| Hot stamping of auto parts is one of effective ways to manufacture lightweight automobiles and improve car safety.Steel sheets are at a high temperature from tranaferring to forming in hot stamping process.Comparing with cold stamping,hot stamping puts forward higher requirements for production process and manufacturing systems.More than 300 hot stamping production lines has been built worldwide,but there is little research about modeling of hot stamping production process,collaboration and scheduling of manufacturing units(including heating unit,transferring unit and forming unit),relationship between production efficiency and energy consumption.In this paper,a forming method with pressure compensation at bottom dead centre is presented,a description model for hot stamping production process is built,and a runtime iterative manufacturing system framework is promoted based on design and practice of hot stamping production line,which implements a monitered,configurable,evolutionary manufacturing system.The system realizes hot stamping batch production,aims to reduce energy consumption,extend equipment lifecycle,and meet the production requirements of different production quantities and delivery periods.This paper systematically makes efforts about hot stamping method,process modeling,multi-device collaboration and rapid transportation,modeling of intelligent manufacturing system.In this paper,positive results are as follows:1)A forming method for hot stamping with pressure compensation at bottom dead centre is presented.in this method,the holding pressure is monitored continuously,and the position of slide is compensated when pressure drops due to sheets temperature falling.A digital mechanical servo press is designed and achieved to meet the requirements of hot stamping,implements high response,speed and load adjustment through matching of driving system and movement system.the press is able to punch rapidly,clamp slowly,dwell steadily and reture fast,is equipped with interfaces for configuration and collaboration.The press cooperates with furnaces and transferring robots,and manufactures hot stamping parts efficiently and stably.An performance evaluation method for digital mechanical servo press is established.The method evaluates 4 aspects: position accuracy,holding capacity,production efficiency and energy consumption.Experiment results show that the precision of the bottom dead center is 0.016 mm,its stamping efficiency is 17.5~45% higher than traditional mechanical press and 53% higher than hydraulic press,it consumes energy 0.1322 kWh per single cycle and 19.83 kWh per hour while using for hot stamping.the mechanical servo press significantly reduces energy consumption and improves efficiency when using for hot stamping comparing with hydranlic press.2)The rapid collaborative transfer in hot stamping line is abstracted as one-dimension collaborative transferring problem(1DCT),and the abstract description of this problem is presented.A mathmatical model is established to describ the kinematics and dynamics equations of 1DCT.overlap displacement and transferring velocity are determinant for 1DCT.In order to obtain the shortest transferring cycle and the best optimization,the overlap displacement should be increased as long as possible,and the driving system should give out as biggest acceleration as possible.Under the same experimental conditions,online collaboration gains smaller synchronization errors than offline.Analysis about nonuniform-velocity online collaboration shows that the higher the response to errors of displacement and velocity,the smaller the synchronization error is.When a total displacement of transferring is 4.9m and the overlap distance is 1.4m,the uniform-velocity collaboration transfer method reduces 34% transferring cycle from 3.2s to 2.1s,the nonuniform-velocity method reduces 25% transferring cycle.Compared with uniform-velocity method,the non-uniform-velocity method gains 50.6% more collaboration time for collaborative operation.3)According to hot stamping process,a model for hot stamping process and automatic production is built by using Finite State Machine(FSM).The model is used to control prodcution process of forming,cold/heated sheet transferring and heating.The 5 manufacturing units in hot stamping process,which are unstacking unit,heating unit,heated-sheet transferring unit,forming unit and part-unloading unit,are described by 5 FSMs and they are connected by 4 sets of trigger.the 5 FSMs and 4 sets of trigger are a complete description of hot stamping process.The biggest contradiction in hot stamping production is the mismatch of heating cycle and forming cycle.The model describs heating mode,especially for roller-hearth furnace and multi-layer furnace,and presents the method to match single forming unit with multiple heating unit.4)the description model for hot stamping production process is adopted for process control of hot stamping line,which is consisted with multi-layer furnace,linear transferring robot,mechanical servo press.the process control system,production supporting system and produciton simulation system are researched and developed to satisfy requirements of hot stamping process,multi-device collaborative scheduling problem is focused on and a bridge for mutiple heating chambers and a single forming die is promoted.Analysis about sequense,energy consumption and delivery cycle of production proves that multi-layer furnace is able to apply to different productin objectives,the hot stamping line can be flexibly configured based on production volume and delivery cycle,the actice configuration helps to extend equipment life,reduce energy consumption and production cost.When more chambers are involved into production,lower energy are consumed for individual part,this mode is suitable for batch production;when less chambers are involved,the whole heating furnace consums less energy,and the production cycle is longer,the mode is suitable for tryout or debuging.5)A framework of runtime iteration manufacturing system(RIMS)is promoted base on design and practice of hot stamping productin line.The framework is an analysisoriented system with evolution paths and itertive during operation.RIMS consists of 6 sections,namely: multiscale analysis of manufacturing systems,process modeling,characterization of production efficiency,multi-device collaboration and analysis of deviceassociated region,deice lifecycle management,optimization process of runtime iteration.the implementation routine of RIMS is proposed.the RIMS framework provides a fundamental schema,integrates variety types of sensor in a distributed way,forms distributed sensor network,acquires production data efficiently,informs system process through analysis of production data,evaluats system efficiency,underlies problemdiscovering and problem-solving for manufacturing system,switches fastly between operating state and debugging state,and achieves samll scale iteration during system operating. |
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