Milling Configurations Research Articles

Pea and lentil flour quality as affected by roller milling configuration

AbstractThis study examined the effects of roller mill configuration on pulse flour quality. Dehulled yellow pea and green lentil were ground to flour using a laboratory roller mill characterized by its flexibility to control particle size reduction while maintaining a constant feed rate. The milling diagram length (long, six passes vs. short, four passes) and sieve sizes (large, 300 μm vs. tight, 180/150 μm) were adjusted for a total of four milling configurations. Each flour stream was characterized with respect to its physical properties and chemical composition. No notable differences were identified between pea and lentil based on how the milling configuration influenced flour characteristics. Overall, combining streams to produce a whole flour did not affect the chemical composition but resulted in variability for physical characteristics as indicated by a tendency toward increased levels of damaged starch with the shorter milling diagram. Damaged starch content was found to be indirectly associated (p < 0.05) with the particle size distribution, where the highest concentrations were noted in flours with median distributions below 30 μm. When individual streams were compared across milling configurations, the stream itself was rarely found to significantly influence flour physicochemical properties. However, the variation exhibited in particle‐size distribution, protein, starch, ash, and damaged starch content could have practical relevance given the many significant (p < 0.05) correlations with functional properties that could subsequently affect the end‐use applicability of flours. This would imply that specialized flours could be made with the intention of being used for defined food applications.

Toward a comprehensive understanding of ultracentrifugal milling on the physicochemical properties and aromatic profile of yellow pea flour

Yellow pea (Pisum sativum L., YP) grain is generally milled into flour for further processing or direct consumption. However, the comprehensive relationship between milling configurations and YP flour properties remains unclear. The aim of this study is to investigate the effect of configurations (screen aperture size and rotor speed) of ultracentrifugal mill on the physicochemical properties and aromatic profiles of YP flours. Starch damage, morphology, particle size distribution, pasting, thermal property, and aromatic profiles of YP flours were studied. Results show that starch damage increased significantly as the screen aperture size decreased. The YP flour produced with a 500 µm aperture screen had the most stable pasting and thermal properties. With untargeted metabolomic approaches, 2-ethyl-1-hexanol could potentially be applied as an aroma maker to distinguish if an excessive milling or inappropriate configurations of ultracentrifugal mill are applied. This work has furnished fundamentals for the milling and application of YP flour.

Feedback Control for the Size and Shape Evolution of Needle-like Crystals in Suspension. III. Wet Milling

Several operating and control strategies with the purpose of manipulating the size and shape of crystals exhibiting needle-like morphology are presented using an ex situ wet mill as the actuator. A model-based operating policy and different model-free controllers are discussed. These controllers were coupled with an online particle size and shape monitoring tool. First, the attainable region in the size and shape space for a wet milling operation was evaluated in a simulation framework using a multidimensional population balance model describing the breakage phenomenon. Second, the operating and control strategies were tested experimentally in a lab-scale setup using two different milling configurations and two different compounds, namely, β l-glutamic acid and γ d-mannitol. The goal of the experiments was to drive various seed populations of the two compounds to several target average lengths in the size and shape space. It was observed that the model-based operating policy, run without any feedback acti...

Topology optimization for multi-axis machining

This paper presents a topology optimization approach that incorporates restrictions of multi-axis machining processes. A filter is defined in a density-based topology optimization setting, that transforms an input design field into a geometry that can be manufactured through machining. The formulation is developed for 5-axis processes, but also covers other multi-axis milling configurations, e.g. 2.5D milling and 4-axis machining by including the appropriate machining directions. In addition to various tool orientations, also user-specified tool length and tool shape constraints can be incorporated in the filter. The approach is demonstrated on mechanical and thermal 2D and 3D numerical example problems. The proposed machining filter allows designers to systematically explore a considerably larger range of machinable freeform designs through topology optimization than previously possible.

Effect of ion milling on the perceived maturity of shale samples: Implications for organic petrography and SEM analysis

Sample polishing by argon ion beam is a widely used method for examining shale samples for inherent porosity characteristics; the high quality of these surfaces suggests that this technique may also be used for optical reflectance measurements to provide information about the thermal maturity of samples. Yet, the inevitable surface heating that this polishing method engenders has raised concerns that the measured reflectance properties are no longer those of the original sample. To explore the impact of ion milling on the maturity of shale samples as measured by vitrinite and solid bitumen reflectance, five different ion milling configurations were applied to a set of organic-rich New Albany Shale (Late Devonian-Early Mississippian) samples that range in maturity from immature to post-mature. Using two ion mill designs, edge milling vs planar milling, single and dual ion beams, variable acceleration voltages, and milling at room temperature vs samples cooled by liquid nitrogen, provided a wide range of beam heating scenarios. Reflectance of macerals was measured before and after ion milling to investigate whether and to what extent various ion-milling approaches change the reflectance values, and by extension the perceived thermal maturity of organic matter in these samples. Our results demonstrate that more aggressive milling methods, such as the use of multiple beams and higher acceleration voltages elevate reflectance values, and that this effect is most pronounced in immature samples and diminishes for samples of increasing original maturity. Specifically, for the two least mature samples, the most aggressive milling method (configuration D) increased reflectance of vitrinite from 0.48% to 0.58%, and from 0.58% to 0.74%. Increase of reflectance (perceived maturity) can be counteracted by reducing beam intensity (e.g., fewer beams, lower voltage) and cooling of samples with liquid nitrogen. The severity of heating artifacts depends partially on the ion mill design, and non-damaging settings must be determined experimentally for a given ion mill model. Because thermal alteration of organic matter typically involves the expulsion of volatiles, there is also a danger that ion beam heating of immature and oil window samples can skew the porosity characteristics of shale samples. Thus, determining non-damaging ion mill settings has the dual benefit of avoiding measuring false maturity levels and misleading porosity characteristics.

