29741 - Machine Design and Drafting T

Learning outcomes

Students deepen their theoretical knowledges on modelling, machine design, tolerancing, material choosing. The course is at the second cycle of the third year of Mechanical Engineering, therefore Students, under the supervision of the Teacher, can apply the content of the theoretical part of this course, together with the whole experience acquired in basic Drawing, Machine Design, Applied Mechanics and Technology to practical applications in the mechanical and industrial fields. Students will disassemble, study, re-design and model actual machine assemblies and components. Modelling is performed by utilizing advanced design-and-drawing CAD 3D tools.

Course contents

Skills acquired during the first-year basic course (Disegno Meccanico e Automatico), inside the present course and in all the others of Machine Design, Applied Mechanics, Technology, etc., are exploited in order to disassemble, measure, re-design and model in 3D some assemblies chosen among mechanical applications and available for the Students during laboratories.

Course consists in theorethical and laboratory activities, that are splitted in two modules:

Theoretical teaching - Module 1

Basic concepts

Assonometric views, actual surface shape recostruction, sheet metal flat pattern drawing.

Dimensional tolerancing

Choice of the right shape, dimensioning and tolerancing of components performed by fusion, forging, stamping, rolling, shearing, punching, drawing and deep drawing; choice of dimensional tolerances in hub-shaft interference fit; functional analysis and identification of the tolerancing chains in actual mechanical assemblies.

Geometrical tolerancing

Feature and Feature of size; Macrogeometrical errors; Form, Orientation, Location and Run-out geometrical tolerancing; Taylor's Rule (or Envelope principle); Maximum Material Requirements, Least Material Requirements, Reciprocity Requirements.

Theoretical teaching - Module 2

 Review of building science

- The Euler-Bernoulli theory

- Analytical solution of straight beams stressed in the plane with normal stress, torsion, shear and bending moment: isostatic case and hyperstatic

- Castigliano's theorem

- Very thick recipients

Matrix calculation of structures: the direct method

- The stiffness matrix of the straight beam stressed under normal stress, torsion, shear and bending moment

- The mass matrix for the vibration analysis of a transmission shaft

- The equilibrium equation of the finite beam element in static and dynamic

- The case of the beam

- The case of the curved beam

Laboratory - Module 1

Teamwork in classroom

Students, divided into groups, measure and sketch existing industrial components and assemblies, perform improvements, shape optimization, dimensioning, tolerancing, material selection, etc.; in developing this activity, Student must compile, take care and conserve a personal copybook with notes, re-designs, projects, etc., testifying the work performed during the year. This copybook will be evaluated by the Teacher in the final exam.

Individual activity

Each Student makes models for components and assemblies studied in the previous step through 3D CAD modeller; afterwards, they carry out constructive 2D drawings from 3D models; optimization or re-design of some peculiar aspects of components or assemblies might be performed.

Laboratory - Module 2

During the hours foreseen for the laboratory, exercises will be carried out suitable for the numerical solution of frames with few degrees of freedom: parallel to the manual solution of the proposed exercises, exercises will be carried out that involve the use of an automatic calculation program, provided by the teacher.

N.B. Given the current emergency situation due to the pandemic affecting our country and given the uncertainties that this causes on teaching methods, the part of the course linked to the collegial work phase in the drawing room can be revised having to take into account possible impossibility to carry out the work in the classroom and especially in a group. This activity can be replaced by individual work on components made available by the teacher, if it is possible to meet in presence, or found by the student independently, under the guidance of the teacher, if instead attendance is excluded. In the further impossibility of finding assembly components from real, the activity can be carried out virtually, using the CAD tool.

Readings/Bibliography

Knowledges and skills pertaining to the first-year course Disegno Meccanico e Automatico (Mechanical Drawing) and the methods of mathematical analysis and the fundamental notions relating to the analysis of stresses and strains must have been acquired by the Students to be able to fruitfully attend to this third-year course.

Contents of the books prescribed during the first-year course are therefore propedeutical for this course.

Direct references to theory lessons

The teaching material, provided by the teacher and referring directly to the lessons, can be found on the teaching on-line Platform, in the section reserved to the course of Disegno di Macchine T (https://virtuale.unibo.it/?lang=en).

Reference books - Module 1

- CONTI, "Disegno Tecnologico", Vol. 1 e 2, Ed. Pitagora, Bologna.

