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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 figure 2a

components figure 2a Screw head on drilling tool Ø 6.5 mm figure 2b Screw head residue with flow chip on drilling tool Ø 12.5 mm figure 2c Screw head residue on drilling tool Ø 12.5 mm made it possible to produce fracture chips suitable for the use of an extraction system. However, in a first test run it could be observed that in about every fifth screwed connection drilled out, a screw head residue in the form of a narrow ring got caught on the main cutting edge of the drilling tool (figure 2c). This screw head residue was then carried along on the main cutting edge to the next screw head to be drilled out. This not only prevented a process-reliable separation of the following screw connection, but also resulted in the tool life limit being reached prematurely after only 32 screw connections. Since it was not possible to reliably separate the screw connections and remove the chips in the drilling processes considered, the separation of screw connections using robot-assisted milling processes was investigated in further test series. Here, circular milling was used as milling strategy. With this type of movement, the milling tool plunges into the screw head with a circular feed movement around its longitudinal axis, which enables the use of a tool-enclosing extraction system for chip collection. Four-edged solid carbide corner radius milling cutters with a diameter of 8 mm and a corner radius of 1 mm of the type NVV 0334 56 081 of the company Pokolm Frästechnik GmbH & Co. KG were used, whereby a speed of n = 4777 min -1 , a feed rate of v f = 1433 mm/min, a cutting speed of v c = 120 m/ min, a helix diameter of D h = 5 mm (drilling diameter D B = 13 mm) and an axial cutting depth per helix revolution of a* p = 0.35 mm were selected. In the milling tests it could be observed that the milling strategy allowed a safe separation of the screw connections (figure 3, a and b). An initial wear test with three test tools also revealed that under the given conditions, around 200 screw connections could be reliably separated with one milling tool until the wear limit was reached. An interchangeable unit-type extraction system was developed to collect the accruing chips (figure 4, a and b). Its functionality was verified in the circular milling process application. The chips were collected via an extraction hood that could be adjusted in z-direction and to which a vacuum cleaner was connected. A brush ring was mounted around the edge of the hood to enclose the milling tool. The brush ring allowed the best possible sealing of the cutting point and avoiding collisions with the battery housing at the same time. The brush ring slowed down the ejected chips during circular milling so that they could be picked up by the air flow of the vacuum cleaner to be transported away. figure 3, a and b Separation of screw connections in the circular milling process 40 no. 3, August 2022

components interchangeable unit with HSK 63F mount clamping chuck connection for vacuum cleaner extraction hood brush ring cutting tool figure 4a Construction of the extraction system figure 4b Extraction system inserted in the high-frequency spindle Disconnecting plug connections Within a second series of tests, the suitability of robot-assisted drilling and milling for the destructive separation of plug connections was investigated. First, four different plug connections were selected on the basis of a plug analysis of the PHEV PB320 battery (table 2). Special care was taken to ensure that the selection covered both the largest and smallest connector in terms of dimensions, the entire material mix of all built-in connectors and all different designs. A modular clamping device was developed for the machining tests, which reproduces the geometric shapes of the respective mating connectors in an exchangeable bar. For clamping, the connectors are clicked into their mating connectors, which are then clamped in the clamping device with the help of screws. The cables crimped with the plugs are fixed by cable tensioning bars. Within the scope of the cutting tests, a double-edged HSS long-hole cutter, type 3453, with center cut and special drill face of the company Gühring KG, with a diameter of 10 mm was used. The cutting strategies considered were circumferential milling in synchronisation, plunging (for plugs whose di mensions are smaller than the cutter diameter) and a combination of plunging and circumferential milling (for plugs whose dimensions are larger than the cutter diameter), where by the process parameters were adapted for each plug type (table 3). In the machining tests (figure 5), the TRU Components pre-fab braid connectors in particular presented a challenge. In some cases, for example, the flexible crimp contacts could not be completely separated by the milling cutter during the plunging strategy. A remedy was provided by circumferential milling, whereby care had to be taken to ensure that the TRU Components pre-fab braid Cimco flat connector AMP Super Seal Molex Micro-Fit table 2 Selected plug connections peripheral milling plunging plunging and peripheral milling TRU Components pre-fab braid v c = 80 m/min n = 2.548 min -1 v f = 382 mm/min n = 2.548 min -1 v f = 305 mm/min v c = 120 Cimco flat connector m/min n = 3.822 min -1 v f = 765 mm/min n = 2.548 min -1 v f = 485 – – mm/min v c = 100 AMP Super Seal m/min n = 3.185 min -1 v f = 446 v c = 100 mm/min v c = 100 Molex Micro-Fit m/min n = 3.185 min -1 v f = 446 – – m/min n = 3.185 min -1 v f = 318 mm/min v c = 80 mm/min m/min n = 2.548 min -1 v f = 306 mm/min table 3 Choice of process parameters no. 3, August 2022 41

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