外文翻译汽车上油壳加工工艺与夹具设计论文.doc

科技大学（筹） 毕业设计（论文）外文翻译课题名称汽车上油壳加工工艺与夹具设计系 别 职业技术教育学院 专 业 机械工程与自动化 班 级 机自Z081 学 号 2 姓 名 何 仕 指导教师 邓 丽 萍 Laboratory for Manufacturing andSustainabilityUC BerkeleyTitle:Energy Consumption Characterization and Reduction Strategies for Milling Machine Tool UseAuthor:Diaz, Nancy, University of California, BerkeleyDornfeld, David, UC BerkeleyPublication Date:05-04-2011Series:Green Manufacturing and Sustainable Manufacturing PartnershipPublication Info:Green Manufacturing and Sustainable Manufacturing Partnership, Laboratory for Manufacturingand Sustainability, UC BerkeleyPermalink:escholarship.org/uc/item/40g995w6Keywords:Green Machine Tools; Energy Consumption Reduction; Specific Energy CharacterizationAbstract:Since machine tools are used extensively throughout their functional life and consequentlyconsuming valuable natural resources and emitting harmful pollutants during this time, this studyreviews strategies for characterizing and reducing the energy consumption of milling machine toolsduring their use. The power demanded by a micro-machining center while cutting low carbon steelunder varied material removal rates was measured to model the specific energy of the machinetool. Thereafter the power demanded was studied for cutting aluminum and polycarbonate workpieces for the purpose of comparing the difference in cutting power demand relative to that of steel.eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamic research platform to scholars worldwide.Energy Consumption Characterization and Reduction Strategies for Milling Machine Tool Use Nancy Diaz，Elena Redelsheimer，David Dornfeld，Laboratory for Manufacturing and Sustainability，University of California at Berkeley, USAAbstract Since machine tools are used extensively throughout their functional life and consequently consuming valuable natural resources and emitting harmful pollutants during this time, this study reviews strategies for characterizing and reducing the energy consumption of milling machine tools during t heir use. The power demanded by a micromachining center while cutting low carbon steel under varied material removal rates was measured to model the specific energy of the machine tool. Thereafter the power demanded was studied for cutting aluminum and polycarb onate work pieces for the purpose of comparing the difference in cutting power demand relative to that of steel. Keywords: Green Machine Tools; Energy Consumption Reduction;Specific Energy Characterization1 INTRODUCTION A product undergoes three life-cycle stages: manufacturing, use and end-of-life. Consumer products whose environmental impact is dominated by the use phase include light fixtures, computers, refrigerators, and vehicles, in general products that are used extensively during their functional life. All the while these products consume resources, in particular energy in the form of electricity or fuel. The machine tool is one such product. The use phase of milling machine tools has been found to comprise between 60 and 90% of CO2-equivalent emissions during its life cycle 1. This study presents a method for predicting the electrical energy consumed in manufacturing a product for the purpose of reducing its environmental impact. In conducting a life cycle assessment, product designers may choose to opt for a process, economic input-output (EIO), or hybrid approach. The drawback of the process LCA, though, is that because this method entails acquiring process-specific data it is time consuming and therefore resource intensive. An alternative to measuring the machine tools electrical energy consumption directly, for example, is to use aggregate data as is done with EIO-LCA 2. An EIO-LCA, therefore, is not specific to the design of a particular product. The strategies presented herein provide a method for more quickly generating manufacturing energy consumption estimates for a particular product. 1.1 Cutting load profile As described by Diaz et al. in 3 the power demand of a machine tool is comprised of cutting, variable, and constant power components. The cutting power is the additional power drawn for the removal of material. The machine tool used in this analysis, the Mori Seiki NV1500 DCG, is a micro-machining center with a relatively low standby power demand when compared to large machining centers. Therefore, the cutting power can comprise a large portion of the machine tools total power demand. Energy consumption for high tare machine tools was found to be primarily dependent on the processing time of the part, which is dictated by the part geometry, tool path, and material removal rate. One such method for optimizing the tool path for minimum cycle time was presented in 4. This paper is