- FILIPPI, "Disegno di Macchine", Vol. 1, 2, Ed. Hoepli, Milano.

- MANFE', POZZA, SCARATO, "Disegno Meccanico", Vol. 1, 2, 3, Ed. Principato, Milano.

- BALDASSINI, “Manuale per Disegnatori Tecnici” or similar.

Reference books - Module 2

- J.S. Przemieniecki, Theory of matrix structural analysis, MacGraw-Hill, 1968

- F. Cesari, Il calcolo matriciale delle strutture, Vol.2, Pitagora, 2019

In-depth books (in alfabetic order inside each thematic area)

List of the recommended books for support or study, organized below in classes of arguments, is extensive in order to provide a wide documentation for the students. This does not imply that they must necessarily be purchased. A large part of them can be consulted in the library and the partition of the students into groups, described above, can facilitate an alternative purchase of the various volumes, with exchange of them between the various members of the group itself.

Design and Drafting

- BERTOLINE, WIEBE, “Fondamenti di Comunicazione Grafica”, McGraw-Hill.

- CALIGARIS, FAVA, TOMASELLO, “Dal Progetto al Prodotto”, Paravia, Torino.

- CHIRONE, TORNINCASA, "Disegno Tecnico Industriale", Vol. 1, 2, Ed. Capitello, Torino.

- STRANEO, CONSORTI, "Disegno di Costruzioni Meccaniche, Vol. 1, 2, Ed. Principato, Milano.

- CARFAGNI, FURFERI, GOVERNI, VOLPE, "Esercizi di disegno meccanico", Ed. Zanichelli, Bologna.

- UNI Ml, "Norme per il Disegno tecnico", Vol. 1 , 2, Pubblicato a cura dell'Ente Nazionale Italiano di Unificazione, Milano.

Machine Design, Strenght od Materials, Material Science and Tecnology

- BELLUZZI, “Scienza delle Costruzioni”, Vol. I, II e III, Zanichelli, Bologna.

- CALIGIANA, CESARI, “I materiali compositi”, Pitagora Editrice, Bologna.

- DEUTSCHMAN, MICHELS, WILSON, "Machine Design - Theory and Practice", Macmillan Publischers, London.

- JUVINALL, MARSHEK, “Fondamenti della progettazione dei componenti delle macchine”, Edizioni ETS, Pisa.

- SHIGLEY, MISCHKE, “Mechanical Engineering Design”, McGraw-Hill International Editions, Singapore.

- SPOTTS, “Design of Machine Elements”, Prentice-Hall, Inc., Englewood Cliffs, New Jersey.

Product development and CAD

- Tutorial on line in web site [http://learningexchange.ptc.com/tutorials/by_sub_product/ptc-creo-parametric]

http://learningexchange.ptc.com/tutorials/by_sub_product/ptc-creo-parametric

 

Teaching methods

Course configuration:

Module 1

- theorethical classroom lessons;
- physical disassemblage of mechanical assemblies (delivered by the Teacher) and hand sketching of the corresponding mechanical components. This task is performed by Students arranged in several working groups

- 3D modelling and 2D layout of assemblies and mechanical components. This task is performed individually by each Student under the supervision of the Teacher.

According to the extremely practical approach of this course to the matter dealed with, frequency to the course and laboratories is fundamental.

Lack of frequency to CAD laboratories implies for the Students a further individual CAD test.

Minimum number of hours to validate frequency depends on laboratory timetable pertaining to the specific academic year and it is specified, at the beginning of the course, by the Teacher.

Module 2

The lessons are held at distance, illustrating the theory through a text whose pdf is provided to students in advance.

The exercises that are carried out manually relate to simple looms with few degrees of freedom; first you do it the setting in a literal way, then the geometric and material data are provided to obtain the numerical solution.

The most important mathematical operations are:

- solution of systems of linear equations

- solution of ordinary differential equations

- solution of eigenvalue problems

- graphs

As an alternative to the manual solution, exercises with frames with many degrees of freedom will be carried out through the use of a automatic calculation program provided by the teacher.

Assessment methods

PREVIOUS SKILLS

Previous skills of the basic course "Mechanical Drawing" and the methods of mathematical analysis and of the fundamental notions relating to the analysis of stresses and strains are necessary. This must be carefully considered by students incoming inside Erasmus exchanges.

