Berend Denkena

Berend Denkena
Leibniz Universität Hannover · Institute of Production Engineering and Machine Tools

Prof. Dr.-Ing.

About

1,298
Publications
136,919
Reads
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9,652
Citations
Additional affiliations
October 2001 - September 2015
Leibniz Universität Hannover
Position
  • Managing Director
October 2001 - September 2015
Leibniz Universität Hannover
Position
  • Director of Institute

Publications

Publications (1,298)
Chapter
Die Reibung am Schneidkeil beeinflusst maßgeblich das Verschleißverhalten in der Zerspanung. Aufgrund der starken örtlichen Varianz von Temperaturen und Spannungen am Schneidkeil unterscheiden sich die Reibver-hältnisse lokal signifikant. In dieser Arbeit wird eine Methode vorgestellt, mit der Normalspannungen, Tangential-spannungen und lokale Reib...
Article
The improved adaption of a modular hip endoprosthesis to patient-specific anatomy by means of a neck adapter is accompanied by the risk of a higher revision rate. This is due to micromotions leading to friction wear and corrosion of the additional taper interface. This results in the need to manufacture a load-adapted interface of modular hip endop...
Article
In aerospace engineering, high temperature alloys such as titanium are the preferred choice. However, machining of such materials remains a major challenge due to high process forces and process temperatures. Currently, machining is performed almost entirely in the presence of oxygen. This results in a process-inherent oxidation of the metal surfac...
Article
Full-text available
Modern cutting tools like end mills, drilling tools, and reamers underlie high requirements regarding geometrical accuracy, cutting edge quality, and production costs. However, the potential for process optimization is limited due to the process kinematics during grinding. Consequently, a novel tool grinding process for the manufacture of cutting t...
Article
Konventioneller Kühlschmierstoffeinsatz in der spanenden Fertigung führt zur Belastung von Umwelt und Gesundheit sowie zu erhöhten Fertigungskosten. Entsprechend weist der zielgerichtete Einsatz von Kühlschmierstoffen ein großes Potenzial zur nachhaltigen Gestaltung der Produktion auf, bringt jedoch auch zahlreiche technologische erausforderungen m...
Article
Full-text available
The milling of titanium and nickel-based alloys leads to high tool wear due to the high thermomechanical load on the tool. By modifying the flank face on end mills, it is possible to limit the increase in the width of flank wear land, thus increasing tool life, component quality and increasing the allowable productivity of the tools. The flank face...
Article
Full-text available
Recent developments in the production processes for cubic boron nitride (CBN) abrasive grains have led to commercially available grain sizes larger than l g > 300 µm. These superabrasive grains allow higher material removal rates during grinding of hardened steel components. Currently, these components are pre-machined by turning processes before b...
Article
Full-text available
Grinding tools can be manufactured from metal, vitrified, and resin bond materials. In combination with superabrasives like diamond grains, metal-bonded tools are used in a wide range of applications. The main advantages of metal over vitrified and resin bonds are high grain retention forces and high thermal conductivity. This paper investigates th...
Article
Full-text available
Non-productive auxiliary processes affect the single part and small badge production of milling tools. The key production process grinding is inevitably linked to the auxiliary conditioning process. The time demand of those process steps decreases the overall productivity of the manufacturing process. However, today the machine operator decides on...
Article
Full-text available
Metal-bonded grinding tools are commonly based on copper as bond material and possess low porosity. The powder metallurgic fabrication and the applied process parameters have a high influence on the mechanical properties of these grinding layers. In this study, Cu–diamond composites are fabricated through Field Assisted Sintering Technology with a...
Article
This article presents a marker-free component identification of milled workpiece surfaces. For the identification, unique features from a 2-D profile are detected in the 3-D frequency domain. Knowing the influence of process parameters, tool runout, cutting edge roughness during flank milling on the stochastic surface generation, a profile cut can...
Article
Increasing productivity of ultra-precision (UP) machining is vital to apply this technology in a broader range of applications. In order to achieve this goal, technologies such as diamond cutting with multiple cutting edges or the application of electromagnetic levitation guides are researched. Due to the additional, influencing factors from these...
Article
Full-text available
The use of natural rocks as cutting tool material poses an environmentally friendly alternative to conventional cutting tool materials. So far, however, the basics of tool grinding processes for rock tools have not been systematically investigated. This study, therefore, presents an investigation of the material removal mechanisms of four different...
Article
Errors in milling processes such as tool breakage or material inhomogeneities are a major risk to the quality of machined workpieces. Errors like a broken tool may also lead to damages to the machine tool. Process monitoring systems allow for autonomous detection of errors, therefore, promoting autonomous production. The parameterization of these s...
