采购与仓储管理-Warehouse science.ppt

1、Warehouse Science,E-mail:第一章 Warehouse rationale,仓库是什么？ Warehouses are the points in the supply chain where product pauses, however briefly, and is touched. 为什么需要仓库？ To better match supply with customer demand: demand can change quickly, but supply takes longer to change. Warehouses can

2、 also buffer against sudden changes in supply. To consolidate product To provide value-added processing,仓库分类 While there are many types of warehouses in the supply chain, there is a systematic way to think about a warehouse system regardless of the industry in which it operates.,第一章 Warehouse ration

3、ale,第二章 Material flow,什么是供应链？ The “supply chain” is the sequence of processes through which product moves from its origin toward the customer. Pipeline 与incompressible fluid model流体模型,流体模型对我们的启发: Keep the product moving; avoid starts and stops, which mean extra handling and additional space requirem

4、ents. Avoid layouts that impede smooth flow. Identify and resolve bottlenecks to flow. 流体模型与JIT的关系 该模型是对现实的一种近似,第二章 Material flow,库位 固定库位： The simplest is dedicated storage, in which each location is reserved for an assigned product and only that product may be stored there. 固定库位的好处（Pros） Because th

5、e locations of products do not change, more popular items can be stored in more convenient locations and workers can learn the layout, all of which makes order-picking more efficient.,第二章 Material flow 库位：固定库位与共享库位Storage: “Dedicated” versus “Shared”,固定库位的缺点（Cons)： The problem with dedicated storage

6、 is that it does not use space efficiently. 共享库位,第二章 Material flow 库位：固定库位与共享库位Storage: “Dedicated” versus “Shared”,共享库位的缺点： 需要仓库管理信息系统的支持 工人操作时间成本及复杂性增加 怎么办？,第二章 Material flow 库位：固定库位与共享库位Storage: “Dedicated” versus “Shared”,共享库位对提高仓库存储空间利用率的测算 How much improvement in space utilization is possible

7、with shared storage? 考虑一种产品，两周的需求量，存储在两个相等大小的库位上且需求速率恒定的情形 空间利用率=平均库存/平均所需存储空间,第二章 Material flow 库位：固定库位与共享库位Storage: “Dedicated” versus “Shared”,第三章：仓库作业 Warehouse operations,仓库作业的总体特点： A warehouse reorganizes and repackages product. Product typically arrives packaged on a larger scale and leaves p

8、ackaged on a smaller scale. In other words, an important function of this warehouse is to break down large chunks of product and redistribute it in smaller quantities. In general, the smaller the handling unit, the greater the handling cost.,仓库作业具体而言，包括以下两大部分： Inbound processes Receiving 收货 Put-away

9、 放置 Outbound processes Order-picking 分拣 Checking, packing, shipping,第三章：仓库作业 Warehouse operations,仓库作业的原则 尽可能减少停顿 保持可视化,第三章：仓库作业 Warehouse operations,Receiving（收货）作业的特点 Receiving may begin with advance notification of the arrival of goods. This allows the warehouse to schedule receipt and unloading

10、to coordinate efficiently with other activities within the warehouse. 伴随接收的可能有检验,扫描输入数据库等. 人力需求不高 对配送中心而言，大约仅占其运作成本的10%左右,第三章：仓库作业 Warehouse operations,Put-away（放置）作业 在物品摆放到货架之前，必须决定好其合适的存储地点并将该信息输入系统 需要较多的人力成本 对配送中心而言，大约仅占其运作成本的15%左右,第三章：仓库作业 Warehouse operations,Order-picking分拣 与其它作业相比，与信息系统的结合更紧密

11、 Order-picking 与收货不同,前者是被动的少量的.而后者是可能事先知道故做了相关准备且是大批的.故前者更费时间. 另外,随着生命周期越来越短,对拣货的时间要求越来越快.,第三章：仓库作业 Warehouse operations,分拣大约仅占仓库运作成本的55%左右，分拣成本进一步可分解为以下各部分,第三章：仓库作业 Warehouse operations,Order-picking 对不同物品的分拣成本是不同的。 提高分拣效率的方法 storing the most popular skus together batch orders 合并订单进行分拣,第三章：仓库作业 War

