Improvement of waterjet and abrasive waterjet nozzle

This investigation is concerned with the improvement of the nozzle design for water and abrasive water jet machining. The mechanism of formation and characteristics of pure water and abrasive water jets are investigated in order to determine quasi-optimal process conditions. To improve the pure water jet machining, a pulsed water jet nozzle, which employs the principle of the Helmholtz type resonator, is investigated experimentally and numerically. The experiments show the advantages of this nozzle over the commercial nozzle in cutting and cleaning. A numerical solution of the differential equations of continuity, momentum conservation, turbulent kinetic energy and dissipation for two dimensional axi-symmetric flow by employing the FIDAP package is developed and used for the numerical prediction of pulsed turbulent flow inside the nozzle. The determination of the optimal nozzle parameters aided by numerical simulation is carried out and the best ratios of the parameters are: h (cavity length) / d1 (diameter of upstream nozzle) = 3.0 and d2 (diameter of downstream nozzle) / d1 (diameter of upstream nozzle) = 1.3. The results of simulation agree well with the experiments. The numerical prediction of the velocity at the exit of the pulsed nozzle is validated by the velocity measurement by a laser transit anemometer. The obtained velocity changes periodically and ranges from 190 m/s to 230 m/s. A numerical analysis enables us to evaluate nozzle design and the effectiveness of the numerical prediction is validated experimentally. The numerical solutions and experimental results present the improvement on the pure water cutting and cleaning and provide a technological basis for the improvement of pulsed water jet machining and technology. To increase the efficiency of abrasive water jet machining, an improved abrasive water jet nozzle is developed and experimentally investigated. The performance of the abrasive water jet is improved by the modification of the abrasive particles path prior to the collision with the water jet. This modification is obtained by control of the angle (a) between the top-shaped surface of the focusing tube and the water flow direction and change of distance (H) between the water nozzle and focusing tube. The improvement of water-particles mixing increases the rate of material removal and simplifies the alignment procedure. It is found that the optimal parameters for the nozzle design are: a = 45° and H = 1.587 mm. The experimental results and analysis show the potential of this modified nozzle for applications in abrasive water jet machining

Ultrasonic Enhancement of Pulsed Electrochemical Machining

Electrochemical machining (ECM) has gained prominence in the field on precise machining and has been subjected to a lot of study in order to bring its use to commercial levels. One of the key issues of electrochemical machining is the lack of proper flushing ECM by-products. Ultrasonic assisted ECM is often used to minimize the flushing issue. This study attempts a novel variation in ultrasonic assistance of ECM by introducing ultrasonic waves in the flowing electrolyte without vibrating tool or workpiece. This ensures intense agitation in the inter-electrode gap (IEG) with relatively simpler set-up. Aluminum 6061 is used as a workpiece material to drill holes. Stainless steel tubes coated with Teflon is used as tool. The Teflon coating minimizes the effect of stray current. Use of pulsed DC current and ultrasonic vibration improves the quality of the ECM’ed holes. The intense ultrasonic cavitation disturbs the anodic reaction in IEG negatively affecting MRR. On the other hand, the de-agglomeration of ECM by-products and depassivation of anodic workpiece improves surface roughness by approximately 50% and the taper angle of the hole by approximately 75%

Ultrasonic Enhancement of Pulsed Electrochemical Machining

Electrochemical machining (ECM) has gained prominence in the field on precise machining and has been subjected to a lot of study in order to bring its use to commercial levels. One of the key issues of electrochemical machining is the lack of proper flushing ECM by-products. Ultrasonic assisted ECM is often used to minimize the flushing issue. This study attempts a novel variation in ultrasonic assistance of ECM by introducing ultrasonic waves in the flowing electrolyte without vibrating tool or workpiece. This ensures intense agitation in the inter-electrode gap (IEG) with relatively simpler set-up. Aluminum 6061 is used as a workpiece material to drill holes. Stainless steel tubes coated with Teflon is used as tool. The Teflon coating minimizes the effect of stray current. Use of pulsed DC current and ultrasonic vibration improves the quality of the ECM’ed holes. The intense ultrasonic cavitation disturbs the anodic reaction in IEG negatively affecting MRR. On the other hand, the de-agglomeration of ECM by-products and depassivation of anodic workpiece improves surface roughness by approximately 50% and the taper angle of the hole by approximately 75%

