15-第十五章 短期调度.doc

Short-Term Scheduling第十五章 短期调度主要内容Outline15.1 短期调度的战略重要性The Strategic Importance of Short-Term Scheduling 高效+高速+低库存+准确的交货期 15.2 调度问题Scheduling Issues 能力计划+综合计划+主生产计划+短期调度正向与逆向调度定制Forward and Backward Scheduling调度准则Scheduling Criteria时间短+利用率高+库存少+等待短15.3 工艺专业化设施的调度Scheduling Process-Focused Facilities 计划文件 15.4 作业分配Loading Jobs 输入-输出控制Input-Output Control固定在制品卡片 甘特图Gantt Charts 分配方法Assignment Method 指派问题-匈牙利法 15.5 作业排序Sequencing Jobs 派工的优先规则Priority Rules for Dispatching JobsFCFS+SPT+EDD+LPT 关键比Critical Ratio剩余交付时间/剩余作业时间 N项作业两台机器的排序问题：约翰逊规则Sequencing N Jobs on Two Machines: Johnsons Rule 基于规则的作业派工系统的局限性Limitations of Rule-Based Dispatching Systems 15.6 有限能力计划Finite Capacity Scheduling (FCS) 15.7 约束理论Theory of Constraints 瓶颈Bottlenecks 鼓、缓冲、绳子Drum, Buffer, Rope节拍+库存+信号 I5.8 重复性设施的调度Scheduling Repetitive Facilities 物料平准化 15.9 服务业的调度Scheduling Services 24/7运作+需求管理+能力管理 用循环调度法编制服务人员的工作班次Scheduling Service Employees with Cyclical Scheduling循环调度 案例 达美航空：天气不佳时的飞行调度Global Company Profile: Delta Air Lines达美航空公司每年有近10%的航班受到各种影响，其中一半是由于天气原因引起About 10% of Deltas flights are disrupted per year, half because of weather公司每年损失4.4亿美元，包括收入损失、加班工资以及乘客的食宿费用Cost is $440 million in lost revenue, overtime pay, food and lodging vouchers公司投入3千3百万建立运营控制中心以适应各种变化通讯+除冰+及时通知乘客+变更航线和保持航班准确运行The $33 million Operations Control Center adjusts to changes and keeps flights flowing每年节约3千五百万Saves Delta $35 million per year15.1 短期调度的战略重要性The Strategic Importance of Short-Term Scheduling综合计划的落实 有效和高效的调度是企业的一个竞争优势Effective and efficient scheduling can be a competitive advantage高效的调度意味着商品或者服务更快的通过生产设施，提高了资产的利用率，从而降低了成本Faster movement of goods through a facility means better use of assets and lower costs高效的调度意味更强的生产能力，更快的吞吐速度以及生产柔性，意味着更快的交货速度从而可以为顾客提供更好的服务Additional capacity resulting from faster throughput improves customer service through faster delivery良好的调度意味着更可靠的交货期Good schedules result in more dependable deliveries15.2 调度问题Scheduling Issues-领导-指挥-战争战役指挥员给我冲+跟我冲调度就是安排各项运作的时间Scheduling deals with the timing of operations调度的任务就是根据设备能力对需求预测+订单进行分配并安排优先级The task is the allocation and prioritization of demand调度要考虑的问题Significant issues are调度的类型，正向还是逆向的The type of scheduling, forward or backward迎战+进攻调度准则的优先标准 The criteria for priorities不同组织调度决策有不同内容Scheduling Decisions 医院、学校、制造商、餐厅及航空公司组织Organization管理人员需要对以下内容进行调度Managers Must Schedule the Following医院Arnold Palmer Hospital手术室的使用Operating room use病人收治Patient admissions护理人员、安全人员以及设备护理人员Nursing, security, maintenance staffs门诊患者的治疗Outpatient treatments大学University of Missouri教室和音响设备Classrooms and audiovisual equipment学生和教师的课表Student and instructor schedules本科生和研究生的课程Graduate and undergraduate courses工厂Lockheed Martin factory产品生产Production of goods物料采购Purchases of materials工人Workers餐厅Hard Rock Cafe厨师、服务员、吧台侍者Chef, waiters, bartenders新食物交付Delivery of fresh foods表演人员 Entertainers餐厅营业时间Opening of dining areas航空公司Delta Air Lines飞机维护Maintenance of aircraft起飞时间表Departure timetables航班机组人员、餐饮服务人员、登机口和检票人员Flight crews, catering, gate, ticketing personnel调度工作计划流程Scheduling Flow 把握组织的能力计划+综合计划+主生产计划+短期调度的关系能力计划长期，年 设备变更设备调整综合计划中期，季度或月设备利用率人员调整分包主生产计划中期，周物料需求计划分解综合生产计划短期调度短期，天、小时或分钟工作中心负荷作业排序/分派15.2.1正向调度与逆向调度Forward and Backward Scheduling正向调度Forward scheduling正向调度一旦需求已知，就开始调度Forward scheduling starts as soon as the requirements are known产生一个可行的时间表，虽然它可能无法满足交货期Produces a feasible schedule though it may not meet due dates经常导致在制品库存积压Frequently results in buildup of work-in-process inventoryDue DateNow案例 医院、诊所、餐厅和机床制造等一般上班前准备好。