立式铣床换刀机构设计——换刀机构设计开题报告

编号无锡太湖学院毕业设计（论文）相关资料题目： 立式铣床换刀机构设计 换刀机构设计 信机 系 机械工程及自动化专业学 号： 0923031学生姓名： 褚 浩 指导教师： 鲍虹苏 （职称：高 工 ） （职称： ）2013年5月25日目 录一、毕业设计（论文）开题报告二、毕业设计（论文）外文资料翻译及原文三、学生“毕业论文（论文）计划、进度、检查及落实表”四、实习鉴定表无锡太湖学院毕业设计（论文）开题报告题目： 立式铣床换刀机构设计 换刀机构设计 信机 系 机械工程及自动化 专业学 号： 0923031 学生姓名： 褚 浩 指导教师： 鲍虹苏（职称：高 工） （职称： ）2012年11月25日 课题来源南京某机械有限公司生产实际。科学依据（包括课题的科学意义；国内外研究概况、水平和发展趋势；应用前景等）该课题主要是为了培养学生开发和创新机械产品的能力，要求学生能够结合企业现有的数控立式铣床，针对实际使用过程中存在的换刀问题，综合所学的机械理论设计与方法，对数控立式铣床换刀装置进行改进设计，从而达到在数控机床实现自动换刀。在设计换刀装置时，在满足产品工作要求的情况下，应尽可能多的采用标准件，提高其互换性要求，以减少产品的设计生产成本。使用自动换刀机构，可以大幅度提高生产效率，节约成本。 应用前景非常广泛，目前国内外都普遍研究开发新的自动换刀机构。 研究内容通过调研应明白要对一个产品进行改进或创新以满足用户的需求，信息的获取是非常重要的，分析数控立式铣床的功能要求，完成数控立式铣床自动换刀装置的结构分析、刀库的设计、刀具交换装置的设计、自动换刀装置的控制原理等，在满足产品工作要求的情况下，应尽可能多的采用标准件，提高其互换性要求，以减少产品的设计生产成本。拟采取的研究方法、技术路线、实验方案及可行性分析通过实践与大量搜集、阅读资料相结合，掌握好基本原理后，对企业现有数控立式铣床自动换刀装置进行数学建模，并通过模拟实验分析建立数控立式铣床自动换刀装置的实体模型，设计出数控立式铣床自动换刀装置，进行现场实验，来进行传动件的最优化设计。研究计划及预期成果研究计划：2012年11月25日-2012年12月25日：按照任务书要求查阅论文相关参考资料，填毕业设计开题报告书。2013年1月10日-2013年2月29日：网上查询相关资料，了解国内外研究发展状况。2013年3月5日-2013年3月12日：按照要求设计换刀机构整体部分。2013年3月13日-2013年3月24日：学习并翻译一篇与毕业设计相关的英文材料。并且开始轴蜗轮蜗杆的计算。2013年3月24日-2013年4月18日：完成刀具换刀机构刀库图，此外还画了其他几张图，并完成了换刀机构液压设计。2013年4月26日-2013年5月21日：毕业论文撰写和修改工作。预期成果：现场调研、模拟、建模、实验、机器调试，达到产品的最优化设计，大大降低劳动强度和提高生产效率。特色或创新之处适用于企业普通数控立式铣床自动换刀装置的优化设计，可降低工人的劳动强度、减少机械加工工艺时间和降低机械零件的生产成本。已具备的条件和尚需解决的问题针对实际使用过程中数控立式铣床自动换刀装置存在的问题，综合所学的机械理论设计与方法，如何对数控立式铣床自动换刀装置进行改进，进而提高学生开发和创新机械产品的能力。指导教师意见 指导教师签名：年 月 日教研室（学科组、研究所）意见 教研室主任签名： 年 月 日系意见 主管领导签名： 年 月 日英文原文Rotary pumpThese are built in many different designs and are extremely popular in modern fluid-power system. The most common rotary-pump designs used today are spur-gear, generated-rotary , sliding-vane ,and screw pump ,each type has advantages that make it the most suitable for a given application .Spur-gear pumps. these pumps have two mating gears are turned in a closely fitted casing. Rotation of one gear ,the driver causes the second ,or follower gear, to turn . the driving shaft is usually connected to the upper gear of the pump .When the pump is first started ,rotation of gears forces air out the casing and into the discharge pipe. this removal of air from the pump casing produces a partial vacuum on the pump inlet ,here the fluid is trapped between the teeth of the upper and lower gears and the pump casing .continued rotation of the gears forces the fluid out of the pump discharge .Pressure rise in a spur-gear pump is produced by the squeezing action on the fluid ad it is expelled from between the meshing gear teeth and casing ,.a vacuum is formed in the cavity between the teeth ad unmesh, causing more fluid to be drawn into the pump ,a spur-gear pump is a constant-displacement unit ,its discharge is constant at a given shaft speed. the only way the quantity of fluid discharge by a spur-gear pump of type in figure can be regulated is by varying the shaft speed .modern gear pumps used in fluid-power systems develop pressures up to about 3000psi.Figure shows the typical characteristic curves of a spur-gear rotary pump. These curves show the capacity and power input for a spur-gear pump at various speeds. At any given speed the capacity characteristic is nearly a flat line the slight decrease in capacity with rise in discharge pressure is caused by increased leakage across the gears from the discharge to the suction side of the pump. leakage in gear pumps is sometimes termed slip. Slip also increase with arise pump discharge pressure .the curve showing the relation between pump discharge pressure and pump capacity is often termed the head-capacity or HQ curve .the relation between power input and pump capacity is the power-capacity or PQ curve .Power input to a squr-gear pump increases with both the operating speed and discharge pressure .as the speed of a gear pump is increased. Its discharge rate in gallons per minute also rise . thus the horsepower input at a discharge pressure of 120psi is 5hp at 200rpm and about 13hp at 600rpm.the corresponding capacities at these speed and pressure are 40 and 95gpm respectively, read on the 120psi ordinate where it crosses the 200-and 600-rpm HQ curves .Figure