Investigation of hybrid manufacturing of stainless steel 316L components using direct energy deposition

Direct energy deposition (DED) has been established as one of the methods for additive manufacturing metallic parts. The combination of DED capabilities with traditional machining centre capabilities has enabled over the past few years the creation of Hybrid manufacturing cells that are able to additively manufacture and finish machine components under one platform. This paper investigates the production of geometries using a hybrid, additive and subtractive approach. The parameters for depositing stainless steel 316L are initially investigated followed by an assessment of machinability of the additively manufactured material. Finally the quality of the deposited and machined material was thoroughly examined with a series of destructive and nondestructive methods

Development of cutting force model and process maps for power skiving using CAD-based modelling

Power skiving is a new gear cutting process that has been recognized to provide a step change in the production rate achieved in the machining of high-precision internal and external involute gears. The process is based on a continuous generating meshing between the workgear and the cutting tool. Understanding of the loads applied in the cutting tool, and therefore some of the sources of tool wear, have not been thoroughly understood. This paper presents a novel model that is able to predict with high accuracy the cutting forces in the power skiving process. The model is based on a solid modelling simulation algorithm that produces high-fidelity solid bodies that are used for the calculations. The results of the model have been experimentally validated. A series of process maps are also produced to assist in the identification of the optimal machining parameters

Calculation of non-deformed chip and gear geometry in power skiving using a CAD-based simulation

Power skiving is a new machining process that allows the manufacturing of external and internal gears while achieving high throughputs. Although the process was first described during the nineteenth century, it is not until lately that advances in machine tool technology allowed for the process to be implemented on an industrial scale. This paper presents a novel simulation model that enables the accurate prediction of the non-deformed chip geometry, the form and dimensions of the chips produced during the cutting process as well as the characteristics of the gear gap. The simulation model is embedded on a CAD environment in order to take advantage of their increased accuracy. Through the simulation code, the virtual simulation of the manufacturing process is realised. The simulation model was verified with the use of analytical equations regarding the form of the gear. Chip geometry and dimensions for internal and external gears machined with different conditions are also presented

Investigation of the influence of CO2 cryogenic coolant application on tool wear

The use of cryogenic coolants has emerged as an environmentally conscious alternative to emulsion coolant options. Cryogenic media can be delivered with a variety of methods to the cutting edge and they can be used in combination with other traditional coolant options such as Minimum Quantity Lubrication (MQL) and compressed air cooling in order to aid dissipation of heat generated in the cutting zone and maximize the lubrication of the cutting edge and thus prolong tool life. This study focuses on the investigation of tool life when milling aerospace grade titanium (Ti-6Al-4 V) under different coolant delivery options. Tool wear progression was recorded for the following coolant options: cryogenic CO 2 , emulsion flood cooling, dry machining, cryogenic CO 2 combined with air or MQL as well as MQL alone

Surface and sub-surface integrity of Ti-6Al-4V components produced by selective electron beam melting with post-build finish machining

The emergence of metal additive manufacturing (AM) processes offer manufacturers a promising alternative to traditional forging and casting techniques for the production of near net shape titanium alloy components. However, limitations in both the surface finish quality and the geometric accuracy of parts produced by AM means that post-build finish machining of the part remains to be a requirement to produce high precision components. Furthermore, the fatigue performance of material produced directly by these processes is often limited by both the poor surface finish and porosity related defects which occur within the material. This study investigates the implications of machining stock allowance on the surface integrity of Ti-6Al-4V specimens produced by selective electron beam melting (SEBM) followed by post-build finish machining. The study revealed that the exposure of porosity related defects on the newly machined surface varied depending on the depth of material removed from the as-built specimen surface during machining. Four point bend fatigue testing of the specimens was carried out to determine the effect of the exposed surface defects on the fatigue performance of the material. This study highlights that the non-uniform distribution of pores within SEBM Ti-6Al-4V means that careful considerations must be given regarding machining stock allowance in the design of these components due to the implications of material removal depth on surface integrity

Online on-board Optimization of Cutting Parameter for Energy Efficient CNC Milling

Energy efficiency is one of the main drivers for achieving sustainable manufacturing. Advances in machine tool design have reduced the energy consumption of such equipment, but still machine tools remain one of the most energy demanding equipment in a workshop. This study presents a novel approach aimed to improve the energy efficiency of machine tools through the online optimization of cutting conditions. The study is based on an industrial CNC controller with smart algorithms optimizing the cutting parameters to reduce the overall machining time while at the same time minimizing the peak energy consumption

A review of CO2 coolants for sustainable machining

In many machining operations, metalworking fluids (MWFs) play an invaluable role. Often, proper application of an intelligent MWF strategy allows manufacturing processes to benefit from a multitude of operational incentives, not least of which are increased tool life, improved surface integrity and optimised chip handling. Despite these clearly positive implications, current MWF strategies are often unable to accommodate the environmental, economic and social conscience of industrial environments. In response to these challenges, CO2 coolants are postulated as an operationally viable, environmentally benign MWF solution. Given the strong mechanistic rationale and historical evidence in support of cryogenic coolants, this review considers the technological chronology of cryogenic MWF’s in addition to the current state-of-the-art approaches. The review also focuses on the use of CO2 coolants in the context of the machining of a multitude of material types in various machining conditions. In doing so, cryogenic assisted machining is shown to offer a litany of performance benefits for both conventional emulsion (flood) cooling and near dry strategies, i.e., minimum quantity lubrication (MQL), as well as aerosol dry lubrication (ADL)

Milling of aerospace alloys using supercritical CO2 assisted machining

Novel “sub-zero” cooling methods are an emerging technology employed in machining of aerospace alloys that has been the focus of substantial ongoing research. A series of different cooling media have been used in an effort to decrease the friction and the amount of heat generated in the cutting zone. This study focused on the use of supercritical carbon dioxide (scCO2) as a coolant in the face milling of titanium alloy Ti-6Al-4V. Traditional flood emulsion coolant was compared with through tool scCO2 as well as scCO2 with minimum quantity lubrication (MQL)

CAD-based 3D-FE modelling of AISI-D3 turning with ceramic tooling

In this study, the development of a 3D Finite Element (FE) model for the turning of AISI-D3 with ceramic tooling is presented, with respect to four levels of cutting speed, feed, and depth of cut. The Taguchi method was employed in order to create the orthogonal array according to the variables involved in the study, reducing this way the number of the required simulation runs. Moreover, the possibility of developing a prediction model based on well-established statistical tools such as the Response Surface Methodology (RSM) and the Analysis of Variance (ANOVA) was examined, in order to further investigate the relationship between the cutting speed, feed, and depth of cut, as well as their influence on the produced force components. The findings of this study point out an increased correlation between the experimental results and the simulated ones, with a relative error below 10% for most tests. Similarly, the values derived from the developed statistical model indicate a strong agreement with the equivalent numerical values due to the verified adequacy of the statistical model

A system approach for modelling additive manufacturing in defence acquisition programs

Defence Contractors and NATOMinistry of Defences (MoDs) are currently exploiting Additive Manufacturing (AM) Technology to improve availability of defence platforms and support soldiers deployed in remote Area of Operations (AO). Additive Manufacturing is considered a disruptive technology when employed in a military context to reduce the reliance on supply chains and improve the responsiveness to Operation Tempo (OT). This papers aims at presenting a novel system approach to model the end-to-end process of delivering a product printed with AM and estimate accurately the time and costs of AM. Understanding better the time and costs of AM will allow the MoDs and Defence Contractors to perform comparison with current practices and support their decision making in AM technology acquisition