逆向调度Backward scheduling逆向调度从计划交付期开始，首先从最后一项作业开始调度Backward scheduling begins with the due date and schedules the final operation first对其他工序逆向依次进行调度Schedule is produced by working backwards though the processes实现调度计划所需资源可能出现匮乏Resources may not be available to accomplish the scheduleDue DateNow案例制造业企业+宴会+安排手术有需求就准备有时两者结合效果更好Often these approaches are combined to develop a trade-off between a feasible schedule and customer due dates15.2.2调度准则Scheduling Criteria调度在于优化资源满足生产目标Optimize the use of resources so that production objectives are met完成时间最短Minimize completion time利用率最高Maximize utilization of facilities在制品库存最少Minimize work-in-process (WIP) inventory顾客等待时间最短Minimize customer waiting time不同工艺流程的调度方法Different Processes/ Different Approaches：工艺专业化设施作业车间+工作单元+重复性生产设施装配线+连续性生产+大规模定制工艺专业化设施Process-focused facilities正向调度Forward-looking schedules MRP due datesFinite capacity scheduling工作单元Work cells正向调度Forward-looking schedulesMRP due datesDetailed schedule done using work cell priority rules重复性生产设施Repetitive facilities正向调度Forward-looking schedule with a balanced linePull techniques for scheduling连续性生产Product-focused facilities正向调度Forward-looking schedule with stable demand and fixed capacityCapacity, set-up, and run times knownCapacity limited by long-term capital investment大规模定制Mass Customization逆向调度Backward scheduling正向调度-效率逆向调度-响应性15.3 工艺专业化设施的调度Scheduling Process-Focused Facilities 工艺专业化设施间歇性设施/作业车间的调度多品种,小批量的生产系统+原料+加工顺序+加工需求+加工时间+调整设备安排订单计划不要超过的能力约束Schedule incoming orders without violating capacity constraints发布一个订单指令前,要检查该部门可用的工具和材料Check availability of tools and materials before releasing an order为每个工作设置完成时间,并检查生产进度Establish due dates for each job and check progress检查在制品情况Check work in progress提供反馈Provide feedback提供工作效率统计和监控操作人员的时间Provide work efficiency statistics and monitor times计划文件Planning Files零件主文件包括企业采购和生产的每个零部件的信息An item master file contains information about each component工艺路线文件用于说明每个零部件在车间内部的工艺流程A routing file indicates each components flow through the shop工作中心主文件包括工作中心的各种信息产能和效率A work-center master file contains information about the work center控制文件Control Files根据每项工作指令的计划来跟踪实际进度Track the actual progress made against the plan15.4 作业分配Loading Jobs 分配Loading是指将工作分配给工作中心和加工中心。作业分配设法将成本、空闲、完成时间最小化Assign jobs so that costs, idle time, or completion time are minimized分配的两种形式Two forms of loading能力导向Capacity oriented将作业分配给特定的工作中心Assigning specific jobs to work centers15.4.1输入-输出控制Input-Output Control识别超负荷或负荷不足Identifies overloading and under loading conditions采取迅速管理行动来解决调度问题Prompts managerial action to resolve scheduling problems通过固定在制品卡片，对运营系统工作任务总量来进行控制Can be maintained using ConWIPconstant working-in-process固定在制品 cards that control the scheduling of batches运作人员可以从以下几方面管理作业流程，实现有效调度Options available to operations personnel include:校正设备性能Correcting performances提高产能Increasing capacity增加或减少工作中心的输入Increasing or reducing input to the work center实际投入Actual Input+实际产出Actual Output15.4.2甘特图Gantt Charts-调度的有效工具甘特图，也称为条状图(Bar chart)，是1917年由亨利甘特开发的，其内在思想简单，基本是线条图，横轴表示时间，纵轴表示活动(项目)，线条表示在整个期间上计划和实际的活动完成情况。它直观地表明任务计划在什么时候进行，及实际进展与计划要求的对比。