An Investigation into the Effect of Electro-Contact Heating in the Machining of Low-Rigidity Thin-Walled Micro-Machine Parts

Low-rigidity thin-walled parts are components of many machines and devices, including high precision electric micro-machines used in control and tracking systems. Unfortunately, traditional machining methods used for machining such types of parts cause a significant reduction in efficiency and in many cases do not allow obtaining the required accuracy parameters. Moreover, they also fail to meet modern automation requirements and are uneconomical and inefficient. Therefore, the aim of provided studies was to investigate the dependency of cutting forces on cutting parameters and flank wear, as well as changes in cutting forces induced by changes in heating current density and machining parameters during the turning of thin-walled parts. The tests were carried out on a specially designed and constructed turning test stand for measuring cutting forces and temperature at specific cutting speed, feed rate, and depth of cut values. As part of the experiments, the effect of cutting parameters and flank wear on cutting forces, and the effect of heating current density and turning parameters on changes in cutting forces were analyzed. Moreover, the effect of cutting parameters (depth of cut, feed rate, and cutting speed) on temperature has been determined. Additionally, a system for controlling electro-contact heating and investigated the relationship between changes in cutting forces and machining time in the operations of turning micro-machine casings with and without the use of the control system was developed. The obtained results show that the application of an electro-contact heating control system allows to machine conical parts and semi-finished products at lower cutting forces and it leads to an increase in the deformation of the thin-walled casings caused by runout of the workpiece.

A Newtonian approach to predict the parameters required to machine high aspect ratio channels of prescribed topography

Control of the microchannels’ cross-sectional shape may be of interest in micro-heat sinks, microfluidic particle sorting, and micro-machine lubrication applications. Previously, inverse methods have been used to determine the abrasive jet micromachining (AJM) traverse speed and path required to sculpt the desired cross-section for low Aspect Ratio (AR, the ratio of depth to width, see page xiv) topographies (<0.06). This thesisintroduces an iterative inverse method which allows prediction of the machining procedure required to sculpt high AR (>0.06-1) microchannels of prescribed cross-sectional shape using mask-less AJM. The predictions were experimentally verified for trapezoidal and semi-circular micro-channels and protruded features in borosilicate glass, and symmetric and non-symmetric wedges in poly-methyl-methacrylate (PMMA). Overall, the average accuracy of the machined profiles was 93.6 % in borosilicate glass and 91 % in PMMA. The methodology opens up new possibilities for the micro-fabrication of high-aspect-ratio micro-features of virtually any desired shape.

A Newtonian approach to predict the parameters required to machine high aspect ratio channels of prescribed topography

Control of the microchannels’ cross-sectional shape may be of interest in micro-heat sinks, microfluidic particle sorting, and micro-machine lubrication applications. Previously, inverse methods have been used to determine the abrasive jet micromachining (AJM) traverse speed and path required to sculpt the desired cross-section for low Aspect Ratio (AR, the ratio of depth to width, see page xiv) topographies (<0.06). This thesisintroduces an iterative inverse method which allows prediction of the machining procedure required to sculpt high AR (>0.06-1) microchannels of prescribed cross-sectional shape using mask-less AJM. The predictions were experimentally verified for trapezoidal and semi-circular micro-channels and protruded features in borosilicate glass, and symmetric and non-symmetric wedges in poly-methyl-methacrylate (PMMA). Overall, the average accuracy of the machined profiles was 93.6 % in borosilicate glass and 91 % in PMMA. The methodology opens up new possibilities for the micro-fabrication of high-aspect-ratio micro-features of virtually any desired shape.

The Effects Of Blast Lag In Abrasive Jet Machined Micro-Channel Intersections

Abrasive jet micro-machining (AJM) uses compressed air carrying abrasive solid particles to micro-machine a variety of features into surfaces. If the features are smaller than a few mm, then a patterned erosion-resistant mask is used to protect the substrate material, leaving exposed areas to define the features. Previous investigations have revealed a ‘blast lag’ phenomenon in which, for the same dose of abrasive particles, the etched depth of micro-channels and holes tends to decrease as the features become narrower. Blast lag occurs when using AJM on brittle substrates because of the natural tendency to rapidly form a V-shaped cross-sectional profile which inhibits abrasive particle strikes on the narrow vertex at the feature centerline. In this thesis, for the first time, the blast lag phenomenon is studied when using AJM to machine a network of microfluidic channels. It is found that, in some cases, differences in blast lag occurring at channel intersections and within the channels themselves, can lead to channel networks of non-uniform depth. A previously developed surface evolution model is used to predict the onset of blast lag in the channels and intersections, and thus explain these differences. Finally, methods to eliminate the differences are discussed.

