November 2021
This research work focuses on the experimental investigations conducted using uncoated cBN tool and (AlCrN) PVD Coated cBN tool for turning Inconel 718. Two different sets of experiments – one with uncoated cBN and another with coated cBN inserts were conducted considering three different levels of cutting speeds, feed rates and depth of cuts. The performance of the coated cBN over the uncoated inserts (…)
The ongoing trend of robotics, automation, quality control and its combination are leading to new possibilities in the field of metrology. The improvements, especially in the handling and accuracy of collaborative robotics, are enabling new applications for automated high-resolution optical 3D measurements. This is the basis for the implementation of a pick-and-place solution for automatic surface textu (…)
The regenerative chatter during milling is a consequence of the machine tool dynamic compliance and the specific setting of the cutting process. The basic request on the machine structure is to enable a stable cut with dominant portion of the installed spindle power. In order to improve the dynamic properties of newly-designed machine tools, the machine tool structures are optimized using various advanc (…)
Ever increasing requirements to machine tool performance lead to a shift from regular roller bearing towards hydrostatic guideways. These have many advantageous properties, such as non-existent stick and slip, nearly no wear, while increasing dampening and stiffness. Compared to traditional guideways, hydrostatic have a constant energy demand, resulting from pump losses. The pump losses are composed out (…)
In the context of increasing digitalization, machine tools have a decisive impact on the manufacturing of technically sophisticated products. The resulting large amount of available data opens up new opportunities for process monitoring and optimization. In this paper, a new in-process tool condition monitoring (TCM) approach for end mills is developed. Besides in-process wear determination, the present (…)
Machine tool thermal errors are an important element in machined workpiece inaccuracies. In the past few decades, thermal errors have been successfully reduced by software compensation techniques such as multiple linear regression analysis, finite element method, neural network and transfer function (TF). A phenomenological approach based on TFs is used for thermal error compensation in this research. T (…)
The optimization of production processes is even in 2021 still an up-to-date topic, where the use of data is discussed, and the utilization has proven to be effective in specific applications in the last 10 years. Despite increasing access to information directly from the production process and more available computing resources, the data still holds unused potential. Even ongoing digitalization does n (…)
The heat generated during the cutting processes significantly influences the manufacturing accuracy. For many machining tasks, the use of cooling lubricant is essential to achieve the necessary cooling and lubricating effect in the cutting zone. A reduction of a coolant supply due to resource-efficient or ecological efforts has an impact on the temperature field in the cutting tool and clamping system, (…)
This study presents an experimental method for detecting and avoiding chatter vibrations that occur during general milling processes. The main idea is to capture the so-called dominant spectral properties from the transient vibrations of the milling process, which gives a good approximation for its dynamical behavior and provides a quantitative measure of stability. To induce transient vibration, the ma (…)
The surfaces of machined workpieces contain the signature of the manufacturing process. Indeed, the surface inaccuracies can be related to process parameters and machine vibrations. This paper aims at using process monitoring to identify the origin of surface topography defects. Thus, vibration and other process parameter measurements are correlated with profile measurements to establish the relationshi (…)
Todays’ heterogeneous manufacturing environments and isolated manufacturing elements hinder the realization of a complete and data consistent digital twin. Against this background, an increased connectivity based on the Industrial Internet of Things (IIoT) might be the future key enabler for the digital twin. However, it requires each domain to transfer, rearrange and rethink their individual data solut (…)
During thin-walled part milling, a dominant flexible direction perpendicular to the feed motion is most likely to exist, which allows to formulate the stability problem in the frequency domain in a very simple form. By these means, the existence of optimal engagements under up-milling strategy for achieving a theoretical infinite Hopf stability have already been demonstrated. However, period-doubling ch (…)
Sawing frozen wood differs significantly from sawing unfrozen wood. Temperatures below zero degrees result in an increasing hardness of wood, rising cutting forces and a progression of tool wear. Currently, the adaption of process parameters due to different wood temperatures is based on operator experience, leading to overloaded saw blades, hence causing considerable economic damage by increasing produ (…)
On-machine measurement by a line laser scanner has a great potential in machining large complex components in aerospace and automation applications. This paper proposes a novel approach for path planning of measuring curved surfaces in a 5-axis machine tool, which takes scanning overlap, visual angle, and working distance into consideration. A conformal mapping algorithm is employed to transform a three (…)
Efficiency plays a major role in many areas of the mechanical processing of metals. Especially in basic provision of raw material, for example by cutting components to length during sawing, high penetration and thus efficiency as well as high robustness of the process is required. Here, the saw-ing tool and its durability is the decisive component in the process. In today's state of the art, at least in (…)
Telescopic covers are components which can have a potentially large impact on machine tool feed drive capabilities. Generally speaking, frictional force modelling is a well-established field of interest in which many approaches and challenges have been identified. This paper addresses frictional force modelling of machine tool feed drive telescopic covers. A sequential assembly approach and control syst (…)
Chatter vibrations during machining operations are large-amplitude self-excited vibrations, which result in the loss of physical contact between the workpiece and the tool. This paper presents an electric contact sensor, which is used to detect the cutting and noncutting periods during the operation. The spectrum of the signal of the electric contact sensor is free from environmental noise and can be us (…)