Modeling knot geometry from branch angles in Douglas-fir (Pseudotsuga menziesii)

Lumber and veneer recovery from Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees depend on the size and distribution of knots. Two approaches have been used to simulate the effect of knots on recovery of these products: (i) prediction of recovery based on mill studies and (ii) simulated milling of virtual trees. A benefit of the latter approach is that different milling configurations may be tested. Knots in virtual logs are usually based on data from X-ray scanning. A novel approach was used in this study to model knot geometry by inferring the development of a branch knot over time from a chronosequence of branch angle and diameter measurements. Branch angle was modeled from a database of 17 953 branch measurements on 412 trees sampled in 16 Douglas-fir plantations. Branch angles from tree tip to crown base were assumed to represent a chronosequence describing the change in branch angle. Knot pith curvature was then derived from this chronosequence of branch angles and modeled as a first-degree inverse polynomial, conditioned on tree size and position within the tree bole. Knot pith curvature was predicted to follow a linear path near the tree tip and became more curved with increasing age and depth into the crown.

Modeling and Analysis of Five-Axis Milling Configurations and Titanium Alloy Surface Topography

Five-axis milling with a ball-end cutter is commonly used to generate a good surface finish on complex parts, such as blades or impellers made of titanium alloy. The five-axis milling cutting process is not straight forward; local cutting conditions depend a lot on the geometrical configuration relating to lead and tilt angles. Furthermore, the surface quality is greatly affected by the cutting conditions that define the milling configuration. This study presents a geometrical model of five-axis milling in order to determine the effective cutting conditions, the milling mode, and the cutter location point. Subsequently, an analysis of surface topography is proposed by using the geometrical model, local criteria, and a principle component analysis of experimental data. The results show the effects of local parameters on the surface roughness, in relation to the lead and tilt angles.

Predicting the dynamic behaviour of torus milling tools when climb milling using the stability lobes theory

This paper investigates stability and dynamic behaviour of torus tool in climb milling on 5 positioned axes. The stability lobes theory is used to enable stable cutting conditions to be chosen. As the adaptation of such a theory to complex milling configurations is a difficult matter, new methods are presented to identify the dynamic parameters. Tool dynamic characteristics (stiffness and natural pulsation) are determined with an original coupled calculations-tests method. Start and exit angles are computed exactly using an original numerical model. A sensitivity analysis highlights the influence of machining parameters on stability of climb milling. This shows that a third region of “potential instability” must be taken into account in plotting stability lobes, due to the uncertainty of prediction due to modelling and identification of parameters. The results were validated experimentally with an innovative approach, especially through the use of high-speed cameras. Analysis of vibrations and the surface roughness allowed the analytical model to be verified so as to optimise the inclination of the tool on the surface.

Experimental Analysis and Geometrical Modeling of Cutting Conditions Effect in 5 Axis Milling with Ti6Al4 V Alloy

The 5 axis continuous milling is an advanced technique for free-form surfaces manufacturing. In finishing, this technique uses ball-end or hemispherical milling cutter. This type of operation for 5 axis milling allows the possibility to tilt the tool with two different angles. As a consequence, a mass of geometrical configurations exists and establishing accurate parameters is quite difficult to define. A geometrical model has been developed to find the effective cutting diameters and cutting speed on the cut and the finished surface. After an experimental validation, this study proposes an analysis of several 5 axis milling configurations in order to perform this technique.

3D FEM simulations of shoulder milling operations on a 304L stainless steel

This paper describes investigations realised to perform simulations of shoulder milling operations on AISI 304L stainless steel using the commercial software LS-Dyna©. A Lagrangian formulation with an explicit solution scheme and a penalty contact algorithm has been used. Many experiments were performed in shoulder milling configurations in order to study the machinability of this material and also to validate the results obtained from the developed 3D finite element model. In the simulations, the material behaviour is modelled with a classical Johnson–Cook law. Some enhancements and simplifications had to be made in geometry, meshing, friction and temperature considerations for limiting the calculation time. The final aim consists to obtain realistic numerical cutting forces for shoulder milling operations.

Intégration de la géométrie d'outil dans la prédiction des efforts de coupe en fraisage de matériaux durs

The knowledge of cutting forces thanks to a, predictive model is very interesting for the choice of a machine tool power, the cutting tools, the optimization of cutting conditions or the control of the occurence of vibrations. It could also be helpful in on-line wear monitoring during milling. This could allow to decrease the number of tests, and to determine the best tool geometry, in relation with a limit level of forces. The objective of the study is the prediction of effects of rake and helix angles on cutting forces variations, and to integrate it in a cutting relation. Tests were made on X 38CrMoV 5 (AISI H11) die and mold steel, with solid carbide milling cutters of various rake angles and straight flutes. A specific configuration has been used to create obliquity. Cutting forces were measured for various feed rates. The results have improved the cutting force model, and allowed to apply it to real milling configurations.

Dynamics of Planetary Ball Milling: A comparison of computer simulated processing parameters with CuO/Ni displacement reaction milling kinetics

A two dimensional, discrete element method computer program has been constructed to predict grinding media motion in a planetary ball mill. Various impact models have been assessed for suitability to simulate actual milling impacts. They include Kelvin and Maxwell viscoelastic models and an elastic/plastic yield model. The computer simulation has then been used to consider variations in processing parameters such as impact frequency and energy associated with different milling configurations. These results have then been compared to the kinetics of the CuO/Ni displacement reaction propagated under these conditions.