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

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

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

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

Workpiece surface flatness improvement by tool length compensation in micromilling

Micromilling quality improvement requires an accurate management of all the involved resources (machine tool, tool, fixture, workpiece). Specific attention has to be paid, comparing to macro operations, also to machining strategies and tool and workpiece measuring strategies. The extreme workpiece accuracy requires to reinterpret some procedures, already applied in the macro world, with the purpose to minimize errors. It is the case of the tool length compensation, which plays a strong role on the micromilling overall performance. In order to demonstrate the importance of factors affecting tool length, as machine spindle thermal transients and tool wear assessment, the present paper takes the workpiece flatness deviation as a case study and presents a manufacturing and measuring strategy able to meet a challenging flatness constraint

Improvement of Procedures for High Accuracy Micromilling of Flat Surfaces

All the resources involved in micromilling operations (machine tool, tool, fixture, workpiece) have to be accurately managed to improve the final workpiece quality. Special attention has to be paid also to system thermal stability, micromilling process parameters and machining strategies, workpiece and tool measurement accuracy. The present paper proposes an easy and industry-oriented procedure to maximize the achievable workpiece accuracy working in absolute coordinates. Accurate plane surfaces with a strict flatness deviation are machined on a CuNi12Zn30Pb1 benchmark workpiece to demonstrate the procedure effectiveness

Improvement of procedures for high accuracy micromilling of flat surfaces

All the resources involved in micromilling operations (machine tool, tool, fixture, workpiece) have to be accurately managed to improve the final workpiece quality. Special attention has to be paid also to system thermal stability, micromilling process parameters and machining strategies, workpiece and tool measurement accuracy. The present paper proposes an easy and industry-oriented procedure to maximize the achievable workpiece accuracy working in absolute coordinates. Accurate plane surfaces with a strict flatness deviation are machined on a CuNi12Zn30Pb1 benchmark workpiece to demonstrate the procedure effectiveness