Conical Mill Research Articles

A general mathematical model for manufacturing Roots pump rotors using conical milling cutters

The rotors are the key components in the Roots pump, and the rotor manufacture time will decide the pump price. In special cases, such as when one rotor shaft has two stages, respectively, with claw-type and Roots profiles, the traditional forming method is unsuitable for manufacturing the Roots rotor stage. Instead, more suitable manufacturing methods, such as planning or end-mill milling, can be applied. However, these two methods take time and effort. Therefore, this study proposes a general mathematical approach for Roots rotor manufacturing using the conical milling cutter as the key tool, which can reduce manufacturing time. The contact points and meshing angles between the rotor and the conical milling cutter can be calculated based on contact conditions. Then, a 3D conical milling cutter surface is obtained based on the cutter profile as a straight line, and the conical cutter is designed and considered to avoid undercutting in the rotor cutting process. The generated Roots rotor can be obtained by applying cutting simulation from the proposed mathematical model. The normal deviations of the rotor can be found by comparing the generated rotor profile to the datum rotor profile. In addition, the influence of axis errors of the conical milling cutter on the tooth profiles of the Roots pump rotor is investigated and discussed. The experimental results based on the proposed mathematical model are obtained and expressed to confirm the practicability of the proposed method.

Simulation and Application of Windowing for High-Grade Steel Thick-Wall Casing in Ultradeep Wells: A Case Study of ST102 Well

Windowing processes in ultradeep wells (> 7000 m) with high steel grade (TP155V) and thick-wall (15.83 mm) casing not only face complex underground environments with high temperature and pressure but also have the difficulty of long operation time and high cost. To improve the success rate and operational efficiency, CAE software was used to establish the casing windowing side-drilling simulation model and optimize the windowing milling cone. Field applications were used to further demonstrate the simulation results. The main conclusions are as follows. The simulation shows that the milling shoulder and the outer circle of the cone top are the main working faces in window opening and window repair. The conical milling cone has the largest windowing stress, highest windowing efficiency, and regular shape of the window. A casing with a depth of 7473 m, wall thickness of 15.83 mm, and steel grade TP155V was successfully windowing using six conical milling cone in the ST102 well, taking 51.76 h, and generating 94 kg iron chips in total; the average milling speed was 0.06 m/h; The casing windowing progress can be determined by observing the return state of the cuttings. ST102 well set three records in China for the deepest drilling depth, highest steel grade, and thickest wall thickness.

Energy-Size Reduction of Magnetite-Calcite Binary Mixture in a Laboratory Wet Conical Ball Mill

Energy-Size Reduction of Magnetite-Calcite Binary Mixture in a Laboratory Wet Conical Ball Mill

Efficient drug development of oseltamivir capsules based on process control, bioequivalence and PBPK modeling

Oseltamivir phosphate is used to treat influenza. For registration of a generic product, bioequivalence studies are crucial, however, in vitro studies can sometimes replace the conventional human pharmacokinetic. To assess whether the dissolution profile is comparable with the in vivo release, physiologically based pharmacokinetic absorption models (PBPK) are being used. The aim of the study was to develop a generic capsule of oseltamivir phosphate 30 mg with process understanding and control, development of PBPK model and comparison of virtual bioequivalence study (VBE) to the real bioequivalence study that was also performed. For that, 30 mg capsules were prepared by wet granulation according to 22 full factorial design. The biobatch was prepared with the selected process and a batch was made with the API from the second manufacture. Both manufactures presented polymorph A and the second manufacture showed higher particle size. Product batches produced without adding water during granulation showed higher dissolution. The addition of water associated with higher conical mill speed, lowered the average weight of the capsules. The biobatch dissolution was similar to Tamiflu; also, they were bioequivalent. The crossover VBE between the biobatch and Tamiflu corroborated with the real bioequivalence study. The same result was found for the batch with higher particle size. PBPK model showed that computer simulations can help pharmaceutical companies to replace in vivo studies.