is based on spur-gear handing a fluid of constant viscosity , as the viscosity of the fluid handle increases (i.e. ,the fluid becomes thicker and has more resistance to flow ),the capacity of a gear pump decreases , thick ,viscous fluids may limit pump capacity t higher speeds because the fluid cannot into the casing rapidly enough fill it completely .figure shows the effect lf increased fluid biscosity on the performance of rotary pump in fluid-power system .at 80-psi discharge pressure the pp has a capacity lf 220gpm when handling fluid of 100SSU viscosity lf 500SSU . the power input to the pump also rises ,as shown by the power characteristics.Capacity lf rotary pump is often expressed in gallons per revolution of the gear or other internal element .if the outlet of a positive-displacement rotary pump is completely closed, the discharge pressure will increase to the point where the pump driving motor stalls or some part of the pump casing or discharge pipe ruptures .because this danger of rupture exists systems are filled with a pressure relief valve. This relief valve may be built as of the pump or it may be mounted in the discharge piping.Sliding-Vane PumpsThese pumps have a number of vanes which are free to slide into or out of slots in the pup rotor . when the rotor is turned by the pump driver , centrifugal force , springs , or pressurized fluid causes the vanes to move outward in their slots and bear against the inner bore of the pump casing or against a cam ring . as the rotor revolves , fluid flows in between the vanes when they pass the suction port. This fluid is carried around the pump casing until the discharge port is reached. Here the fluid is forced out of the casing and into the discharge pipe.In the sliding-vane pump in Figure the vanes in an oval-shaped bore. Centrifugal force starts the vanes out of their slots when the rotor begins turning. The vanes are held out by pressure which is bled into the cavities behind the vanes from a distributing ring at the end of the vane slots. Suction is through two ports A and AI, placed diametrically opposite each other. Two discharge ports are similarly placed. This arrangement of ports keeps the rotor in hydraulic balance, reliving the bearing of heavy loads. When the rotor turns counterclockwise, fluid from the suction pipe comes into ports A and AI is trapped between the vanes, and is carried around and discharged through ports B and BI. Pumps of this design are built for pressures up to 2500 psi. earlier models required staging to attain pressures approximating those currently available in one stage. Valving , uses to equalize flow and pressure loads as rotor sets are operated in series to attain high pressures. Speed of rotation is usually limited to less than 2500rpm because of centrifugal forces and subsequent wear at the contact point of vanes against the cam-ring surface. Two vanes may be used in each slot to control the force against the interior of the casing or the cam ring. Dual vanes also provide a tighter seal , reducing the leakage from the discharge side to the suction side of the pump . the opposed inlet and discharge port in this design provide hydraulic balance in the same way as the pump, both these pumps are constant-displacement units.The delivery or capacity of a vane-type pump in gallons per minute cannot be changed without changing the speed of rotation unless a special design is used. Figure shows a variable-capacity sliding-vane pump. It dose not use dual suction and discharge ports. The rotor rums in the pressure-chamber ring, which can be adjusted so that it is off-center to the rotor. As the degree of off-center or eccentricity is changed, a variable volume of fluid is discharged. Figure shows that the vanes create a vacuum so that oil enters through 180 of shaft rotation. Discharge also takes place through 180 of rotation. There is a slight overlapping of the beginning of the fluid intake function and the beginning of the fluid discharge.Figure shows how maximum flow is available at minimum working pressure. As the pressure rises, flow diminishes in a