Feed Grinding Research Articles

On the kinematics of creep feed grinding

We consider kinematic dependences of creep feed grinding. We give an analytical model of this process and formulas that relate the area of a nominal section removed during one turn of the grinding disk and the arc length of the contact during grinding stages. Using the obtained relations, we perform a kinematic analysis of the process and derive functional dependences of the nominal section area and thickness, the run, and the cutting ability on the contact arc length and time for different grinding stages and modes. These functional dependences are polynomials of the first to third degrees.

Creep feed grinding of gamma titanium aluminide and burn resistant titanium alloys using SiC abrasive

Following a brief introduction to titanium alloys and their machinability, the cutting performance of a gamma titanium aluminide intermetallic ( γ-TiAl) alloy: Ti–45Al–8Nb–0.2C wt% and a burn resistant titanium (BuRTi) alloy: Ti–25V–15Cr–2Al–0.2C wt%, is compared with creep feed grinding using SiC abrasive. The work utilised 2 separate L9 Taguchi fractional factorial arrays. Typically G-ratios were a factor of ∼10× greater for γ-TiAl than BuRTi, with on average ∼10% lower maximum power and ∼25% lower maximum specific energy for the γ-TiAl alloy. A combination of a moderately high wheel speed: 35 m/s, low depth of cut: 1.25 mm and low feed rate: 150 mm/min, produced the lowest average workpiece surface roughness (Ra∼1.4 μm). Workpiece surface integrity evaluation indicated that with lower operating parameter levels, in particular a wheel speed of 15 m/s, surfaces free of burn and cracks could be produced, while at higher wheel speeds: 35 m/s, extensive workpiece surface burn was evident, with the γ-TiAl alloy suffering extensive cracking. Microhardness measurements showed in some instances slightly increased workpiece surface hardness of around 50–60HK 0.025 for the BuRTi alloy and 200HK 0.025 for the γ-TiAl material over respective bulk hardness values of 375HK 0.025 and 400HK 0.025.

Research of Surface Hardening Based on Transverse Feed Grinding

The structure and performance of the hardened layer in this paper has been researched by means of transverse feed grinding 40Cr steel on a plane grinding machine, the result shows that under the action of the grinding temperature field, there are different structural change rules and distributing characteristics of micro-hardness. Although there is always a softened band, which is made up of a transitional area and an unhardened area or a temper area in the hardened layer, the reasonable softened band is conducive to the improvement of wear-resistant quality of a hardened layer under the condition of oil lubrication.

Experimental Research on the Ground Surface Quality of Creep Feed Ultrasonic Grinding Ceramics (Al2O3)

In order to grind the ceramic blade surface with the Numerical Control contour evolution ultrasonic grinding method using the simple shape grinding wheel, primary comparative experiments of creep feed grinding with and without ultrasonic vibration were carried out to grind Al2O3 ceramics so as to implore the effects of different process parameters on the machined surface quality. It can be concluded that when the direction of ultrasonic vibration is parallel to the direction of creep feed, the value of the surface roughness will be decreased; otherwise the surface quality will become worse. With the ultrasonic grinding method, the slower feed-rate, the smaller grinding depth, the higher grinding speed and the compound feed grinding method should be applied in order to improve the surface quality. The creep feed grinding mechanisms with and without ultrasonic vibration were analyzed theoretically from the experimental results. With the selected grinding parameters resulted from the experiments, the feasibility experiment of ultrasonic grinding ceramic blade surface was carried out.

The effect of expander processing and screen size on nutrient digestibility, growth performance, selected faecal microbial populations and faecal volatile fatty acid concentrations in grower–finisher pigs

A 2 × 2 factorial experiment with grower–finisher pigs was conducted to investigate the effect of screen size and expander processing (yes and no) on digestibility, pig performance, selected faecal microbial populations and faecal volatile fatty acid concentrations. The feed was ground at two levels (using a 3 or 6 mm hammermill screen) to obtain a fine or coarse feed and given to the pigs as either raw or expanded feed. The diets were expander processed at 105 °C for 5 s at 35-bar pressure. Fine grinding increased the coefficient of total tract apparent digestibility (CTTAD) of gross energy of the diets (P<0.05) and reduced faecal dry matter concentration (P<0.05). Pigs offered the 3 mm diets had a lower (P<0.05) feed intake (2.47 kg/day versus 2.55 kg/day, S.E.M. 0.029) and a better (P<0.01) feed conversion ratio (2.61 kg/kg versus 2.80 kg/kg, S.E.M. 0.034) than the pigs offered the 6 mm diets. Expander processing had no effect on CTTAD or growth performance. There was a significant interaction (P<0.05) between screen size and expander processing on the faecal Lactobacilli and Enterobacteria population. Coarse grinding increased (P<0.05) the faecal Lactobacilli population and decreased (P<0.05) faecal Enterobacteria population when the diets were not heat treated. However, screen size had no effect on Lactobacilli and Enterobacteria population when the diets were expanded. Coarse grinding increased (P<0.05) the total faecal volatile fatty acid concentration and molar proportions of propionic acid and butyric acid while decreasing (P<0.05) the faecal proportions of acetic acid compared to fine grinding. In conclusion, fine grinding of feed improved feed intake and feed conversion ratio. However, it did increase faecal Enterobacteria populations. Expander processing had no effect on pig performance.

