Possibilities of 3D machining of materials by abrasive water jets

Machining of materials through classical way, i.e. using conventional tools for turning, drilling, milling, grinding and polishing, has some limits that can be overcome applying an abrasive water jet (AWJ). Therefore, some possibilities of 3D machining by AWJ placed on 6 axes robot have been tested. Programming of traverse speeds and tilting angles of cutting head was based on Hlaváč’s theoretical model. Low pressure pump has been used for tests. Because of very low pumping pressure, a selfdesigned and manufactured special mixing chamber was used in the experiments. The article deals with preliminary results and points at the direction of further research

Self-excited vibrations in turning: cutting moment analysis

This work aims at analysing the moment effects at the tool tip point and at the central axis, in the framework of a turning process. A testing device in turning, including a six-component dynamometer, is used to measure the complete torsor of the cutting actions in the case of self-excited vibrations. Many results are obtained regarding the mechanical actions torsor. A confrontation of the moment components at the tool tip and at the central axis is carried out. It clearly appears that analysing moments at the central axis avoids the disturbances induced by the transport of the moment of the mechanical actions resultant at the tool tip point. For instance, the order relation between the components of the forces is single. Furthermore, the order relation between the moments components expressed at the tool tip point is also single and the same one. But at the central axis, two different order relations regarding moments are conceivable. A modification in the rolling moment localization in the (y, z) tool plan is associated to these two order relations. Thus, the moments components at the central axis are particularly sensitive at the disturbances of machining, here the self-excited vibrations.Comment: 8 page

A Review of State-of-the-Art Large Sized Foam Cutting Rapid Prototyping and Manufacturing Technologies.

Purpose – Current additive rapid prototyping (RP) technologies fail to efficiently produce objects greater than 0.5?m3 due to restrictions in build size, build time and cost. A need exists to develop RP and manufacturing technologies capable of producing large objects in a rapid manner directly from computer-aided design data. Foam cutting RP is a relatively new technology capable of producing large complex objects using inexpensive materials. The purpose of this paper is to describe nine such technologies that have been developed or are currently being developed at institutions around the world. The relative merits of each system are discussed. Recommendations are given with the aim of enhancing the performance of existing and future foam cutting RP systems. Design/methodology/approach – The review is based on an extensive literature review covering academic publications, company documents and web site information. Findings – The paper provides insights into the different machine configurations and cutting strategies. The most successful machines and cutting strategies are identified. Research limitations/implications – Most of the foam cutting RP systems described have not been developed to the commercial level, thus a benchmark study directly comparing the nine systems was not possible. Originality/value – This paper provides the first overview of foam cutting RP technology, a field which is over a decade old. The information contained in this paper will help improve future developments in foam cutting RP systems

Effects of Gravity and Non-Perpendicularity during Powder-Fed Directed Energy Deposition of Ni-Based Alloy 718 through Two Types of Coaxial Nozzle

The consequences of gravity and the nozzle inclination angle in the powder-fed Directed Energy Deposition (DED) process were examined in this study. We also sought to define guidelines and manufacturing strategies, depending on the DED system configuration and the nozzle type. To do so, two nozzle types were used: a continuous coaxial nozzle with a slit of 0.5 mm and a four-stream discrete coaxial nozzle. Although the main effects of the configurations and the nozzles are well-known, their effects on the clad characteristics and the deposition strategy are as yet unclear. In this paper, measurements of a single clad and the effects of different deposition strategies on cladding applications and inclined walls are presented, and the consequences for manufacturing processes are discussed. Based on a complete study of a single clad, working vertically, five different tilted deposition strategies were applied: three to a single clad and two to an inclined wall. The results for both the single clad and the inclined wall reflect a pattern of changes to height, width, area, and efficiency, at both small and large nozzle angles and deposition strategies. The inclined wall presents a maximum horizontal displacement that can be reached per layer, without geometrical distortions. The amount of material per layer has to be adapted to this limitation.This research was funded by the European Commission through the project "PARADDISE: a Productive, Affordable and Reliable solution for large scale manufacturing of metallic components by combining laser-based Additive and Subtractive processes with high Efficiency” (Grant Agreement 723440), an initiative of the Public–Private Partnership “Photonics and Factories of the Future”. This research was also funded by European Institute of Innovation & Technology (EIT), through the project "DEDALUS: Directed Energy Deposition machines with integrated process ALgorithms Under dedicated monitoring and control System” (ID 20094), and by the vice-counseling of technology, innovation and competitiveness of the Basque Government (Eusko Jaurlaritza), under the ELKARTEK Program, PROCODA project, grant number KK-2019/00004