concerned with the effect of the material removal rate on energy consumption. The material removal rate for a 3-axis machining center can be varied by changing the feed rate, width of cut, or depth of cut. Since increasing the feed rate was found to have dire consequences on the cutting tool life 5, the experiments conducted herein varied material removal rate through width of cut and depth of cut experiments for the purpose of analyzing the material removal rates effect on cutting power and more importantly, energy consumption. Although increases in the material removal rate translate to faster machining times, the loads on the spindle motor and axis drives increase as well, resulting in higher power demand. Since our main interest is energy consumed in product manufacture, the trade-off between power demand and machining time was analyzed to confirm that the increased loads due to faster material removal was not increasing the total energy consumed. 2 POWER DEMAND FOR VARIED M.R.R.S Since machine tool programmers and operators have an array of options when defining the process plan for part production, this analysis strives to reduce energy consumption by process parameter selection of a machine tool. Specifically, the parameters concerning material removal rate (M.R.R.) were varied on a Mori Seiki NV1500 DCG while selecting appropriate tooling. The power demand was measured with a Wattnode MODBUS wattmeter. In previous work, experiments we re conducted in which spindle speed, feed rate, feed per tooth, and cutter type were varied to analyze the change in energy consumption while milling a low carbon steel, AISI 1018 steel 5. Also, 6 conducted experiments on face milling, end milling, and drilling operations in which the energy consumption, machining cost, and tool wear were compared for increased cutting speeds. Tool wear and, consequently, cutting tool cost increased significantly when the process parameters veered away from the recommended cutting conditions. So in the following experiments the cutting tool type was changed to maintain the recommended process parameters, but reduce energy consumption while machining, nonetheless.2.1 Width of Cut Experiments Given the energy savings from changing the cutter type this project focused on varying material removal rate. First the width of cut was increased while machining with a: 1. 2 flute uncoated carbide end mill, 2. 2 flute TiN coated carbide end mill, and 3. 4 flute TiN coated carbide end mill. Peripheral cuts were made along the y-axis at a depth of cut of 2 mm with an 8 mm diameter end mill over a length of 101 mm in a 1018 steel work piece. The width of cut was varied by 1 mm increments between 1 mm and 7 mm, in addition to a 7.5 mm width of cut. Table 1 summarizes the cutting conditions used. The chip load was maintained at approximately 0.03 mm/tooth to avoid excessive tool wear and breakage. Table 1: Process parameters for width of cut experiments.Once the power was measured for each width of cut experiment,the power demand was measured for the machine tool while air cutting, that is, while running the tool path without material removal. This way the power associated with the material removal process could be extracted, known hereafter as the cutting power demand. The average air cutting power demand was found to be 1510 W for the cutter (2) process parameters, so it was subtracted from the average total power demand. Figure 1 shows the cutting power demand as a function of the M.R.R. for cutter (2). This plot has a slightly parabolic trend with a point of inflection at approximately 75 mm3/s. The cutting power demand for the 7.5 mm width of cut was almost nine times greater than the 1 mm width of cut. Since the total air cutting power demand was only 1510 W, though, the resulting increase in total power demand of the machine tool was only 28%. Thus in terms of energy consumption, the operator still experiences energy savings with the increase in M.R.R.Figure 1: Cutting power demand using cutter (2) while cutting 1018 steel. Figure 2 shows the average power demand of the NV1500 DCG for cutters (1)(3). The relationship between power and M.R.R. shifts from parabolic to linear in moving from the conditions imposed on cutter (1) to cutter (3). The increase in power demand is the greatest for cutter (3), but the load on the spindle motor and axis drives is also much greater than that of the 2 flute cutting tools since the feed rate is twice as large or greater. Figure 2: Average total power demand as a function of M.R.R. 2.2 Depth of Cut Experiments Depth of cut experiments were also conducted on a 1018 steel work piece 101 mm in length. Cuts were made along the y-axis using 8 mm diameter, 2 flute