It's a grind [grinding technology

VIPER grinding was developed by Rolls Royce in collaboration with the Grinding Division of Makino-NCMT as a replacement for creep feed grinding of Inconel and other nickel-based alloys using CBN wheels. Using inexpensive vitrified aluminum oxide wheels of small diameter mounted in the spindle of a horizontal machining center (HMC), VIPER grinding has been shown to be 10 times faster at removing metal than milling. To fully understand the potential of the VIPER technology, the paper describes the features of several machining centers including the Makino A55, the Makino A99, and the Makino A100.

Creep Feed Surface Grinding NC Technology by Cup Wheel in Radome Machining

The radome made of special ceramic is a workpiece needed to be machined precisely. The machining precision of the exterior contour of the workpiece effects the performance of the radome directly. Around improving on machining technology of the traditional radome’s exterior-surface, the creep feed surface grinding by cup wheel based on line enveloping is presented in this paper. Due to combining the advantages such as large material removal rate, high machining precision and high efficiency of creep feed grinding and the superiority of cup wheel, the workpiece with perfect surface quality can be reached. Furthermore, the mathematics model of the geometric locus of grinding wheel head rotating center is established by using the linear interpolation algorithm, with a combination of the equal-space and equal-error method. The existing NC grinding machine with 2-axis simultaneous motion is transformed into 3-axis simultaneous motion (adding an axis of rotation B) and its feasibility applied to the exterior contour machining has been verified.

Measuring detergent fibre and insoluble protein in corn silage using crucibles or filter bags

Different methods exist for the determination of fibre concentration in feeds. To determine, whether fibre recovery and the contamination of fibre by nitrogenous compounds are altered, we measured fibre concentrations in a diverse set of corn silages using three method modifications and two extraction/filtration systems. Thirty-three corn silages, obtained from a commercial feed analysis laboratory, were dried (55°C for 24 h) and ground to pass through a 1-mm screen of a cutter mill before analysis. All samples were extracted in neutral detergent with the inclusion of sodium sulphite (neutral detergent fibre or NDF), α-amylase (neutral detergent residue or NDR) or both (amylase-treated neutral detergent fibre or aNDF), and using either Gooch crucible (CRUC) or filter bag (FBAG) systems. The aNDF method obtained the lowest and similar average fibre concentrations for both CRUC and FBAG (433 and 433 g/kg, respectively). Fibre concentration of NDR was greater (456 and 449 g/kg for CRUC and FBAG, respectively) than aNDF. Fibre concentration was greater for NDF (473 g/kg) than for NDR and aNDF (449 and 433 g/kg, respectively) when using FBAG. Poor extraction occurred for FBAG when α-amylase was not used. For CRUC, NDF and NDR concentrations were similar (456 g/kg), although filtration of fibre residue after extraction without α-amylase was difficult. Neutral detergent insoluble crude protein (ICP) was similar for NDF and aNDF, and slightly greater FBAG than for CRUC systems (8.4 and 9.6 g/kg, respectively). With both FBAG and CRUC, ICP was greater for NDR determined without sulphite (12.5 and 14.2 g/kg, respectively) than for aNDF (8.6 and 9.7 g/kg, respectively). The lower fibre concentration for aNDF method was attributed to less starch contamination when compared to NDF and to less protein contamination and possibly to extraction of phenolic compounds when compared to NDR. Concentration of acid detergent fibre (ADF) was greater for CRUC than for FBAG, although this difference was minimal (266 and 261 g/kg, respectively). Acid detergent ICP was similar for CRUC and FBAG systems and averaged 4 g/kg. We observed that amylase and sulphite affect the measurement of NDF concentration in corn silage. It is crucial that authors and laboratories accurately describe how they measure NDF and clearly indicate by acronym the method they used. Although the extraction/filtration system did not affect the determination of NDR and aNDF, the FBAG system generated higher NDF concentrations for corn silage when amylase is not used.

