The basic language of all engineering activities is represented, in the majority of cases, by design processes that involve the engineer in two distinct activities: modeling and communication. In areas such as systems design and analysis, industrial plants and processes, which are typical fields of automotive engineering, the engineer uses technical drawings in order to identify construction solutions, carry out design calculations, and perform a technical-economic comparative analysis of the various solutions. In this sense, technical drawing is not merely a graphical exercise, but becomes a synthesis of the engineer's expertise about a product which must respect economic, manufacturing and functional specifications. Today, the engineering drawing is a document to communicate, in a complete, precise, unambiguous and rigorous way, all information of an industrial component with the main objective of its manufacturing. The course provides the theoretical notions related to the formalization of shape, dimensions, technological, dimensional and geometrical information that will permit the student to make the technical drawing of any mechanical part.

The course offers the students the knowledge and methodologies required for modeling and graphic representation of machine components, with particular reference to national and international standards. In particular, the course will deal with aspects of design standardisation, projection and section methods, representation of dimensional and geometric errors. The main mechanical parts will also be described, as well as their representation and dimensioning regulations. The students are expected to acquire the ability to represent and to dimension the most common industrial components, considering their functional and manufacturing requirements, as well as interpreting unambiguously and correctly drawings of parts and assemblies. The module therefore intends to provide undergraduate engineers the knowledge and methodologies necessary for components modeling and graphic description, in accordance to national and international Standards. In more detail, the course deal with the drawing norms, the projection and section methods, the representation of dimensional and geometrical errors. The main mechical parts will be described, with the corresponding norms for representation and dimensioning. Students need to acquire the abilities of interpreting univocally and correctly drawings of parts and assemblies, of representing and dimensioning common machine parts, and choosing autonomously: - the required number of views for a complete representation of the part, - the section techninque more fitting to the part morphology, - the dimensioning method more suitable for describing the functional, techinological and checking requirements and to calculate taper and inclination parameters, - the dimensional tolerances for fits, and their characterization, - the dimensionale tolerances for functional dimension defined by tolerance stack-up analysis - then geometrical tolerances and their datums, - the application and drawing of mechanical connection parts. The study cases proposed during the practice hours offer an application background oriented to common problems that can be found in the professional career. Moreover it is required the cability to manually sketch drawings of mechanical components, to produce 3D models and 2D drawings with Cad tools. The practice assignments offer a background of applications related to common problems and solutions found in the engineering practice.

Basic IT knowledge. Basic principles of orthographic representations.