12、ehouse operations,是否应合并订单进行分拣取决于订单结构 single-line orders Very large orders Intermediate-size orders 注意,Batching Picking可能会减少Responsiveness, 因为还需再次分拣,第三章：仓库作业 Warehouse operations,分拣的其它问题 分拣工人的合作分拣问题 可分为product-to-picker 与Picker-to-product,第三章：仓库作业 Warehouse operations,Checking and packing 对人力需求大 Litt

13、le Walking 保证订单准确性，避免错发货 对客户的订单尽可能提高包装的容积率,第三章：仓库作业 Warehouse operations,总结 Most of the expense in a typical warehouse is in labor; most of that is in order-picking; and most of that is in travel. 仓库的其它作业 handle returns labeling Postponement of final assembly Invoicing,第三章：仓库作业 Warehouse operations,

14、确定仓库需要的月台（DOCK） 的数量nD=dt/qT 仓库容量的决定 (以托盘的数量为计算单位) 1:Dedicated storage policy 2:Random storage policy 3:Class-based storage policy 计算实例 计算储存区的长宽高 高是由储存的技术来决定的(如叉车最高能多高,如是人力的话最高能多高) 长与宽的决定 Lx Ly Nx Ny 计算实例,第六章 仓储规划,确定仓库需要的月台（泊位）数量,确定仓库需要的月台（泊位）数量,仓库容量的决定,The area of the storage zone must be large enou

15、gh to accommodate goods in peak periods. On the other hand, if the storage zone exceeds the real needs of the firm, storage and retrieval times become uselessly high. This could reduce the throughput or increase material handling cost.,计算储存区的长宽高,计算储存区的长宽高,计算储存区的长宽高,计算储存区的长宽高,计算储存区的长宽高,计算储存区的长宽高,第六章

16、仓库内部规划,因而，为了最小化行走成本（Travel cost) : 将所有的库位按照di 从小到大进行排序 将所有的物品按周转速度从大到小进行排序 Move down the list, assigning the pallets of the next fastest-turning skus to the next best locations available.,第六章 仓库内部规划,第六章 仓库内部规划-确定收货与发货区的位置,第六章 仓库内部规划-确定收货与发货区的位置,哪种更好? 取决于流入流出仓库物品的总体结构 If there will be a small amount

17、of very fast-moving skus, it may be more efficient to put receiving and shipping on the same side of the facility, because the savings from the few very convenient locations may offset any loss due to the greater number of less convenient locations.,第六章 仓库内部规划,第一种：贯通式Flow-through configuration,这两种规划

18、各自的特点characteristics of each type of layout:,第一种：贯通式 收发货区位于仓库的两侧 使得很多存储库位处于同等便利的位置 保守设计: More reasonably convenient storage locations 但很少的库位处于非常便利的位置 更适合于流量非常大的仓库 适合于仓库长而狭窄时的情形 Limits opportunity for efficiencies by dual transactions,两种规划各自的特点,第二种： U-形设计,这两种规划各自的特点characteristics of each type of lay

19、out:,第二种：U-形设计 收发货区位于库房的同侧 Makes the most convenient locations still more convenient, less convenient locations even worse. 适合于当物品的周转速度呈现较强的ABC特点时的情形 提高了收发货区使用的效率及柔性 提高了叉车的使用效率 节省了库房前道路的投资费用 Allows expansion along other three sides of warehouse.,这两种规划各自的特点characteristics of each type of layout:,仓库货区

20、的其它的规划方式,提高仓库容积利用率的两种方法 : 利用托盘货架增加堆垛的高度 Pallets that can be stacked high allow many pallet positions per square foot of floor space. Conversely, pallets that are unusually heavy or fragile or that have uneven top surfaces cannot be stacked very high and so render unusable all the space above. This w

21、aste may be avoided by installing pallet rack（货架）, so that pallets may be stored independently of each other.,第六章 仓库内部规划,它能使存放的物品更易存取，因而能够减少人力。如下图：,第六章 仓库内部规划,储存货架的深度Lane depth,储存货架的深度Lane depth,这里存在着背反: The single-deep layout has eight aisles and provides 196 pallet storage locations, all of which

22、are directly accessible, which means that they are available for reassignment as soon as the current pallet is shipped out. In contrast, the double-deep layout has only six aisles and provides 280 pallet storage locationsbut only 140 of them are directly accessible. 因而：更深的货架能够产生更多的库位但其价值是递减的。,储存货架的深

