Grinding Device Research Articles

An Efficient, Robust, and Inexpensive Grinding Device for Herbal Samples like Cinchona Bark.

An effective, robust, and inexpensive grinding device for the grinding of herb samples like bark and roots was developed by rebuilding a commercially available coffee grinder. The grinder was constructed to be able to provide various particle sizes, to be easy to clean, and to have a minimum of dead volume. The recovery of the sample when grinding as little as 50 mg of crude Cinchona bark was about 60%.Grinding is performed in seconds with no rise in temperature, and the grinder is easily disassembled to be cleaned. The influence of the particle size of the obtained powders on the recovery of analytes in extracts of Cinchona bark was investigated using HPLC.

Design of an electrochemical micromachining machine

Electrochemical micromachining (μECM) is a non-conventional machining process based on the phenomenon of electrolysis. μECM became an attractive area of research due to the fact that this process does not create any defective layer after machining and that there is a growing demand for better surface integrity on different micro applications including microfluidics systems, stress-free drilled holes in automotive and aerospace manufacturing with complex shapes, etc. This work presents the design of a next generation μECM machine for the automotive, aerospace, medical and metrology sectors. It has three axes of motion (X, Y, Z) and a spindle allowing the tool-electrode to rotate during machining. The linear slides for each axis use air bearings with linear DC brushless motors and 2-nm resolution encoders for ultra precise motion. The control system is based on the Power PMAC motion controller from Delta Tau. The electrolyte tank is located at the rear of the machine and allows the electrolyte to be changed quickly. This machine features two process control algorithms: fuzzy logic control and adaptive feed rate. A self-developed pulse generator has been mounted and interfaced with the machine and a wire ECM grinding device has been added. The pulse generator has the possibility to reverse the pulse polarity for on-line tool fabrication.

Modelling of vertical spindle mills. Part 1: Sub-models for comminution and classification

A new mechanistic model for vertical spindle mills (VSM) has been developed by Julius Kruttschnitt Mineral Research Centre (JKMRC) at the University of Queensland. Unlike the previous work in the literature, which treats the VSM as a “black box”, the present work incorporates two sets of variables in the model: (1) the coal specific property, and (2) the machine specific variables. The VSM model is presented in two parts/papers. The first part presents the sub-models for comminution and classification in the VSM. The second part describes the integration of the sub-models to simulate industrial scale E-Mill, MPS and CKP mills. The sub-models include mill power prediction, size specific energy calculation, size dependent breakage function, product size distribution estimation, elutriation classification and gas cyclone classification. The coal breakage property was measured with a JKFBC grinding device and modelled using a size-dependent breakage function. The machine specific variables include mill geometry, air classifier geometry, coal feed rate, primary air flow rate, air temperature, air pressure, grinding table rotational speed, mill spider hydraulic load and mill power draw. These variables are incorporated in the comminution and classification functions based on physical principles.

Model predictive control of semiautogenous mills (sag)

The present manuscript focuses on the development of a multivariable control based on the MPC strategy for a semiautogenous grinding (SAG) device. A previously published specific SAG model that uses a deep analysis of the internal device behavior was used for the MPC strategy development. SimulinkTM software was used for the dynamic representation and control development. The selection of controlled and manipulated variables took into account performance and functional criteria. The power draw, volumetric filling level, and a size reduction percentage were the controlled variables, while the fresh ore feed rate, fresh water feed rate, and the SAG rotation speed were the manipulated variables. The controller response showed a suitable control behavior independent of the noisy multivariable modification.

