Actual Feed Rate Research Articles

0527 A Method for Identification of Control Parameters of NC Machine Tool and its Utilization for High-Speed Machining and Accurate Machining Time Estimation

When cutting freeform surface using NC machine tools, two problems occurred. The first arises because the actual feedrate deviates from the command feedrate. The second is the decreasing surface quality due to the large acceleration and deceleration of the control axes. The main cause is the fact that the toolpath of the NC program does not consider control characters .In this paper, an automatic identification method of a sampling time and a generation method of an NC program that considers sampling time are proposed. In addition, a system is proposed to estimate the machining time. The effectiveness of the proposed methods is confirmed by experiments.

Material removal with constant depth in CNC laser milling based on adaptive control of laser fluence

Computer numerical control CNC laser milling is an innovative technology to produce precision parts in micron and even nanometer scale. However, due to the restriction of dynamic performance of the machine tool, the preset feed rate cannot be reached immediately, and the actual feed rate is unpredictable when the part with rapidly varied geometric feature is machined. At this moment, the incident laser energy is still the default value, so the feed rate below the target value will cause excessive accumulation of laser fluence into the workpiece surface, eventually leading to an inhomogeneous milling depth and developing the excessive heat affect zone (HAZ). Aiming at the problem in CNC laser milling of the parts with rapidly varied geometric feature in this study, a method of real-time adaptive control of laser fluence according to actual feed rate was proposed. Firstly, a prediction model of laser milling depth was established. Then, based on the model and small amount of preliminary trials, laser fluence required at arbitrary feed rate was obtained to realize the material removal with constant depth. Furthermore, the adaptive control technology of laser fluence on the basis of actual feed rate was investigated. By monitoring the actual feed rate of the machine tool and regulating the laser fluence with it, the machining depth of the parts with rapidly varied geometric feature by CNC laser milling can remain constant. CNC laser milling experiments conducted in this paper demonstrate the feasibility and veracity of the adaptive control strategy.

Application of Siemens 840Di System in the Reconstruction of KISC Roll Collar Grinder

This work studies the reconstruction of high-speed roll grinder for sculptured surfaces with high feed rates. Experiments and predictions were focused on representative surfaces of dies and molds, whose geometric complexity and complexity distribution were modified parametrically. CNC programs for machining these surfaces were executed in a HERKULES HSF2CNC machining center with a SIEMENS 840D controller, with different levels of programmed feed rate. Discrepancies between programmed and actual feed rates were evaluated. A mechanistic approach for roll grinder in high-speed milling of sculptured surfaces is proposed. The mechanistic model construction is based on: (a) the frequency distribution of linear interpolation path lengths in the CNC program and (b) a characterization of the machine tool for brisk and smooth movements. Two case studies were used to demonstrate the effectiveness of the proposed approach. The reconstruction model is capable of the manufacturing.

Scale-up and optimization of a two-stage molten salt oxidation reactor system for the treatment of cation exchange resins

A prototype two-stage MSO (molten salt oxidation) reactor system with a capacity of 10kg/h was developed based on the test results of lab-scale and bench-scale MSO systems. This study first discusses the features of the prototype MSO reactor system. The second part of the study attempts to identify the proper conditions of the prototype two-stage MSO reactor system, where each reactor performs different functions. The volatility of radioactive elements doped in the spent resins was first investigated to establish the proper operating conditions of the primary MSO reactor. A parametric model study of the secondary MSO reactor for the oxidation of hydrocarbons from the primary reactor and an experimental validation were then performed to establish the optimum conditions for the two-stage MSO reactor system. The retention of cesium was greatly influenced by the pyrolysis temperature. The highest pyrolysis temperature with cesium retention of ≥99.9% was 790°C and this was established as the optimum primary reactor temperature. The optimum conditions of secondary MSO reactor for the substantial oxidation of hydrocarbons generated from the primary MSO reactor were determined to be λ (the ratio of actual air feed rate per stoichiometric air rate) of 2, and a temperature of 800°C.