Study on Forming Mechanism of Surface Hardening in Two-Pass Grinding 40Cr Steel

We had done the two-pass grind-hardening experiment on 40Cr steel using the conventional aluminum grinding wheel on a surface grinder, compared the structure and performance of the hardened layer of one-pass grinding with those of two-pass grinding and analyzed the forming mechanism of two-pass grinding hardened layers. The results show that there are a similar martensite structure and change rules of hardened layer of one-pass grinding and two-pass grinding in spite of the different of initial structures, for martensite has tempered by the action of the creep feed grinding temperature field. The depths of hardened layer, microhardness and wear resistance have further improved, but the maximal compressive residual stress and its influencing depth of hardened layer have decreased. The forming mechanism of the two-pass grinding hardened layer is the same as that of the grinding hardened layer of quenched steel.

Research on Genetic Optimization of Special Spiral Rod Grinding Process

In the grinding process of special spiral rods, the actual feed rate is far below the allowable limit, resulting in great efficiency waste. To tackle the problem, this paper presents a controlling strategy which significantly improves rough grinding efficiency through changing grinding feed rate, enhances work-piece surface quality and shortens the processing time. Based on the establishment of the work cycle model of the special spiral rod grinding process, the strategy sets the grinding efficiency of each individual rod section as the objective function, thus via genetic algorithm realizes an optimal calculation on grinding feed rate variable and resolves the power and roundness constraint problem. Through computer simulation, an optimal grinding control plan is obtained which can help the grinding process to achieve overall optimization.

Heat flux distribution model by sequential algorithm of inverse heat transfer for determining workpiece temperature in creep feed grinding

The purpose of this study is to determine the heat flux distribution and to estimate the workpiece temperature in creep feed grinding. The sequential algorithm of the inverse heat transfer was used for determining the heat flux distribution. The amount of heat flux to the workpiece, the energy partition and the convective heat transfer coefficients both at the front and at the back of the heat flux were determined. Three heat source models using the determined amount of heat flux were applied to estimate the workpiece temperature. The workpiece temperatures estimated by the heat source models were compared with that measured by the embedded thermocouple. The scalene triangle model correlated best with measured and theoretical temperature profiles obtained for creep feed grinding.

Profile Grinding of Superalloys with Ultrafine-Crystalline cBN Wheels

This paper deals with the grinding characteristics of newly developed polycrystalline cBN (cBN-U) abrasives in creep feed profile grinding of nickel-based superalloys. Experiments for producing a V-shaped groove on a flat surface in one pass by creep feed grinding have been carried out using the new polycrystalline cBN-U and representative conventional cBN (cBN-B) grits. When grinding with cBN-U abrasives, both radial wear and profile wear are less, and hence the grinding ratio is around 10 times higher than that with the conventional cBN-B abrasives. Grinding forces in grinding with cBN-U abrasives are reduced by 20-30% compared with those in Grinding with cBN-B abrasives. The cBN-U abrasive is suitable for the applications with a high dimensional accuracy in creep feed profile grinding for nickel-based superalloys, because it gives less profile wear, and hence better form retention, than conventional cBN abrasive.

Selections of working conditions for creep feed grinding. Part(II): workpiece temperature and critical grinding energy for burning

In this study, the workpiece temperature is predicted by the thermal model presented in the previous paper. Also, the grinding energy when the fluid begins to cause boiling is defined as the critical grinding energy for the workpiece burning. Thus, a sequence of experiments are performed. The results show that the predicted workpiece temperatures have great agreement with experimental and published data. Hence, the validity of the thermal model is proved. From the measured signals of grinding force and workpiece temperature, the occurrence of workpiece burning is accompanied with the abrupt rise of both signals. At the moment, the experimental grinding energy is also greater than the critical grinding energy. Thus, the workpiece burning can be predicted or evaluated so as to avoid the working conditions of burning occurrence.

Selections of working conditions for creep feed grinding. Part(III): avoidance of the workpiece burning by using improved BP neural network

In this study, the grinding force of the creep feed grinding are modeled and forecasted by using the improved back propagation neural (BPN) network. The results show that the grinding energy can be accurately predicted by the application of the grinding force model. Due to the previous paper, the workpiece burning occurs as the grinding energy is greater than the critical grinding. Thus, a judgment for the occurrence of the workpiece burning can be achieved. Comparing with the experimental results, the applied algorithm of the improved BPN network is proved to be effective in forecasting the working conditions of the workpiece burning. Thus, a selection scheme of working conditions in view of the avoidance of the workpiece burning is further developed. Considering the working efficiency, the working conditions are selected to maximum metal removed rate, MRRmax. The results show that a larger size of wheel is available to have a better working efficiency.

Design of Implantable Microstrip Antenna for Communication With Medical Implants

The objective of this paper is to design a microstrip patch antenna for communication with medical implants in the 402-405-MHz Medical Implant Communications Services band. Microstrip antenna design parameters are evaluated using the finite-difference time-domain method, and are compared to measured results. The effects of shape, length, size, location of feed point and ground point, substrate and superstrate materials, and their thicknesses are evaluated. An extensive study of the performance of the antennas to changes in these parameters was undertaken. The results of this paper provide guidance in the design of implantable microstrip antennas.