A new purge and trap headspace technique to analyze low volatile compounds from fluid inclusions of rocks and minerals

A new method for the analysis of trace gases from fluid inclusions of minerals has been developed. The purge and trap GC–MS system is based on the system described by Nolting et al. (1988) and was optimized for the analyses of halogenated volatile organic compounds (VOCs) having boiling points as low as −128°C (carbon tetrafluoride).The sample preconcentration cold trap consists of a U-shaped glass lined steel tube (GLT™), that is immersed into a small liquid nitrogen Dewar vessel for cooling. A rapid desorption step heats up the preconcentration tube in <30s from −196°C to 200°C. The process is carried out by using a pressurized air stream to dissipate the liquid nitrogen followed by resistive heating of the trap. The design of the cold trap and the direct transfer of desorbed analytes onto the GC column via a deactivated capillary column retention gap made sample refocusing within the GC oven unnecessary. Furthermore, a special air-tight grinding device was developed in which samples ranging from soft halite (hardness 2, Mohs scale) to hard quartz (hardness 7) are effectively ground to average diameters of 1000nm or below, thereby releasing gases from fluid inclusions of minerals. The gases are then purged from the grinding chamber with a He carrier gas flow. The detection and quantitative determination of gases, such as SF6 and CF4 released from fluorites and CH3Cl from halite samples is demonstrated.

Experimental Study on Ultrasonic Grinding of Nano-ZrO&lt;sub&gt;2&lt;/sub&gt; Ceramics by Single-Grit

The ultrasonic-assisted single-grit grinding device is designed which can be used to efficiently simulate grinding process, and the comparative tests of single-grit ultrasonic grinding are carried out between Nano-ZrO2 ceramics and ZTA ceramics under different grinding depth. The experimental results show that the bigger the scratch depth was, the greater damage degree of material was, nano-ZrO2 ceramics’ grooves is smoother than that of ZTA ceramics and the damage of its material is minor; ultrasonic vibration broadens the range of plastic cutting of Nano-ZrO2 ceramics in some degree. The experimental phenomena also show that the rolling role of abrasive particle can be conducive to material plastic deformation.

Methodology An improved protocol and a new grinding device for extraction of genomic DNA from microorganisms by a two-step extraction procedure

Current protocols to extract genomic DNA from microorganisms are still laborious, tedious and costly, especially for the species with thick cell walls. In order to improve the effectiveness of extracting DNA from microbial samples, a novel protocol, defined as two-step extraction method, along with an improved tissue-grinding device, was developed. The protocol included two steps, disruption of microbial cells or spores by grinding the sample together with silica sand in a new device and extraction of DNA with an effective buffer containing cell lysis chemicals. The device was prepared by using a commercial electric mini-grinder, adapted with a grinding stone, and a sample cup processed by lathing from a polytetrafluoroethylene rod. We tested the method with vegetative cells of four microbial species and two microbial spores that have thick cell walls and are therefore hard to process; these included Escherichia coli JM109, Bacillus subtilis WB600, Sacchromyces cerevisiae INVSc1, Trichoderma viride AS3.3711, and the spores of S. cerevisiae and T. viride, respectively, representing Gram-positive bacteria, Gram-negative bacteria, yeast, filamentous fungi. We found that this new method and device extracted usable quantities of genomic DNA from the samples. The DNA fragments that were extracted exceeded 23 kb. The target sequences up to about 5 kb were successfully and exclusively amplified by PCR using extracted DNA as the template. In addition, the DNA extraction was finalized within 1.5 h. Thus, we conclude that this two-step extraction method is an effective and improved protocol for extraction of genomic DNA from microbial samples.

Investigation of Surface Quality on Dry Belt Grinding of Ti6Al4V Alloy

This paper deals with an investigation of surface integrity of Ti6Al4V alloy with zirconia alumina and SiC belts. The experiments were conducted under dry grinding environments in milling machine XS5040 equipped with belt grinding device. Microcosmic geometry parameters were measured with TALYSURF5 instrument, the surface morphology machined workpiece and the phase structure was analyzed using 3D viewer microscope, surface hardness for ground surface was measured by HXS-1000A instrument. The results show that surface quality maintain better level during a long period, the grinding affected zone was small(≤15μm), zirconia alumina belt has excellent performance than SiC belt during dry grinding Ti6Al4V alloy.