Article
Tailored forming is used to produce hybrid components in which the materials used are locally adapted to the different types of physical, chemical and tribological requirements. In this paper, a Tailored Forming process chain for the production of a hybrid shaft with a bearing seat is investigated. The process chain consists of the manufacturing st...
Article
Regeneration processes of complex capital goods such as components of aircraft engines are highly complex and require a multi-disciplinary perspective, bringing together expertise from different fields such as production engineering, image-based measuring technology, turbomachinery, and operations management. Sustainability requirements and digital...
Article
The contact length is one of the most important factors to evaluate the chip formation process and the mechanical loads in metal cutting. Over the years, several methods to identify the contact length were developed. However, especially for wet cutting processes the determination of the contact length is still challenging. In this paper, three meth...
Article
Abstract This paper presents a novel approach of adaptive inspection planning which allows a targeted, production-parallel adaptation of the inspection plan by using virtual quality inspections. The reduction of already unambiguously inspected characteristics results in a considerable potential for the reduction of inspection efforts and costs with...
Article
By combining linear and rotary movement in one single drive, the overall dynamics of machine axes can be enhanced, and the installation space can be reduced. Existing concepts for linear-rotary drives either have low power density or load capacity, and the installation space of the guideways are not sufficient for applications in machine tools. Thu...
Article
Full-text available
The need for rare resources, such as tungsten or cobalt, combined with the high energy requirements to produce cutting materials, is forcing research and development to work out environmentally friendly alternatives. Natural rocks could be an alternative since they are available in large quantities worldwide, have a potentially suitable property pr...
Article
Full-text available
Due to the increased integration of functions, many components have to meet high and sometimes contradictory requirements. One way to solve this problem is Tailored Forming. Here, hybrid semi-finished products are manufactured by a joining or cladding process, which are then hot-formed and finished. For the design of hybrid components for a possibl...
Article
Full-text available
The varying related material removal rate during deep grinding of cemented carbide end mill cutters results in an unevenly wear of the grinding wheel. This study therefore presents a simulation-based model for the load-adjusted design of grinding wheels to achieve balanced radial wear, as well as an evaluation of this model. The related material re...
Article
Summary Employee competencies are a key factor for the enhancement of productivity and flexibility in production. However, they have received inadequate consideration in work planning so far. In this paper a methodology for technology- and competencebased work planning as well as work instructions for an integrated work scheduling are derived. In a...
Article
Full-text available
Production planning is a critical step for the implementation of sustainable production. It is necessary to consider energy and resource efficiency in all planning phases to promote sustainable production. In this paper, an approach for environmental impact assessment in all phases of process chain planning supported by process models is presented....
Article
For the realization of efficient production processes, an understanding of the appropriate application of metal working fluids (MWF) is necessary. In addition to knowledge about the process-related aspect of chip transport and the macroscopic cooling effect, the characteristics and properties of the lubrication film thickness and the cooling condit...
Article
Full-text available
Metal working fluids are used in machining processes of many hard-to-cut materials to increase tool life and productivity. Thereby, the metal working fluids act on the thermal and on the mechanical loads of the tool. The changing mechanical loads can mostly be attributed to the changing friction between rake face and chip and changes in the chip fo...
Article
In BTA deep hole drilling straightness deviation of the bore is a very important quality criteria. The avoidance of straightness deviation is not possible due to the many influencing variables. Currently used methods for compensation require significant additional time, as they either require the interruption of the drilling process, or require an...
Article
Abstract The depth and width of cut are important factors for productivity and quality in milling operations. Up to now, suitable values have been determined manually by timeconsuming running-in processes. Intelligent systems for autonomous parameter adaption could simultaneously increase productivity and minimize the manual effort required for pro...
Article
Full-text available
Polycrystalline cubic boron nitride is a very hard material. Machining of this material is performed by grinding with diamond tools. Due to its high hardness, grinding tools are subjected to severe microscopic and macroscopic tool wear. This wear leads to short tool life and results in high effort in conditioning the abrasive layer. Contrary to the...
Chapter
Production planning and control can be supported by Digital Factory methods to optimize production processes and workflows. A central component of the Digital Factory is simulation, which is used to represent real objects and processes in a virtual environment. This virtual environment is suitable for performing analyses and planning processes so t...
Chapter
Full-text available
As a recently coined buzzword without a clear definition, Digital Twin relies on the high-fidelity digital representation of the physical product and the continuously accumulated data and real-time presentation of the collected data to simultaneously update and modify with its physical counterpart. In research and practice, many types and expressio...
Chapter
Setting up a virtual model of a production system is time-consuming and requires expertise in the use of simulation software as well as knowledge of the operations in production systems. For this reason, the creation of virtual models as a basis for the Digital Twin of a production system is hardly feasible for many companies. This chapter presents...
