Carbon fibre recycling from milling dust for the application in short fibre reinforced thermoplastics

A new approach to reuse accruing chips and dust from milling operations of carbon reinforced plastics (CFRP) is studied, show-ing how CFRP milling dust, in comparison to primary and pyrolysed fibres, can find application as a filler material in thermo-plastic granulates. Recent examinations show an overall better handling of milling dust when separating it into different classes of fibre lengths reaching up to 600 µm, which typically occur while machining reinforced plastics. Furthermore, the carbon rein-forced polypropylene granulates have improved material properties, e.g. increased rigidity and tensile strength in dependence of their respective filler content towards non-reinforced plastics

Advances in Tool Grinding and Development of End Mills for Machining of Fibre Reinforced Plastics

The extensive use of lightweight construction materials in the aerospace industry poses a great challenge for tool manufacturers. Materials like carbon fibre reinforced plastics (CFRP) are difficult to machine and therefore put high demands on cutting tools in terms of the cutting material as well as the macro- and microscopic design. In this paper two approaches for the improvement of CFRP milling processes are presented. One approach involves the optimization of the flute grinding process for cemented carbide milling tools by the use of innovative grinding wheel specifications and their influence on cutting-relevant tool features. The other approach deals with the development of ceramic end mills for CFRP machining. Investigations about the influence of different process- and tool-related parameters on the work result and process parameters are presented

Studies on conventional cutting of intermetallic nickel and titanium aluminides

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Owing to the high percentage of covalent bonds, intermetallic nickel and titanium aluminides have specific physical and chemical characteristics that predestine them for components under high thermal and mechanical load. However, the relatively low ductility and thermal conductivity at room temperature, linked to high tensile strength, impede the machining with geometrically defined cutting edges in series production. The conventional machining process is characterized by microcrack formation at the component surface. One possible way is to warm up the intermetallic alloys locally above the quasi-brittle-ductile transition temperature by the interaction of the workpiece material and the tool. The subjects of investigation were the influences of feed rate and cutting speed on the tool-face temperature and cutting force as well as on the chip formation and fringe-area formation during longitudinal cylindrical turning. The experiments were carried out with intermetallic nickel and titanium aluminides in an as-cast and extruded state. The goal was to elaborate the technological basic knowledge for a damage-minimized and productive machining of intermetallic aluminides with geometrically defined cutting edges

A Time Domain Simulation Approach for Micro Milling Processes

AbstractPrediction of Process Machine Interactions (PMI) can be achieved using models for conventional milling processes in the time and frequency domain. However, instabilities such as regenerative chatter can also be observed in micro milling processes using filigree cemented carbide end mills. The dominant chatter frequencies are basically related to the end mills eigenfrequencies. Nevertheless, the dynamic characteristics of the machine tool structure and the work piece must not be neglected. In this paper a comprehensive time domain process model is presented. The machine tool dynamics are considered as non-coupled oscillators based on measured frequency response functions at the tool holder. The end mill is modeled as rotating Euler-Bernoulli beam with variable boundary conditions at the tool clamping. At first, the parameter identification for a geometric cutting force model is described. It contains the cutting edge radius as a time-depended parameter. Thereafter, the modeling and parameter identification of the structural parts are presented. A stability criterion is defined with special regard to the tool deflection at the TCP. Finally, simulation results at different stable and unstable operating points for full immersion cutting are discussed in detail and compared to experimental tests

Influence of the built-up edge on the stress state in the chip formation zone during orthogonal cutting of AISI1045

In-situ strain measurements with high energy synchrotron radiation during orthogonal cutting of AISI1045 were carried out. Thereby it was possible to determine the stress state in the chip formation zone during the cutting process. As such, observations regarding the formation of built-up edges during the cutting process have been made. The formation of a built-up edge on the cutting tool is a common phenomenon during cutting of mild steel and other ductile materials, in particular at low cutting speeds. This may result in increased tool wear and a decrease in the resulting surface quality. By analyzing the chip roots of the in-situ experiments, it was possible to determine the geometry of the built-up edges on tools with a rake angle of γ = 0° and cutting edge radii of rβ = 30 μm and rβ = 60 μm. Using the obtained data a simulation model which represents the built-up edge could be established with two versions of the built-up edge: a solid one as part of the rigid tool and an elastic one in front of the tool. Using FEM cutting simulations with and without built-up edges, it was possible to show the influence of a built-up edge on the chip formation and the stress state in the chip formation zone. With this data, a comparison of the results of the cutting simulations with those of the in-situ experiments was conducted