INTRODUCTION TO TECHNICAL DRAWING [4 hours]: Drawing as a graphic language for the communication of technical information. Placement of the drawing in the life cycle of the product. The digital prototype. Standardisation and unification in the technical drawing field: scales, sheet sizes, lines and graphic symbols. ORTOGONAL PROJECTIONS [5 hours]: Orthographic projections of solids: central and parallel projections, orthogonal and oblique projections, axonometries and orthographic projections. Arrangement of the views according to the first and third angle methods (European and American standards). Auxiliary views. Representation of features (virtual edges, flattened surfaces, interrupted views of large parts, detail views). Compenetration of basic solids (flattened cylinder, radial hole on solid and hollow cylindrical shaft, keyways). SECTIONS [6 hours]: Sections, their necessity and their representation standards. Hatching and characterization of the material. Hatching of assemblies. Special cases (thin solids, large parts, ribs) and exceptions (standardised parts, solids, shafts, bearings). Section methodologies: full section, offset section, aligned sections, section with general surface, half-sections, broken-out sections, revolved section, offset sections) DIMENSIONING [5 hours]: The elements of dimensions, their layout and the relevant regulations. Classification of the dimensions (size and location) and criteria for their arrangement. Dimensioning systems (technological, functional and for inspection). The arrangement of the dimensions (series, parallel, combined, superimposed coordinates). Dimensioning of circular elements (circles and cylinders or holes). Special dimensioning features (pattern of holes, fittings, chamfers, arcs, angles, ropes, spheres, squares). Margin notes to simplify dimensioning. Dimensioning of symmetrical and semi-sectioned parts. Description, calculation and prescription of taper, inclination and tilt. Technological dimensioning of the main production processes for chip removal (turning, milling, drilling) for plastic objects obtained by moulding, die-casting and sand casting (die separation plane and rake angles). Processing material allowance. REPRESENTATION OF DIMENSIONAL ERRORS [7 hours]: Dimensional tolerances and their justification with respect to technical, economic, logistical and commercial objectives. Notes on control instruments: differential gauges. Definition of fits: clearance, interference, transitional. Characterization of the fits in minimum and maximum material conditions. Definitions: shaft and hole, nominal dimensions, basic size line, limit dimensions, deviations and their calculation. Graphic representation of the dimensional tolerance range. The system of tolerances according to the ISO standard. Tolerance grades and fundamental deviations. Examples of fit characterization with ISO tolerances and their graphical representation. Representation of tolerances for part and assembly drawings. General tolerances for dimensions, angles, chamfers and fittings and their relative degrees of precision. The basic-hole and basic-shaft systems. Criteria for the selection of recommended dimensional tolerances and fits. Part drawings and assembly drawings. Indications in the assembly drawing (position numbers, bill of materials). ROUGHNESS [2 hours]: Mathematical definition of the average roughness parameter and other roughness parameters. Influence on static and fatigue mechanical strength, corrosion resistance, wear, coupling forcing. Measurement of roughness. Indication on drawing. Symbols of orientation of the roughness texture. Typical values of roughness of main production processes. Dependency between dimensional accuracy and roughness. The grinding process and the grinding grooves. TOLERANCE STACK-UP ANALYSIS [5 hours]: Identification of the functional dimensions ON the assembly drawings. Setting of the ordered sequence of dimensions (origin, direction, dimension vectors). Stack-ups of parts and assemblies. Tolerance allocation. Comparison between functional and technological dimensioning. Technological transfer of functional dimensions. Geometric factor. GEOMETRIC TOLERANCES [9 hours]: Basic terms and concepts. Form tolerances (straightness, flatness, circularity, cylindricity and their application. Reference systems (definition and choice of DRF, shift applied to FOS, FOS datum pattern and partial references) and application examples. Orientation tolerances (parallelism, perpendicularity, inclination) and examples. Position tolerances (virtual condition, bonus, shift). Use of codatum. Pattern of Cartesian and polar FOS. Use of minimum and maximum modifiers. Projected tolerance zone. Tolerances of concentricity, symmetry and oscillation. Profile tolerances. Comparison between ASME and ISO. CONNECTIONS [6 hours]: Threads: The Iso triangular thread and its profile. Helix angle pitch, major and minor diameters. Dimensions of the profile fillets and chamfers. Direction of the helix winding and multiple threads. Standard dimensions and pitches (fine and coarse). Thread types (trapezoidal, square, buttress, Edison). Withworth and Gas threads (sealed and non-tight) and their indication on drawing. Conventional representation and dimensioning of visible and sectioned screws and nuts. Representation in the assembly drawing. Dimensioning of threaded blind holes and relationship with the machining process and inspection. Threads grooves and description of their shape and dimensioning. Threaded parts: Definitions. Shape of the heads and points of the screws. Screw connections: cap screw, bolt and captive screw. Dimensioning of drilling and threading depths. Drawing of hexagonal heads in orthogonal projection. Threaded nuts and ring nuts. Locknuts (devices to avoid unscrewing): washers, spring washers, cotter pins and their application. Designation of the threaded elements in the bill of materials. Dimensional tolerances of the threaded elements. Calculation of the position tolerance when tightening parts (Fixed and Floating Fasteners Formulas) Pins and coupling pins: Reference or connection function. Coupling pins mounting criteria: choice of coupling tolerances. Cylindrical, elastic, conical and slotted pins. Areas of application and mounting instructions. Retaining rings: Types: axially assembled, radially assembled. Mounting sequence and tools. Size and dimensioning of the grooves for retaining rings, including tolerances and functional constraints on the maximum axial load. Hub and shaft connections with keys and parallel keys: Description of the slot dimensions depending on the shear or compression stress of the connection. Typical key shapes and corresponding shaft mounting slots. Dimensions and tolerances. Typical key tolerances and fits with keyways. Machining and dimensioning of the slots. Special executions of tabs and their use. Splines: Splines with parallel and involute flanks. Internal, external or flank centering and its relationship with the machining processes. Conventional representation and symbols. Conventional dimensioning. Representation of spline assemblies. Typical dimensional and geometric tolerances. TRANSMISSION [3 hours]: Gears: Property of the involute curve, its mathematical description and its discretization or parametric representation. Notes on the machining processes of gears. Conventional representation of cylindrical gears with straight, helical and conical teeth and indication of the helix windings. Representation of a single gear and assembled gears. Dimensioning with data separation: dimensioning for turning operations and additional table with teeth characteristics. Typical dimensional and geometric tolerances. Notes on special inspection instruments. Transmission with belts and sprockets: Flat belts and pulleys and dimensioning examples. Crowning. Trapezoidal belts and pulleys: standardised dimensions and dimensioning examples. Notes on Poly-V belts and pulleys. Sprockets: shape of sprockets, typical sections of chain links. BEARINGS [3 hours]: Sliding bearings. Mounting tolerances, surface finish, lubrication systems. Rolling bearings: General structure (rings, cage, rolling elements), types of rolling elements, designs and their ISO designation. Diameter and dimensional series. Mounting shemes for radial bearings and the problem of thermal expansion. Locking of the bearings: shoulders, spacers, circlips, ring nuts, lock washers. Axial bearings: mounting criteria (clearance and coupling) for single-effect, double-effect and self-aligning bearings. Geometrical constraints in mounting with self-aligning and radial bearings to ensure orientable axis. Preload systems. Mounting of face to face and back to back of angular contact bearings and adjustment devices. Housings: dimensions and fittings, shoulders, surface roughness, criteria for choosing the fit dimensional tolerances, dimensioning the seats with geometric tolerances. Lubrication devices. Sealing components: felt rings and their grooves, shaft seals, V-rings, O-rings and groove sizing and their tolerances. Seat tolerances and surface finishes of active surfaces. Labyrinth seals. ASSEMBLY DRAWING ANALYSIS [3 HOURS]: Sealings of hydraulic actuators, electric motor (radial bearings), circular saw spindle (radial bearings and labyrinth seals), column drill (pulley, key, ring nuts, axial and radial bearings, rack and pinion), Grinding wheel (double oblique bearings), manual drill with speed change (bearings, gearbox, front tooth clutch), 3rd slider of the lathe (axial bearings, threaded nuts, graduated drum adjustment), truck differential (bevel gears and angular contact bearings), milling gearbox (bevel gears with positional adjustment system)

