Journal of Mechanical Engineering 52 (2006) 7-8
Using Neural Networks to Follow the Wear of a S390 Twist Drill
Corresponding author - Zdravko Krivokapić
Authors - Vukasin Zogović - Obrad Spaić
Abstract
This paper deals with the use of neural networks for the integration of information as well as the parameters of the cutting process (speed, feed and diameter). Two sharpening methods and different working times related to the wear parameters are studied. The material used for the twist drill (S390) is obtained with power technology. Experimental results are used to train the neural networks, as one approach to the modeling of this process. The back-propagation algorithm is used as a model for neural networks. The neural networks with test shapes are trained (offline). The obtained results are presented.
Keywords - neural networks, drilling, twist drill, wear processes
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 437-442
UDC 519.65:621.95
Using Neural Networks to Follow the Wear of a S390 Twist Drill (pdf)
The Effect of Pressure Fluctuations on the Cutting Ability of Pure Water Jet
Corresponding author - Michele Monno
Authors - Chiara Ravasio
Abstract
Water jets and abrasive water-jet technology are the focus of concentrated research. This research area is oriented to understand the material-removal mechanisms and to optimise the process parameters (fluid dynamical and technological) of various applications. The optimisation of the process parameters is especially difficult because of their instability during the process. Many authors have inquired into the physical-mechanical aspects of the interaction between the jet and the mechanical properties of the material and they have developed models and different interpretations. However, the existing models, mostly try to describe the cutting mechanism only for abrasive water-jet (AWJ) technology. The interpretation of the mechanism of striation formation in AWJ cutting does not explain the striation formation in the pure WJ process. In fact, whereas in the cutting surface realised by a pure WJ cutting along the whole surface there are irregularities (striations); the surface generated by AWJ cutting is characterized by a streaked morphology in the bottom zone of the cutting surface. Previous studies have demonstrated that the cutting surface realised by WJ is not influenced either by the pressure fluctuations or the pressure signal form, but depends strongly on the exogenous and endogenous vibrations. In fact, a considerable reduction of these vibrations makes it possible to obtain remarkable improvements in the surface quality, especially as regards the striation morphology. Although the pressure fluctuation does not have substantial effects on the WJ surface quality, it should have an influence on the depth of cut. In this work the effect of the pressure fluctuation on the depth of cut in no-passing WJ cuts has been analysed. In order to do this, the thrust trend of the water jet on a plane surface has been analyzed. The aim of this experiment has been to analyze the penetration ability trend of the jet at the exit of a passing cut; afterwards, the correlation between the thrust signal and the bottom profile generated by a no-passing cut on polycarbonate slabs has been analyzed.
Keywords - water jet cutting, pressure fluctuation
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 443-450
UDC 621.9.044
The Effect of Pressure Fluctuations on the Cutting Ability of Pure Water Jet (pdf)
Heat Generation During Abrasive Water-Jet Osteotomies Measured by Thermocouples
Corresponding author - Christian Biskup
Authors - Manuel Höver - Ralf Versemann - Friedrich-Wilhelm Bach - Stefan Krömer - Ludger Kirsch - Arnim Andreae - Frank Pude - Stephan Schmolke
Abstract
Water-jet technology is known in industry as a cold-cutting process because no significant thermal effects are observed at the cutting edges of, e.g., metallic workpieces. Thus, water jets are mostly used for applications where no structural changes are allowed. For medical applications the critical temperature is much lower than for industrial use, because bones react very sensitively to heat. The damage to the tissue depends on the temperature and the time of exposure. The tissue is irreversibly destroyed after a period of approximately 10 seconds at 57°C. To avoid this effect, which causes the so-called necrosis formation, and which results in poor bone healing, heat management is required for water-jet osteotomies. The first step is made in this paper. The heat generation during abrasive water-jet osteotomies was measured by thermocouples that were inserted into the cortical hollow bone segments of cattle. The influence of parameters like pressure, traverse rate, abrasive flow rate and abrasive material are shown in this paper together with the influence of the location of thermocouples, which represents an increment of the bone tissue.