Finite element simulation of diamond tool geometries affecting the 3D surface topography in fly cutting of KDP crystals

Diamond tool has significant influences on the finished surface quality in fly cutting of potassium dihydrogen phosphate (KDP) crystals. In this work, the nanoindentation and dimensional analysis are employed to establish the material constitutive equation of KDP crystals, i.e., the variation curve of flow stress vs. plastic strain. As expected, a novel 3D finite element (FE) model is developed for diamond fly cutting of KDP crystals, and the generation of 3D surface topography is simulated by multi-run cutting calculations, in which the movements of diamond tool are configured to be identical to the actual feed rate and cutting velocity. Subsequently, the coordinates of the nodes on the topmost surface as freshly machined are collected to evaluate the surface roughness, which enables the detailed analyses of the effect of diamond tool geometries on the achieved surface roughness of KDP crystals. The results suggest an optimal selection of tool geometries, i.e. −25° rake angle and 8° clearance angle. With the increment of tool nose radius, surface roughness decreases correspondingly. Moreover, the larger defect or sharpness of tool cutting edge produces the worse surface roughness. Diamond fly cutting experiments are carried out with different rake angles, in which the cutting parameters are the same as the values used in FE simulations. The measured surface roughness has a satisfied consistency with the simulated data, which demonstrates that the developed 3D FE cutting model and the related simulations are reliable.

The effects of intermittent food-deprivation on growth, digestive enzyme activities and serum biochemical indices in the rice-field eel(Monopterus albus)

The experiment was carried out to investigate the effects of intermittent food-deprivation on growth,digestive enzyme activities and some serum biochemical indices in the rice-field eel,Monopterus albus.A 64-day growth trial with five feeding regimes was conducted using the live tubificid worms(Limnodrilus hoffmeisteri)as the food at(25±1)℃.Groups of fish were deprived of food for 1,2,4,8 day(s)and then followed by satiation re-feeding for the corresponding day(s),respectively(i.e.S1F1,S2F2,S4F4 and S8F8 groups).The fish fed to satiation daily throughout the experiment served as the control group(i.e.C).The results showed that,deprived fish had significantly lower specific growth rates(SGR),relative weight gains and final body weights,but significantly higher actual feeding rates,than that of the control fish(P0.05).Moreover,the fish in S1F1 group had significantly higher feed conversion efficiency(FCE)than those of any other groups(P0.05).It indicated that the partial growth compensation was elicited by various extents of intermittent food-deprivation,and that the fish of S1F1 group showed the best growth compensation.The protease activity of stomach in the S1F1 group was significantly higher than that in the S2F2 group(P0.05),and the protease activities of stomach in both of the two groups were significantly higher than those in other groups(P0.05).There was no difference in amylase activities of liver,stomach,foregut and hindgut among fish in all groups(P0.05).In the liver and hindgut,the S1F1 group had significantly higher lipase activities than other groups of the control,the S4F4 or the S8F8(P0.05).In all groups of the deprived fish,the serum total protein contents and glucose contents were slightly higher and lower than that in the control group,respectively,however,there was no significant difference among the five treatments(P0.05).There was no significant difference in serum total cholesterol level between the control group and S1F1 group(P0.05),and the serum total cholesterol levels in these two groups were significantly higher than that of any other group(P0.05).In contrast,among the groups of S2F2,S4F4 or S8F8,the serum total cholesterol level gradually descended with the more serious intermittent food-deprivation.These results suggested that the growth compensation in the rice-field eel could be achieved partially through the enhancement of the activities of some of digestive enzymes,food utilization efficiency,and the physiological adaptability of digestion,and the desirable growth compensation could be elicited through mild intermittent food-deprivation that incorporates one-day of feed-deprivation with one-day of re-feeding.

Parametric glass milling with simultaneous control

Parametric glass milling is presented to machine periodical circular channels on the glass plates for manufacturing micro testing devices. An end mill traverses in the linear motion during the workpiece rotation, which are synchronized by simultaneous control. The glass milling is controlled by 4 parameters in a mathematical model without NC program. Based on the principle of the parametric machining and the effect of the cutter axis inclination on the cutting process, a milling machine was developed to perform the parametric glass milling with an inclined ball end mill. The cutter axis inclination and the actual feed rate are associated with the critical feed rate, the maximum feed rate at which a crack-free surface is finished. As a machining example, a periodical circular channel was machined with a transparent surface by the simultaneous control.

