Optimization of 5-axis milling processes using process models

Productivity and part quality are extremely important for all machining operations, but particularly for 5-axis milling where the machine tool cost is relatively higher, and most parts have complex geometries and high quality requirements with tight tolerances. 5- axis milling, presents additional challenges in modeling due to more complex tool and workpiece interface geometry, and process mechanics. In this paper, modeling and optimization of 5-axis processes with cutting strategy selection are presented. The developed process models are used for cutting force predictions using a part-tool interface identification method which is also presented. Based on the model predictions and simulations, best cutting conditions are identified. Also, for finish process of a complex surface, machining time is estimated using three machining strategy alternatives. Results are demonstrated by example applications, and verified by experiments

Simulation of multi-axis machining processes using z-mapping technique

Parameter selection in machining operations is curial for product quality and high productivity. Process parameters such as feed, spindle speed and depth of cuts are often chosen by trial-error methods. Mathematical models can be employed to predict the mechanics and the dynamics of the process. In this study, Z-mapping technique is utilized to simulate the process step by step by updating the workpiece according the given tool path where the cutter engagement areas are also determined. Using the numerical generalized process model, whole process is simulated for any milling tool geometry including intricate profiling tools, serrated cutters and tools with variable edge geometries

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

Investigation of lead and tilt angle effects in 5-axis ball-end milling processes

5-axis milling is widely used in aerospace, die-mold and automotive industries, where complex surfaces and geometries are machined. Being special parameters of 5-axis milling, lead and tilt angles have significant effects on the process mechanics and dynamics which have been studied very little up to now. In this paper, first of all, effects of tool tip contact on the surface finish quality is presented, and conditions to avoid tip contact in terms of lead and tilt angles and depth of cut are stated. The effects of lead and tilt angles on cutting forces, torque, form errors and stability are investigated through, modelling and verified by experimental results. It is shown that the cutting geometry, mechanics and dynamics vary drastically and nonlinearly with these angles. For the same material removal rate, forces and stability limits can be quite different for various combinations of lead and tilt angles. The results presented in the paper are expected to help understanding of complex 5-axis milling process mechanics and dynamics in a better way. The results should also help selection of 5-axis milling conditions for higher productivity and machined part quality

5 eksen frezeleme süreçlerinin modelleme yoluyla benzetimi ve eniyilenmesi

Özet: 5 eksenli frezeleme, havacılık ve kalıpçılık sanayilerinde karsılasılan karmasık yüzeylerin imalatında yaygın olarak kullanılmaktadır. Çok değiskenli ve karmasık bir mekaniğe sahip bu süreçlerin uygulanmasında uygun ve en iyi kesme kosullarının belirlenmesi verimlilik ve kalite açısından çok önemlidir. Genelde, 3 eksen frezeleme modellerini kullanarak hassas sonuçlar elde edilmesi çok mümkün değildir. Bu çalısmada, 5 eksen frezeleme süreçlerinin benzetimi ve en iyilemesi yapılmıstır. Geometrik modelleme için gerekli olan parametreler, verilen bir takım yolu dosyasından elde edilmistir. Elde edilen parametreleri kullanarak takım ve parça kesisim sınırları, eğilme-yatma açıları gibi kesme kosullarının hesaplanması anlatılmıstır. Bu değerler mevcut bir kuvvet modeline uygulanıp frezeleme kuvveti benzetimi yapılmıstır. Benzetimde elde edilen sonuçlara göre kesme kuvveti açısından kesme parametrelerinin en uygun değerleri bulunmustur. Hesaplanan eniyi değerler deneysel sonuçlarla doğrulanmıstır.{|}5 axis machining is widely used in die-mold and aerospace industries where complex surfaces are required to be manufactured. Identification of the optimum and appropriate cutting parameters of processes, which has complex mechanics, is very important from the productivity and quality perspectives. It is not possible to apply 3 axis machining models in these cases for accuare results. In this paper, simulation and optimization of 5 axis machining processes are performed. The required parameters for geometrical modeling are obtained from a CL-file. Calculation of cutting conditions such as engagement boundaries, lead-tilt angles from the obtained parameteres is shown. Those parameters are applied to an existing 5 axis force model, and then force simulations are performed. According to the simulation results, the best values of cutting parameters are identified from the milling forces point of view. The optimal values are verified with experimental results