Investigation of Abrasive Wear in the Dry Belt Grinding of Titanium Alloy

This paper was dedicated to elucidate an investigation of abrasive wear and surface topography of Titanium alloy TA15 on dry grinding with zirconia alumina belt. In the investigation, experiments were performed on milling machine XS5040 equipped with assembled belt grinding device. The wear abrasive, surface morphology of machined belt in different phase were analyzed using 3D viewer microscope. The results show that the wear of belt abrasive is mainly steady attritions wear since zirconia alumina belt was stable on dry grinding. At higher grinding force, the abrasive was found to undergo dislodging prior to being gradually worn. So zirconia alumina belt has excellent performance in the dry grinding titanium alloy.

Potential of dry fractionation of wheat bran for the development of food ingredients, part I: Influence of ultra-fine grinding

Wheat bran is an undervalued by-product of white flour and has great nutritional potential due to its high content in fibres and bioactive compounds. Micronized bran could be used as a food ingredient to improve the nutritional potential of cereal products, or be used as a starting material for other processes (bioactive compound extraction or bran fractionation). The aim of this work was to find a way to efficiently decrease the particle size of bran. The influence of the grinding temperature (ambient or cryogenic grinding) on the granulometric distribution of particles, their composition, and their microstructure was studied, at lab-scale and pilot-scale. It showed that the intrinsic characteristics of bran (glass transition within intermediate layers at −46 °C) had more influence on its grinding behaviour than the type of grinding device used: the particles size distributions obtained after grinding at lab-scale and pilot-scale were very similar. At both scales, the granulometric curves were narrow for cryogenic grinding, while for ambient grinding they were spread over the whole particle size range. Ultrafine particles were obtained in both ambient and cryogenic conditions. Negative temperatures, by increasing the material’s brittleness, favoured a fast fragmentation of bran: one step of cryogenic grinding allowed a median particle size of nearly 50 μm to be reached, whereas three successive steps of ambient grinding were needed for the same result. On the other hand, ambient temperature favoured the dissociation of the different constituent layers of wheat bran, and produced less composite particles than cryogenic grinding.

Design and Study of Lapping Device in Large Caliber Spherical Surface Valve Core

A special grinding device is designed to solve the problems of the shape precision, surface quality and grinding efficiency. The device is based on the sine generator and triaxial speed to achieve the ideal Grinding trajectory. The accuracy of grinding in spherical valve core &amp; surface quality is assured and improved by three-dimensional elastic support, pressurized floating contact and auto centering device in core and lapping tools. The grinding efficiency is highly enhanced by using the lateral and vertical speeding workpiece installration and the automatic control. The device is worth widely being applied to achieve a good large diameter hemispherical workpiece grinding.

Study on Precision Grinding of Involute Cams on a Double-Disc Device

The involute cam is used for generating tooth form of an involute gear in gear grinder with involute cam-link stopper, and its profile error is one of the factors which decide the tooth form precision of gear. The conventional processing means of involute cams can't achieve a sufficient accuracy. In this paper, a double-disc mode grinding device is introduced. Based on analysis of grinding principle, the device's structure and working process are described, and the main sources of grinding profile errors are analyzed. It is confirmed that the introduced device has the ability of accomplishing a highly precise grinding of involute cams.

Entwicklung einer Kryo-Schlifftechnik für Felsenbeinpräparate: eine neue Möglichkeit zur Beurteilung ex vivo implantierter CI-Test-Elektroden / A novel cryo-grinding technique for evaluating new cochlear implant electrodes after ex vivo insertions in temporal bone specimens