Ultrasonic Enhancement of Pulsed Electrochemical Machining

Electrochemical machining (ECM) has gained prominence in the field on precise machining and has been subjected to a lot of study in order to bring its use to commercial levels. One of the key issues of electrochemical machining is the lack of proper flushing ECM by-products. Ultrasonic assisted ECM is often used to minimize the flushing issue. This study attempts a novel variation in ultrasonic assistance of ECM by introducing ultrasonic waves in the flowing electrolyte without vibrating tool or workpiece. This ensures intense agitation in the inter-electrode gap (IEG) with relatively simpler set-up. Aluminum 6061 is used as a workpiece material to drill holes. Stainless steel tubes coated with Teflon is used as tool. The Teflon coating minimizes the effect of stray current. Use of pulsed DC current and ultrasonic vibration improves the quality of the ECM’ed holes. The intense ultrasonic cavitation disturbs the anodic reaction in IEG negatively affecting MRR. On the other hand, the de-agglomeration of ECM by-products and depassivation of anodic workpiece improves surface roughness by approximately 50% and the taper angle of the hole by approximately 75%

Water droplet machining and droplet impact mechanics

Water Droplet Machining (WDM) is a new manufacturing process, which uses a series of high-velocity, pure-water droplets to impact and erode metal workpieces, for the purpose of through-cutting, milling and surface profiling. The process is conducted within a vacuum environment to suppress aerodynamic drag and atomization of the waterjet and droplet stream. This preserves droplet momentum and allows for a more efficient transfer of energy between the water and workpiece, than in standard atmospheric pressure. As a new manufacturing technique, parameter-specific details and characteristics of this process are absent from the scientific literature. Furthermore, the erosion mechanisms involved in droplet-solid interactions are not well-understood. Therefore, this research aims to elucidate the capabilities of WDM, and uncover the mechanics involved in droplet impact. This is done by investigating the force imparted by liquid droplets across a wide range of impact parameters, where a novel force model is developed for inertial-dominated impacts. A force comparison is made between continuous jet and droplet train impacts, where the findings show that a droplet train has a higher erosive potential than its continuous jet counterpart, owing to the higher forces exerted by individual droplets. In addition, the stress state inside of a material subject to a Hertzian contact, which is connected to this research as it emulates the axisymmetric nature of a droplet-like loading, is explored using integrated photoelasticity. Finally, the process parameters and erosion characteristics of WDM are investigated using a custom-fabricated machine, where a range of waterjet-types (and droplet trains) are produced. The industrial efficacy of this process is evaluated by manufacturing a diverse array of engineering materials

Energy distribution modulation by mechanical design for electrochemical jet processing techniques

The increasing demand for optimised component surfaces with enhanced chemical and geometric complexity is a key driver in the manufacturing technology required for advanced surface production. Current methodologies cannot create complex surfaces in an efficient and scalable manner in robust engineering materials. Hence, there is a need for advanced manufacturing technologies which overcome this. Current technologies are limited by resolution, geometric flexibility and mode of energy delivery. By addressing the fundamental limitations of electrochemical jetting techniques through modulation of the current density distribution by mechanical design, significant improvements to the electrochemical jet process methods are presented. A simplified 2D stochastic model was developed with the ability to vary current density distribution to assess the effects of nozzle-tip shape changes. The simulation demonstrated that the resultant profile was found to be variable from that of a standard nozzle. These nozzle-tip modifications were then experimentally tested finding a high degree of variance was possible in the machined profile. Improvements such as an increase in side-wall steepness of 162% are achieved over a standard profile, flat bases to the cut profile and a reduction of profile to surface inter-section radius enable the process to be analogous to traditional milling profiles. Since electrode design can be rapidly modified EJP is shown to be a flexible process capable of varied and complex meso-scale profile creation. Innovations presented here in the modulation of resistance in-jet have enabled electrochemical jet processes to become a viable, top-down, single-step method for applying complex surfaces geometries unachievable by other means