Keywords - medicine, osteotomy, abrasive water jet, temperature measurement, thermocouples
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 451-457
UDC 611.71:621.9.02
Heat Generation During Abrasive Water-Jet Osteotomies Measured by Thermocouples (pdf)
Hybrid Dry-Ice Blasting Laser Processing: Nd-YAG-Laser-assisted Dry-Ice Blasting for De-Coating
Corresponding author - Eckart Uhlmann
Authors - Robert Hollan - Adil El Mernissi
Abstract
In the case of high-value raw materials or high manufacturing costs, the recycling of products is reasonable because it helps to save money and resources. However, recycling usually makes a cleaning or de-coating process necessary. Normally, these processes are based on conventional cleaning and de-coating methods. Dry-ice blasting and laser processing are two environmentally friendly alternatives that have different advantages over the conventional methods. However, both have technological and economic limitations. The effect of dry-ice blasting is based upon a mechanical, a thermal and a sublimation mechanism that allow a soft de-lamination, cleaning and pre-treatment while the workpiece remains undamaged. Laser processing offers the possibility of a defined removal of the coating/contamination and a treatment of the surface of the workpiece itself. Both technologies do not increase the amount of waste. Strongly adhering or hard contaminations and protective or functional coatings are difficult to remove with dry-ice blasting, while laser processing is unsuitable for removing thick coatings or contaminations. The combination of both technologies offers different strategies for machining. On the one hand the laser can be applied in de-focused mode for heating up the surface of the workpiece, thereby increasing the thermal mechanism of dry-ice blasting. On the other hand a focused laser application makes a defined surface structuring or smoothing possible. In addition, both methods can be applied at the same focal point. In order to measure the area-related cleaning efficiency a PUR-2 component varnish-substrate combination was chosen as a standard among the multitude of materials, coatings and contaminations available. The material removal rate achievable with dry-ice blasting was increased using the hybrid technology by up to 49%. The results show that an individual optimization of the parameters for the application is a pre-condition. Only then is the hybrid technology competitive in relation to conventional cleaning technologies.
Keywords - dry ice blasting, laser processing, cleaning, de-coating, hybrid systems
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 458-462
UDC 621.594+544.53
Hybrid Dry-Ice Blasting Laser Processing: Nd-YAG-Laser-assisted Dry-Ice Blasting for De-Coating (pdf)
Cutting Performance and Obtainable Quality when Applying 6000-Bar Abrasive Water-Jets
Corresponding author - Holger Werth
Authors - Waldemar Hiller - Christoph Luetge - Joerg-Peter Koerner - Frank Pude - Inge Lefevre - Roland Lefevre
Abstract
UHDE HPT has been developing, designing and building high-pressure intensifiers to cover the widest range of applications for more than 40 years. The operating pressure can reach an incredible 14,000 bar (203,280 psi). For water-jet technologies UHDE HPT has developed two concepts for the 6,000 bar (87,000 psi) pressure range. Both concepts have proven themselves in practical applications. The incremental increase of the working pressure greatly improves the working efficiencies and the economic benefits: higher cutting speed, improved cutting quality at the same cutting speed, deeper cuts without adding abrasives and low operating costs. In this paper the results of comparisons between 3,500- and 6,000-bar abrasive water-jet cutting operations will be presented.
Keywords - abrasive water jet cutting, cutting performance, surface roughness
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 463-469
UDC 621.9.044
Cutting Performance and Obtainable Quality when Applying 6000-Bar Abrasive Water-Jets (pdf)
Investigation and Development of a Fiber-Optic Vibrometer for Use in Totally Implantable Hearing Aids
Corresponding author - Zoran Djinović
Authors - Miloš Tomić - Aleksandar Vujanić - Robert Pavelka - Sladjan Mitić - Dušan Vujanić - Mathias Cordes
Abstract
In this paper we present the results of the research and development of a fiber-optic-based vibrometer for use in totally implantable hearing aids (TIHAs). We addressed the most important issues regarding the projected vibrometer: the optoelectronic measurement technique and signal processing, the optomechanical positioning of the sensing fiber, the surgical implantation technique and the material’s biocompatibility. We performed in-vitro and in-vivo measurements of the target (e.g., incus) vibrations with a sub-nanometer resolution over the whole audio range, using low and/or high coherence techniques. A breakthrough is made by a dramatic reduction of the power consumption of the optoelectronic and signal-processing unit to about 2 mA at 2.2 VDC by introducing a digital signal processing (DSP) technique.
Keywords - vibrometry, fiberoptics, hearing aids, implants, DSP
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 470-476
UDC 681.7.068:612.85
Investigation and Development of a Fiber-Optic Vibrometer for Use in Totally Implantable Hearing Aids (pdf)
Implementation of Information Technology for the Purpose of Quality Management System Improvement
Corresponding author - Aleksandar Vujović
Authors - Zdravko Krivokapić
Abstract
In this paper software for the macro-control of Quality management system (QMS) nonconformities, with the aim to classify them according to the JUS ISO 9001:2001 standard’s areas and to mark those areas in which the major part of the nonconformities has emerged, is described. Detailed analyses for each respective area and the defined proposals for corrective and preventive actions for improving the QMS, based on the obtained results and on the inspection of the identified area, are given.