Prior to clinical application, newly developed prototypes of cochlear implant electrode arrays must prove their suitability with the smallest possible tissue damage in ex vivo temporal bones. So far, after insertion of the electrodes the temporal bone specimens have to be processed in a rather intricate technique, including embedding, sectioning or grinding prior to histological evaluation. The question remains whether for special indications this time-consuming method, which even causes artifacts, can be replaced by a new technique based on cryo-grinding. The main principle of the method described is to grind the temporal bone with the inserted electrode in a frozen state, provided by a fixation device filled with dry ice. After creating a plane surface and staining it (still in a frozen state), the specimen can be examined and photographed with a projection microscope. This procedure is continued by subsequently grinding and examining new surfaces in defined distances. In numerous trial runs the method proved feasible, saving much time and manpower. After grinding, each plane could be examined sufficiently; the site of the electrodes and the corresponding tissue damage could be documented properly. The new concept of cryo-grinding provides relatively easy and fast examinations of temporal bones after inserting test electrodes. The examiner is enabled to correlate his "sensations" during the insertion (e.g., smoothness, resistances) almost directly with the morphologic findings, without having to wait a long time while the temporal bone specimens are being processed conventionally. Furthermore, this method avoids artifacts due to soft tissue shrinking during drying. In further steps of development, the grinding device will be optimized for standard use.

Mathematical Models for a Closed-Circuit Grinding

New continuous and discrete mathematical models are elaborated for describing some types of closed-circuit grinding mill-classifier systems. Based on the discrete model computer simulation is also developed for investigation of grinding processes. The starting point in developing the model is the continuous grinding equation for the open-circuit grinding which is a partial integro-differential equation describing axial mixing and breakage of particles in the grinding mill. The convective flow in the mill is modeled as particle size-dependent process. The boundary conditions at the inlet and outlet of the mill, the initial conditions, and the equations describing the operation of the classifier and its mass balance are the additional equations of the model. The properties and capabilities of the new computer model are demonstrated and analyzed by simulation developed in Matlab environment. The effects of all parameters of the grinding process, among others of parameters of the classifier, are studied via simulation. The main statistical characteristics of the steady states, the hold-up of the grinding device and the operation of the classifier are also studied. The models presented appear to be very flexible and useful tools for analysis and design of closed-circuit grinding processes, and are suitable for the deeper understanding of the aimed processes.

Identification at autopsy of pulverized pills in lungs of a first-time methadone user

We recently encountered a 25-year-old white man who died of substance abuse including methadone. The route of administration of the drug(s) appears to have been insufflation. He was found dead at home. There were bottles of prescribed medications and an empty bottle of non-prescribed methadone. There was a grinding device nearby. At autopsy, no needle tracts were identified. Microscopically, the bronchi had desquamated ciliated respiratory epithelium admixed with red-brown pigment, which was found under plane-polarized light to be comprised of birefringent finely-granular material consistent with pulverized pills. Blood toxicology was positive for tetrahydrocannabinol, sertraline, nicotine, and methadone. The cause of death was ruled drug interactions with cerebral and pulmonary edema, the manner of death accidental. The decedent fit a profile of a victim of prescription drug abuse, for whom the mode of administration of drugs may be altered from intended use in as many as 80% of cases.

A Micro Ultrasonic Grinding Device with Very High Frequency and its Application

A Micro Ultrasonic Grinding Device with Very High Frequency and its Application

Liberated 0–10 μm particles from sulphide ores, their production and separation—Recent developments and future needs

The general types of industrial behaviour of liberated valuable sulphide minerals in the 0–10 μm size fraction are described and tests to explore on-site at a concentrator the general nature of any deficient behaviour are discussed. In addition, the general types of behaviour of the gangue minerals in this size fraction are also described in terms of their mechanisms for recovery. These behaviours are also discussed in terms of the type of grinding device and grinding environment in which they were produced and the target grinding product size. Major recent improvements in the industrial capabilities of grinding devices are discussed. Present difficulties in characterization of particles in the 0–10 μm range are described and desirable improvements for the future are outlined. Further, desirable improvements for industrial processing of valuable minerals in this size range are discussed along with some remedial actions.

