This paper presents an innovative approach for the accuracy and precision analysis of the ultraprecision machining systems, further supported in experiment trials and data on ultraprecision machining ...of contact lens mould inserts. Statistical models are developed for analysing the measurement data of geometrical runout of the insert components before and after the ultraprecision machining. The maximum standard deviation of 16 nm and 5 nm residual in geometrical runout is achieved after ultraprecision machining of all 26 contact lens mould insert components. The system obtained 76% of accuracy and precision confident with positioning range of 2–40nm, according to data collected from the experimental trials. The surface finishing is very encouraging with the maximum 4 nm of Ra and 43 nm of PV as achieved from the experiments. Furthermore, it has been found that the clamping stiffness of the smart chuck has a positive effect on the accuracy of the machining system. The experimental trial results show the smart chuck can be used as a universal highly effective device, particularly for ultraprecision production purpose.
In current precision and ultraprecision machining practice, the positioning and control of actuation systems, such as slideways and spindles, are heavily dependent on the use of linear or rotary ...encoders. However, positioning control is passive because of the lack of direct monitoring and control of the tool and workpiece positions in the dynamic machining process and also because it is assumed that the machining system is rigid and the cutting dynamics are stable. In ultraprecision machining of freeform surfaces using slow tool servo mode in particular, however, account must be taken of the machining dynamics and dynamic synchronization of the cutting tool and workpiece positioning. The important question also arises as to how ultraprecision machining systems can be designed and developed to work better in this application scenario. In this paper, an innovative dynamics-oriented engineering approach is presented for ultraprecision machining of freeform surfaces using slow tool servo mode. The approach is focused on seamless integration of multibody dynamics, cutting forces, and machining dynamics, while targeting the positioning and control of the tool–workpiece loop in the machining system. The positioning and motion control between the cutting tool and workpiece surface are further studied in the presence of interfacial interactions at the tool tip and workpiece surface. The interfacial cutting physics and dynamics are likely to be at the core of in-process monitoring applicable to ultraprecision machining systems. The approach is illustrated using a virtual machining system developed and supported with simulations and experimental trials. Furthermore, the paper provides further explorations and discussion on implementation perspectives of the approach, in combination with case studies, as well as discussing its fundamental and industrial implications.
This study delves into the intricacies of ultraprecision machining, particularly in the context of machining optical freeform surfaces using Diamond Turning Machines (DTMs). It underscores the ...dynamic relationship between toolpath generation, hydrostatic bearing in DTMs, and the machining process. Central to this research is the innovative introduction of Metal Matrix Composites (MMCs) to replace the traditional materials used in designing linear bearings. This strategic substitution aims to dynamically enhance both the accuracy and the quality of the machined optical freeform surfaces. The study employs simulation-based analysis using ADAMS to investigate the interfacial cutting forces at the tooltip and workpiece surface and their impacts on the machining process. Through simulations of STS mode ultraprecision machining, the interfacial cutting forces and their relationship with changes in surface curvatures are examined. The results demonstrate that the use of MMC material leads to a significant reduction in toolpath pressure, highlighting the potential benefits of employing lightweight materials in improving the dynamic performance of the system. Additionally, the analysis of slideway joints reveals the direct influence of interfacial cutting forces on the linear slideways, emphasising the importance of understanding and controlling these forces for achieving higher-precision positioning and motion control. The comparative analysis between steel and MMC materials provides valuable insights into the effects of material properties on the system's dynamic performance. These findings contribute to the existing body of knowledge and suggest a potential shift towards more advanced precision forms, possibly extending to pico-engineering in future systems. Ultimately, this research establishes a new standard in the field, emphasising the importance of system dynamics and interfacial forces in the evolution of precision manufacturing technologies.
This study focuses on the analysis of a linear hydrostatic bearing using harmonic frequency response and harmonic response simulations. The aim is to evaluate the feasibility of replacing the ...existing alloy steel material with a metal matrix composite (MMC) in terms of its performance and dynamic characteristics for both the base and carriage parts. The simulation results indicate that the MMC material exhibits higher resonant frequencies and improved damping capabilities compared to the structural steel material. The higher resonant frequencies observed in the MMC material are attributed to its stiffness and structural properties. These properties contribute to increased natural frequencies and improved vibration damping characteristics. This suggests that incorporating the MMC material in the bearing design could enhance motion control, improving the ability to precisely control and manipulate the movement of components or systems. In the context of ultraprecision machining applications, incorporating the MMC material in the hydrostatic bearing design can also lead to a more accurate and controlled motion, resulting in improved precision and finer machining outcomes. The displacement analysis confirms that both materials meet the specifications provided by the manufacturer, supporting the viability of using MMC as an alternative. However, further experimental validation and considerations of material feasibility, manufacturing factors, and cost-effectiveness are necessary before implementing the MMC material in practical applications. Overall, this research highlights the potential benefits of MMC in the design of linear hydrostatic bearings, paving the way for enhanced performance in ultraprecision machining processes.