ASSESSMENT

Exam consists in a written test (compulsory for admission to the speech) and a speech (oral test).

Written test consists in redesigning a teacher's assigned assembly that contains incomplete parts to be interpreted and integrated with standard and non-standard components. During the test, it is permissible to consult texts, notes, tables and manuals. There are four hours available for the written test.

The number of drawings to be performed depends on the mechanical assembly assigned. Drawings can be performed with instruments or in free hand, as the Candidate would prefer; the Students must hold with him a couple of paper sheet, for each format A4 and A3, useful to perform the written test. Sheets can be prearranged with printed title block by utilizing CAD software emploied in laboratory during the year.

Teacher provides paper sheet for notes and rough sketches necessary during the re-design activity and the choice of standard or non standard components. Much more details the Student adds in this sheet, more faitful and sound will be the right evalutaion of the test by the Teacher.

Admission to oral test is conditioned upon being successful in written test; Student must reach 18/30, which is the mean score obtained in every question contained in the written test (the score of each question is measured on a base of thirty). The exact number of questions depends, obviously, on the peculiar test proposed.

Results of written test are provided before the next oral test, which is usually after about a week from the written test; timetable of the oral tests (exactly as that of the written tests) are at disposal of the Student on Almaesami [https://almaesami.unibo.it/almaesami/welcome.htm]; in any case, positive results to the written test are considered valid until the winter session of the next solar year (that is, before the beginning of the next cycle of lessons), so Students, which succed in written test, can afford oral test in every session until the winter session of the next solar year (included);

If there is lack in frequency to the CAD laboratory, the Student is required to sustain a further test, by utilizing the solid modeler, in a date to be agreed with the Teacher who holds the CAD laboratory and, in any case, before the oral exam.

Oral test

During oral test, the Student performs the survey of a real component assigned by the Teacher and makes the corresponding technical drawing in accordance with the current rules;

The Teacher asks some questions about the items explained during the course, he evaluates drawings, notes and work done by the Student during the year and evaluates the survey made in the first step of oral test. The exact number of the questions depends on results of the written test, the value of the drawings performed in laboratory during the year, the value of the projects and notes included in the copybook.

Each Students must take with him at the oral test all the drawings (CAD drawings must be brought in a printed version) and their personal copybook (with notes, re-designs, projects, etc), testifying the work performed during the year.

Global score depends on answers to the oral tests, value of the drawings performed in laboratory during the year, value of the notes and projects containded in the copybook, value of the survey made in the first step, score obtained in the written test.

The knowledge learned during the development of Module 2 will be checked by the teacher who, on a weekly basis, will submit to the students a structure to be calculated with the methods developed during the theoretical lessons.

The exercises set in the classroom and partially carried out with a calculation program must then be completed and collected in a notebook to be presented to the oral exam which will take place in the manner described above.

IMPORTANT NOTES

Student must book his exam in Almaesami [https://almaesami.unibo.it/almaesami/welcome.htm] web site.

Results of the written test can be found on the teaching on-line Platform, in the section reserved to the course of Disegno di Macchine T (https://virtuale.unibo.it/?lang=en).

As a concluding remarks, during written session, Student must hold with him all the tools to perform drawings and a couple of paper sheets of each A3 and A4 format; he can take all the books, notes, drawings, useful to perform the test. Obviously, no web or phone connections are allowed.

During oral session Student must hold with him all the tools to perform drawings, all the drawings (CAD drawings in a printed version) performed during the year, the copybook (with projects, notes, re-design activities, etc.) and a USB flash drive with all the source files of CAD drawings to be stored by the Teacher.

Teaching tools

Slides and other information can be found on the teaching on-line Platform, in the section reserved to the course of Disegno di Macchine T (https://virtuale.unibo.it/?lang=en).

LABORATORY INFORMATIC SUPPORTS

CAD SOFTWARE UTILIZED:

- CREO

CALCULATION OF STRUCTURES:

In order to perform the exercises efficiently, the teacher is responsible for describing:

- the use of a calculation program to carry out the above mentioned elementary operations

- the use of a calculation program for the automatic solution of the frames

Further informatic support can be obtained by connecting to web site:

- http://learningexchange.ptc.com/tutorials/by_sub_product/ptc-creo-parametric

Office hours

See the website of Daniela Francia

See the website of Francesco Cesari