uncoated and TiN coated carbide end mills under near slotting conditions (a width of cut of 7.5 mm). The power demand was measured at depths of cut of 1, 2, 4, and 8 mm. The chip load was maintained constant across the various cutters at 0.051 mm/tooth. The spindle speed and feed rate were varied, though, to account for higher loads on the machine tool during the depth of cut experiments (see Table 2 for a summary of the processing conditions). Table 2: Process parameter ranges for depth of cut experiments. Figure 3 summarizes the power demanded by the NV1500 DCG for the 2 flute TiN coated end mill (cutter (2) and the energy consumed as a function of material removal rate. Although the power demand increases with load the energy consumption still drops drastically with the increase in material removal rate. The machine tool experiences a power demand increase of approximately two-thirds, whereas the energy consumption reduces to less than one-third of its original value. This shows that the decrease in processing time effectively dominates over the increase in power demand due to increased loads.Since the power demand was shown to increase with load, and experimentally this increase in load was not enough to increase the overall energy consumption, the trade-off between power demand and processing time will be analyzed. Figure 3: Energy and power demand as a function of M.R.R. for depth of cut experiments with cutter (2). 2.3 Trade-off Between Power Demand and Processing Time The machine tools electrical energy consumption is dependent on the power demand, p avg, and processing time, t, as seen in Equation（1）. Since the power demand shows some variability due to the internal cooling unit of the machine tool, the average power demand, p avg , will be used. As was mentioned previously, the average power demand is composed of a cutting, p cut, and air cutting, pair, component; consequently the energy consumption can be expanded as follows: (1)Two scenarios will be compared. Scenario (1) is the base scenario, while scenario (2) will be the scenario in which the material removal rate is increased for the purpose of reducing processing time. The constants,and, were created to represent the increase in p cut and decrease in t, respectively (see Equations 2 and 3). Note that both constants are less than unity. (2) (3)Equation 4 shows the relationship between p avg1 and Pavg2, which assumes that the air cutting power demand, pair, remains relatively constant for both scenarios. (4)If the relative size of the air cutting power demand is denoted by: (5)where i is 1 or 2 for scenarios 1 and 2, respectively, then the inequality presented in Equation 6 shows the condition that must be met in order for the energy consumption of scenario (2) to be smaller than that of scenario (1). (6)So if is less than , then e2 will always be less than e1. Also, as2 increases (i.e. if the air cutting power demand comprises a large portion of the total power demand) then the probability of e2 being less than e1 increases. This would be the case for machine tools with large work volumes which have a high standby power demand. Further work can be conducted in which the assumption that the air cutting power demand does not stay constant to expand the applicability of the power and processing time trade-off analysis. 3 CHARACTERIZING THE SPECIFIC ENERGY The specific energy of various manufacturing processes was previously summarized by Gutowski et al. 7, but for any given manufacturing process the data was limited to only a sample of process rates. This study, though, will focus on milling machine tools and the operable range of the machining center when characterizing the specific energy. In characterizing the energy consumption of a machine tool, as the M.R.R. approaches infinity the specific energy is expected to reach a steady state of zero. But, given the work volume, spindle speed, and table feed constraints of a machine tool as well as the maximum loads that can be applied without deforming the main body frame or breaking the spindle motor, the operator will never reach a M.R.R. anywhere near infinity. So under the constraints of the M.R.R. a curve of the following form: (7)was fit to the data from the width of cut and depth of cut experiments. Note that the constant, k, essentially has units of power and b represents the steady-state specific energy. The total specific energy, which accounts for cutting and air cutting power demand, was indeed found to have an inverse relationship with the M.R.R. (see Figure 4). The air cutting power demand dominated the specific energy. The impact of the cutting power demand on the specific energy was minimal since at high loads (i.e. at high M.R.R.s)