Mika Lohtander

Chatter Detection in Turning Processes Using Coherence of Acceleration and Audio Signals

Chatter is an unfavorable phenomenon in turning operation causing poor surface quality. Active chatter elimination methods require the chatter to be detected before the control reacts. In this paper, a chatter detection method based on a coherence function of the acceleration of the tool in the x direction and an audio signal is proposed. The method was experimentally tested on longitudinal turning of a stock bar and facing of a hollow bar. The results show that the proposed method detects the chatter in an early stage and allows correcting control actions before the chatter influences the surface quality of the workpiece. The method is applicable both to facing and longitudinal turning.

Stray inductance estimation with detailed model of the IGBT module

Stray inductances cause various problems in a power inverter and should be appraised and minimized at an early design stage to avoid later required countermeasures and redesign after the device prototype has been built. The stray inductances of the commutation loops of an Active Neutral Point Clamped (ANPC) inverter are estimated in this paper. Detailed model of the Insulated Gate Bipolar Transistor (IGBT) module is created to improve the accuracy of the stray inductance calculation. The influence of the coupling between the IGBT modules and between the IGBT modules and the busbars on the commutation loop inductance is considered. The partial inductances of the components of the commutation loops are estimated by AnSYS Q3D parasitic extractor to calculate the total stray inductance. It is found that the commutation loop inductances of the studied ANPC inverter are overestimated by neglecting the couplings between the IGBT modules and between the IGBT modules and the busbars.

Graph-Based Analysis of Metal Cutting Parameters

In this work, the interdependencies of different metal cutting parameters are examined. In order to ensure competitiveness in the field of manufacturing, the quality, productivity and costs of the work must be in optimal balance. The parameters affecting the end result of a metal cutting process form a complex web of interdependencies. In this work, graph-based modularity analysis is applied in order to impose a structure on the network of parameters. This allows the identification of the parameters that are to be used in more thorough examination of the individual cases. Combined with an understanding of the graph topology such as parameterized relationships between different factors, this enables powerful heuristic tools such as expert systems to be created.

Modelling of low inductive busbars for medium voltage three-level NPC inverter

Design of low inductive busbars for medium voltage Neutral Point Clamped (NPC) inverter is studied. In a hard-switched inverter the stray inductance causes various problems, such as over voltages, current unbalance, and possible resonance with DC-link capacitors. These problems lead to improper operation of the inverter and an increased level of electromagnetic interference (EMI). The laminated busbars are known to be a good solution for minimizing the stray inductance. It is important to estimate and minimize the stray inductance of the busbars in an early design stage. FLUX3D is used to compare three physical layouts and analyze the influence of the placement of the main circuit components on the inductance value.

Improvement of IGBT model characterization with experimental tests

The dynamic IGBT model is characterized with a circuit simulator characterization tool by utilizing datasheet information and after that the model is tuned by using data from experimental measurements. The circuit simulator simulation results from both models are compared with the experimental results and the possible accuracy improvements are reported. The main research question of this work is how well these models can describe the semiconductor loss behaviour and the different voltage and current overshoots in IGBT switching event and what is the usability of the models. These issues are mainly observed and compared near the nominal collector current, but some example results with higher and smaller current are presented as well. A commercial software tool Simplorer 11 is used for the simulations and the component that is used in the comparison is FZ400R17KE4. Experimental test measurements are performed with an IGBT double pulse tester system. The comparison between the simulation models and the experimental data is reported and conclusions are made. The simulation results show that the characterized IGBT model is usable for voltage behaviour investigation of the IGBT in the hard switched operation. In addition, the measurement data characterized model achieves an acceptable accuracy considering the switching losses.

Review of Design for Manufacturing and Assembly Aspects to Designing Modern Micro-Wave and Sheet Metal Products

In this paper, we present different points of view to make the sheet metal and micro-wave product as manufacturing friendly as possible. Within DFM(A)-research (Design for Manufacturing and Assembly), engineering design and manufacturability of Micro-Wave (MW) and sheet metal products has been studied. Other aspects of DFM(A) have risen from novel material applications and the development of CAD (Computer Aided Design) environments. In this paper, practical examples are presented to show how to apply DFMA-rules to MW- and sheet metal components, in particular, and how to develop DFM(A)-rules for these purposes.

Between product development and mass production: Tensions as triggers for concept-level learning

Purpose – This paper aims to analyze learning in organizational transformations by focusing on concept-level tensions faced in two young companies, which were searching for a reorientation of activity with a production network between innovative product development and efficient mass production. Design/methodology/approach – An intervention-based research project was carried out with two manufacturing companies. The data originate from workshops, whose aim was to identify learning needs based on the discussion of practices of networked production. Concept-level learning is analyzed by examining the dynamic relationships between production concepts and product concepts. Findings – The most influential concept-level tension stemmed from the co-existence of two production concepts, product development and mass production, which manifested as ambiguity about proper actions in the production network. Other focal tensions were identified between the production and product concepts and within the companies’ netw...

Manufacturability of Sheet Metal Design with the Help of Product Data Management (PDM)

In the today’s industry the sheet metal design plays a huge role, it has been said that almost the half of the designing is concentrating to sheet metals. But the lack of knowledge of the typical sheet metal aspects and basic rules of sheet metal designing, has led in to situation where more and more products are poor designed. This automatically leads to situation that the products are not manufacturing friendly. Designing time is shortening year after year, so the pressure to design the part as fast as possible is huge. Unfortunately all the design information and the design intent is processed and filtered to be fit for the Product Data Management (PDM) system. As the PDM was firstly designed to be used only for the storage base for the design drawings and other data; the feature-information and design intent is lost. This paper deals with two distinct yet interlinked themes. The first theme is the new requirements set for the new Product (Life-time) Information systems that can save the product information and design intent. And the second theme is the modern, light-weight and updatable product-services that allow the manufacturability to be ensured before product realization. With the help of novel product-service such as Design Manufacturing and Assembly (DFMA) for sheet metal industry designers will able to design in shorter time manufacture friendly sheet metal products.

Product Knowledge and Lifecycle Management in Project-Based Manufacturing

Changes taking place in project-based manufacturing emphasize the importance of agile manufacturing, product knowledge management and product lifecycle information. The paper describes dependencies between product definition and production strategy covering also other potential areas of research i.e. growth of industrial service business and development of manufacturing and supply networks. As an outcome it can be argued that more research is needed to align product lifecycle management in project-based manufacturing, as well as to cover the evolving information needs of internal and external stakeholders. Due to the increase of industrial services, also services should be included as a part of product definition; the extended product description introduces a new set of requirements that need to be taken into account as a part of product and production strategy definition.

Relationships of Factors in a Manual Assembly Line Environment

This study makes a proposal and then presents the information required to describe operations and human resources management factors in a manual assembly line environment. This information is needed since the purpose of this study is to increase the understanding of the effects of the factors and their interrelationship on system performance. Because of the complex nature of the socio-technical assembly environment the present study focuses on task- and worker-related matters as a basis for conceptual-level analysis and factor connections flow. The study uses the Gephi software for analyzing factor clusters, occurrences, and connections by means of a relationship network. As a result, the software produced four different factor clusters, each characterized by strong mutual relationships between the factors comprising them. Further, the results of this study help to identify the factors that are to be used in more thorough analysis, from assembly environment development up to semi-intelligent decision-making systems.