Six Sigma methodology: an effective tool for quality management.

The quality standards of the output, the features of delivery and the introduction of new services are becoming the most important factors to success in business performance. In this context, the application of new methodologies is essential to increase the business performance. Six Sigma can give an important solution for those companies that intend to highlight the customer satisfaction focusing on the continuous improvement of the processes. The purpose of this paper is to show the power of the Six Sigma methodology in increasing the performance level of industrial processes and systems. The paper shows a Six Sigma case study applied to the automotive market

A Differential Mechatronic Device: Design, Simulation and Experimental Results

Differential mechanisms are widely studied in literature, from a theoretical viewpoint and for applicative reasons. A differential mechanism is a mechanical system with one or more output motions resulting from the combination of different input motions acting on the same degree of freedom. In this work, we point the attention on planar differential systems (a monoaxis and a Cartesian device) composed by belts and pulleys. Particularly the Vernier effect is used to realize high-speed and highaccuracy devices with low-cost components. Simplified models of these two systems are presented to show the main kinematic and dynamic features. An advanced model is then realized for the Cartesian device with the aid of the Dymola software and simulation results are compared with the expected ones from the simplified model. The control of the system is realized with three PI systems (proportionalintegrative) optimized via an adaptive logic. Finally early experimental results are presented only for the monoaxis system

Design and Analysis of a Fibre-Shaped Micro-Actuator for Robotic Gripping

A prototype of an automatic micropositioning system was developed. This prototype uses a shape memory alloy (SMA) actuator, a dedicated PI controller and a piece of software to command a desired motion profile for the actuator. The proposed micropositioning system is characterized by a 4 mm stroke, a 1 μm resolution and a 70 g nominal force and can be commanded directly from a personal computer and without human retroaction. The closed loop positioning resolution (1 μm) is obtained in spite of inaccurate system behaviour during its movement

Improvement through process integration using a simulative, dynamic method

The need for globalisation, the saturation and instability of markets, the life-cycle time reduction of products, the growth of item variety, the customer demands have been main factors contributing to a radical change of management conceptions and strategies. This complex environment has induced companies to search the keys to achieve competitiveness, focusing on process integration. The purpose of the paper is to explain how managing the internal functions of a company in an integrated way can lead to an effective improvement. In order to represent the flows and to quantify improvements, a simulative, dynamic and integrated model is developed

Advanced composite materials in precision machine tools sector - Applications and perspectives

The most recent R&D activities and applications of advanced materials for designing and fabrication of light and damped structures of precision machine tools (MT), are here presented. These new solutions include carbon fibres reinforced polymers (CFRP), hybrid sandwiches and novel multifunctional smart structures

A Novel Logic and Approach to Speed up Simulation and Analysis of Production Systems

The paper describes a novel logic to model, simulate and analyze production systems using Discrete Event Simulation tools. An adaptable and flexible DES model has been developed to represent different manufacturing environments. The goal of the proposed DES-based parametric model is to offer to industrial analysts a compact, fast and easy way to configure and use decision support tools. The logic is based on elementary structures with a vertical multilayer architecture that permits entities to access and loop in multiple times. Since it has been assumed manufacturing systems are combination of elementary parts, the architecture of the model becomes quite simple since representing few structures only, and the simulation of heterogeneous systems is the result of as many iterations as needed by a user. This approach is adaptable both to SMEs and large companies, permitting to avoid the use of dedicated SW and allocated skilled person

Reliability characterization of a piezoelectric actuator based AVC system

Reliability and Maintainability analyses are becoming an increasing competitive advantage in machine tool design. In particular, the goal of machine tools for Ultra High Precision Machining is to guarantee high specified performances and to maintain them over life cycle time. A structured reliability approach applied to such complex and innovative systems must be integrated in the early phase of the design. In this paper, the reliability characterization of an adjustable platform for micromilling operations is presented. The platform is intended to improve the surface finishing of the workpiece, through a broadband Active Vibration Control device based on high performance piezoelectric multilayer actuators. The study intends to assess the capability of the system to maintain along the life cycle the appropriate reduction of the chattering vibrations without any shape error. By dividing the system through a morphological-functional decomposition, the critical elements are detected and their reliability issues are extensively discussed. Their lifetimes are described through opportune distributions and models. The study is completed by the quantitative reliability prediction of the overall system. Finally, a sensitivity analysis is performed and reliability allocation implications are evaluated to determine the effect of every component on the system reliability characteristics and life cycle cost

Design of piezo-based AVC system for machine tool applications

The goal of machine tools for Ultra High Precision Machining is to guarantee high specified performances and to maintain them over life cycle time. In this paper the design of an innovative mechatronic subsystem (platform) for Active Vibration Control (AVC) of Ultra High Precision micromilling Machines is presented. The platform integrates piezoelectric stack actuators and a novel sensor concept. During the machining process (e.g. milling), the contact between the cutting tool and the workpiece surface at the tool tip point generates chattering vibrations. Any vibration is recorded on the workpiece surface, directly affecting its roughness. Consequently, uncontrolled vibrations lead to poor surface finishing, unacceptable in high precision milling. The proposed Smart Platform aims to improve the surface finishing of the workpiece exploiting a broadband AVC strategy. The paper describes the steps throughout the design phase of the platform, beginning from the actuator/sensor criteria selection taking into account both performance and durability. The novel actuation principle and mechanism and the related FE analysis are also presented. Finally, an integrated mechatronic model able to predict in closed-loop the active damping and vibration-suppression capability of the integrated system is presented and simulation results are discussed

Extended pkm fixturing system for micro-positioning and vibration rejection in machining application

The paper aims to present a mechatronic device able to micro-position the workpiece and to reject disturbances due to machining operation. A decoupling method is proposed for a parallel kinematic machine (PKM) fixturing platform composed by a 3-DoF flexure-based piezo-actuated mechanism. The parallel platform, with a vertical motion and two rotations, is described and its kinematics and dynamics are studied. The coupling undesirable effect is investigated based on a set of poses. To improve the quasi-static regulator model for a set-point following system, a bump less switching controller and a fine-tuning procedure, to estimate the parameter uncertainty and enable the external disturbance containment in an extended broadband frequency range, are presented. The platform and the piezo-actuator controllers are modelled based on a gain scheduling, standard ISA form method, to guarantee the stability. The accuracy is demonstrated through a set of simulations and experimental comparisons. A sensitivity analysis that evaluates the tracking performance and the disturbance rejection based on the number of signal amplitudes, frequencies, and phases is discussed. A validation phase has shown that the developed architecture presents a steady state error lower than 1.2 µm, a vibration reduction of 96% at 1130 Hz with a maximum resolving time of 6.60 ms