Investigation on the Influence of Machining Fluid on Processing Characteristics in Micro-EDM

In this paper the influence of machining liquid on the processing characteristics, such as the tool electrode wear and the tool actual feed were discussed. Micro EDM drilling was carried out using deionized water and oil dielectric as the machining liquid. It was found that using deionized water reduced the tool electrode wear. Also, occurrence of short-circuits during the processing is one of the reasons for causing large electrode wear. In the case of using oil dielectric, processed depth influences the tool electrode wear greatly and causes the change in the actual feed rate. While using deionized water, processed depth also causes the change in the actual feed rate, but nearly had no influence on the tool electrode wear. Meanwhile, when using deionized water, although the small electrode wear and high machining speed can be obtained, electrolytic dissolution may occur. Therefore, the effective method of decreasing the open voltage and increasing the feed rate to prevent the electrolytic dissolution was mentioned and experimentally verified.

A framework for machining optimisation based on STEP-NC

Inappropriate machining conditions such as cutting forces cause tool failures, poor surface quality and worst of all machine breakdowns. This may be avoided by using optimal machining parameters, e.g. feed-rate, and continuing to monitor it throughout the machining process. To optimize feed-rate, we propose a system that consists of an optimisation module, a process control module and a knowledge based evaluation module. STEP-NC is the underlying data model for optimisation. Given the nominal powers, the cutting force can be estimated based on the higher-level production information such as workpiece properties, tool materials and geometries, and machine capabilities. The main function of the Process Control module is process monitoring and control. The output is the desired actual feed-rate. Finally, the actual feed-rate is recorded and evaluated in the Knowledge Based Evaluation module.

Machining chatter in flank milling

The axial depth of cut in flank milling is typically quite large, which makes this operation highly prone to machining chatter. Although considerable amount of research exists on geometrical aspects of flank milling, yet the dynamics of this efficient milling operation have not been given the proper attention. In this paper, a dynamic model is presented to study chatter in the flank milling of curved surfaces on a 5 axis machine. The actual feedrate is calculated by post-processing of the tool path. The grazing surfaces generated by the tool motion are used for the analytical calculations of the entry and exit angles in the finishing pass. The chatter simulation is conducted in the time domain. It is shown that the model is capable of predicting the stability conditions at different segments of the tool path accurately. Cutting experiments are also conducted and the results are shown to agree with the numerical predictions closely.

Breast feeding practices and views among diabetic women: A retrospective cohort study

Objective to explore the pattern and experiences of breast-feeding practices among diabetic women. Design retrospective cohort study using maternal records and postal questionnaires in a Baby-Friendly hospital. Participants diabetic mothers including women with gestational diabetes, and type 1 and 2 diabetes mellitus. Findings from the total group of respondents, 81.9% intended to breast feed. The actual breast feeding rates were 81.9% at birth, 68.1% at 2 weeks and 28.7% at 6 months postpartum. Major themes that were identified from women's experiences included information and advice, support vs. pressure, classification and labelling, and expectations. Conclusions more than two-thirds of the diabetic women intended to breast feed and actually did breast feed in this study. For both the total study population and the type 1 and 2 diabetics alone, more than half were still breast feeding at 2 weeks postpartum, and approximately one-third were still breast feeding at 6 months postpartum. Implications for practice structured support, provided for women through Baby-Friendly initiatives, was appreciated by the diabetic women in this study. The extent to which this support influenced the highly successful breast feeding practices in this group of women needs focused investigation. The need for a delicate balancing act between pressure and advice in order to prevent coercion was noted.

Actual Feed Rate per Tooth at Micro Milling

Miniature structures can be produced economically by micro end milling as single parts or parts in small and medium lot sizes. The micro end milling process has to be analyzed particularly for the purpose of applying a well controlled and repeatable process. There are many specific characteristics in the micrometric scale of dimensions, whose role is negligible at the conventional processing technologies. One of these special features of micro end milling is the observation that the set value of the feed rate per tooth generally differs from the thickness of the actual removed material layer. Feed rate per tooth is practically defined as the distance, which is run by the edge lengthwise of the groove during one revolution of the tool. Accordingly the feed rate per tooth corresponds to the thickness of the material layer removed by one edge of the tool. This correspondence exists at conventional manufacturing methods but not at micro end milling. This fact is attended by more special features of the micro end milling process, which are multiple cutting, different machining conditions of the edges and tool deflection. This paper introduces the results of improvement of my earlier research on this field [1]. An enhanced flowchart was constructed, which provides the calculation of the thickness of the actual removed material layer at micro end milling under all possible circumstances.