Load chart shows the loading and idle times of departments, machines, or facilities，Displays relative workloads over time，Schedule chart monitors jobs in process，All Gantt charts need to be updated frequently to account for changes15.4.3任务分配方法Assignment Method-指派问题属于线性规划问题，按照资源分配任务或工作A special class of linear programming models that assign tasks or jobs to resources目标：成本和时间的最小化Objective is to minimize cost or time一项作业分配给一台设备Only one job (or worker) is assigned to one machine (or project)两个纬度：任务-完成者作业分配是一种关注运作负荷的生产能力控制技术。15.5 作业排序Sequencing Jobs 排序Sequencing规定各项作业被完成先后顺序。15.5.1派工的优先规则Priority Rules for Dispatching Jobs-指导方针-适用于工艺专业化设施确定工作的顺序,即工作应该那个工作中心先实施Specifies the order in which jobs should be performed at work centers优先规则用于对工作进行分派和排序Priority rules are used to dispatch or sequence jobs先到先服务FCFS: First come, first served最短加工时间SPT: Shortest processing time最早交货时间EDD: Earliest due date最长加工时间LPT: Longest processing time作业加工时间Job Work (Processing) Time (Days)+预定交货时间Job Due Date (Days)规则Rule平均完成时间Average Completion Time (Days)利用率Utilization (%)系统中的平均作业数量Average Number of Jobs in System平均作业延迟Average Lateness (Days)医院一般会采用先到先服务，但急诊室有时候会例外。比较排队规则Comparison of Sequencing Rules没有哪个规则在所有方面都好No one sequencing rule excels on all criteria最短加工时间-加工时间短SPT does well on minimizing flow time and number of jobs in the system，But SPT moves long jobs to the end which may result in dissatisfied customers先到先服务-公平FCFS does not do especially well (or poorly) on any criteria but is perceived as fair by customers最早交货时间-延迟最短EDD minimizes lateness15.5.2关键比Critical Ratio关键比是一个数值指标，可以用距预订交货期限的剩余时间与剩余工作时间的比值来表示An index number found by dividing the time remaining until the due date by the work time remaining on the job作业的关键比较低比值低于1说明其已落后于计划，大于1的关键比意味着该作业超前于计划Jobs with low critical ratios are scheduled ahead of jobs with higher critical ratios与优先规则不同，关键比是动态的，易于进行更新Performs well on average job lateness criteria关键比的作用Critical Ratio Technique确定某项作业的进度情况Helps determine the status of specific jobs确定各项作业之间的相对优先顺序Establishes relative priorities among jobs on a common basis将备货生产和订货生产联系起来Relates both stock and make-to-order jobs on a common basis自动调整优先顺序（修改进度计划），根据需求和作业进度的变化情况Adjusts priorities automatically for changes in both demand and job progress对作业进度情况实行动态跟踪Dynamically tracks job progress15.5.3 N项作业2台机器的排序:约翰逊规则Sequencing N Jobs on Two Machines: Johnsons Rule适用于两个或两个以上的工作,任务通过两台机器或工作中心的排序问题Works with two or more jobs that pass through the same two machines or work centers最小化加工时间，最小化空闲时间Minimizes total production time and idle time约翰逊规则Johnsons Rule第一步：从零件在两台设备的加工时间中，找出最小值，若有两个或几个相同的最小值，任取一个。List all jobs and times for each work center，Choose the job with the shortest activity time. 第二步：若最小值出现在前一设备上，则该零件应最先加工，若出现在后一设备上，则该零件应最后加工。If that time is in the first work center, schedule the job first. If it is in the second work center, schedule the job last. 