Chapter
Contract manufacturing companies have to calculate offer prices for individualized products in cost-driven markets with experience-based estimations on limited data. Especially, the estimation of processing and set-up times is time-consuming and challenging. Algorithms providing suitable and transparent estimations with low configuration effort and...
Article
Full-text available
This study presents an investigation of the usability and suitability of natural rocks as cutting tool materials. Therefore, indexable inserts are manufactured from eight different rocks and two mono minerals in this study and are used for turning of an aluminium alloy. Besides that, a characterization of the rock properties is performed. The wear...
Chapter
While electromagnetic levitation systems are already available for ultra-precision applications, they are limited to inspection or measurement tasks and non-mechanical processing due to their severely limited stiffness. This contribution introduces a novel electromagnetic linear guide, which was specifically developed for use in ultra-precision hig...
Chapter
Axis controls of ultra-precision machine tools have to fulfill demanding requirements regarding position and velocity tracking accuracy, disturbance rejection, and avoidance of vibration. Within this project, an axis concept for ultra-precision machining utilizing an electromagnetic linear guide is investigated. The axis concept offers additional,...
Article
Das Gewindewirbeln ist ein flexibles und produktives Verfahren zur Herstellung von Gewindespindeln unterschiedlicher Gewindetypen. Nachteilig ist jedoch, dass die Gewinde derzeit erst nach dem Prozess auf ihre Qualität überprüft werden können.
Article
Um den Zerspanungsprozess energieeffizienter und somit ökologisch nachhaltiger zu gestalten, muss der Kühlschmierstoff (KSS)-Druck optimal eingestellt werden. Im beschriebenen Projekt wurde eine Methode entwickelt, mit welcher der optimale KSS-Druck in Abhängigkeit des auftretenden Werkzeugverschleißes ermittelt werden kann – und damit bis zu 33 %...
Article
Der Herstellprozess eines Schleifwerkzeugs ist je nach Einsatzzweck sehr unterschiedlich. Lässt sich die komplexe Prozesskette simulieren, so wird es möglich, den gesamten Ablauf wissensbasiert auszulegen. Die Schleifwerkzeuggestaltung wird optimiert, flexibilisiert, effizienter angegangen und an den Schleifprozess angepasst.
Article
Full-text available
Wire arc additive manufacturing (WAAM) offers great potential for the production of automobile components due to its high material deposition rates, low costs and design freedom. In order to meet the requirements regarding surface integrity and lifetime, the parts must be mechanically finished after WAAM. However, the subsurface properties (e.g. re...
Article
Full-text available
In metastable austenitic steels like AISI 304, martensitic surface layers can be created by cryogenic external longitudinal turning which results in a hardening of the surface. It is possible to identify the correlation between process parameters and the formation of deformation-induced martensite with machine learning methods. Based on this, evolu...
Article
Das große Potential belastungsoptimierter Schneidkantenmikrogeometrien wurde bisher im Orthogonal- und Außenlängsdrehen nachgewiesen. Andere Prozesse, wie das Innendrehen und das Aufbohren, führen aufgrund veränderter Prozesskinematiken zu abweichenden Kontaktbedingungen. Eine Kooperation verspricht auch hier neue Erkenntnisse.
Article
Full-text available
The automated process chain of an unmanned production system is a distinct challenge in the technical state of the art. In particular, accurate and fast raw-part recognition is a current problem in small-batch production. This publication proposes a method for automatic optical raw-part detection to generate a digital blank shadow, which is applied...
Article
Full-text available
Grinding is mostly considered as a finishing operation by which a high surface quality is achieved. An increase in productivity is therefore limited by maintained surface properties such as the roughness or tensile residual stresses. Thus, a roughing operation is inevitable followed by a finishing operation, while both operations are separated, lea...
Article
Deep rolling consists of plastic deformation of the workpiece surface layer without material removal. Although deep rolling has been systematically investigated over the last decades, the role played by the temperature developed during the process has not been fully understood yet, especially owing to the presence of a white layer seldom found bene...
Article
Full-text available
The performance of grinding tools in grinding processes and the resulting surface and subsurface properties depend on various factors. The condition of the grinding tool after dressing is one of these factors. However, the influence of the dressing process on the condition of the grinding tool depends on the selected process parameters and is diffi...
Article
Machining of tungsten carbide requires the use of highly wear resistant grinding tools, like metal bonded grinding tools. The abrasive layer of these grinding tools can be regarded as Metal-Matrix-Composites reinforced with diamond particles. Copper-Matrix-Composites already are being used as heat sink materials through their outstanding high therm...