Geometrical Analysis and Optimization of 5-Axis Milling Processes

5-axis milling processes are widely used in industries where complex surfaces are machined, and cutter accessibility is limited due to geometrical constraints on the workpiece. Additional motion capability increases the accessibility of the cutting tool, so it becomes possible to machine complex surfaces despite the geometrical constraints. In most of these industries dimensional tolerance integrity, surface quality, and productivity are of great importance. Therefore, identification of optimal or nearoptimal process conditions, and selection of appropriate machining strategy for a given workpiece are required. Increased motion capability in 5-axis complicates the geometry and the mechanics of the process. Thus, optimization of 5-axis milling processes becomes a complex engineering problem. In order to solve such a problem, process models should be used together with geometrical analysis methods. In selection of appropriate machining strategy, surface characteristics should be known together with the process mechanics. In this thesis, a complete geometrical model is presented for 5- axis milling processes using ball-end mills. The developed model is integrated with an existing 5-axis process model in order to simulate the cutting forces throughout a given toolpath. Also, the effect of lead and tilt angle pair on process mechanics is investigated, and optimized values of those under various conditions are identified. In addition, a model suggesting the most appropriate strategy among various machining strategies for roughing and finishing operations for regular free form surfaces is presented. The developed models are verified through experiments and their applications are demonstrated on complex surfaces

Volumetric and three-dimensional examination of sella turcica by cone-beam computed tomography: reference data for guidance to pathologic pituitary morphology

Background: The aim of the study was to assess the dimensions and volume of sella turcica in healthy Caucasian adults with normal occlusion and facial appearance from cone-beam computed tomography (CBCT) images. Materials and methods: CBCT images of 80 Caucasian adult patients (40 males, 40 females) with normal facial appearance and occlusion taken previously for diagnostic purposes were evaluated. Two groups were constructed in accordance to gender. The volume, length, diameter, and depth of the sella turcica were measured by Romexis software programme. Mann-Whitney U test and Independent t-tests were used for statistical analysis. Results: The mean lengths of the sella were 9.9 mm and 10.2 mm, depths were 9.2 mm and 8.8 mm and diameters were 12.3 mm and 12.1 mm in female and male groups, respectively. Between the genders, no statistically significant differences were found for any of the measurements. There were significantly higher values for the volume of sella turcica in males than in females (1102 ± 285.3 mm3 and 951.3 ± 278.5 mm3, respectively). Conclusions: The dimensions of sella turcica in healthy Caucasian adults with normal occlusion and facial appearance revealed nonsignificant differences between the genders. Individual variability in dimensions and gender differences in the volume are of importance in comparison of patients with craniofacial syndromes and aberrations. Knowledge concerning the dimensions and volume of sella turcica will be clinically relevant for a guidance to consciously realize pituitary disorders

Investigation of process damping effect for multi-mode milling systems

Process damping acts as a significant cause of increased stability in milling particularly at low cutting speeds, which has been studied only for single-mode systems in the literature. Chatter frequency, which depends on the component causing chatter, strongly influences process damping coefficient, which is expected to vary with modes of the system. In this paper, the effect of process damping on chatter stability is investigated considering multi-mode dynamics of the system. The process damping coefficients are simulated for the fundamental chatter frequency of each significant mode and then used in the stability solution in frequency domain. An iterative milling stability solution is used as the process damping coefficients depend on the cutting depth. The stability lobe diagram is constructed with respect to multiple mode characteristics of the system. The theoretical predictions are verified through representative experimental cases and the results are discussed

Modeling and simulation of 5-axis milling processes

5-axis milling is widely used in machining of complex surfaces. Part quality and productivity are extremely important due to the high cost of machine tools and parts involved. Process models can be used for the selection of proper process parameters. Although extensive research has been conducted on milling process modeling, very few are on 5-axis milling. This paper presents models for 5-axis milling process geometry, cutting force and stability. The application of the models in selection of important parameters is also demonstrated. A practical method, developed for the extraction of cutting geometry, is used in simulation of a complete 5-axis cycle

Analysis of circular reflectors by complex source-dual series approach

In the present paper, two dimensional circular reflector antennas are analyzed by a rigorous analytical-numerical technique for both E and H polarization cases. The method is used in combination with the complex source approach. The convergence of the solution is guaranteed and any desired accuracy can be obtained. Some principal results of reflector antennas are examined by the exact circular reflector solution