concept of homography and stereography.

SECTIONS
Purpose of the sections: ideal section plan. Flat sections of prisms and pyramids. Sections of revolution solids (cylinder, cone, sphere, torus). Determination of the contour lines of the sections: method of generating lines and method of auxiliary section planes. Solids obtained through section planes (truncated pyramid, cone, oblique cylinder, etc ...). Use of the PATTERN to obtain the backgrounds in the CAD system. SOLID CONCEPTIONS
Generality. Compenetration of prisms and pyramids. Particular uses of auxiliary section plans. Determination of the intersection line relative to the interpenetration of solids of revolution: method of generatrixes, method of auxiliary section planes, method of auxiliary spheres.

Dimensioning
General criteria, dimensioning and reference lines, arrangement and reading of quotas. Dimensioning systems (in series, in parallel, with overlapping dimensions, combined dimensioning, in coordinates, in polar coordinates). Particular dimensioning conventions (solids of revolution, circles, spherical surfaces, squares, bevels and roundings, elements regularly or irregularly arranged). Criteria for choosing the reference elements and general rules for a correct dimensioning.
Use of DIMENSION commands and their setting for a correct drawing of the drawing.

PRINCIPLES OF 3D CAD SYSTEM OPERATION
Coordinate systems and reference systems
· Coordinate systems:
· Cartesian coordinates
· Cylindrical coordinates
· Spherical or Polar coordinates
· Homogeneous coordinates
· Reference systems
· Local
· Global
· Of the observer
· Of view Representation on video of graphic primitives and notes on classical algorithms.
ELEMENTARY GEOMETRIC UNITS
Methods of representation of the main elementary geometric units.
Transformations:
· Translations
· Rotations
· Scale transformations
· Symmetry and Reflection

Readings/Bibliography

CHIRONE, TORNINCASA, Disegno Tecnico Industriale, ed. Il Capitello, Torino.

CONTI, Disegno tecnologico, vol. 1, 2, ed. Pitagora, Bologna.

SOBRERO, Corso di Disegno, solo vol. 1, ed. Pitagora, Bologna.
FILIPPI, Disegno di Macchine, vol. 1, 2, ed. Hoepli, Milano.
Mortenson, Modelli geometrici in computer graphics, McGraw-Hill.

Teaching methods

The course consists of a theoretical part, given in unified shifts in frontal classroom mode. At the link: https://iol.unibo.it it is possible to download the slides of the course and the exercises developed in the exercises.

The exercises take place in two separate shifts: first round for students with initials of the surname A-K and second shift with students with initials of the last name L-Z. The two shifts have the same contents.
Up to the maximum capacity of the laboratory (120 workstations) it is also possible to attend both shifts and / or refraction. If the capacity is exhausted, priority must be given to the holders of the first-year shift.

In the laboratory guided exercises will be performed by hand and / or by computer. Each student will have a configured station available and will have to develop the exercises himself.
The teacher performs most of the exercises on the projector.
Students must carry out the exercises carried out in the laboratory and, possibly, exercises indicated as to be carried out independently or optional. It is possible to have an educational software license available for installation on your notebook: information on this will be given at the beginning of the course for the best information update. Use of the notebook in the laboratory is not recommended.

The student must save the exercises performed on his own USB memory unit from time to time.

Assessment methods

The exam consists of:


1) a multiple-choice test ("Part 1") lasting 30 minutes on the theoretical topics carried out during the course;

2) a 90-minute computer test ("Part 2"), which involves 3D modeling and "constructive table setting" of an assigned component;

3) a final interview in which issues addressed in the written part and the verification of the models and the tables created and / or assigned during the course will be discussed. The student can choose to continue with a theoretical question if he intends to improve his voting proposal (only if it is higher than enough: 18/30). Failure to verify the tables performed during the course negates the exam completely.

Passing the initial test (the minimum grade will be defined from time to time based on the complexity and number of applications) allows admission to the written test.

Part 1 and possibly Part 2 will be held in the same location (PC) in the computer lab. The final interview can be fixed following the written or other date (with communication at the end of the written). If it is on the same day, a period of time will be required that is variable from the number of the appeal for the correction of the written tests.
Registration for the exam takes place through AlmaEsami [http://almaesami.unibo.it]

Remote assessment procedure:

http://platone.host2go.net/ProcedureEsame/EsameTelematicoDAC.pdf

 

Teaching tools

Frontal lectures.

The course involves the use of computers in the computer lab equipped with a 3D CAD system for parametric solid modeling and automatic drawing.

Links to further information

https://iol.unibo.it

Office hours

See the website of Alfredo Liverani