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hpt 2022 #3

  • Text
  • High precision tooling
  • Change of mobility
  • Hard metal
  • Cbn
  • Cvd
  • Pvd
  • Pcd
  • Disassembly of batter systems
  • Harnischcom
  • Processes
  • Connections
  • Precision
  • Materials
  • Components
  • August
  • Milling
  • Automation
  • Grinding
  • Machining
■ Seeing mobility change as an opportunity ■ Stable trend towards automation in the metal cutting industry ■ Tradition. Passion. Innovation: How it all began ■ Automated disassembly of battery systems

components

components Robot-assisted separation of screw and plug connections Automated disassembly of battery systems written by Thomas Götz and Andreas Gebhardt, Fraunhofer Institute for Manufacturing Engineering and Automation IPA Electromobility plays a decisive role in the design of sustainable mobility concepts, as it forms the basis for a sustainable reduction of environmentally harmful emissions. However, the transformation towards electromobility presents the German automotive industry with technical and structural challenges, which are also associated with economic and social implications. [1] The raw materials required for the production of lithium-ion batteries, such as lithium, cobalt, nickel or manganese, are proving to be particularly problematic. Their supply situation is risky due to the monopolistic market position of some production countries [2, 3] and their extraction and production are accompanied by significant ecological and social problems [4] . Against this background, a systematic recycling of battery components is imperative from an ecological, economical and strategic supply perspective. In view of the expected shortage of raw materials in the future and the simultaneous increase in demand, the recovery of technology metals by means of recycling will play a key role. This applies in particular to the materials used in electrodes. [5] Further potentials are provided by both the reprocessing and reuse of individual battery components and by the reassembly of still functioning individual parts into functional modules [6] . However, such a systematic recycling of central components requires large-scale industrial dismantling concepts with a high degree of automation [7] . dismantling level battery pack battery module detachable connection type screw connection latching welding/ soldering • housing • module contacting system • battery management system • cooling system • connections • module management system • connections • battery modules • clamping elements • wiring • connections • module housing • clamping elements • wiring • connections • wiring • connections • module housing table 1 Connection types of battery components [9] An important component for the fully automated dismantling of battery systems is the separation of screw and plug connections. Corresponding processes were investigated within the framework of the joint project DeMoBat – “Industrial Disassembly of Battery Modules and E-Motors”, which is the subject of this article. Structure and disassembly of battery systems Due to their high energy density, lithium-ion batteries form the basis for most modern concepts for powertrain electrification of all types of vehicles [8] . This battery technology uses lithium-ion cells that are connected in series in a module. In addition to the cells, the module contains other electronic components such as cooling modules, a cell overvoltage monitor, wiring, connections to the outside and a module management system. Several modules and other peripheral components such as clamping elements, wiring, contacting systems, external connections and the battery management system are then assembled into a battery system, which is dimensioned differently depending [9, 10] on the required performance data. The individual components are assembled into the battery system using various connection technologies, with both detachable and non-detachable techniques being employed [9] . Table 1 lists typical connection types of the individual components. For battery dismantling, the first recycling concepts for high-performance batteries of electric vehicles were developed within the research project LiBRi - “Lithium-Ion Battery undetachable • cell contact system • wiring • connections bonding • connections • cooling plates • connections Recycling Initiative”. In this context, guidelines for a recyclingcompatible battery design were also derived. Easy dismantling respectively the use of detachable connections (e.g. screw connections, latches) for cells and electronics were identified as central prerequisites for a dismantlingfriendly design. [11] In the research project Litho- Rec – “Recycling of Lithium-Ion Batteries”, the mechanical disassembly of vehicle batteries in individual components was investigated in practice. Due to 38 no. 3, August 2022

components the expected diversity of battery designs, the disassembly work was carried out as purely manual activities by skilled electricians with the aid of standard manual or mechanical tools. Standard tools such as screwdrivers, spanners, but also pneumatically or electrically driven screwdrivers were used for unscrewing screw connections (figure 1a). In the case of vehicle batteries that were installed on the subfloor and exposed to moisture, the housing screws could be oxi dised, so that stuck screws had to be removed destructively using chisels or angle grinders. Plug connections were opened manually (figure 1b), whereby manufacturer-spe cific plugs could usually only be opened with special tools. In case the connectors could not be opened manually, the cables were cut with cable cutters. [12] Since a higher degree of automation in the dismantling of battery systems makes an important contribution to increasing the efficiency and cost-effectiveness of the hitherto purely manual dismantling process, the first tests on the semi-automated dismantling of battery systems were carried out in the follow-up project LithiumRec II. A human- machine collaboration was investigated, in which complex disassembly activities such as loosening plug connections were carried out by a human and simple activities by a robot. Among other things, a robotic end effector was developed for automated disas sembly of screw connections, based on a cordless drill for manual handling and equipped with an additional singlefinger gripper for screw removal. [13] drilling and milling processes were investigated in detail as part of the DeMoBat project. A six-axis KUKA KR600 R2830F articulated robot with a Siemens SINUMERIK 840D controller and an HSD ES951 L 1612 S high-frequency spindle used to carry out the experiments. To ensure the safety of destructive dismantling, technical requirements were therefore placed on the machining process. For example, the use of coolants and lubricants must be avoided, as moisture inside the battery can lead to short circuits. Metal chips must also be collected and removed by an appropriate extraction system, as they can lead to short circuits or other damage inside the battery. Separation of screw connections The aim of the first series of tests was to investigate robotassisted drilling and milling for the destructive separation of screw connections. For the machining tests, a simplified test carrier was developed, consisting of an aluminium tube with attached aluminium plate, both connected to each other via a steel ring with the aid of galvanised DIN 7985 pan-head screws with TORX drive of size M6 x 12 mm. The test carrier forms the components and materials of the battery housing type PHEV PB320 from Accumotive GmbH & Co.KG which was considered in the DeMoBat project. It was clamped onto the machining table by means of a three-jaw chuck. Within the scope of the test series concerning the separation of screw connections by means of robot-assisted drilling methods, the process variant of solid drilling was examined more closely, using solid carbide twist drills of the type DIN 6537K of the company Gühring KG. figure 1a Manual disassembly of screw connections [14] figure 1b Manual disassembly of plug connections [15] Design and execution of experiments In order to enable automated disassembly of corroded or stuck housing screws and plug connections beyond the current state of the art, strategies for the destructive separation of screw and plug connections by means of robot-assisted As a cutting strategy, the reaming of the thread passage was considered first. A twist drill with a diameter of 6.5 mm was used to drill directly to the target depth at a cutting speed of v c = 80 m/min and a feed rate of f = 0.15 mm (“oneshot drilling” process). Since the complete screw head was stuck on the main cutting edge of the drilling tool during the drilling of the threaded passage (figure 2a) and thus the separation of a second screw connection with this tool was prevented, the drilling of the complete screw head (screw head diameter 12 mm) offered itself as a second strategy, which was also investigated as a one-shot drilling process using a twist drill with a diameter of 12.5 mm. Here, a cutting speed of v c = 160 m/min and a feed rate of f = 0.25 mm were selected. When using this strategy, a screw head residue with continuously running and coherent chip elements settled on the drilling tool in the form of flow chips (figure 2b). For this reason, the alternative strategy of reaming the screw head as a drilling cycle with chip breaking (“peck drilling” process) was chosen. In this drilling cycle, drilling was carried out successively to the target depth, with a feed interruption after every 0.5 mm advance in z-direction followed by a short retraction in the opposite direction. This no. 3, August 2022 39

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