predetermined pattern. As the flow decreases to a minimum valve, the pressure increases to the maximum. The pump delivers only that fluid needed to replace clearance floes resulting from the usual slide fit in circuit components.A relief valve is not essential with a variable-displacement-type pump of this design to protect pumping mechanism. Other conditions within the circuit may dictate the use of a safety or relief valve to prevent localized pressure buildup beyond the usual working levels.For automatic control of the discharge , an adjustable spring-loaded governor is used . this governor is arranged so that the pump discharge acts on a piston or inner surface of the ring whose movement is opposed by the spring . if the pump discharge pressure rises above that for which the by governor spring is set , the spring is compressed. This allows the pressure-chamber ring to move and take a position that is less off center with respect to the rotor. The pump theb delivers less fluid, and the pressure is established at the desired level. The discharge pressure for units of this design varies between 100 and 2500psi.The characteristics of a variable-displacement-pump compensator are shown in figure. Horsepower input values also shown so that the power input requirements can be accurately computed. Variable-volume vane pumps are capacity of multiple-pressure levels in a predetermined pattern. Two-pressure pump controls can provide an efficient method of unloading a circuit and still hold sufficient pressure available for pilot circuits.The black area of the graph of figure shows a variable-volume pump maintaining a pressure of 100psi against a closed circuit. Wasted power is the result of pumping oil at 100psi through an unloading or relief valve to maintain a source of positive pilot pressure. Two-pressure type controls include hydraulic, pilot-operated types and solenoid-controlled, pilot-operated types. The pilot oil obtained from the pump discharge cannot assist the governor spring. Minimum pressure will result. The plus figure shows the solenoid energized so that pilot oil assists compensator spring. The amount of assistance is determined by the small ball and spring, acting as a simple relief valve. This provides the predetermined maximum operating pressure.Another type of two-pressure system employs what is termed a differential unloading governor. It is applied in a high-low or two-pump circuit. The governor automatically, Through pressure sensing, unloads the large volume pump to a minimum deadhead pressure setting. Deadhead pressure refers to a specific pressure level established as resulting action of the variable-displacement-pump control mechanism. The pumping action and the resulting flow at deadhead condition are equal to the leakage in the system and pilot-control flow requirements. No major power movement occurs at this time, even though the hydraulic system may be providing a clamping or holding action while the pump is in deadhead position The governor is basically a hydraulically operated, two-pressure control with a differential piston that allows complete unloading when sufficient external pilot pressure is applied to pilot unload port.The minimum deadhead pressure setting is controlled by the main governor spring A. the maximum pressure is controlled by the relief-valve adjustment B. the operating pressure for the governor is generated by the large-volume pump and enters through orifice C. To use this device let us assume that the circuit require a maximum pressure of 1000psi, which will be supplied by a 5-gpm pump. It also needs a large flow (40gpm) at pressure up to 500psi; it continues to 1000pso at the reduced flow rate. A two-pump system with an unloading governor on the 40-gpm pump at 500psi to a minimum pressure setting of 200psi (or another desired value) , which the 5-gpm pump takes the circuit up to1000psi or more.Note in figure that two sources of pilot pressure are required. One ,the 40-gpm pump, provides pressure within the housing so that maximum pressure setting can be obtained. The setting of the spring, plus the