Cycle time prediction in high-speed milling operations for sculptured surface finishing

This work studies the cycle time prediction of high-speed milling for sculptured surfaces with high feed rates. Experiments and predictions were focused on representative surfaces of dies and molds, whose geometric complexity and complexity distribution were modified parametrically. CNC programs for machining these surfaces were executed in a HURON KX-10 machining center with a SIEMENS 840D controller, with different levels of programmed feed rate. Discrepancies between programmed and actual feed rates were evaluated. A mechanistic approach for cycle time evaluation in high-speed milling of sculptured surfaces is proposed. The mechanistic model construction is based on: (a) the frequency distribution (histogram) of linear interpolation path lengths in the CNC program and (b) a characterization of the machine tool for brisk (large changes in tool path direction) and smooth movements (small changes in tool path direction). Two case studies were used to demonstrate the effectiveness of the proposed approach (a set of representative sculptured surfaces with spherical caps and a forging die surface). Comparing the actual cycle time versus ideal cycle time under programmed feed rates up to 16 m/min, discrepancies of 300–800% were found. The proposed model is capable of predicting cycle time with a maximum error of 5–22%.

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.

Identification of acceleration deceleration profile of feed drive systems in CNC machines

In process planning, trajectory planning has generally disregarded the limitations of the feed drive systems in terms of acceleration, jerk, and motion blending. It results in poor prediction of the feed rate mainly in the transient phases and affects, consequently, the machining integrity and safety. Therefore, identifying and integrating the feed drive system limitations with the trajectory planning of the tool path are crucial in order to achieve the desired feed rate at the appropriate tool position. In this paper, a methodology based on time series modeling is proposed to identify the acceleration/deceleration (Acc/Dec) profile of a feed drive system. This profile provides the relationship between the actual feed rate, assumed proportional to the tachometer signal, and the commanded feed rate specified in the G-Code file. A particular shape of the input has been addressed to allow the application of the time series modeling. The different characteristics of this input are carefully considered to avoid both nonlinear response due to saturation and excitation of the high frequency components of the feed drive. The resulting model is transformed into a Finite Impulse Response (FIR) filter and applied as an (Acc/Dec) processor to determine the actual feed rate from the commanded feed rate. The good agreement between the model output and the experimental results demonstrates the effectiveness of the proposed identification method. It is demonstrated that integrating these limitations with the trajectory planing results in a feasible trajectory.

Influence of tool path strategy on the cycle time of high-speed milling

This work at first look discusses the influence of the tool path strategy on the cycle time of high-speed milling operations. Experiments and predictions were focused on pocketing operations with a zig-zag tool path, quantifying the significant discrepancy between the programmed feed rate and the actual average feed rate. A mechanistic approach for cycle time evaluation is proposed. The mechanistic model construction is based on the experimental measurement of the machine tool acceleration and specific geometric assumptions regarding tool motion. For high feed rates, the proposed approach is capable of capturing the influence of the zig-zag tool path orientation on the machining cycle time.

A noncontact laser technique for circular contouring accuracy measurement

The worldwide competition in manufacturing frequently requires the high-speed machine tools to deliver contouring accuracy in the order of a few micrometers, while moving at relatively high feed rates. Traditional test equipment is rather limited in its capability to measure contours of small radius at high speed. Described here is a new noncontact laser measurement technique for the test of circular contouring accuracy. This technique is based on a single-aperture laser Doppler displacement meter with a flat mirror as the target. It is of a noncontact type with the ability to vary the circular path radius continuously at data rates of up to 1000 Hz. Using this instrument, the actual radius, feed rate, velocity, and acceleration profiles can also be determined. The basic theory of operation, the hardware setup, the data collection, the data processing, and the error budget are discussed.

