Browsing by Subject "CP titanium"

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Open Access
Identification of internal process parameters of micro milling considering machined surface topography
(2022-07) Masrani, Abdulrzak
Micro-milling is a fast and versatile machining method that can be used to manufacture three-dimensional parts of a wide range of materials with high accuracy. Modeling of micro-milling processes is complex due to size effects, where the chip thickness becomes comparable to the cutting edge radius. Furthermore, tool runout and deflection effects on the process outputs are amplified and cannot be neglected. As the process is scaled down where micrometer accuracy is required; modeling and identifying the process parameters becomes essential to optimize or monitor the process. This study presents a systematic approach to force modeling and parameter identification of micro-milling processes. Finite element analysis of tool deflection is integrated into mechanistic modeling of micro-milling forces together with considering the trochoidal trajectory of the cutting teeth, tool runout, and chip thickness accumulation due to minimum uncut chip thickness. The internal process parameters are identified using the experimental cutting forces and machined surface topography with a novel methodology. The research results are experimentally validated by slot and side micro-milling tests on commercially pure titanium, using coated carbide micro-end-mills with diameters of 0.2 and 0.4 mm, and accurate predictions of model parameters and cutting forces are obtained. The proposed force models can be used in smart manufacturing and digital twin applications to reduce the time and costs associated with process optimization. The proposed parameter identification techniques can also help to reduce the need for advanced measurement systems.
Open Access
Investigating the effect of CP titanium microstructure on the mechanics of microscale machining
(2019-09) Aksın, Alp
Metal cutting in microscale brings along many challenges and unanswered questions. Mechanical response of the material to the micro-cutting process is one of them, since feed values and the edge radius of the tool can be in the magnitude of order of the material's grain size. In addition, the grain morphology of the material may affect process outputs. This study investigates microstructure effects of the commercially pure titanium (CP Ti) based on analytical and mechanistic modeling approaches. A slip line field model was studied considering fracture toughness and edge radius effects. Orthogonal micro-cutting tests were performed on different morphologies at feed levels ranging from 0.25 to 6 µm per revolution and cutting force data were collected. Cut chip thickness values were measured by using SEM and used as in-process output in the model. The model outputs were fit to force data and unknown model parameters were identified. Those determined parameters were compared with measurements. The study show that the rake angle and tool edge radius parameters have a consistent disparity between measured and identified values. Evidence of possible wear and material build up at the tool have been observed. Using Bayesian inference, possible range of rake angle values have been further investigated and probability distributions of the rake value were identified for different feed levels. Micromilling of CP titanium has also been considered and a relationship between microscale orthogonal cutting and micromilling has been sought. CP titanium was tested by conducting full immersion micromilling experiments based on mechanistic modeling. In uence of the grain morphology on model coefficients, surface texture and hardness have been discussed.