Web site: http://www.polito.it/disegno

Le lezioni si svolgono in aula convenzionale e forniscono le nozioni teoriche indicate nel programma. Le esercitazioni a squadre si svolgono nelle aule da disegno e consistono nella rappresentazione grafica tradizionale, anche a mano libera, in assonometria ed in proiezione ortogonale quotata di parti o organi presentati singolarmente, o estratti da complessivi. I componenti devono essere rappresentati nelle viste e sezioni più opportune, indicando quote, tolleranze e rugosità. Devono inoltre essere calcolati giochi ed interferenze. Viene richiesto il metodo di quotatura funzionale. Mediante un software di disegno assistito 2D e 3D parametrico, nelle esercitazioni di laboratorio si realizzano i modelli tridimensionali dei componenti, che verranno poi assemblati con opportune relazioni di accoppiamento per formare un complessivo. Attraverso il software devono essere generate le tavole 2D dei particolari e la distinta dei materiali.

1. S. Tornincasa,Technical product documentation using ISO GPS - ASME GD&T standards, Ed. Il Capitello 2018 2. Colin H. Simmons, Dennis E. Maguire "Manual of Engineering Drawing", 2nd edition, e-copy of textbook, Elsevier, 2004 3. B. Griffith, Engineering drawing for manufacture, Kogan page science 3) C. Jensen, J. D. Helsel, Engineering drawing and design, Mc Graw-Hill 4. Frederick E. Giesecke et al. “Technical Drawing”, Textbook (hardcopy) Pearson 2009

Modalità di esame: Prova scritta su carta con videosorveglianza dei docenti;

A graphic test evaluates the student's ability to represent and dimension common machine parts, autonomously choosing the minimum number of views required for the complete representation of the part, the section technique best suited to the morphology of the part, the most appropriate dimensioning system based on functional, technological or control requirements, dimensional tolerances of fit, geometric tolerances and DRF. The student should also be able to represent and dimension the mechanical connections, applying the appropriate standards. At the same time, the ability to perform dimensional fit calculations, with geometrical tolerances, the characterization of the taper, tilt and taper parameters, the tolerance stack-up calculation on simple assemblies will be tested. The test is evaluated according to the quality of the graphic representation, the correctness of the graphic representation, the dimensions, the ability to perform the required calculations. The verification of the theoretical skills possessed by the student, with particular reference to national and international standards, is evaluated with a series of questions included in the graphic test. The duration of the test does not exceed 3 hours and allows to obtain the maximum evaluation of 28/30. Practice drawings must be delivered week by week for evaluation an can increase the final result of 2 point maximum. "L" honors will be conceded on the basis of a good graphical representation. There is no oral examination.

Modalità di esame: Prova scritta (in aula);

A graphic test evaluates the student's ability to represent and dimension common machine parts, autonomously choosing the minimum number of views required for the complete representation of the part, the section technique best suited to the morphology of the part, the most appropriate dimensioning system based on functional, technological or control requirements, dimensional tolerances of fit, geometric tolerances and DRF. The student should also be able to represent and dimension the mechanical connections, applying the appropriate standards. At the same time, the ability to perform dimensional fit calculations, with geometrical tolerances, the characterization of the taper, tilt and taper parameters, the tolerance stack-up calculation on simple assemblies will be tested. The test is evaluated according to the quality of the graphic representation, the correctness of the graphic representation, the dimensions, the ability to perform the required calculations. The verification of the theoretical skills possessed by the student, with particular reference to national and international standards, is evaluated with a series of questions included in the graphic test. The duration of the test does not exceed 3 hours and allows to obtain the maximum evaluation of 28/30. Practice drawings must be delivered week by week for evaluation an can increase the final result of 2 point maximum. "L" honors will be conceded on the basis of a good graphical representation. There is no oral examination.