A new turn for e-mobility

Die vertikale Bearbeitung bietet Vorteile. Zum einen eine platzsparende Verkettung der einzelnen Bearbeitungseinheiten, der optimale Transport von Spänen und Prozesshilfsstoffen sowie eine kompakte Maschinenbauweise mit geringer Aufstellfläche inklusive einem Pick-up System.

„Beim Drehen ist das Pick-up eine übliche Lösung, wie sie bei vergleichbaren Teilen heute schon vielfach genutzt wird. Diese Beladung ist für eine automatisierte Großserienfertigung von Statorgehäusen ideal konzipiert“, berichtet Thomas Lötzsch, Verkaufsleiter bei NILES-SIMMONS. 

Der entscheidende Vorzug des neu entwickelten Prozesses ist die damit mögliche Steigerung der Produktivität. Auf Anhieb ist es gelungen, die Produktionszeit für das Bauteil im kombinierten Dreh-Bohr-Verfahren gegenüber dem konventionellen Drehprozess um 50 Prozent zu verkürzen. Daniel Pilz, der das Projekt bei NILES-SIMMONS leitete, beschreibt, wie die Zeit in den einzelnen Arbeitsschritten eingespart wird, bei denen sich von Fall zu Fall Werkstück, Werkzeug oder beide gleichzeitig drehen.
 

In the second machining step, a bell-shaped tool developed by NILES-SIMMONS is used for the outer contour, while a MAPAL ISO boring tool is used for semi-finishing the inner diameter. The inside and outside of the workpiece are machined at the same time. “What’s special is that a statio­nary, vertical external machining tool is attached to the spindle housing. The spindle drives the internal machining tool,” says Daniel Pilz, describing the setup. The workpiece dips into the annular gap formed by these two tools. All diameters are produced with one single feed movement – for this specific part, this amounts to three inner and three outer diameters. Four blades are used for each diameter. “As well as being able to machine the inside and outside simultaneously, altogether we take just an eighth of the time we would need for conventional turning,” says Pilz. Other benefits include the following:

•    Due to the counteracting cutting forces of the internal and external machining, a lower torque must be maintained on the workpiece clamping device. 
•    Vibrations in the thin-walled part during machining are absorbed by the simultaneous cutting action of the inserts on the inside and outside.

In this test, simultaneous internal and external machining took place with a cutting speed of 700 m/min. Machining using the sandwich method with the workpiece in the middle ensures that the part is stabilised during machining, as the inserts are cutting on both sides at the same time and thus guiding the part. Complex clamping technology with vibration dampening is not required, which has a noticeable impact on costs. While industry already uses MAPAL’s tool on horizontal machining centres for the internal machining of stator housings, the bell-shaped external tool from NILES-SIMMONS was newly developed and a patent was filed for the innovative process.
 

In addition to the successfully implemented vertical concept, NILES-SIMMONS is also investigating the possibility of refitting existing horizontal machines. The Chemnitz-based company has over 300 turn-broaching and crankshaft milling machines currently in use in car manufacturers’ crankshaft production lines worldwide. Both the innovative process and MAPAL’s tools can also be integrated into a horizontal version of the concept. MAPAL also offers the possibility of using additively-manufactured tools in which weight savings are not the sole focus and coolant outlets can be geared even more specifically towards the cutting edge.

Apart from the machining of stator housings, the process can also be used for other workpie­ces from a wide range of sectors, such as cooling elements for hybrid engines, pipe and flange couplings for the oil and gas industry, bearing and housing components for general machining, and workpieces for the plastics industry. This makes this process relevant for a very wide range of different workpieces with tube- and pot-shaped geometry requiring tolerances less than or equal to IT6 and with ultra-precise shape and position tolerance.