In this paper, an analytical scientific approach is presented for the design and analysis of an air-turbine-driven paint spray spindle, and it is used to improve further the design concept of the ...existing spindle applied in automotive coating and paint spraying applications. The current spindle on the market can operate at a maximum speed of 100,000 rpm and features a maximum bell size of 70 mm diameter. Given the increasing demands for high automotive coating/painting quality and productivity in assembly, the design and development of a paint spray spindle with a speed of 145,000 rpm or higher is needed. Computational fluid dynamics (CFD)-based simulation is applied in the approach. Accordingly, CFD simulation-based design and analysis are undertaken, covering the characteristic factors of velocity, pressure of the air supply, rotational speed of the air-turbine, and torque and force reaction on the turbine blades. Furthermore, the turbine blade geometric shape is investigated through the simulations. Three geometrical concepts have been investigated against the original model. The results on Concept_03 verified the higher angular velocity speeds against the theoretical model. The pressure and velocity effects in the blades have been investigated. The results show that the pressure and velocity of the air supply driving the turbine are critical factors influencing the stability of turbine spinning. The results also demonstrate that the force acting on the blades is at the highest level when the adjacent face changes from a straight surface into a curve. Finally, changing the geometrical shape in the turbine likely increases the tangential air pressure at the blades surface and relatively increases the magnitude of the lateral torque and force in the spindle. Notwithstanding this condition, the analytical values surpass the theoretical target values.
Polytetrafluoroethylene (PTFE) is a thermoplastic polymeric material with various applications including aerospace, automotive, biomedical and electrical. PTFE surface is smooth, wear resistant, ...non-sticky and slippery in nature. Combined with such useful properties, the material conveys various other features such as temperature resistance up to 260°C, exceptional chemical stability, corrosion resistance, good fatigue strength and sterilisable. This work involved mechanical testing of convoluted PTFE tubes with different thicknesses, diameters and lengths. This included the following tests: volumetric expansion, tensile and elongation, rolling u wear and burst tests by applying real industrial pressures. The mechanical testing showed promising results for the convoluted PTFE tubes which could undergo extreme elongation due to the elastic nature. The % volumetric expansion exceeded the expected values (on average, 3-5% higher than the expected values). The results for the rolling u wear, burst and tensile tests also showed good properties. Based on its mechanical properties, convoluted PTFE seemed to be an appropriate material for replacing damaged/diseased arteries.
Abstract
There are various types of pulse oximeters (POs) including ‘reflectance POs’, which can be used on more sites like the forehead, chest or cheeks and work the same way as ‘transmission POs’ ...which is the most commonly used device for the continuous measurement of % blood oxygen saturation and pulse/heart rate. This paper describe the design and development of a low cost pulse oximeter (PO) specifically focused on the use of ‘Reflectance Photo-Plethysmo-Graphy’ (RPPG) technology, and compare with commonly used pulse oximeter devices at the East Lancashire Hospitals. The design arrangement involved the use of an Arduino Mega 2560 Circuit Board as microcontroller, Pulse Sensor, Light Emitting Diodes (LEDs) and Liquid Crystal Display (LCD), which allowed subsidising to make a functional device for accurate readings of Heart Rate (HR) in beats per minute (BPM) and % Blood Oxygen Saturation (SpO2). RPPG technique was successfully implemented within the design and development of the PO prototype, contrasting against the more conventional method of transmission pulse oximetry for obtaining HR and SpO2 values. It is concluded that the RPPG pulse oximeter is a more cost effective method of operation with comparable results.
Cytokines are extremely potent biomolecules that regulate cellular functions and play multiple roles in initiation and inhibition of disease. These highly specialised macromolecules are actively ...involved in control of cellular proliferation, apoptosis, cell migration and adhesion. This work, investigates the effect of transforming growth factor-beta2 (TGF-β2) on the biological regulation of chondrocyte and the repair of a created model wound on a multilayer culture system. Also the effect of this cytokine on cell length, proliferation, and cell adhesion has been investigated. Chondrocytes isolated from knee joint of rats and cultured at 4 layers. Each layer consisted of 2 × 10
5
cells/ml with and without TGF-β2. The expression of mRNA and protein levels of TGF-β receptors and Smad1, 3, 4, and 7 have been analysed by RT-PCR and western blot analysis. The effect of different supplementations in chondrocyte cell proliferation, cell length, adhesion, and wound repair was statistically analysed by One-way ANOVA test. Our results showed that the TGFβ2 regulates mRNA levels of its own receptors, and of Smad3 and Smad7. Also the TGF-β2 caused an increase in chondrocyte cell length, but decreased its proliferation rate and the wound healing process. TGF-β2 also decreased cell adhesion ability to the surface of the culture flask. Since, TGF-β2 increased the cell size, but showed negative effect on cell proliferation and adhesion of CHC, the effect of manipulated TGF-β2 with other growth factors and/or proteins needs to be investigated to finalize the utilization of this growth factor and design of scaffolding in treatment of different types of arthritis.
