Abstract: A powder bed additive manufacturing apparatus includes a build sleeve, a build platform for supporting a powder bed and object during a build, the build platform lowerable in the build sleeve, and at least one acoustic sensing system. The acoustic sensing system includes an acoustic emission sensor and an acoustic waveguide. The acoustic waveguide extends through the build platform such that a receiving end of the acoustic waveguide distal from the acoustic emission sensor abuts a surface of a build substrate removable mounted to the build platform to transmit structure-borne acoustic waves from the build substrate to the acoustic emission sensor.

Abstract: A method of aligning an on-axis melt pool sensor in an additive manufacturing apparatus. The method includes scanning a first laser beam along a first scan path across a working surface using a first optical train to generate a melt pool along the first scan path and scanning a field of view of an on-axis sensor along a second scan path across the working surface using a second optical train for steering a second laser beam. The first and second scan paths intersect. An adjustment to be made to an alignment of the field of view of the on-axis sensor with an optical axis of the second optical train is determined from a variation in the signal generated by the on-axis sensor as the field of view is scanned along the second scan path.

Abstract: A powder bed additive manufacturing apparatus includes a build sleeve, a build platform for supporting a powder bed and object during a build, the build platform lowerable in the build sleeve, and at least one acoustic sensing system. The acoustic sensing system includes an acoustic emission sensor and an acoustic waveguide. The acoustic waveguide extends through the build platform such that a receiving end of the acoustic waveguide distal from the acoustic emission sensor abuts a surface of a build substrate removable mounted to the build platform to transmit structure-borne acoustic waves from the build substrate to the acoustic emission sensor.

Abstract: A backpack with integral garment hanging means is herein disclosed, comprising a large rear compartment that can neatly store clothes by means of folding hangers. To access the rear compartment, one would disconnect a pair of shoulder straps and open a zipper along both sides and upper surfaces of the backpack, thereby leaving the front cover hinged at the base. When disconnected it exposes a rounded “headstone”-shaped rear compartment having a plurality of folding garment hangers attached at the top. The hangers have a short neck and are hinged at their outward points to accommodate the small confines of the compartment. This backpack allows for the placement of several articles of clothing on folding hangers inside the backpack minimizing wrinkling. The hangers can be removed and used on a conventional closet rod. The exterior covering of the backpack is of a waterproof textile material to allow use in the rain as well.