Within the context of molds and dies production, frequent changes in design and increased competitiveness require an overall optimized manufacturing process. The finishing process is typically composed of an accurate milling stage to manage shape deviations, followed by polishing operations to reach required surface roughness. Local improvements of milling and polishing set independently do not necessarily lead to an optimal manufacturing process planning. This study aims to propose a method to improve the whole sequence of milling and polishing considering constraints from polishing process and machine tool. The turning point between milling and polishing operations consists in linking them by the evaluation of the surface topography obtained after milling. From there, thanks to a predictive model of surface roughness, the design of polishing operations can be performed, and polishing time evaluated. On the other hand, for a given machine tool and a desired intermediate surface topography, milling parameters for finishing can also be modified and actual machining time predicted. Thus the whole process is evaluated balancing the milling and polishing times to reduce the total manufacturing time. Experiments are carried out on an aluminum mold for blowing process of plastic bottles.
This paper deals with singular configurations of a 5-axis machine tool in high speed milling which may lead to the appearance of large incoherent movements of rotary axes near singularity points. These movements generate slowdowns of the actual feedrate during the execution of the tool path, which affect quality and productivity. Thus, this paper proposes a method to detect these behaviors during machining simulation and correct the tool path. Unlike the literature methods, this correction consists in modifying the tool axis orientation by going through the singularity point while respecting maximum velocity, acceleration and jerk of the rotary axis. For that purpose, the initial articular positions of the rotary axis near the singularity point are fitted with B-spline curves, modified and finally discretized for linear interpolation. Experimental investigations on a test part are carried out to show the efficiency of the method.
International audienceIn 5-axis high speed milling, large incoherent movements of rotary axes around the singular point are known to be a problem. Correction methods found in the literature deal mostly with the collision that may happen between the tool and the part but not with the feedrate slowdowns which affect surface quality and machining productivity. The method proposed in this paper addresses both geometrical and productivity issues by modifying the tool axes orientation while respecting maximum velocity, acceleration and jerk of the machine-tool axes. The aim is to detect these behaviors and replace the considered portion of the tool path by a patch curve respecting kinematical contraints of the machine tool. Compare to previous works, the inserted patch curve is not constrained to pass through the singularity but respect tangential contrains to ensure the monotony of the tool path and is also connected with the rest of the tool path to ensure a continuity up to the third derivative in order to fulfill jerk limitations. For that purpose, the initial articular positions of the rotary axes around the singular point are fitted with B-spline curves, modified and finally discretized for linear interpolation. Experimental investigations on a test part are carried out to show the efficiency of the method in terms of feedrate and surface quality
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