EVs and their impending onset has prompted completely new challenges for the automotive supply chain and, in particular, cutting-tool manufacturers.
One of the core challenges in the powertrains of EVs is the high-precision machining of the main bore in the stator housing. All other steps in the production of the stator housing can be carried out on machines with an HSK A63 spindle configuration. However, in most instances, the main stator bore requires machining with an HSK A100 spindle. Two factors are at play here. Firstly, high cutting torque requirements of up to 500 Nm and, secondly, maximum permissible tool weight and tilting moment.
Cost-effective manufacturing with short cycle times calls for a solution whereby complete machining can be carried out on a single machine with small spindle connections, chiefly because these machines are characterised by their high spindle speeds, lower investment and operating costs, and lower energy consumption.
In order to meet these demands, Mapal has developed a fine-boring tool with an ultra-light design. The low weight of around 10 kg meets the precondition for use on machines with smaller spindles. In addition to the weight reduction, Mapal has also optimised the cooling channels, introducing a special back-flushing system that ensures more effective removal of chips, preventing them from scratching machined surfaces.
Another challenge for those serving the EV market is achieving the chatter-free machining of highly complex, thin-walled battery housings. Here, Mapal offers the necessary tools with the optimum strategy for the different variants of battery housing. PCD is applied as a cutting material and MQL technology is introduced for maximum cost effectiveness. Furthermore, different milling technologies are employed to reduce the cutting force, which depends upon the required stock removal, machining application and component.
The SPM milling cutter from Mapal is suited to this application. Thanks to its high positive geometry and optimised chip flutes, cutting force is reduced by up to 15% compared with conventional milling cutters, says the company. If deep pockets are to be machined, Mapal employs special PCD milling cutters with cutting edges arranged in both positive and negative axis angle configurations. In combination with a trochoidal milling strategy, the cutting force is kept very low during the machining operation.
Aside from the drive and the energy storage systems being affected by the electrification of the modern vehicle, many auxiliary units and peripheral parts are also impacted by this relentless vehicle development. One example is the electric refrigerant compressor, at the heart of which are two nested aluminium spirals, the scroll stator and scroll rotor. The efficiency of the electric refrigerant compressor depends essentially on the precision of these parts.
Demands on form and positional tolerances lie in the range of a few microns. A particular challenge here is the machining of the ‘screw’. A defined rectangularity of less than 0.04 mm and a surface roughness (Rz) in the single-digit micron range are essential. Despite these requirements, the thin walls and the depth of the part, finishing has to be carried out in a single pass.
Mapal has developed an SPM milling cutter with a finishing geometry and highly positive rake angle for this application. The tool ensures low-vibration cutting and features an additional chamfer on the diameter. Mapal’s SPM cutter can perform the machining of the base, wall and chamfer in a single step, ensuring that the close tolerances for rectangularity and surface finish can be achieved reliably.