Keywords - software, quality assurance, nonconformity
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 477-483
UDC 004:006.06
Implementation of Information Technology for the Purpose of Quality Management System Improvement (pdf)
Mechanical Micro-Machining Using Milling, Wire EDM, Die-Sinking EDM and Diamond Turning
Corresponding author - Alberto Herrero
Authors - Igor Goenaga - Sabino Azcarate - Luis Uriarte - Atanas Ivanov - Andrew Rees - Christian Wenzel - Claas Müller
Abstract
From among all the different techniques currently applied for micro-manufacturing, this paper focuses on those techniques that can be considered as conventional techniques because of their direct relationship with standard machine tools. The following processes are discussed: ultra-precision milling, thin-wire EDM, die-sinking micro-EDM and diamond turning. Despite the mentioned relationship with conventional machine tools, they all have special characteristics that enhance the capability of the machining principle. The processes are analysed, showing the differences with respect to the corresponding conventional processes and stating their current limitations. A review of the state of the art, applications and potential markets is presented. Finally, the capabilities of these technologies and the other micro-manufacturing techniques (lithographic processes) are compared in order to highlight the possible competences and complementariness that they present.
Keywords - ultra-precision machining, micromachining, milling, diamond turning, EDM
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 484-494
UDC 621.914+621.941
Mechanical Micro-Machining Using Milling, Wire EDM, Die-Sinking EDM and Diamond Turning (pdf)
Microforming – Current Status and Future Demands
Corresponding author - Stefan Geißdörfer
Authors - Alexander Putz - Ulf Engel
Abstract
Microforming technology is gaining increasing interest from the metal-forming community. This can be explained by the large number of new applications and products delivered to market in the past, yielding smaller and smaller geometrical dimensions of the final products and thus demanding the smallest specimens to be manufactured in large quantities. Up to now, most of these parts were being manufactured by machining technology, well suited to the production of small series. The analysis of the current market situation shows that the steadily increasing trend towards the smallest products is continuing in the future and thus requires new manufacturing technologies for large-quantity production. Forming technology seems to be well suited due to its high production output and high accuracy. The aim of this paper is to give an overview of the current research activities related to microforming technology, showing microforming technology’s capabilities and problems. The analysis of the current status will give a hint to existing gaps in knowledge and finally describe the future demands.
Keywords - microforming, current status, future demands
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 495-505
UDC 621.7+621.9:658.5
Microforming – Current Status and Future Demands (pdf)
Integrated Design of Mycro-Electro-Mechanical Systems
Corresponding author - Matthieu Museau
Authors - Cedric Masclet
Abstract
This paper is a first attempt to qualify the design process in the field of micro-electro-mechanical systems products. Through this study we try to analyse how the issue of manufacturability is addressed. This requires an understanding of the specificities of the manufacturing process involved in the realization of these products (we focus on a process derived from the electronics industry). Then we look at the main design methodologies to understand how the manufacturing can be taken into account. Computer-aided tools associated to these methodologies are presented at the same time. Finally, we conclude on the need for specifications for the design methodology that would provide designers with greater independence from manufacturing constraints.
Keywords - MEMS, DFM, manufacturing constraints, design methodology
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 506-514
UDC 658.512.2:621.38
Integrated Design of Mycro-Electro-Mechanical Systems (pdf)
The Twelve “Death Signs” for a Growing Manufacturing Company
Corresponding author - Paul Levy
Authors - David Knowles - Chris Stagg - Mihael Junkar
Abstract
Based on extensive work with small and medium-sized enterprises (SMEs), this paper describes the early-warning signs for SMEs in manufacturing, which, if ignored, later result in business decline and even failure. There is a high failure rate for SMEs during the start-up phase of 1 to 3 years, but also a significant failure rate in companies that are less than ten years old. Failure to innovate, the business process, and products and services are the key elements. This paper presents a typology of the “death signs” that can form the basis of a proactive innovation agenda. The concept of “preventive healthcare” is applied to product and process innovation, and cases are cited of companies taking such preventive steps. Drawing on literature and experience from the fields of technology and innovation management the paper focuses on specific methods of innovation that can help a small-to-medium-sized manufacturing firm thrive over the longer term. The concept of “recession-proofing” is also introduced and applied to innovation in SMEs.
