Micro-Drilling of ZTA and ATZ Ceramic Composit: Effect of Cutting Parameters on Surface Roughness

Ceramics are a class of materials widely used during last fifteen years for orthopaedic applications. It is well known that they are characterized by low wear rate, and friction coefficient. However, these materials are very difficult to machine into complex shapes because of their brittleness and high hardness. The most effective method to increase the crack resistance is the formation of a composite structure. This class of materials, composed by two or more different ceramics, can present higher characteristic respect to the single component, like fracture toughness and flexural strength. This paper presents a study of the influence of cutting parameters (cutting speed, feed rate and step number) onto the hole surface roughness and deformation due to the drill operation. The ceramic composite materials AZT (alumina toughened zirconia) and ZTA (zirconia toughened alumina) were first characterized in terms of hardness and roughness. After the drilling test, the holes were analyzed using scanning electron microscope (SEM) and an advanced 3-dimensional non-contact optical profilomete

Improvement of surface flatness in high precision milling

The use of high precision micro components has increased in various industrial fields in recent years. Repeatable techniques are needed to face very tight tolerances and make micro fabrication processes industrially feasible against current micro machining limitation. Improving surface flatness in high precision milling is the main target of the present research. Critical issues such as machining strategy, spindle thermal transient management and tool wear compensation were considered for machining operations on a representative part

Thin wall geometrical quality improvement in micromilling

Micromilling is one of the most versatile tooling processes being able to effectively manufacture three-dimensional complex features on moulds and dies achieving a good accuracy performance. Typical and challenging features for these microcomponents are high aspect ratio thin walls but no systematic approaches, as the one presented in this paper, exist in literature dealing with the relationship between nominal workpiece characteristics/process parameters, cutting forces, and workpiece quality. The present study focuses on 0.4 % carbon steel (C40) thin wall micromilling and evaluates two approaches for the thin wall geometrical quality improvement: a direct approach (relating process parameters, material and nominal workpiece characteristics to the workpiece quality characteristics) and a force-based approach (relating the same quantities through the cutting forces determination). The force-based approach relates the process parameters to the workpiece quality introducing physical quantities as cutting forces, which are suitable for monitoring and controlling purposes. A suitable experimental campaign has been designed in order to statistically analyze the cutting force responses, and a proper technique (ANalysis of COVAriance) has been applied to remove the tool wear effect. The relationship between cutting forces and workpiece quality has been quantitatively studied; this way, the feasibility of a general approach able to meet tolerances by controlling forces has been demonstrated

Geometrical quality improvement of high aspect ratio micromilled pins

Mechanical micromachining is a reference process for producing 3D complex microparts and specifically tools for other processes as molds for micro injection molding and males for microextrus ion. High aspect ratio features as bars , ribs , pins , etc. are very common in these cases and their quality strongly affects the final plastic part quality. This paper focuses on high aspect ratio steel pins, since they are one of the most challenging features to be manufactured on microextrusion males. The pin geometrical quality has been defined according to the standards and a suitable measurement procedure has been set up with the aim to study the micromilling process parameters effects on the most representative pin quality characteristics . The statistical analysis results point out some criteria for selecting the best process parameters

Finite element modeling of micro-orthogonal cutting process with dead metal cap

Dead metal cap plays an important role in the microcutting process because target material piled up on the tool–chip– workpiece interface can alter the cutting geometry. The target of this study is to model and simulate the microorthogonal cutting process in the presence of dead metal cap in order to investigate the effects of this phenomenon on the micromachining process outputs (cutting force, thrust force and chip thickness) and stress distribution, equivalent plastic strain and temperature inside the workpiece shear zones. For this purpose, the finite element method with explicit dynamic solution and adiabatic heating effect along with arbitrary Lagrangian–Eulerian approach is used. It is shown that the finite element models with current state-of-the-art assumptions cannot take into account the dead metal cap by default. For this reason, dead metal cap is artificially introduced on the rounded tool edge in this study for carrying out a proper analysis. Several simulations with different dead metal cap geometries are performed and obtained results show that prediction of cutting force, thrust force and chip thickness are sensitive to the presence of dead metal cap and its geometry. Micro-orthogonal cutting experiments are carried out on tubular AISI 1045 workpieces for validating and interpreting simulated results. The error between predicted and experimental data is calculated, and it is shown that simulation performances can be improved by considering the dead metal cap into the process model. For example, it is possible to reduce the error to less than 5% in case of thrust force prediction. This study points out how the target material’s Von Mises stress, equivalent plastic strain and temperature distribution are sensitive to any alteration of the edge geometry due to the dead metal cap. The best dead metal cap configuration in terms of agreement with experiments is also the one introducing a more homogeneous distribution of these quantities along the shear plane

robotic am system for plastic materials tuning and on line adjustment of process parameters