Effects of physical properties of feed on microbial ecology and survival of Salmonella enterica serovar Typhimurium in the pig gastrointestinal tract.

A two-by-two factorial experiment with pigs was conducted to study the effect of feed grinding (fine and coarse) and feed processing (pelleted and nonpelleted) on physicochemical properties, microbial populations, and survival of Salmonella enterica serovar Typhimurium DT12 in the gastrointestinal tracts of pigs. Results demonstrated a strong effect of diet on parameters measured in the stomachs of the pigs, whereas the effect was less in the other parts of the gastrointestinal tract. Pigs fed the coarse nonpelleted (C-NP) diet showed more solid gastric content with higher dry matter content than pigs fed the fine nonpelleted (F-NP), coarse pelleted (C-P), or fine pelleted (F-P) diet. Pigs fed the C-NP diet also showed significantly increased number of anaerobic bacteria (P < 0.05), increased concentrations of organic acids, and reduced pH in the stomach. In addition, pigs fed the C-NP diet showed increased in vitro death rate of S. enterica serovar Typhimurium DT12 in content from the stomach (P < 0.001). Pigs fed the C-NP diet had a significantly higher concentration of undissociated lactic acid in gastric content than pigs fed the other diets (P < 0.001). A strong correlation between the concentration of undissociated lactic acid and the death rate of S. enterica serovar Typhimurium DT12 was found. In the distal small intestine, cecum, and midcolon, significantly lower numbers of coliform bacteria were observed in pigs fed the coarse diets than in pigs fed the fine diets (P < 0.01). Pigs fed the C-NP diet showed the lowest number of coliform bacteria in these segments of the gastrointestinal tract. Pigs fed the coarse diets showed increased concentration of butyric acid in the cecum (P < 0.05) and colon (P < 0.10) compared with pigs fed the fine diets. It was concluded that feeding a coarsely ground meal feed to pigs changes the physicochemical and microbial properties of content in the stomach, which decreases the survival of Salmonella during passage through the stomach. In this way the stomach acts as a barrier preventing harmful bacteria from entering and proliferating in the lower part of the gastrointestinal tract.

Selections of working conditions for creep feed grinding. Part(I)?thermal partition ratios

A thermal model focused on the heat transfer to the fluid, workpiece and grain is developed for creep feed grinding. In this model, the conduction effect in the moving direction of the workpiece is considered which is found to be very significant especially for creep feed grinding. Moreover, the thermal partition ratios to the workpiece, fluid and grain are well defined and discussed. The results reveal that the cooling effect of the fluid is more crucial especially at larger grinding depth and smaller workpiece speed. Furthermore, the promotion of the wheel speed is helpful to reduce the fraction of heat entering the workpiece. Also, the workpiece thermal partition ratio is greatly influenced by the workpiece speed. Its value is even less than 5% as the workpiece speed is smaller than 4 mm/s. Comparing the thermal partition of wet grinding to that of dry grinding, the abrupt increase of heat entering the wheel and workpiece due to the occurrence of boiling in the fluid is verified.

Study on Material Removal Mechanism in Creep Feed Grinding of Alumina Ceramics

Study on Material Removal Mechanism in Creep Feed Grinding of Alumina Ceramics

Basics for In-Process Roundness Error Improvement by a Functional Workrest Blade

A centerless plunge feed grinding process can be conducted “below center” in order to increase process productivity. This statement results from the fact that the workpiece, in such a set up of the grinding gap, is fixed between grinding wheel, control wheel and workpiece rest blade, thus allowing higher feed rates of the grinding wheel support. But when grinding “below center”, the advantage of a higher productivity is accompanied by a negative effect, the arise of a polygonal workpiece form. Regarding only the geometrical rounding effect as one reason for this process characteristic phenomenon, different workpiece center displacements are examined and analytically described. The knowledge of relevant workpiece center movements within a centerless grinding application allows a quantified analysis of the influence of these displacements on the geometrical rounding effect. Deriving from such an analysis, a functional workrest blade is discussed, which influences the stability of the geometrical rounding effect.

Automatic chatter detection in grinding

Two methods for automatic chatter detection in outer diameter plunge feed grinding are proposed. The methods employ entropy and coarse-grained information rate (CIR) as indicators of chatter. Entropy is calculated from a power spectrum, while CIR is calculated directly from fluctuations of a recorded signal. The methods are verified using signals of the normal grinding force and RMS acoustic emission. The results show that entropy and CIR perform equally well as chatter indicators. Based on the normal grinding force, they detect chatter in its early stage, while only cases of strong chatter are detected based on RMS acoustic emission.