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ORIGINAL ARTICLE

Efficient abrasive water jet milling for near-net-shape fabrication of difficult-to-cut materials 1 · Thomas Braun1 ¨ Eckart Uhlmann1,2 · Constantin Mannel

Received: 2 June 2020 / Accepted: 9 September 2020 / Published online: 2 October 2020 © The Author(s) 2020

Abstract The utilization of materials with high strength to density ratio enables efficiency improvements and is therefore demanded for many applications, particularly in the aerospace and other mobility sectors. However, the machining of these typically difficult-to-cut materials poses a challenge for conventional manufacturing technologies due to the high tool wear. Abrasive water jet (AWJ) machining is a promising alternative manufacturing technology for machining difficult-to-cut materials, since the tool wear is low and material independent. However, AWJ machining is limited regarding the producible geometries when conducting cuts through a material. This limitation can be resolved with AWJ milling operations which on the other hand are time-consuming. To approach this challenge, an enhanced AWJ milling operation is presented and investigated in this paper with the aim to expand the producible geometries. This operation consists of two kerfs, inserted from different sides of the workpiece, which intersect at their kerf ground. Consequently, a piece of material is separated without the cut material being entirely chipped. Thus, the operation possesses a high aggregated material removal rate. The investigations presented in this paper show and evaluate the effects that occur during the milling of kerfs with variable depths on titanium aluminide TNM-B1. Furthermore, a method to compensate these effects is introduced and thus the producible geometries for effective AWJ milling could be enhanced. Keywords Abrasive water jet · Near-net-shape fabrication · Titanium aluminide · AWJ milling Nomenclature ˙A Abrasive flow rate m Adjusted angle of cut α c Constant angles of cut αc(y) Actual cutting angle αc,real αc Angle of cut Opening angle of the jet forerun for concave αjf,a shapes αjf,x Opening angle of the jet forerun for convex shapes Opening angle of the jetlag for concave shapes αjl,a αjl,x Opening angle of the jetlag for convex shapes AWJ Abrasive water jet Kerf development coefficient 1 c1 c2 Kerf development coefficient 2  Constantin M¨annel

[email protected] 1

Technische Universit¨at Berlin, Institute for Machine Tools and Factory Management (IWF), Berlin, Germany

2

Institute for Production Systems and Design Technology (IPK), Fraunhofer-Gesellschaft, Berlin, Germany

c3 cp CFRP CMC df dJ dK,c dK,diff dK,max dK,min dK,m dK,p dK,s dK1 dK do e EDM fa fx fps

Kerf development coefficient 3 Power coefficient Carbon fibre-reinforced polymers Ceramic matrix composites Focus tube diameter Jet diameter Average cumulated kerf depth Difference between lowest and the deepest kerf depth Maximum kerf depth Minimum kerf depth Measured kerf depth Kerf depths on the primary target part Kerf depths on the secondary target part Kerf depth for