Modelling the feeding rate of the sea urchin Strongylocentrotus nudus (A. Agassiz) on kelp

This paper presents mathematical models for estimating the amount of kelp eaten by sea urchins Strongylocentrotus nudus (A. Agassiz) using five data sets available from four different research groups or persons who have performed laboratory feeding experiments. These experiments used as food large brown algae, Laminaria spp., Eisenia bicyclis Setchell and Undaria pinnatifida Suringar, which commonly occur in the S. nudus habitats. Non linear regression analysis using three data sets from the experiments with Laminaria fed is carried out to estimate model parameters. Two models are presented for estimating the daily feeding rate. The first model is described as a function of water temperature and test diameter, and the second model is given by multiplying the first model by a seasonal factor that is expressed as a function of day of the year. On the basis of Akaike's information criterion, the second model is selected as a better model for the data given. The model selected predicts that the feeding rate is proportional to the 2.1 power of test diameter; begins to increase at 1 °C and reach a maximum at 10 °C, beyond which it decreases and finally ceases at 28 °C; varying sinusoidally with season by more than 30% of the rate predicted only from temperature and the test diameter. Analysis of the deviations between observed and predicted feeding rates shows that the predicted rates are in good agreement with the observed ones over all factors, on average. Application of the model to feeding rates on kelp species other than Laminaria suggests that the model may also give a reasonably good estimate for the feeding rate for Eisenia bicyclis, but may give a substantial underestimate for Undaria pinnatifida. More detailed analyses of model parameters indicate that the exponent of the feeding rate on test diameter may differ seasonally from the estimate of the model, probably due to reproductive activity. In addition, the analyses suggest that actual feeding rates may change with season, before or after the predicted ones. Despite the presence of unexpected seasonal fluctuations in daily feeding rate, the amount of annual feeding per animal is proportional to about the 2.1 power of test diameter with a very high correlation. The result suggests that daily feeding rates vary with a size-dependent limit in the amount of annual feeding.

マシニングセンタの生産性向上に関する研究 (第1報)

The productivity of machining centers is influenced strongly by the quality of NC programs. To investigate the productivity, an NC program simulator has been developed to analyze and evaluate an NC program by decoding its NC codes. With the simulator, even before the actual machining, the tool paths can be displayed and the operational times occupied in the positioning feed motion and cutting feed motion, etc. can be calculated. The effects of the maximum speed and the acceleration of positioning feed on the productivity have been analyzed. Additionally, the influence of feedrate override function to shorten the operational time has been investigated in the conventional and the high speed cutting, respectively. From the results obtained from analyzing three NC programs, it is found that the effectiveness of the override function depends on the relation among the average moving distance, the commanded feedrate and the acceleration of cutting feed. Especially, in the case of the NC program for machining dies or molds, the productivity will be hardly improved using faster feedrate, because the actual feedrate hardly increases as expected due to the tiny moving distances of NC blocks. High speed & high precision function, which is an advanced optional function, is much more effective not only to improve the productivity but also to keep the machining accuracy of high speed cutting.

最近の舶用低速ディーゼル機関のシリンダライナ及びピストンリングの摩耗実績

A previous investigation regarding actual circumstances of the wear of low speed, long stroke 2 stroke marine diesel engines clarified their abnormal wear conditions. Since then makers have taken various countermeasures against wear, and in order to confirm the effects, the Japan Ship Owners Association has been collecting wear data. This report describes the results of wear conditions, based on the data of two years (April 1987-March 1989). 1. Statistics of Oil Feed Rate of each type. There are no differences between the actual feed rates converted in catalogue MCO of A type and C type. 2. Analysis of Wear Rate of Linear and Piston Ring. Liner wear characteristics of A type is getting stable comparing with the last investigation. But on the contrary, excessive wear of ring takes place similarly on A type, C type and D type. 3. Analysis of Oil Feed Rate - Wear Rate. It has been clarified that wear rate differs with each diesel maker. 4. Analysis Derating Rate - Wear Rate - Oil Feed Rate. A higher wear rate is found in the higher derating engine, and it is clarified that the oil feed rate on a high derating engine is too small.