Keywords - company failures, early-warning signs, innovation management, recession-proofing
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 515-525
UDC 65.011.7
The Twelve “Death Signs” for a Growing Manufacturing Company (pdf)
The Role of Virtual Networks in a Virtual Enterprise
Corresponding author - George Dragoi
Authors - Costel Emil Cotet - Luminita Rosu - Sebastian Marius Rosu
Abstract
Advances in product development concepts have demonstrated the trend for integrating different development phases through the integrated product data model and collaboration technologies. Future product-development processes will take all aspects of the whole product lifecycle into account. At the same time, interaction and communication technologies will allow people with different knowledge backgrounds and dealing with different aspects of a product work together to achieve the best product design. This paper sketches a future vision of product development with an emphasis on the support of creative design. We call it direct digital design. This paper presents a vision of next-generation enterprise working environments and describes a core information technology that future systems can be built on. The concepts of a virtual enterprise (VE) and of virtual teams, enabled by a new generation of internet/intranet/extranet-based services are discussed here, as a means to stay competitive and to thrive in a turbulent market.
Keywords - virtual enterprises, virtual teams, virtual networks, internet technologies
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 526-531
UDC 004.738.5:65
The Role of Virtual Networks in a Virtual Enterprise (pdf)
An Introduction to the Diagnosis of the Delamination Process for Glass/Epoxy Composites During High-Pressure Abrasive Water-Jet Cutting
Corresponding author - Andrzej Karpiński
Abstract
The main problem during the abrasive water-jet cutting of fibre-reinforced composites is delamination. This delamination is a phenomenon specific to composite materials, which is independent of the machining method used. In this paper the concept of a diagnostic system is presented, based on a digital time and frequency signal analysis, for the online detection of the delamination in glass-fibre-reinforced composites. The applied measurement equipment is described and the research results are presented.
Keywords - diagnostic systems, composites materials, abrasive water jet cutting
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 532-538
UDC 678:621.9.044
An Introduction to the Diagnosis of the Delamination Process for Glass/Epoxy Composites During High-Pressure Abrasive Water-Jet Cutting (pdf)
Characterization of a Pure Water-Jet Cleaning Process – Process Simulation
Corresponding author - Friedrich-Wilhelm Bach
Authors - Hartmut Louis - Ralf Versemann - Alexander Schenk
Abstract
Water-jet cleaning is a widely used technology for decoating surfaces. Its applications range from rough ship-wall cleaning jobs to the surface processing of turbine parts as part of maintenance operations. However, the jetting task layout and planning is very dependent on the particular user’s skill and often requires preliminary tests in order to ensure a reliable and reproducible surface condition. The presented work describes procedures, techniques and tools for dealing with this problem and introduces an integrated tool and decoating process model. This environment enables the user to design and simulate a complete cleaning task, including tool behaviour and surface reaction and thereby to determine the optimum parameters and machine setups before even switching on the pump for the first time. To put the simulation on solid ground, it is based on a special standardized experiment to normalize the nozzle behaviour and the material’s response. Another application of the package is the design and optimisation of the jetting tool itself, e.g., the geometrical arrangement of its nozzles to ensure a homogenous surface load. This can drastically reduce the costs as well as the time-to-market of a new water-jet cleaning device.
Keywords - cleaning, de-coating, water-jet, models, simulations
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 539-545
UDC 621.694.3:004.94
Characterization of a Pure Water-Jet Cleaning Process – Process Simulation (pdf)
The Constructive and Geometrical Optimization of the Junctions in Structures Made from Laminated Composite Materials
Corresponding author - Anton Hadăr
Authors - Mariana N. Nica - Ioan N. Constantinescu - Ştefan Dan Pastramă
Abstract
Failure mechanisms for composite materials and especially for laminated composites are different and more complex than for homogeneous and isotropic materials. This is why the modeling and analysis of such structures are done with the main aim being to determine the local stress states in the zones where high stress gradients occur, e.g., supports, points where loads are applied, geometric discontinuities, and junctions. In the case of junctions, one should elaborate constructive and technological solutions that ensure the maximum mechanical strength, taking into account the interpenetration between the layers. The next step is the optimization of the geometric and constructive configurations for the junctions. Here we propose a methodology for the geometrical and constructive optimization of the junctions in structures made from laminated composite materials. Some examples of modeling for junctions in industrial structures, using the finite-element method, are presented.
Keywords - laminated composites, optimization, junctions, finite-element methods
Paper's information
Strojniški vestnik - Journal of Mechanical Engineering 52(2006)7-8, 546-551
UDC 621.792.05:678
The Constructive and Geometrical Optimization of the Junctions in Structures Made from Laminated Composite Materials (pdf)