Article
Tool deflection is a major cause for shape deviations in milling. Therefore, an approach is presented to compensate tool deflection based on the drive signals of a milling center. First, a real-time capable model is implemented to reconstruct static process forces by using the drive signals of a machine tool. To calculate the actual deflection, the...
Article
Full-text available
The performance of cutting tools can be significantly enhanced by matching the cutting edge rounding to the process and material properties. However, the conventional cutting edge rounding design is characterized by a significant number of experimental machining studies, which involve considerable cost, time, and resources. In this study, a novel a...
Article
Full-text available
Mobile diamond wire sawing is a highly flexible, productive and, versatile cutting process. Accordingly, it is used in many areas, such as the dismantling of nuclear power plants or wind turbines. Despite the widespread use of the process, the cutting process requires continuous manual monitoring by the machine operator. This is due to the continuo...
Article
Full-text available
Process and tool condition monitoring systems are a prerequisite for autonomous production. One approach to monitoring individual parts without complex cutting simulations is the transfer of knowledge among similar monitoring scenarios. This paper introduces a novel monitoring method which transfers monitoring limits for process signals between dif...
Article
Increasing demands regarding productivity and component quality are a major challenge in turning. To meet these demands, complex multiaxial turning processes like enhanced variants of the trochoidal turn-ing processes are increasingly used. For these processes, the tool path is optimized to achieve advanta-geous cutting conditions and thus higher p...
Article
Full-text available
This paper presents an approach for the simulation of cutting processes with a dexel based-simulation considering process damping. The approach allows an independent modeling of engagement parameters for both rake and flank faces of arbitrary tool and workpiece geometries including dynamic behavior for the first time. A method is introduced for cal...
Article
Full-text available
Data-based methods are capable to monitor machine components. Approaches for semi-supervised anomaly detection are trained using sensor data that describe the normal state of machine components. Thus, such approaches are interesting for industrial practice, since sensor data do not have to be labeled in a time-consuming and costly way. In this work...
Article
Für produzierende Unternehmen sind Produktionsdaten das neue Gold. Insbesondere für die Produktionsplanung und -steuerung sind die Qualität und die Aktualität der erfassten Daten entscheidend. Der aktuelle Stand der Technik beim Schürfen des Goldes ist jedoch noch immer geprägt von manuellen Tätigkeiten. Wie effizient diese Praxis bei der Erfassung...
Article
Full-text available
This paper presents a novel method for a precise localization of the automated-fiber-placement head, without the need for a data access to the machine control. It is based on a sub-pixel accurate optical-flow-algorithm which determines information about the heads movement by means of the material flow in sequences of IR images. Using local curvatur...
Preprint
Full-text available
The varying related material removal rate during deep grinding of cemented carbide end mill cutters results in an unevenly wear of the grinding wheel. This causes a reduced geometrical precision of the manufactured tools. Consequently, the intervals between dressing steps are reduced and the dressing infeed increases. The aim of this research proje...
Preprint
Full-text available
Non-productive auxiliary processes affect the single part and small badge production of milling tools. The key production process grinding is inevitably linked to the auxiliary conditioning process. The time demand of those process steps decreases the overall productivity of the manufacturing process. However, today the machine operator decides on...
Article
This study shows the performance improvements achieved by AutoML to predict shape errors that can occur during milling. For this purpose, a series of experimental investigations was conducted to collect representative data in a varying pocket milling process of cold working steel 1.2842. We show that we can achieve substantial improvements in terms...
Poster
Full-text available
Metalworking fluids (MWFs) are of great importance in machining. They dissipate heat generated during machining and reduce the friction between interfaces of chip-tool sliding contact and tool- workpiece contact. Additives are added for these purposes in MWFs, in addition to the base oil and the water phases. Typically, defoamers, biocides, emulsif...
Preprint
Full-text available
Polycrystalline cubic boron nitride (PcBN) is an extremely hard material. Machining of the material is performed by grinding with diamond tools. Due to its high hardness, the grinding tools underlie a severe microscopic and macroscopic tool wear. This wear leads to a short tool life and results in high effort in conditioning the abrasive layer. Con...
Book
Full-text available
The focus of this book is an application of Digital Twin as a concept and an approach, based on the most accurate view on a physical production system and its digital representation of complex engineering products and systems. It describes a methodology to create and use Digital Twin in a built environment for the improvement and optimization of fa...
Conference Paper
Additive manufacturing is established for the production of polymer and metal structures in many branches of industry. For glass materials, the feasibility of additive manufacturing was recently demonstrated. The Laser Glass Deposition (LGD) is one of the methods to manufacture glass components on a glass substrate with a CO2 Laser. Fused silica fi...