Machining strategy development in 5-axis milling operations using process models

Increased productivity and part quality can be achieved by selecting machining strategies and conditions properly. At one extreme very high speed and feed rate with small depth of cut can be used for high productivity whereas deep cuts accompanied with slow speeds and feeds may also provide increased material removal rates in some cases. In this study, it is shown that process models are useful tools to simulate and compare alternative strategies for machining of a part. 5-axis milling of turbine engine compressors made out of titanium alloys is used as the case study where strategies such as flank milling (deep cuts), point milling (light cuts) and stripe milling (medium depths) are compared in terms of process time by considering chatter stability, surface finish and tool deflections

Ceramic applications in turbine engines

Ceramic material characterization and testing of ceramic nozzle vanes, turbine tip shrouds, and regenerators disks at 36 C above the baseline engine TIT and the design, analysis, fabrication and development activities are described. The design of ceramic components for the next generation engine to be operated at 2070 F was completed. Coupons simulating the critical 2070 F rotor blade was hot spin tested for failure with sufficient margin to quality sintered silicon nitride and sintered silicon carbide, validating both the attachment design and finite element strength. Progress made in increasing strength, minimizing variability, and developing nondestructive evaluation techniques is reported

Automatic re-contouring of repair-welded tool moulds

The process of repairing damaged tool moulds is conducted manually in the industry. This results in long process times as well as a high dependence of the repair result on the experience of the worker. After a visual inspection, the detected damages are removed by metal cutting and the missing material is filled by a build-up welding process. Afterwards, the target geometry is restored via machining re-contouring process. Because of the individual tool mould surface and welded seam, each repair case requires an individual machining strategy as well as toolpaths and process control parameters to ensure high surface quality and shape accuracy. This paper introduces an innovative design for re-contouring of repair-welded tool moulds, which takes into consideration the individual mould surface, repair welding and material properties. For that purpose, the actual geometry of the tool mould is measured directly in the CNC machine using an optical profile line sensor. Based on the measurement, the re-contouring process is planned automatically by means of a computer aided manufacturing (CAM) software. A material removal simulation with cutting force prognosis is carried out to adapt the process parameters individually with regard to repair time and surface quality. To set up the force and surface simulation model with high model quality, re-contouring experiments are carried out on welded seams made of 1.2343 (AISI H11) as well as on Toolox 44 and 1.2343 workpieces for comparison

Ceramic applications in turbine engines

The design and testing of gas turbine engines employing ceramic components is discussed. Thermal shock and vibration test results as well as spin tests of various engine components are discussed

FABRICATION OF CERAMIC MICROPATTERNS AND THEIR IMPACT ON BONE CELLS

The main objective of this study is to elucidate possible methods of producing ceramic calcium phosphate micropatterns ranging from 5 to 100 µm. Today, micropatterned ceramic surfaces are of great interest for fundamental materials research as well as for high-end industrial processes, whereas the fabrication of these patterns in the sub-100 µm range is still a challenge. Therefore, six different patterning techniques have been applied in order to generate ceramic patterns: Microtransfer molding (µTM), modified micromolding (m-µM), Aerosol-Jet® printing, CNC-micromachining, laser ablation and direct laser interference patterning (DLIP). The patterning techniques have been evaluated concerning their capability of fabricating ceramic patterns smaller than 100 µm. Another objective of this study has been the investigation of the influence of ceramic patterns on human osteoblasts (HOB). This investigation has revealed that ceramic hydroxyapatite-based patterns ranging from 16 to 77 µm in widths have a strong influence on the contact guidance of the HOB, whereas the cells showed distinct orientations between 0°-15° in reference to the pattern direction

Polymer Based Miniature Fabry-Perot Pressure Sensors with Temperature Compensation: Modeling, Fabrication, and Experimental studies

Miniature Fabry-Perot (FP) pressure sensors have been of great interest because of their advantages of small sizes, high performance, and immunity to electromagnetic interference. Most of these sensors are built with silicon/silica materials that have good mechanical, chemical, and thermal stabilities. However, due to the large Young's modulus of silica/silicon, developing a high sensitivity miniature sensor becomes difficult. In addition, fabrication of these sensors often involves high temperature fusion bonding and harsh acid etching. On the other hand, a polymer material becomes an attractive choice for high sensitive and miniature pressure sensors due to its small Young's modulus relative to that of silicon/glass. Moreover, polymer processes can be performed under ambient pressure and temperature without hazardous chemicals. However, a polymer-based sensor suffers from high temperature sensitivity, which must be compensated to obtain accurate pressure measurements. In this dissertation, three types of polymer based FP miniature sensors for static or quasi-static pressure measurements are investigated through modeling, microfabrication, and experiments. First, co-axial and cross-axial FP sensors with a built-in fiber Bragg grating (FBG) for temperature measurement and compensation are studied. In both sensors, the FP cavity is precisely self-aligned with the optical axis by using the fiber as a natural mask, which eliminates the need for a photo mask and tedious optical alignments. Second, a FP sensor composed of a UV-molded optical cavity with a pre-written FBG is developed. For the first time, a UV molding process with an optical fiber based mold is developed for fabrication of miniature FP sensors. This process enables high accuracy optical alignment for UV molding. Taking advantage of the UV molding process, the third type of sensor features a hybrid dual FP cavity for simultaneous temperature and pressure measurements. A novel signal processing method is developed to retrieve the multiple cavity lengths with an improved speed, resolution, and noise resistance. Experimental studies show that these polymer based sensors have good pressure and temperature sensing performance as well as temperature compensation capabilities. In addition, blood pressure and intradiscal pressure measurements of a swine are performed, which demonstrates the feasibility of these sensors for biomedical applications

Miniature micromachined quadrupole mass spectrometer array and method of making the same

The present invention provides a quadrupole mass spectrometer and an ion filter, or pole array, for use in the quadrupole mass spectrometer. The ion filter includes a thin patterned layer including a two-dimensional array of poles forming one or more quadrupoles. The patterned layer design permits the use of very short poles and with a very dense spacing of the poles, so that the ion filter may be made very small. Also provided is a method for making the ion filter and the quadrupole mass spectrometer. The method involves forming the patterned layer of the ion filter in such a way that as the poles of the patterned layer are formed, they have the relative positioning and alignment for use in a final quadrupole mass spectrometer device