To reduce the size of exit burrs induced by broaching, it is possible to use a low value martyred part clamped to the functional one on the tool exit side. Thence, this research work deals with an in-situ analysis of the burr formation at a bi-specimens interface in orthogonal cutting configuration. New mechanisms of burr formation at the interface formed by Inconel 718 and cast iron specimens are ident (…)
Additively manufactured multi-materials promise unique combinations of different material properties. However, the machining behavior of these materials is widely unknown. In this study, fundamental investigations on chip formation and morphology, cutting force, workpiece temperature after cutting and surface quality were conducted in orthogonal cutting experiments. Additively manufactured test specime (…)
Manufacturing process monitoring is showing great advances thanks to increasing sensor availability and the development of edge to cloud IoT systems. However, the application of this technology in industry is slowed down due to cyber security policies, the coexistence of old manufacturing systems, with limited monitoring capabilities, with newer and fully monitored ones, and the lack of application-orie (…)
This paper presents a further elaboration of the use of the digital twin concept in digital machining. The main goal of the research is an attempt to combine digital representations of different objects involved in the machining process in a holistic manner. Digital twins of the in-process workpiece, cutting tool, clamping, and machine tool along with the process twin are connected in a framework in whi (…)
The production of carbon fiber reinforced plastic (CFRP) parts requires edge trimming after primary shaping. Heat accumulates in convex workpiece sections, leading to increased temperatures compared to straight edges, possibly compromising the material. Existing analytical models assume constant thermal conditions and are therefore unable to calculate temperature fields of curved workpiece contours. Ac (…)
In recent years, cryogenic minimum quantity lubrication (CMQL) has been established in comparison to pure cryogenic cooling. The used oil has a crucial influence on the success of the technology. The aim of this study is to investigate the influence of oils from renewable resources with regard to their miscibility with carbon dioxide (CO2) and their spraying behavior. Ten different bio-based oils (synth (…)
Cryogenic minimum quantity lubrication using liquid carbon dioxide (CO2) has increasingly become the focus of research in recent years. With this cooling strategy it is possible to cool and lubricate the cutting zone individually by regulating the oil and liquid CO2 flow. The oil used has a significant influence on the process stability and performance. The aim of this study is to identify the influence (…)
Approaches to detect energy efficiency measures are associated with time consuming analysis requiring expertise. Against this background, this paper presents an expert system to identify potentials for improving the energy efficiency of metal cutting machine tools based on measurement and meta data of 35 machines. For this purpose, it is necessary to determine energy states of machine tools and control (…)
The simulation of machining processes holds the opportunity for process improvement on many levels. Possible benefits that can be derived from accurate representations of the real processes on the tool from simulations include a prediction of tool wear, the shape of the chips produced, the forces, frictions and temperatures that arise and the residual stresses in the workpiece. These predictions can be (…)
The increasing availability of data recording solutions in the field of machining in combination with major developments in Machine Learning and Artificial Intelligence enable new approaches towards optimization in the industrial environment. In the aviation industry, critical components must fulfil extremely high quality standards. This requires a stable and error-free manufacturing process, as well as (…)
More and more forming and punching tools as well as wear parts are made from cemented carbide. The large variety and the geometry of these components are often reasons for finish machining by milling, but the tool wear is very high. For the investigations, end mills with different diamond material tips or coatings are used. The cemented carbide specimens exhibit an average tungsten carbide particle size (…)
To fulfill service life and integrity requirements when using a non-conventional process in aerospace industry, a comprehensive validation needs to be carried out. According to the state of the art, the characteristically resulting recast layer of wire electrical discharge machining (WEDM) can be reduced to a few microns. To meet existing requirements for eliminating the recast layer, it is essential fo (…)
As the process parameters in the LPBF-process influence the microstructure, density and hardness of the produced parts, their influence on the milling process is suspected. For this reason the new maraging tool steel alloy Specialis® has been investigated on its machinability depending on the built parameters. The influence of the energy density, laser power and scan speed in the LPBF-process on the mil (…)
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 turning processes are increasingly used. For these processes, the tool path is optimized to achieve advantageous cutting conditions and thus higher productivity. However, the process forces and their relatio (…)
The ongoing climate change and increasingly strict climate goals of the European Union demand decisive action in all sectors. Especially in manufacturing industry, demand response measures have a high potential to balance the industrial electricity consumption with the increasingly volatile electricity supply from renewable sources. This work aims to develop a method to forecast the electrical energy de (…)
Cutting forces analysis is one of the most important means of improving machining quality and productivity. In 3-axis milling, the frequency domain analysis of the cutting forces provides information which can be adopted for both predicting and monitoring the cutting process. However, the evaluation of the cutting forces spectra requires the application of specific tools (i.e., Fourier’s Transform) to t (…)
The production of shape accurate forming dies in the toolmaking industry requires a high degree of manual labour. To achieve a higher level of automation, machine-based approaches are necessary. Therefore, robot-based milling experiments of difficult-to-machine cold work steel 1.2379 are carried out. This paper presents an experimental study of different path strategies using an industrial robot to mil (…)