A Continuous Conical-Mill Operation for Dry Coating of Pharmaceutical Powders: The Role of Processing Time

Over the last decade, the conical mill has emerged as a potential piece of equipment to use for continuous dry coating pharmaceutical powders. In this work, silicon dioxide was used as a guest particle on two excipients, fast flow lactose (FFL) and grade PH200 microcrystalline cellulose (MCC), for dry coating by a conical mill with a modified screen that permitted batch and continuous mode operation. Samples were pre-processed in a V-blender. SEM images, particle size distribution, and EDS mapping were used to characterise the treated powders. Pre-processed samples showed some discrete coating of the host particle. After batch processing, the samples were covered with a complete coating. When processed at high impeller speed, coating of FFL was a mix of A200P and FFL fines generated by attrition. Continuous mode processed samples, which had a lower processing time, were coated discretely and showed a better coating than the pre-processed samples. Increasing guest/host mass ratio with FFL host particle had a positive impact on the quality of the coating. These results help to build the case that the processing time of the conical mill is a key parameter to the success of the conical mill as dry coating equipment in the pharmaceutical industry.

Preferential Oxycodone Loss of Physically Manipulated Abuse Deterrent Oxycodone HCl Extended Release Tablets Prepared for Nasal Insufflation Studies.

A method to reproducibly mill abuse deterrent oxycodone hydrochloride (HCl) extended release (ER) tablets was developed for a nasal insufflation pharmacokinetic (PK) study. Several comminution methods were explored before determining that a conical mill resulted in controlled milling of tablets to a size range equal to or below 1000μm. However, milling resulted in significant loss of oxycodone from abuse deterrent oxycodone HCl ER tablets compared to minimal oxycodone loss from oxycodone HCl immediate release (IR) tablets. Characterization of milled tablet powder showed that loss of oxycodone was not attributed to analytical procedures or oxycodone phase change during high intensity milling processes. The content uniformity of oxycodone in the milled tablet powder varied when ER and IR tablets were milled to a particle size distribution equal to or below 500μm but did not vary when particles were sized above 500 µm to equal to or below 1000μm. In addition, the initial excipient weight to drug substance weight ratio impacted the amount of oxycodone lost from the respective formulation. However, dissolution demonstrated that when oxycodone HCl ER tablets are milled, differences in excipient weight to drug substance weight ratio and particle size distribution of milled tablets did not result in significantly different release of oxycodone.

Fine grade engineered microcrystalline cellulose excipients for direct compaction: Assessing suitability of different dry coating processes

Recent work showed that contrary to conventional wisdom, fine surface engineered excipients outperform their larger counterparts in blends of highly loaded blends of cohesive drug powders in terms of their packing, flowability and tablet tensile strength. Here, two continuous devices, fluid-energy mill (FEM) and conical mill (Comil), are compared with LabRAM, a batch device used in previous work, for nano-silica dry coating of microcrystalline cellulose (MCC) excipients, 20 and 30 μm. Coated MCCs from all three devices had higher bulk densities and flow function coefficients (FFCs) compared with Avicel PH-102. Silica coating quality was best with LabRAM, but also good with FEM and Comil, although Comil was less effective for the finer MCC. However, the better coating quality of LabRAM had a downside of having poorer compaction properties. The most surprising outcome was that multi-component blends of 17 wt% coated MCC with 60 wt % Ibuprofen 50 had higher bulk density, higher or similar flowability, higher tablet tensile strength, and comparable Ibuprofen dissolution from tablets, compared to those with Prosolv 50, a silicified excipient. The FEM dry coated MCC blends, having only 0.17 wt% silica, performed the best, having desirable bulk density, FFC, and tensile strength that could facilitate high-speed direct compression tableting. In summary, considering that achieving best coating quality need not be the primary objective, FEM may be the best option for producing desired sized dry coated fine excipients.

Continuous high-shear granulation: Mechanistic understanding of the influence of process parameters on critical quality attributes via elucidating the internal physical and chemical microstructure

Over the past decade, continuous wet granulation has been emerging as a promising technology in drug product development. In this paper, the continuous high-shear mixer granulator, Lӧdige CoriMix® CM5, was investigated using a low-dose formulation with acetaminophen as the model drug. Design of experiments was deployed in conjunction with multivariate data analysis to explore the granulator design space and comprehensively understand the interrelation between process parameters and critical attributes of granules and tablets. Moreover, several complementary imaging techniques were implemented to unveil the underlying mechanisms of physical and chemical microstructure in affecting the tablet performance. The results indicated that L/S ratio and impeller speed outweighed materials feeding rate in modifying the granule and tablet properties. Increasing the degree of liquid saturation and mechanical shear input in the granulation system principally produced granules of larger size, smaller porosity, improved flowability and enhanced sphericity, which after compression generated tablets with slower disintegration process and drug release kinetics due to highly consolidated physical microstructure. Besides, in comparison to batch mixing, continuous mixing integrated with a conical mill enabled better powder de-agglomeration effect, thus accelerating the drug dissolution with increased surface area.