The influence of mold temperature on the fit of cast crowns with commercially pure titanium

Commercially pure titanium (CP Ti) has been widely applied to fabricate cast devices because of its favorable properties. However, the mold temperature recommended for the manufacture of casts has been considered relatively low, causing inadequate castability and poor marginal fit of cast crowns. This study evaluated and compared the influence of mold temperature (430 degrees C--as control, 550 degrees C, 670 degrees C) on the marginal discrepancies of cast CP Ti crowns. Eight bovine teeth were prepared on a mechanical grinding device and impressions were used to duplicate each tooth and produce eight master dies. Twenty-four crowns were fabricated using CP Ti in three different groups of mold temperature (n = 8): 430 degrees C (as control), 550 degrees C and 670 degrees C. The gap between the crown and the bovine tooth was measured at 50 X magnification with a traveling microscope. The marginal fit values of the cast CP Ti crowns were submitted to the Kruskal-Wallis test (p = 0.03). The 550 degrees C group (95.0 microm) showed significantly better marginal fit than the crowns of the 430 degrees C group (203.4 microm) and 670 degrees C group (213.8 microm). Better marginal fit for cast CP Ti crowns was observed with the mold temperature of 550 degrees C, differing from the 430 degrees C recommended by the manufacturer.

Microgrinding of deep micro grooves with high table reversal speed

Recent progress in the miniaturization of electronic items introduces manufacturing challenges for achieving both better surface integrity and high throughput. Controlled thermal interaction processes physically vaporize the material for producing the miniature components but the poor surface and sub-surface characteristics introduce a niche for thermo-mechanical processes, particularly microgrinding. Prior microgrinding attempts have focussed on axi-symmetrical components of hard-brittle materials. For non-axi-symmetrical, high-aspect ratio miniature components, edge chipping was encountered. This paper reports a new grinding method that uses “high table reversal speeds” for reducing the “grit cut load” and hence facilitates the microgrinding process. An arrangement that functions on the principles of four bar linkage with a sliding and rotating pair was devised. This arrangement was designed to reciprocate between 300–1000 strokes/min for a stroke length of 10–70 mm. As a result the table feed rate range was increased from the conventional 300–20 000 mm/min to 5000–55 000 mm/min. Process characterization of the new grinding method was observed for hard-brittle materials. A physical model was developed which links the process parameters with appropriate boundary conditions and the model was verified experimentally. The experimental model was used to explain the mechanism of grinding while employing high table reversal speeds. Process characterization includes grinding force, grinding-ratio, grinding wheel topography, surface finish and SEM study. Also, the process was applied to produce mold-insert which in turn was used for molding the micro-mechanical cantilever sensor parts. Deep slots of size: 1.2×0.1×1.5 mm with an aspect ratio of 15 was successfully produced with this method. The new grinding device and method promote microgrinding through integration to an existing grinder and therefore reduces the additional cost on the capital resources.

Comparison of enzymatic and mechanical methods for the collection of bovine preantral follicles

AbstractA comparison was made of various devices to obtain preantral follicles from bovine ovaries. The most productive collection methods in terms of number of follicles obtained were the tissue chopper and the grinder method, with an average number of 122·25 (s.e. 5·06) and 120·45 (s.e. 6·89) preantral follicles, respectively. These were followed by ficoll gradation (119·90, s.e. 7·95), mincer (101·75, s.e. 3·98), cell dissociation sieve (100·50, s.e. 3·42) and homogenizer (95·75, s.e. 6·38). For enzymatic digestion, more time was needed and the method was less productive. Microdissection could supply good quality (80% live when collected), larger sized follicles (120 to 220 µm) but with the lowest yield (10·65, s.e. 0·94) per ovary. The isolated follicles did not show any difference (P &gt; 0·05) in viability until day 7 of in-vitro culture irrespective of method used to harvest follicles. Accordingly the new grinding device can be recommended as a replacement for the existing mechanical devices as it can yield the same percentage (47%) of live preantral follicles but of a wider diameter range (40 to 180 µm) per ovary.