Aim and contents of course
The course provides the guidelines to functional mechanical design, focusing on the systems and mechanisms for motion transformation. Criteria and methodologies are given in order to choose, analyse, synthesize plane and spatial mechanical devices with particular reference to the field of industrial automatic machines.
In-depth attention is paid to the design of motion law (i.e. motion planning) and to the sizing of suitable actuation systems capable of achieving the performance required.
Lessons are combined with practice exercises in the IT classroom with the object of analysing and synthesising the systems studied. The practice exercises are developped by groups of students and deal with design problems directly linked to the manufacturing industry.
Topics deal with
The functional design of a mechanical system. Introduction to motion law design, motion laws, mechanisms and actuation system classification.
Motion law. Motion law definition for the automation industry and properties of the acceleration diagram. Motion law adimensionalization and characteristic coefficient definition (velocity coefficient, acceleration coefficient, jerk coefficient, etc). Analysis of the principal requirements in motion law design (maximum acceleration limit, maximum velocity limit, ecc) with reference to the basic motion law. The improvement of motion law (basic motion law modified and polynomial motion law). Limits to the improvement attainable.
Cam Mechanisms . Description and analysis of cam mechanisms used in the industrial automation with particular reference to the manufacturing environment by means of a selection of industrial case studies. Pressure angle definition and undercutting analysis. Kinematic analysis of cam mechanisms through the inversion of motion and equivalent mechanisms. Cam profile determination for radial cam with translating roller follower, translating flat-faced follower and with oscillating roller follower. Methodologies to reduce the cam dimensions. Contact typologies between cam and follower: force close cam joint, form close cam joint and joint with “clearance ramps”. Reference to devices capable of modifying the movements of cam mechanisms.
Linkage Mechanisms: Definition and classification of linkage mechanisms based on the number of the links (four bars mechanisms, five bars mechanisms, etc.). Kinetostatic analysis and kinetostatic duality: transmission angle and generalized transmission ratio. Kinematic analysis of a linkage mechanism by means of vector closure equation and the Newton-Raphson method (coupler curve plotting for a four bar mechanism). Introduction to methods for direct and indirect kinematic synthesis of linkage mechanisms. Reference to kinematic optimisation. Quick return mechanisms and mechanisms with delays (superimposition of the dead centres method) and force multiplier mechanisms. Introduction to compliant mehanisms.
Actuators: Electrical motors used in automation: catalogue reading and typical problems in choosing electrical motors. Motor-reducer sizing methodology: accelerating factor and load factor, transmission ratio choosing and check of motor-reduce choice. Pneumatic actuators for industrial machines: devices and design of elementary circuits.