Badania symulacyjne siły skrawania w procesie obróbki powierzchni prostokreślnych frezem stożkowym

Presented is the analysis of the cutting force in the flank milling process with a conical mill. The tests were carried out for various twist angles of the machined surface and different values of the lead angle.

Highly accurate 5-axis flank CNC machining with conical tools

A new method for 5-axis flank computer numerically controlled (CNC) machining is proposed. A set of tappered ball-end-mill tools (aka conical milling tools) is given as the input and the flank milling paths within user-defined tolerance are returned. Thespace of lines that admit tangential motion of an associated truncated cone along a general, doubly curved, free-form surface is explored. These lines serve as discrete positions of conical axes in 3D space. Spline surface fitting is used to generate a ruled surface that represents a single continuous sweep of a rigid conical milling tool. An optimization-based approach is then applied to globally minimize the error between the design surface and the conical envelope. The milling simulations are validated with physical experiments on two benchmark industrial datasets, reducing significantly the execution times while preserving or even reducing the milling error when compared to the state-of-the-art industrial software.

Badania symulacyjne strefy styku w pięcioosiowej obróbce powierzchni prostokreślnych frezem stożkowym

The article presents the analysis of the influence of a conical mill’s lead angle on cutter-workpiece engagement. A methodology of performing a machining simulation as well as its results during machining of ruled surfaces with varying angles of torsion is presented.

Experimental determination of residence time distribution in continuous dry granulation

With increasing importance of continuous manufacturing, the interest in integrating dry granulation into a continuous manufacturing line is growing. Residence time distribution measurements are of importance as they provide information about duration of materials within the process. These data enable traceability and are highly beneficial for developing control strategies. A digital image analysis system was used to determine the residence time distribution of two materials with different deformation behavior (brittle, plastic) in the milling unit of dry granulation systems. A colorant was added to the material (20%w/w iron oxide), which did not affect the material properties excessively, so the milling process could be mimicked well. Experimental designs were conducted to figure out which parameters effect the mean residence time strongly. Moreover, two types of dry granulation systems were contrasted. Longer mean residence times were obtained for the oscillating mill (OM) compared to the conical mill (CM). For co-processed microcrystalline cellulose residence times of 19.8–44.4s (OM) and 11.6–29.1s (CM) were measured, mainly influenced by the specific compaction force, the mill speed and roll speed. For dibasic calcium phosphate anhydrate residence times from 17.7–46.4 (OM) and 5.4–10.2s (CM) were measured, while here the specific compaction force, the mill speed and their interactions with the roll speed had an influence on the mean residence time.

Macro- and micro-mixing of a cohesive pharmaceutical powder during scale up

Efficient powder mixing involves a macro- and micro-mixing mechanism, achieved by a combination of various types of mixers. Selection of the mixer is based on the understanding of the cohesiveness of the components in the mixture. In the current study, a cohesive active pharmaceutical ingredient (API), X, was used as the model compound to study the effectiveness of convective mixing in a bin blender and intensive shear mixing with a comil (conical mill). Convective mixing in the bin blender only delivered limited macro-mixing for API X and the resulting blend was heterogeneous at both micro- and macro-scales. After blending in the bin blender, the comilling process added micro-level mixing by introducing locally intensive mechanical shear. The resulting blend showed improved homogeneity at the micro-scale, but was still heterogeneous at the macro-scale. An additional mixing step in the bin blender after comilling was required to ensure the uniformity of the mixture at both micro-and macro-scales. The significance of the second convective mixing to micro-mixing was underscored at commercial-scale manufacture as compared to the development scale. Despite the scale dependency on the comilling step, the extensive shear exerted during the comilling step facilitated further micro-mixing by the convective mixing in the second bin mixing step. The investigation demonstrates that a rational selection of mixing steps with various types of mixers is crucial to achieve both macro- and micro-mixing of cohesive materials from development to commercial scales.