Micro, meso and macro materials processing using high-speed liquid projectiles

The objective of this research is developmentof aknowledge base of materials processing by the impact of high-speed liquid projectiles. The work involved experimental study of generation and applications of high-speed liquid projectiles. The projectiles were generated by the launchers, which used gunpowder as an energy source. The experiments were carried out at the low (O.35g of the powder), middle (1.2g) and high (10g to 70g) levels of energy consumptions and at several different launchers modification. Experimental investigation of effect of gun powder mass on energy of projectile was conducted for ductile and brittle targets. An array of experimental techniques for projectile\u27s external ballistics investigation was developed. Laser Particle Velocitimeter (PIN) and high speed filming were used for velocity measurements and visualization of images of water projectiles high speed filming revealed pulsing nature of projectile. A piezoelectric sensor and a pendulum were used to monitor the impact force and the projectile momentum. Range of materials was investigated in this study. Namely, investigation of deformation, forming, micro-forming, and welding of ductile materials was carried out. Demolition and boring of brittle materials was performed. Modes and mechanisms of deformation of ductile and brittle materials were studied and explained. High plasticity, high rate of deformation, temperature at the impact zone, hardness and micro-hardness distribution and degree of deformation work for ductile materials were determined and materials behavior knowledge base needed for materials processing was acquired. Modes and mechanisms of failure of ductile, brittle and composite materials were studied. Fractography study revealed three mechanisms: ductile overload fracture, brittle fracture and combination of the two. Six failure modes: brittle fracture, radial fracture, ductile hole growth, plugging, fragmentation and petaling were identified. An array of material processing operations using high speed projectiles impact was investigated. Full scale experimental investigation of terminal ballistics of high speed water projectiles was performed. Material processing operations included: piercing of metals, piercing of composite targets, explosive set ups neutralization, demolition of brittle materials, boring of granite and marble, punching of steel plates, complex shape punching in steel, forging of metals on macro and meso scale. Mechanisms of punching and forming of metals were identified and proposed. Welding of similar and dissimilar metals was conducted and high potential for novel stitch and spot welding formations was confirmed. Micro scale materials processing investigation involved range of studies. Submilimeter geometry scale forming of metals, fine stamping, micron scale forming and micron scale extrusion investigation were conducted and validation of novel technologies was achieved. Full scale topography and surface characterization of generated geometries was conducted and obtained quality proved to be at a competitive level with existing technologies. State of the art methods were used for investigation of generated samples. Scanning electron microscopy, infinite focus microscopy, 3 D digital microscopy, optical microscopy, 3-D digital profiler, Knoop and Vickers micro hardness testers, nano hardness indenter were used for characterization of generated samples. Full scale characterization on all levels of conducted materials processing was conducted and effect of high speed water projectile impact on mechanical properties of impacted materials was quantified and presented. Investigation of peculiarities of impact based micro-forming was conducted. The info acquired as result of investigation of geometry and topography of micro-forming processing. Accuracy of micro scale deformation was estimated, particularly it was shown that deviation of actual part from the die was at the acceptable level. Also was shown that size of generated parts was rather stable and roughness and waviness of the generated surfaces was in the acceptable range. The foundation of knowledge base for liquid based forming, welding and demolition processes was developed and the process technology will be developed on the base of the acquired knowledge. Theory of impact based high rate material deformation was enhanced. The emerging industrial scale demolition, forming and welding technologies will utilize the acquired knowledge

Review Study and Importance of Micro Electric Discharge

Micro EDM process is one of the micro- machining processes. It can be used to machine micro features and makes a micro parts. There is a huge demand in the production of microstructures by a non-traditional method which known as Micro-EDM. Micro-EDM process is based on the thermoelectric energy between the work-piece and an electrode. Micro-EDM is a newly developed method to produce micro-parts which in the range of 50 μm -100 μm. Micro-EDM is an efficient machining process for the fabrication of a micro-metal hole with various advantages resulting from its characteristics of non-contact and thermal process. A pulse discharges occur in a small gap between the work piece and the electrode and at the same time removes the unwanted material from the parent metal through the process of melting and vaporization. This paper describes the importance, parameters, principle, difference between Macro and micro EDM, applications and advantages of µ-EDM and discuss about the literature reviews based on performance measure in micro- EDMP process. Keywords: Micro EDM, MRR, TWR, S