The Effects Of Blast Lag In Abrasive Jet Machined Micro-Channel Intersections

Abrasive jet micro-machining (AJM) uses compressed air carrying abrasive solid particles to micro-machine a variety of features into surfaces. If the features are smaller than a few mm, then a patterned erosion-resistant mask is used to protect the substrate material, leaving exposed areas to define the features. Previous investigations have revealed a ‘blast lag’ phenomenon in which, for the same dose of abrasive particles, the etched depth of micro-channels and holes tends to decrease as the features become narrower. Blast lag occurs when using AJM on brittle substrates because of the natural tendency to rapidly form a V-shaped cross-sectional profile which inhibits abrasive particle strikes on the narrow vertex at the feature centerline. In this thesis, for the first time, the blast lag phenomenon is studied when using AJM to machine a network of microfluidic channels. It is found that, in some cases, differences in blast lag occurring at channel intersections and within the channels themselves, can lead to channel networks of non-uniform depth. A previously developed surface evolution model is used to predict the onset of blast lag in the channels and intersections, and thus explain these differences. Finally, methods to eliminate the differences are discussed.

A non-contact system for the assessment of hand motor tasks in people with Parkinson’s disease

Clinical diagnosis of Parkinson’s disease (PD) motor symptoms remains a problem. Most of the current studies focus on objective evaluations to make the evaluation more reliable. Most of these systems are based on the use of inertial and electromyographic sensors that require contact with the body part being assessed. Contact sensors restrict natural movement, may be uncomfortable and may require preparation of the body, which may cause irritation. As an alternative to contact sensors for the study of hand motor tasks performed by subjects with and without PD, electrical potential sensing technology is used in this research. A custom hardware has been designed to enable data collection by hand movement. A micro-machine system validated the developed system, and a relationship model was established between hand displacement and non-contact capacitive (NCC) sensor response. An experiment was conducted, including 57 subjects, 30 with PD (experimental group) and 27 healthy control group, followed by an analysis of statistical features extracted from the instantaneous mean frequency (IMNF) of NCC sensor. These results were compared with those obtained from gyroscope signals that are considered in the field to be the gold standard. As a result, NCC responses were correlated linearly with hand displacement (R2 = 0.7692 and $${\text{R}}_{\text{adj}}^{2}$$ R adj 2 = 0.7631). The statistical evaluation of IMNF features showed, that both, contact and non-contact sensors, were able to discriminate movement patterns of the control group from the experimental one. The results confirm statistical similarity between features extracted from NCC and gyroscope signals.

Kinematic calculation of micro mirror elements in micro electro-mechanical systems (MEMS)

Currently, the development and application of micro machines is an important direction in the development of microelectromechanical systems (MEMS) technologies. In these devices, electromechanical energy conversion occurs, as a result of which forces arise that carry out mechanical work within the dimensions of the microcircuit case. The paper considers the kinematic calculation of the design of a micromirror with a reflective layer of high optical quality of the surface for deflecting the reflected laser beam. By changing the angle of inclination of the micromirror, the laser beam enters the various input channels of the optical sensor. In this case, a control signal is generated for the further operation of the microcircuit. Thus, the micromirror performs the function of a switch of input optical channels, connecting in various combinations certain input or output elements of the microcircuit for further processing. The article presents the calculation of the kinematic parameters of the mechanical structure of the micro mirror. Practical recommendations are given for choosing the optimal range of variation of the micro mirror tilt angles in order to increase the strength of its structure, as well as to reduce the power of the mechanical drive of the micro machine required to change the micro mirror tilt angles

Research on aerodynamic characteristics of two-stage axial micro air turbine spindle for small parts machining

In order to meet the requirements of output torque, efficiency and compact shape of micro-spindles for small parts machining, a two-stage axial micro air turbine spindle with an axial inlet and outlet is proposed. Based on the k-ω turbulence model of SST, the flow field and operation characteristics of the two-stage axial micro air turbine spindle were studied using computational fluid dynamics (CFD) combined with an experimental study. We obtained the air turbine spindle under different working conditions of the loss and torque characteristics. When the inlet pressure was 300 KPa, the output speed of the two-stage turbine was 100,000 rpm, 9% higher than that of a single-stage turbine output torque. The total torque reached 6.39 N·mm, and the maximum efficiency of the turbine and the spindle were 42.2% and 32.3%, respectively. Through the research on the innovative structure of the two-stage axial micro air turbine spindle, the overall performance of the principle prototype has been significantly improved and the problems of insufficient output torque and low working efficiency in high-speed micro-machining can be solved practically, which laid a solid foundation for improving the machining efficiency of small parts and reducing the size of micro machine tool.

Precision Control of Micromechanical Automatic Manufacturing Based on Nanotechnology

Segment precision affects the accuracy level of micro machine manufacturing, only for the linear change is not big, more straight segment control, easy to cause dimensional deviation, so a precision control method of micro machine automatic manufacturing based on nanotechnology is proposed. The white noise is selected as random sequence to eliminate the concentrated trend and high frequency components in the input and output data. The precision control parameters of micromechanical automatic manufacturing are adjusted by setting the current loop, speed loop and position loop. According to the setting results, the contact area of micromechanical automation manufacturing is established in the coordinate system o-xy, and the equivalent curvature radius of the contact surface is calculated. Through coordinate transformation, the pressure distribution in the circular contact area is obtained, and the precision control area model of micromanical automation manufacturing is established. According to the model and the finite element analysis method, the control flow is designed to realize the precision control of the automatic manufacturing of micromachines. The experimental results show that the design method can reduce the precision control error of the automatic manufacturing of micromachines and improve the construction level of micromachines.