Lake Urmia (LU) once was the second largest hypersaline lake in the world, covering up to 6000km2, but has undergone catastrophic desiccation in recent years resulting in loss of 90% of its area and ...extensive coverage by playas and marshlands that represent a source of salt and dust. This study examines daily Aerosol Optical Depth (AOD) data from the Moderate Resolution Imaging Spectroradiometer (MODIS) between 2001 and 2015 over northwestern Iran, which encompasses LU. Intriguingly, salt emissions from the LU surface associated with ongoing desiccation do not drive the study region's AOD profile, whereas pollution transported from other regions and emissions around LU are more important. Signatures of increasing local crustal emissions are most evident outside of the peak dust season (January, February, and October) and on the periphery of LU. AOD has generally increased in the latter half of the study period with the onset of the AOD ramp-up starting a month earlier in the spring season when comparing 2009–2015 versus earlier years. Results indicate that suppression of emissions on the LU border is critical as the combined area of salt and salty soil bodies around LU have increased by two orders of magnitude in the past two decades, and disturbing these areas via activities such as grazing and salt harvesting on the lake surface can have more detrimental impacts on regional pollution as compared to benefits. These results have important implications for public health, climate, the hydrological cycle, and pollution control efforts.
Display omitted
•AOD characteristics examined over Lake Urmia in northwestern Iran between 2001 and 2015.•No significant relationship found between lake water level and AOD.•Interannual AOD variability driven mainly by transport from upwind regions.•Enhanced emissions from salty/soil areas around the lake in the latter years•Activities like grazing can disturb the remaining playa and lead to salt emissions.
The concept of the smart tooling system for ultraprecision machining of freeform surfaces compromises the high intensity of developing adaptable technologies towards innovative holding the workpiece ...and cutting tool mechanisms. This is in line with the emerging development of smart applications in precision engineering and industrial-scale ultraprecision production. Furthermore, due to rapidly growing requirement for three-dimensional micro and miniature components or products in high precision, the ultraprecision and micromanufacturing are getting increasingly applied in aerospace, automotive, medical engineering, optics, and microelectronics in particular. Over the last decade or so, ultraprecision machining has become a key enabling technology for machining complex freeform surfaced components and products in an industrial scale. From the dynamics point of view, freeform surface with a large depth machining using diamond turning machine can be difficult challenging and in some cases. Despite substantial research and investigation were employed in this field, there are some critical issues remained and needing to be addressed desperately. Nowadays, ultraprecision machining is gradually progressing or maturing over time to meet the full range of requirements for exceptional accuracy and desirable surface quality for freeform surface applications. In current precision engineering, actuation systems for precise positioning and motion control of spindles and direct-drive slideways are profoundly reliant on using rotary and linear encoders. Notwithstanding, in the dynamic machining process, the positioning and control are somehow 'passive' and unable to directly monitor and control the tool and workpiece statuses. The machining system is hypothetically rigid, and the cutting dynamics are stable. Nevertheless, machining dynamics and the dynamic synchronization of the cutting tool and workpiece positioning have compelled the challenges on the machining system, which should be carefully considered versus conforming requirements of high productivity for the fulfilment of high precision products in particular. It is also imposing the question in the driving and development of next-generation ultraprecision machining systems operating towards higher or even picoprecision. Overall, this PhD research is focused on the fundamentals and implementation perspectives, as discussed above. In this research work, an innovative dynamic cutting force orientated approach is presented for motion control and positioning in ultraprecision machining of freeform surfaces mainly using either slow tool servo or fast tool servo mode machining techniques. This novel method is developed using seamless integration of cutting forces and machining dynamics with the aid of multi-body dynamics analysis. The positioning and dynamic motion between the workpiece freeform surface and cutting tool are achieved under interfacial interactions at the tooltip and workpiece surface. Necessarily, the interfacial cutting dynamics and physics are the foundation for developing the higher-level of positioning and motion control for the next generation ultraprecision machining system. Thus, the critical interfacial areas were identified and researched accordingly. A novel and dynamics-orientated freeform surface toolpath generation were developed to enable the detection of the dynamic effects of the interfacial cutting forces in the process. Also, an innovative smart chuck for freeform surface workpiece holding was designed and developed to fulfil the requirements of positioning and motion control for next-generation ultraprecision machining systems. The approach is further described using analytical and comparative methodology with an in-depth investigation on employing light material such as MMC material for designing the hydrostatic bearing supported direct-drive slideway. The investigation is supported with simulations and experimental trials for evaluation and validation. The results are auspicious and remarkably promising in overcoming the conventional limitation in positioning and motion control. The research concludes with a further discussion on an extensive application case study using this methodology, and its manufacturing and industrial associations and beyond.
PDF