Abstract Additive Manufacturing (AM) techniques based on thermoplastic polymer extrusion allow the manufacture of complex parts, but their slow printing speed limits their use for mass production. To overcome this drawback, an industrial screw-based extruder has been mounted on an anthropomorphic robot, realizing a flexible AM platform for big objects. The most important process parameters have been set by a suitable experimental campaign, ensuring a regular deposited layer geometry. A closed-loop control has been implemented to further improve the process parameter setting based on data measured during the deposition, in this way compensating the material withdrawal or other unexpected defects

Applicability of an orthogonal cutting slip-line field model for the microscale

Mechanical micromachining is a very flexible and widely exploited process, but its knowledge should still be improved since several incompletely explained phenomena affect the microscale chip removal. Several models have been developed to describe the machining process, but only some of them consider a rounded edge tool, which is a typical condition in micromachining. Among these models, the Waldorf’s slip-line field model for the macroscale allows to separately evaluate shearing and ploughing force components in orthogonal cutting conditions; therefore, it is suitable to predict cutting forces when a large ploughing action occurs, as in micromachining. This study aims at demonstrating how this model is suitable also for micromachining conditions. To achieve this goal, a clear and repeatable procedure has been developed for objectively validating its force prediction performance at low uncut chip thickness (less than 50 mm) and relatively higher cutting edge radius. The proposed procedure makes the model generally applicable after a suitable and nonextensive calibration campaign. This article shows how calibration experiments can be selected among the available cutting trial database based on the model force prediction capability. Final validation experiments have been used to show how the model is robust to a cutting speed variation even if the cutting speed is not among the model quantities. A suitable set-up, especially designed for microturning conditions, has been used to measure forces and chip thickness. Tests have been performed on 6082-T6 Aluminum alloy with different cutting speeds and different ratios between uncut chip thickness and cutting edge radius

Assessing the Relationships between Interdigital Geometry Quality and Inkjet Printing Parameters

Drop on demand (DoD) inkjet printing is a high precision, non-contact, and maskless additive manufacturing technique employed in producing high-precision micrometer-scaled geometries allowing free design manufacturing for flexible devices and printed electronics. A lot of studies exist regarding the ink droplet delivery from the nozzle to the substrate and the jet fluid dynamics, but the literature lacks systematic approaches dealing with the relationship between process parameters and geometrical outcome. This study investigates the influence of the main printing parameters (namely, the spacing between subsequent drops deposited on the substrate, the printing speed, and the nozzle temperature) on the accuracy of a representative geometry consisting of two interdigitated comb-shape electrodes. The study objective was achieved thanks to a proper experimental campaign developed according to Design of Experiments (DoE) methodology. The printing process performance was evaluated by suitable geometrical quantities extracted from the acquired images of the printed samples using a MATLAB algorithm. A drop spacing of 140 µm and 170 µm on the two main directions of the printing plane, with a nozzle temperature of 35◦C, resulted as the most appropriate parameter combination for printing the target geometry. No significant influence of the printing speed on the process outcomes was found, thus choosing the highest speed value within the investigated range can increase productivity

Micro-Drilling of ZTA and ATZ Ceramic Composit: Effect of Cutting Parameters on Surface Roughness

Ceramics are a class of materials widely used during last fifteen years for orthopaedic applications. It is well known that they are characterized by low wear rate, and friction coefficient. However, these materials are very difficult to machine into complex shapes because of their brittleness and high hardness. The most effective method to increase the crack resistance is the formation of a composite structure. This class of materials, composed by two or more different ceramics, can present higher characteristic respect to the single component, like fracture toughness and flexural strength. This paper presents a study of the influence of cutting parameters (cutting speed, feed rate and step number) onto the hole surface roughness and deformation due to the drill operation. The ceramic composite materials AZT (alumina toughened zirconia) and ZTA (zirconia toughened alumina) were first characterized in terms of hardness and roughness. After the drilling test, the holes were analyzed using scanning electron microscope (SEM) and an advanced 3-dimensional non-contact optical profilometer

Simulation of Corona Electrostatic Separator for End-of-Life Management in Printed Circuit Boards

Printed circuit boards (PCBs) are made of several materials, including platinum, gold, silver, and rare earth elements, which are very valuable from a circular economy perspective. The PCB end of life management starts with the component removal, then the PCBs are shredded into small particles. Eventually, different separation methods are applied to the pulverized material to separate metals and non-metals. The corona electrostatic separation is one of the methods that can be used for this purpose since it is able to separate the conductive and non-conductive materials. However, the lack of knowledge to set the process parameters may affect the efficiency of the corona electrostatic separation process, ultimately resulting in the loss of valuable materials. The simulation of particle trajectory can be very helpful to identify the effective process parameters of the separation process. Thus, in this study, a simulation model to predict the particles trajectories in a belt type corona electrostatic separator is developed with the help of COMSOL Multiphysics and MATLAB software. The model simulates the particle behavior taking into account the electrostatic, gravitational, centrifugal, electric image, and air drag forces. Moreover, the predicted particles trajectories are used to analyze the effects of the roll electrode voltage, angular velocity of roll electrode, and size of the particles on the separation process