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

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

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

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 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

A Testpart for Interdisciplinary Analyses in Micro Production Engineering

In 2011, a round robin test was initiated within the group of CIRP Research Affiliates. The aim was to establish a platform for linking interdisciplinary research in order to share the expertise and experiences of participants all over the world. This paper introduces a testpart which has been designed to allow an analysis of different manufacturing technologies, simulation methods, machinery and metrology as well as process and production planning aspects. Current investigations are presented focusing on the machining and additive processes to produce the geometry, simulation approaches, machine analysis, and a comparison of measuring technologies. Challenges and limitations regarding the manufacturing and evaluation of the testpart features by the applied methods are discussed