Feature Line Method of Tool Axis Trajectory Planning for Non-developable Ruled Surface Flank Milling with Conical Tools

Aiming to the problem of complex tool axis trajectory planning for flank milling non-developable ruled surface with conical milling tools,an intuitive and simple tool axis trajectory generation method is presented. According to the properties of conical surface,the normal mapping curve is defined,i.e. the set of points which are the normal projection of all points of tool axis on the design curved surface,so that the problem of tool envelope surface approximating to design surface,is convert into the least squares approximation problem of normal mapping curve to characteristic curve for every tool position,and the generation method of ideal feature line of single tool position before the formation of tool envelope surface is given. Using the two-offsetting method the initial tool position is generated. Then based on this,the tool axis pose can be described by a function of three rotational and three translational motion parameters,consequently,a non-dominant function between single tool position optimization condition and six motion parameters is built. In the solving process,the experimental design method of Latin hypercube is used,and through analyzing and optimizing the influence factors of calculation,the optimal tool position is obtained,and then the optimized tool axis trajectory surface is obtained. The actual example calculation showed that the envelope error of optimized tool axis is reduced significantly,and the calculation results are stable. This method provides the theoretical basis for flank milling non-developable ruled surface with conical tools.

Optimizing conditions for wet grinding of synthetic rutile using response surface methodology

In this paper, response surface methodology was applied to optimize the experimental conditions for the wet grinding of synthetic rutile. The effects of parameters such as rotation speed, solids concentration and duration of grinding on grinding efficiency were systematically investigated and the process conditions were optimized, using a nonlinear regression model based on central composite design. The statistical analysis of the results showed that in the range studied, the grinding efficiency of synthetic rutile was significantly affected by the rotation speed of the conical ball mill. According to results from analysis of variance, the value of the determination coefficient (R2=0.9989) indicates that the predicted values are found to be in good agreement with experimental values. The optimized experimental conditions were as follows: a rotation speed of 350 rpm, a solids concentration of 27.31% and a grinding time of 50.31 min, respectively. Under optimum conditions, the predicted grinding efficiency of 94.79% is obtained. The experimental values from the validation experiments were well within the predicted value of the model.

Population Balance Model-Based Hybrid Neural Network for a Pharmaceutical Milling Process

Population balances are generally used to predict the particle size distribution resulting from the processing of a particulate material in a milling unit. The key component of such a model is the breakage function. In this work we present an approach to model breakage functions that has utility for situations in which determination of the breakage function from first principles is difficult. Traditionally, heuristic models have been used in those situations but the unstructured nature of such models limits their applicability and reliability. To address this gap, we propose a semi-empirical hybrid model that integrates first principles knowledge with a data-driven methodology that takes into account the material properties, mill characteristics, and operating conditions. The hybrid model combines a discrete form of population balance model with a neural network model that predicts the milled particle size distribution given material and mill information. We demonstrate the usefulness of this approach for compacted API ribbons milled in a lab scale Quadra conical mill for different materials and mill conditions. Comparisons are also given to the predictions obtained via a purely neural network model and a population balance model with a linear breakage kernel.

Advancing Pharmaceutical Dry Milling by Process Analytics and Robustness Testing

The objectives of this work were to implement on-line dynamic image analysis and to introduce a novel at-line flowability analyzer in pharmaceutical dry milling. We used a pilot-scale conical mill and flowability of a placebo granulate was monitored using a powder avalanching analyzer. Experiments were designed and evaluated by means of response surface methodology in conjunction with robustness testing. The process parameters impeller speed and screen size significantly affected the particle size distribution and flow rate of the milled granules. Feeder speed did not affect the particle size, but displayed a statistically significant influence on the flow responses. Robustness testing was able to capture the effect of noise factors on the responses and showed clear differences between different lots of the placebo granulate in addition to temperature-dependent changes in flow behavior. Thus, on-line dynamic image analysis and at-line flowability characterization, together as complementary process analytical tools, provided valuable information. The combined analysis was of particular interest for testing the process and noise factors so that future process development can profit from this advancement in dry milling.

Different modes of dynamic image analysis in monitoring of pharmaceutical dry milling process

This article focuses on the process analytical technology (PAT) of pharmaceutical dry milling. The first objective is to compare different modes of dynamic image analysis namely, on-line, in-line and at-line for monitoring powder milling. The second objective is to introduce time evolving size and shape analysis (TESSA). Thus, a conical mill was equipped with a dynamic image analysis system which consisted of a xenon flash light and charge-coupled device (CCD) camera. Different pharmaceutical excipients and granulates were chosen as models. The results from the on-line, in-line and the at-line measurement modes showed similar size distributions for the various materials studied, however differences were observed that were mainly attributed to sampling and dispersion. A high correlation of 0.975 ( p < 0.001) was observed between on-line d 50 and at-line d 50 when compared to 0.917 ( p < 0.001) between in-line d 50 and at-line d 50. The concept of TESSA was found to be useful in detecting changes in milling conditions including the successful detection of a damaged screen when intentionally introduced in the milling process. This monitoring approach of particle size and shape has potential to reduce product variability, facilitates process development, and ultimately helps in establishing quality by design concept for the manufacture of solid dosage forms.