pressure within the governor housing, determines the maximum pressure capacity of the 40-gpm pump. The second pilot source is the circuit proper, which will go to 1000psi. this pilot line enters the governor through orifice D and acts on the unloading piston E . the area of piston E is 15 percent greater than the effective area of the relief poppet F. the governor will unload at 500psi and be activated at 15percent below 500psi, or 425psi. By unloading, we mean zero flow output of the 40-gpm pump.As pressure in the circuit increases from zero to 500psi, the pressure within the governor housing also increases until the relief-valve setting is reached, at which time the relief valve cracks open, allowing flow to the tank.The pressure drop in the hosing is a maximum additive value, allowing the pump to deadhead. Meanwhile, the system pressure continues to rise above 700psi, resulting in a greater force on the bottom of piston E than on the top. The piston then completely unseats poppet F, which results in a further pressure drop within the governor horsing to zero pressure because of the full-open position of the relief poppet F. flow entering the housing through orifice is directed to the tank pass the relief poppet without increasing the pressure in housing. The deadhead pressure of the 40-gpm pump then decreases to the lower set value. Thus , at the flow rate to the unloading governor ,the 40gpm pump goes to deadhead. The flow rate to the circuit decreases to 5gpm as the pressure to 1000psi, the 5-gpm pump is also at its deadhead setting, thus only holding system pressure.The 4-gpm pump unloads its volume at 500psi. It requires a system pressure of 600psi to unload the 40-gpm pump to its minimum pressure of 200psi. the 600-psi pilot supply enters through orifice D and acts on the differential piston E. The pumps volume is reduced to zero circuit-flow output at 500psi. The additional 100-psi pilot pressure is required to open poppet F completely and allow the pressure within the housing to decrease to zero.As circuit pressure decreases ,both pumps come back into service in a similar pattern.CNC machine toolsWhilethespecificintentionandapplicationforCNCmachinesvaryfromonemachinetype toanother,allformsofCNChavecommonbenefits.Herearebutafewofthemoreimportant benefitsofferedbyCNCequipment.ThefirstbenefitofferedbyallformsofCNCmachinetoolsisimprovedautomation.The operatorinterventionrelatedtoproducingworkpiecescanbereducedoreliminated.ManyCNCmachinescanrununattendedduringtheirentiremachiningcycle,freeingtheoperatortodoother tasks.ThisgivestheCNCuserseveralsidebenefitsincludingreducedoperatorfatigue,fewer mistakescausedbyhumanerror,andconsistentandpredictablemachiningtimeforeach workpiece.Sincethemachinewillberunningunderprogramcontrol,theskilllevelrequiredof theCNCoperator(relatedtobasicmachiningpractice)isalsoreducedascomparedtoamachinistproducingworkpieceswithconventionalmachinetools.ThesecondmajorbenefitofCNCtechnologyisconsistentandaccurateworkpieces.TodaysCNCmachinesboastalmostunbelievableaccuracyandrepeatabilityspecifications.Thismeans thatonceaprogramisverified,two,ten,oronethousandidenticalworkpiecescanbeeasily producedwithprecisionandconsistency.AthirdbenefitofferedbymostformsofCNCmachinetoolsisflexibility.Sincethese machinesarerunfromprograms,runningadifferentworkpieceisalmostaseasyasloadinga differentprogram.Onceaprogramhasbeenverifiedandexecutedforoneproductionrun,itcan beeasilyrecalledthenexttimetheworkpieceistoberun.Thisleadstoyetanotherbenefit,fast changeover.Sincethesemachinesareveryeasytosetupandrun,andsinceprogramscanbe easilyloaded,theyallowveryshortsetuptime.Thisisimperativewithtodaysjust-in-time(JIT) product requirements.Motioncontrol-theheartofCNCThemostbasicfunctionofanyCNCmachineisautomatic,precise,andconsistentmotion control.Ratherthanapplyingcompletelymechanicaldevicestocausemotionasisrequiredon mostconventionalmachinetools,CNCmachinesallowmotioncontrolinarevolutionarymanner2.AllformsofCNCequipmenthavetwoormoredirectionsofmotion,calledaxes.Theseaxes canbepreciselyandautomaticallypositionedalongtheirlengthsoftravel.Thetwomostco