The production of individual work pieces in small to medium batch sizes requires an adaptation of the manufacturing strategy. Particularly, the manufacturing of multi-material components out of metal and plastic is characterized by high production costs as well as high production times. To resolve this challenge, a new, modular process chain for the production of these structures in a single manufacturi (…)
Gantry stages, consisting of two parallel acting drives, are a well-known example, where a significant interaction between all control systems’ in- and outputs is present due to structural coupling. Stability issues and therefore the limitation of the bandwidth of the position control can be a consequence of this effect. The adjustment of the systems mechanical properties using compliant joints, as well (…)
Circular shallow recess bearings generate a not rotationally symmetrical pressure profile if they are not aligned parallel. The throttling effect of the shallow recess makes this response possible. Furthermore, the generated pressure profile acts against the tilting. As a result, a shallow recess bearing generates a tilting stiffness. This article outlines an experimental approach to characterize the ti (…)
The comparison between measured and simulated machining forces enables the evaluation of workpiece quality, process stability, and tool wear condition. To compute the machining forces that occur, mechanistic cutting force models are typically used. The cutting force coefficients (CFCs) of mechanistic force models are directly linked to the mechanics of chip formation and, thus, depend on the tool-workpi (…)
Monitoring the tool condition of machining processes is important but challenging. Several automated tool condition monitoring solutions are available, but often not used due to existing restrictions or disadvantages. A new approach can be the detection and measurement of tool conditions analyzing the sound of an air jet impingement on tools. Due to the availability of compressed air as a working and cl (…)
In the course of the digitization of modern production systems, a reliable parameterization of the digital twin of machining processes is essential. For example, the digital representation of milling operations enables the process parameter selection without time-consuming and expensive test series by using stability lobe diagrams (SLD). However, the parameterization of the underlying process force mode (…)
Additive manufacturing techniques are increasingly used in industry. However, the direct usage of additively manufactured parts is limited due to their relatively low surface quality. Especially to achieve functional surfaces, post-processing has to be carried out. Post-processing methods include traditional mechanical cutting processes as well as electrical and chemical processes. Since previously depo (…)
The objective of this paper is to determine whether it is possible to compare the lubricating properties of different Metal working fluids (MWF) for a defined cutting application using easily reproducible tribological tests. The idea is that this will eventually allow users of MWF to select the most suitable MWF for a specific application without the need to run expensive and time-consuming tests on a m (…)
The metastable austenitic stainless steel AISI 347 offers the possibility to induce a phase transformation from γ-austenite to ε- and α’-martensite when machining. This knowledge is well understood during cryogenic turning and was already applied to improve the surface morphology of metastable austenitic steel. However, the potential of this in-process hardening method is so far limited to rotationally (…)
During the metal cutting process, finite element (FE) simulation has been acknowledged as an efficient way to provide designers more in-depth understanding. Furthermore, constitutive model parameters of the experimental material play a crucial role in determining the accuracy of FE simulation results. In this study, three different sets of Johnson-Cook (J-C) constitutive model parameters (A, B, n, c, an (…)
The performance of the PVD coated carbide insert with micro-holes is experimentally compared with that of the conventional inserts while machining Inconel 718 under Dry and MQL condition (Canola Oil, 0.25% Gr with Canola Oil). The machining performance of textured tool is found to be relatively good when compared to untextured tool in terms of the cutting force, surface roughness, flank wear and crater (…)
Currently, in view of the fact that almost all the tasks of the practice of controlling CNC machine and robot drives cannot be accurately represented by linear models, and there is no solution to non-linear models in the general case, a very important task is to develop control algorithms based on discrete models. Discrete models of nonlinear systems assume variable state, control, and measurement matri (…)
The paper describes a diagnostic system for electromechanical equipment with a decision-making block based on a neural network. An asynchronous gear drive was used as a control object. Decision making was carried out on the basis of a comprehensive analysis of vibration data (from the gear drive) and the current consumption of the induction motor. Vibration velocity, vibration acceleration and current i (…)
The total world energy consumption is permanently growing during last 30 years. Alternative energy sources are one of the best ways to save the environment polluted by the combustion products of gasoline, diesel fuel, and even methane or propane. The main idea of the article is to analyse the possibility and it influence of integration of the electric vehicles on battery and fuel-cells base in the trans (…)
The paper deals with the verification of the possibility of replacing natural aggregate with recycled aggregate concrete (RAC) in the production of precast concrete. In the practical experimental part, concrete mixtures with different proportions of recycled concrete are tested. The results shows that the use of recycled concrete as a substitute for aggregates is possible. However, the ratio of replaced (…)
The article presents the current state of the use of cobalt in various industries and its possible elimination in the field of welding. In this area, it is used in the form of cobalt alloys which are affected by various mechanical and chemical influences. These alloys are produced by the secondary metallurgical area. The primary area is the chemical industry which reserves all the use of cobalt for the (…)
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