Tool path generation method for multi-axis machining of helical milling cutter with specific cross-section profile

The geometry of helical milling cutter with specific cross-section profile is normally generated with form cutter by the toolpath generating method. The general purpose CAD/CAM software can generate the cutter location file of this class of product only by the sculpturing method. To obtain the flexibility of machining process, this paper presents an interference-free toolpath generating method for semi-finish and finish machining of the helical milling cutter. The method for design and machining of the helical milling cutter is established based on the differential geometry and the enveloping theory. In the finish machining of helical milling cutter, the form grinding wheel profile is firstly derived. To reduce the cost and lead time of the generating method with the form-mill cutter for semi-finish machining, a toolpath generating method which combines the advantages of the generating method and sculpturing method was presented. The cutter location uses ball-nose conical end mill is derived according to the geometric characteristics of the enveloping element. The cutting simulations with solid model were performed to verify the proposed toolpath generation method.

Shaping of helical surfaces by profiling circles

The helical surfaces (HSs) have found wide application in the structures of various articles (lead screws, screw conveyors, twist drills, conical milling cutters, and so on). The most common method for obtaining the HSs is machining by the disc milling cutters and the abrasive wheels. The HS is a complex surface, the profile of which does not coincide with the disc tool at any section. Therefore we must solve the profiling problem, i.e., we must define the shape and dimensions of the tool and the workpiece. In this connection we can identify the direct and inverse profiling (shaping) problems, and they are both ambiguous. The result of their solution depends on the adopted values of the parameters of the setting of the tool relative to the workpiece. The setting parameters influence the constructive parameters of the tool or the workpiece, and also the producibility of the design, the effectiveness of the tool, and the very feasibility of the machining of the HS (in solving the direct problem). It is possible to solve the direct and inverse profiling problems by various methods: graphic, analytic, and grapho-analytic. The analytic methods deserve the most attention, since they not only make it possible to determine the profile of the tool or the part, but also make it possible to analyze the influence of each basic parameter on the profile and the dimensions of the tool or the part. These methods are based on the search for the common tangents or normals at the points of touching of the disc tool and the part, and also the derivation and solution of the contact equations that define the moments of the touching of the surfaces of the part and the tool. In view of the use of the quite complex mathematical apparatus, the analytic methods are characterized by the difficulty of the calculations; moreover, these methods do not ensure clarity of the design process and are quite complex for the development of the universal models. However, the analytic profiling methods dominate at the present time, since they are characterized by a high level of the accuracy of the calculations with the use of the modern computers. The large number of these methods (1‐3 and others] and their variety requires rational recommendations relating to the use of any particular technique; these recommendations are not available at the present time. The selection process is further complicated by the fact that the profile of the part is specified by various techniques in the different methods. The shaping of the HS is accomplished by the points of the cutting edges of the tool that lie on its outer surface. Thus, at any section of the disc tool along its axis the shaping process is performed by an elementary circle of definite radius. The contact equation that is obtained for the elementary circle is independent of the shape of the disc tool, i.e., it is a general expression. Examining a sufficient number of these circles, we can determine the coordinates of the points of the contact of the tool with the part along the entire profile. The method of profiling circles is based on this concept [4]. There is no fundamental difference between the direct and inverse profiling problems, since the same shaping scheme is used. But it is simpler to solve the inverse problem because of the absence of the transcendental equation of the contact. Therefore, we shall first examine the application of the profiling circle method for the solution of the inverse profiling problem . The analytic scheme of the shaping of the HS by a contour milling cutter of curvilinear profile is shown in Fig. 1. We fix the coordinate system (CS) X 1 Y 1 Z 1 with the workpiece, directing the axis X 1 along the workpiece axis; we fix the CS X 0 Y 0 Z 0 with the tool (milling cutter of diameter D φ ). We shall consider that at the initial moment of time the origins O 0 and O 1 of the two CSs coincide, the axis Z 0 coincides with the axis Z 1 , and the axes X 0 , Y 0 , X 1 , and Y 1 lie in the same plane (the axis Y 0 is parallel to the axis of the tool). We take the following initial values. The setting parameters : the interaxis distance A ; the angle e of crossing of the axes of the tool and the part; the lateral