第三步：将已排加工顺序的零件除去，再重复第一、第二步，照此思路，直到把所有零件排Once a job is scheduled, it is eliminated from the list，Repeat steps 2 and 3 working toward the center of the sequence15.5.4基于规则的作业派工系统的局限性Limitations of Rule-Based Dispatching Systems 调度是动态的，各种规则需随着订单、工艺、设备、产品作相应的调整Scheduling is dynamic and rules need to be revised to adjust to changes各种规则没有顾及生产流程上下游的变化Rules do not look upstream or downstream各种规则没有顾及预订交付期之外的因素库存+订单Rules do not look beyond due dates15.6 有限能力计划Finite Capacity Scheduling (FCS) 通过为调度人员提供交互式计算机图形系统输出，克服了基于规则的排队系统的缺陷Overcomes disadvantages of rule-based systems by providing an interactive, computer-based graphical system除使用优先规则外、甘特图、还使用专家系统或仿真允许实时响应系统的变化May include rules and expert systems or simulation to allow real-time response to system changes初始数据经常来自于MRP系统Initial data often from an MRP system可以根据生产效率对需求交付进行动态平衡FCS allows the balancing of delivery needs and efficiency15.7 约束理论Theory of Constraints 约束理论（Theory of Constraints, TOC）是以色列物理学家、企业管理顾问戈德拉特博士(DrEliyahu MGoldratt)在他开创的优化生产技术(Optimized Production Technology，OPT)基础上发展起来的管理哲理，该理论提出了在制造业经营生产活动中定义和消除制约因素的一些规范化方法，以支持连续改进(Continuous Improvement)。产销量指的是企业生产并销售出去的产品数量。Throughput is the number of units processed through the facility and sold 约束理论是一个知识体系，用于处理任何限制组织实现目标的能力问题TOC deals with the limits an organization faces in achieving its goals通过五步来识别并管理这些限制条件识别约束Identify the constraints制定计划来克服已识别的约束Develop a plan for overcoming the constraints集中资源来完成计划Focus resources on accomplishing the plan通过减少负荷或扩大能力来减少约束的影响Reduce the effects of constraints by off-loading work or increasing capacity克服旧约束，识别新约束Once successful, return to step 1 and identify new constraints15.7.1瓶颈Bottlenecks 瓶颈是工作中心的一种约束，限制了生产的产出Bottleneck work centers are constraints that limit output 生产的变化引起瓶颈产生Common occurrence due to frequent changes处理瓶颈的方法Management techniques include: 提高瓶颈环节的能力Increasing the capacity of the constraint 交叉培训员工和加强设备维护Cross-trained employees and maintenance改变工艺路线、加工过程或寻求分包商Alternative routings, procedures, or subcontractors 将检查和测试移到瓶颈环节的紧前位置Moving inspection and test调整产销计划、使其与瓶颈环节相匹配Scheduling throughput to match bottleneck capacity 15.7.2鼓、缓冲、绳子Drum, Buffer, Rope 鼓是指系统的-节拍，提供作业计划-决定系统生产率The drum is the beat of the system and provides the schedule or pace of production缓冲指的是系统资源-库存The buffer is the inventory necessary to keep constraints operating at capacity绳子可以被认为是看板-信号The rope provides the synchronization necessary to pull units through the systemI5.8 重复性设施的调度Scheduling Repetitive Facilities 重复性生产企业希望满足顾客需求、降低在制品资金投入、减少批量规模、充分利用设备和工艺流程Level material use can help repetitive facilities：Better satisfy customer demand，Lower inventory investment，Reduce batch size，Better utilize equipment and facilities调度重点在于实现物料平准化，其是按照准时制要求，实行频繁的、高质量的小批量生产模式。-这正是世界级生产企业的管理实践平准化的优势Advantages include:降低库存水平Lower inventory levels加快产出速度Faster product throughput提高零部件质量Improved component quality减少占地面积需要Reduced floor-space requirements改善员工沟通Improved communications使生产过程更顺畅Smoother production process15.9 服务业的调度Scheduling Services 服务系统和制造系统的差异Service systems differ from manufacturing制造业调度Manufacturing服务业调度Services机器和原料Schedules machines and materials人员Schedule staff使用库存平滑需求 Inventories used to smooth demand很少维持库存Seldom maintain inventories机器密集型和需求可以平滑Machine-intensive and demand may be smooth劳动密集型服务需求是变化的Labor-intensive and demand may be variable调度受到工会协议的限制Scheduling may be bound by union contracts法律因素限制灵活的调度Legal issues may constrain flexible scheduling较少社会和行为问题Few social or behavioral issues社会和行为问题比较重要Social and behavioral issues may be quite important医院医院拥有复杂的调度系统来处理复杂的流程和材料要求Hospitals have complex scheduling system to handle complex processes and material requirements银行交叉培训、灵捷的劳动力和兼职人员Banks use a cross-trained and flexible workforce and part-time w