Discrete Element modelling of drag finishing

Drag finishing is a machining process that is used to improve the surface topology of workpieces. Workpieces are moved through a bulk of differently shaped abrasives, the so called media. Material removal is caused by the relative motion between workpiece and media. The material removal rate is mainly depending on the contact intensity between workpiece and media. Up to now there is no viable way to determine the intensity of single contacts empirically. However, a sound understanding of single contacts with respect to impact forces and velocities could greatly improve process comprehension and reduce trial and error process design efforts. For that reason the movement of media and workpiece is modelled using the Discrete Element Method (DEM). In this paper a comprehensive approach is presented covering formulation, calibration, validation and utilization of the DEM. Media is considered as an aggregation of elastic particles that are subject to contact, damping and gravitational forces causing particle movement. Geometric boundary conditions, i.e. workpiece and drag finishing bowl, are implemented as elastic facets. Contact forces are calculated according to a non-linear, simplified Hertz-Mindlin contact force model. Energy is dissipated by viscous damping and friction at contacts. Necessary parameters of the model are determined experimentally. The validation of the model's behaviour shows good agreement with experimental data. Finally the model is used to determine local contact intensities on the workpiece surface and between particles. By analysing simulated contact forces, the formation of dominant contact chains between particles is observed and investigated

Application of spindle speed increaser as sustainable solution to upgrade machine tools

Due to varying machine operations, cutting material and feed motion of the respective milling machine, a wide range of spindle speed is required. Modern machine tools are therefore occasionally equipped with two spindles to cover a wider application scope. Especially while increasing the cutting removal rates for soft materials like aluminium alloys, outdated machine tools fail to provide high spindle speed. Spindle speed increasers (SSI) are possible solutions in order to flexibly increase the cutting removal rates of milling machines. In this paper, the state of the art of SSI is investigated regarding its application in different milling machines and with respect to resource and energy efficiency. Therefore, based on the respective machining operations, spindle input and milling machine, a selection methodology is provided to prove the feasibility of the application of existing SSI. This allows estimating the sustainable benefit on theoretical basis.DFG, 199828953, SFB 1026: Sustainable Manufacturing - Globale Wertschöpfung nachhaltig gestalte

An evaluation of building sets designed for modular machine tool structures to support sustainable manufacturing

The modularization of machine tool frames is an approach when designing new machine tool structures in a sustainable context. By integration of microsystem technology and designing lightweight modules, a smart alternative to conventional machine tool frames is developed. In previous studies, this concept has been evaluated along with a compilation of the possible use-case scenarios and the potential benefits from using modular electronics. In the presented paper, the geometric requirements from the selected use-case scenarios for machine tool structures are identified by dividing the structures in their ideal mechanic equivalents. A set of rules is developed driven by the generalized geometric requirements of the machine tool frames. Three different approaches of polyhedral building sets are shown and evaluated for their merits based on criteria of geometric functionality and sustainability. Finally, a prototypical modular portal frame is presented for the proof of concept

Influence of the Built-up Edge on the Stress State in the Chip Formation Zone During Orthogonal Cutting of AISI1045

AbstractIn-situ strain measurements with high energy synchrotron radiation during orthogonal cutting of AISI1045 were carried out. Thereby it was possible to determine the stress state in the chip formation zone during the cutting process. As such, observations regarding the formation of built-up edges during the cutting process have been made. The formation of a built-up edge on the cutting tool is a common phenomenon during cutting of mild steel and other ductile materials, in particular at low cutting speeds. This may result in increased tool wear and a decrease in the resulting surface quality. By analyzing the chip roots of the in-situ experiments, it was possible to determine the geometry of the built-up edges on tools with a rake angle of γ = 0° and cutting edge radii of rβ = 30 μm and rβ = 60 μm. Using the obtained data a simulation model which represents the built-up edge could be established with two versions of the built-up edge: a solid one as part of the rigid tool and an elastic one in front of the tool. Using FEM cutting simulations with and without built-up edges, it was possible to show the influence of a built-up edge on the chip formation and the stress state in the chip formation zone. With this data, a comparison of the results of the cutting simulations with those of the in-situ experiments was conducted

Innovative manufacturing technologies for the disassembly of consumer goods

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Ecological harmless disposal of used technical consumer products will become mandatory for producers and importing companies. This disposal policy will focus on product and material loops; used products will be disassembled and the parts and materials then recycled. Owing to environmental and legislative reasons, the importance of disassembly as a step in the process of recycling is steadily rising. The article presents developed technologies and tools for the disassembly of consumer goods. The aim is to recover materials and reusable components within a semiautomatic pilot disassembly system. Different destructive processes were optimized to disassemble washing machines