Plunge milling time optimization via mixed-integer nonlinear programming

International audiencePlunge milling is a recent and efficient production mean for machining deep workpieces, notably in aeronautics. This paper focuses on the minimization of the machining time by optimizing the values of the cutting parameters. Currently, neither Computer-Aided Manufacturing (CAM) software nor standard approaches take into account the tool path geometry and the control laws driving the tool displacements to propose optimal cutting parameter values, despite their significant impact. This paper contributes to plunge milling optimization through a Mixed-Integer NonLinear Programming (MINLP) approach, which enables us to determine optimal cutting parameter values that evolve along the tool path. It involves both continuous (cutting speed, feed per tooth) and, in contrast with standard approaches, integer (number of plunges) optimization variables, as well as nonlinear constraints. These constraints are related to the Computer Numerical Control (CNC) machine tool and to the cutting tool, taking into account the control laws. Computational results, validated on CNC machines and on representative test cases of engine housing, show that our methodology outperforms standard industrial engineering know-how approaches by up to 55% in terms of machining time

Early-infantile onset epilepsy and developmental delay caused by bi-allelic GAD1 variants.

Gamma-aminobutyric acid (GABA) and glutamate are the most abundant amino acid neurotransmitters in the brain. GABA, an inhibitory neurotransmitter, is synthesized by glutamic acid decarboxylase (GAD). Its predominant isoform GAD67, contributes up to ∼90% of base-level GABA in the CNS, and is encoded by the GAD1 gene. Disruption of GAD1 results in an imbalance of inhibitory and excitatory neurotransmitters, and as Gad1-/- mice die neonatally of severe cleft palate, it has not been possible to determine any potential neurological dysfunction. Furthermore, little is known about the consequence of GAD1 disruption in humans. Here we present six affected individuals from six unrelated families, carrying bi-allelic GAD1 variants, presenting with developmental and epileptic encephalopathy, characterized by early-infantile onset epilepsy and hypotonia with additional variable non-CNS manifestations such as skeletal abnormalities, dysmorphic features and cleft palate. Our findings highlight an important role for GAD1 in seizure induction, neuronal and extraneuronal development, and introduce GAD1 as a new gene associated with developmental and epileptic encephalopathy

Optimizing plunge milling aeronautical parts via MINLP

International audienceno abstrac

Optimizing plunge milling aeronautical parts via MINLP

International audienceno abstrac

Variability influence of machining context on tool tips wear estimation - Application to dry turning of 42CrMo4 steel

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A new machining strategy for roughing deep pockets of magnesium-rare earth alloys

International audiencePlunge milling is an efficient machining process for roughing deep pockets. Its efficiency is mainly due to low radial forces on the cutter. This leads to reduced bendings and vibrations that allow one to improve cutting parameter values. The machining time can then be reduced with respect to machining processes with constant Z-level. Recently, another machining process has been introduced, called ”balancing of the transversal cutting force” (BotTCF), that is also characterized by a suitable distribution of forces on the cutter. It has been applied only to finishing operations on complex surfaces. In this paper, we present two main contributions. First, we extend the BotTCF concept to roughing open deep pockets and semi-open pockets opened from side to side. This is mainly based on successive parallel ramping trajectories, defined by an optimal angle which ensures a good balancing of the transversal cutting forces. This can be applied to 3-axis and 5-axis computer numerical control (CNC) machine tools. Second, we propose a new, hybrid methodology for roughing semi-open pockets (not opened from side to side) and closed pockets. It is based on the combination of ramping trajectories with BotTCF and plunge milling. The proposed methodology is developed for three-axis machining and can be extended to five-axis machining. Based on an identical criterion (identical maximum force acting on the cutters), we perform a fair machining-time comparison of plunge milling with the proposed hybrid method applied on a closed deep pocket: a simplified aeronautical housing made of magnesium-rare earth alloy. Results show a significant gain in machining time when the hybrid method is applied

Comparison of methods for measuring atmospheric deposition of arsenic, cadmium, nickel and lead

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Nitrogen Deposition on Danish Nature

Eutrophication events are frequent in Inner Danish waters and critical loads are exceeded for much of the Danish sensitive terrestrial ecosystems. The Danish air quality monitoring program combines measurements and model calculations to benefit from the complementarities in data from these two sources. Measurements describe actual status, seasonal variation, and temporal trends. Model calculations extrapolate the results to the entire country and determine depositions to specific ecosystems. Measurements in 2016 show annual depositions between 7.5 and 11 kg N/ha to terrestrial ecosystems, and a load to marine waters of 5.3 kg N/ha. The deposition on Danish marine waters in 2016 was calculated to be 73,000 tons N with an average deposition of 6.9 kg N/ha. For terrestrial areas, the deposition was calculated to be 57,000 tons N with an average deposition of 13 kg N/ha. This is above critical loads for sensitive ecosystems. Long-term trends show a 35% decrease since 1990 in measured annual nitrogen deposition. At two out of four stations in nature areas, measured ammonia levels exceeded critical levels for lichens and mosses. Conclusions: Nitrogen loads and levels to Danish nature is decreasing, but critical loads and levels are still exceeded for sensitive ecosystems. Combining measurements and model calculations is a strong tool in monitoring

The DESCARTES-Nantes survey of kidney transplant recipients displaying clinical operational tolerance identifies 35 new tolerant patients and 34 almost tolerant patients

Kidney recipients maintaining a prolonged allograft survival in the absence of immunosuppressive drugs and without evidence of rejection are supposed to be exceptional. The ERA-EDTA-DESCARTES working group together with Nantes University launched a European-wide survey to identify new patients, describe them and estimate their frequency for the first time.status: publishe