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- Aganovic, Dario, 1974-
(författare)
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On Manufacturing System Development in the Context of Concurrent Engineering
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents an extension of the contemporaryengineering design theory towards a unified view onsimultaneous development of products and manufacturing systems,i.e. concurrent engineering. The traditional engineering design theory explains therealization of a product design as a development of productstructure from four perspectives: technical process, function,technical solution, and physical embodiment. This thesisextends the engineering design theory with a set of definitionsand universal statements. These definitions and universalstatements describe manufacturing systems from same fourperspectives. In that context they also describe therelationship between a product and its manufacturing system.The thesis contributes to the creation of a single theoreticalsystem based on an integration of theories from two engineeringdesign schools, the WDK and the Axiomatic Design. WDKtheoriesare in this new context utilized for qualitative synthesis ofthe developed artifacts, while the Axiomatic Design is utilizedfor structuring and analyzing the corresponding quantitativeparameters. The definitions and universal statements describe thedevelopment structures for productsand manufacturing systems.This description is utilized for definition of a system fordevelopment of these structures, i.e. (i) a stage-gate-basedmanufacturing system development process, (ii) a developmentmethodology toolbox, and (iii) an information managementframework consisted of an information model harmonized with thesystems engineering data management standard STEP AP 233. The research has been carried out in a close collaborationwith Swedish manufacturing industry. The utilized researchmethodology is the hypothetic- deductive method, with casestudy as an observation method. Keywords:Concurrent Engineering, Engineering Design,Development Methods and Tools, Manufacturing System,Information Management.
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- Bayard, Ove, 1967-
(författare)
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Investigation of Forces and Contact Area for Modelling Turning Processes
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis is focused on an investigation of forces andcontact area for modelling turning processes. The primary taskin short term research has been to take a first steptowards animproved model of the cutting process. The ultimate goal is tofind predictive models and thereby reduce the number of cuttingtests necessary to perform before an“unknown”tool-material combination can be considered for machining.Today, lot of time and money is spent to gather appropriatecutting data and material parameters. This is, nevertheless,necessary to understand and characterise the fundamentalbehaviour of a workpiece, when it is machined. To describe the complicated nature of the deformationprocess in cutting, analytical shear plane models are oftenemployed. In this thesis, a review of some classic models ispresented. The validity of a proposed model can be confirmed ifthe values generated can be correlated to experimental results.A difficulty is often to find a method that gives the desiredexperimental parameters. An important source for information isthe samples generated through Quick Stop tests. A reliableQuick Stop Device (QSD) has therefore been developed and ispresented in the thesis. Since the focus for this investigation has been to propose atentative model for cutting forces in turning, a number offorce measurements have been performed. Two different steelgrades have been evaluated in orthogonal machining, AISI-1045and AISI-12L13. Cutting force measurements (feed- and maincutting force), were conducted with a high accuracydynamometer. To investigate contact area conditions, Quick Stopspecimens, chips and inserts were examined. The evaluation wasperformed both in an Optical Light Microscope and a ScanningElectron Microscope. Three different models can be used tocharacterise the contact area. According to the contactconditions these models refer to sticking friction, flow-zoneand sliding friction region. Results from model simulations were fitted to those ofexperimental cutting investigations in order to evaluate theaccuracy of the cutting force and contact area approach. Thetest results are also used as reference data for a proposedsimple tentative model presented in this thesis. The model isrestricted to orthogonal machining. The proposed model consistsof several steps. The first step is to determine the maincutting force Fc. Expressions that describe Fcas a function of the cutting velocity (vc) for different feed (f) values have been derived.To be able to evaluate the feed force, the contact length lchas first to be determined. Relationships where lcis expressed as a function of vcfor different feeds have been derived. Tocalculate the feed force, a formula for Ff/Fcas a function of lcis applied. Equations for determiningΛ, hchandΦ have also been derived. In short,the functions found are: Fc= f(vc; f), lc= f (vc; f), Ff= f(Fc; lc),Λ = f(lc; f) andΦ = f(vc; f). This research work shows that it is of utmost significance,in order to generate realistic values, that a predictive modelis supported by adequate reference data. It is also shown thatthe contact area is an important parameter that has to beconsidered in modelling. Keywords:Modelling, turning processes, cutting forces,contact length, Quick Stop Device, QSD, simulation programs,FEM, predictive models.
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- Bejhem, Mats
(författare)
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Machining Monitoring and Control : Based on Parametric Modelling
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The objective of this work was the development of aMachining Control prototype system for turning, whichintegrates three fundamental aspects of Machining Controltechnology: Monitoring, Control and Optimisation. MachiningControl refers to the detection and automatic handling ofdisturbances in machining processes. Consequences ofdisturbances can be classified in three major groups:Breakdowns, production rejects and non-optimal production. Byminimising these consequences, the efficiency of the machiningprocess can be improved, which in turn will have a major impacton productivity, machining economy and product quality as well.This calls for user friendly supervisory systems that cansupport the human operator and perform monitoring, control andoptimisation tasks, i.e. Machining Control (MC) systems. The MC system presented in this thesis is developed around aturning centre, and consists basically of a PC equipped with amodular DSP multiprocessor, sensor systems for vibration andcutting force measurements, as well as machine tool interfaces.The basic structure of the MC system allows flexibleimplementation of tasks, which can interact with the machinetool controller and other auxiliary devices. In other words,the MC system combines virtually all essential features toperform advanced real time supervision. An important aspect in the development of this MC system wasthe access to accurate data, reflecting the underlyingmachining process. Therefore, the turning centre is equippedwith an integrated dynamometer and an acoustical sensor systemthat have access to the tool-workpiece interface. To ensurereliable cutting force measurements, a three-axis calibrationmethod has been developed that performs a transformation ofoutput signals from the force sensor system to accurate cuttingforces at the tool tip. A good knowledge of tool vibration andinstantaneous cutting forces allows the safer use of moreaggressive machining operations, thus utilising most of theavailable tool life withoutcausing costly breakdowns andproduction rejects. Two MC functions for in-process tool condition monitoringhave been developed and are discussed from both theoretical andexperimental point of view. Classical models have been used toanalyse the dynamic behaviour of the machining system, whileparametric modelling was employed for in-process monitoring andcontrol of dynamic stability. It is shown that an efficientcontrol of dynamic stability only can be performed if propertooling is selected. Some efficient solutions for improving thedynamic properties of tooling are presented. Finally, a modulefor an automatic optimisation of cutting conditions isdescribed. This module takes advantage of all the features thatare implemented in the MC system. This research work shows a successful application of anintegrated MC system for an effective combination betweenpeople and technology in future manufacturing systems. Keywords:Machining Control, tool condition monitoring,in-process dynamic stability monitoring and control,optimisation of cutting conditions, MC, DSP, TCM
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