23、度Lane depth,对单个物品的分拣是库房操作中最费人力的作业，因为其操作对象为最小的单位。 Warehouses that, 20 years ago, might have shipped cartons to customers now ship pieces and much more frequently. The importance of piece-picking has greatly increased because of pressures to reduce inventory while expanding product lines. 为了提高分拣效率，库房应

24、该考虑的是将储存作业（区域）与分拣作业（区域）分开。,快速分拣区的设计Design of a fast pick area,什么是快速分拣区 A separate picking area, sometimes called a fast-pick or forward pick or primary pick area, is a sub-region of the warehouse in which one concentrates picks and orders within a small physical space. 快速分拣区一般采用固定库位的方式,快速分拣区的设计Desig

25、n of a fast pick area,设置快速分拣区的好处: Many of the most popular stock keeping units (skus) are stored there in relatively small amounts, so that most picking can be accomplished within a relatively small area. This means that pickers do less unproductive travel and may be more easily supervised. Reduced

26、pick costs and increased responsiveness to customer demand. 弊端：需要不断从存储区域补货,快速分拣区的设计,设计快速分拣区要考虑的基本问题: 哪些SKUs应放在快速分拣区？以及 每一种sku 放多少，空间多大 估算补货成本 补货的成本取决于以下因素 The number of times the sku requires replenishment. The number of storage units to be replenished.,快速分拣区的设计Design of a fast pick area,为简单起见，我们假设补

27、货的成本仅与补货的次数有关，这与现实是近似的。 补货次数的估计 If sku i flows through the warehouse at rate fi cubic feet per year then we can estimate that sku i will require about 其中:fi= vi is the volume cubic-feet of sku i stored in the fast-pick area.,快速分拣区的设计Design of a fast pick area,快速分拣区的设计Design of a fast pick area,令 V 为

28、快速分拣区的总容量，我们的问题为： 不失一般性，我们仅考虑两种A and B. 则问题为 将第一个约束条件用等式vA+vB = V代替并代入到目标函数。,快速分拣区的设计Allocating space in the fast-pick area,目标函数变为 对VB微分求一阶条件，我们得到: 更一般化,我们有以下结论：,快速分拣区的设计Design of a fast pick area,该结论显示： 分配给某SKU的最优存储空间不仅取决于自己的流动速度 fi ，而且还取决于所有其它SKU的流动速度 进一步，我们有以下推论：,快速分拣区的设计,现实中两种通常使用的快速分拣区存储空间的分配方法

29、 等空间分配（Equal Space Allocation）: Allocates the same amount of space to each sku, so that, if V cubic feet are available, vi = V/n and sku i is restocked nfi/V times a year. 等时间分配（Equal Time Allocation）: stores an equal time supply of each sku, so that vi/fi = vj/fj .,快速分拣区的设计,定理:无论为等空间分配还是等时间分配，所需要的补

30、货次数是一样的，相应地，两种方式所产生的总补货成本也相同。,快速分拣区的设计,例：考虑分拣区总空间为1，两个SKU A 与 B 其fi 分别为16与1，则两种不同的空间分配方式的结果如下：,快速分拣区的设计,结论: 各SKU流速f的差异越大，则使用最优的空间分配方法所减少的补货次数越多，进而对减少总补货成本的效果越明显。 比如: 6,000 fast-moving skus of a major drug store chain; Equal Time Allocations require almost 50% more restocks than optimum. With over 10

31、0 order-pickers and 20 re-stockers, this suggests that only about 70 order-pickers and 14 re-stockers were necessary, which means a significant direct savings in labor.,快速分拣区的设计,进一步，有如下定理： Theorem (“Law of Uniform Restocking”) Under Optimal Allocations each unit of storage space will be restocked at

32、 the same frequency.,快速分拣区的设计,按组存储（Storage by family） 将相关物品存放在一起的原因： To get good space utilization, product of similar sizes or shapes might be stored together. To simplify put-away, product might be stored by vendor so that all product arriving on a truck goes to the same region of the warehouse. P

33、roduct may be grouped by security requirements.,快速分拣区的设计的其它问题,Slotting refers to the careful placement of individual cases/ pieces within the warehouse/cases. It may be thought of as layout in the small. Slotting 的目标包括： 在给定的空间装入更多的物品 通过将周转速度快或较重的物品放在合适的位置比如waist level来提高人体工程学的效率。,仓库规划-微观Pieces: Geom

34、etry of slotting装箱,装箱(Packing)问题: 有三类 One-dimension 仅考虑重量, 对那些密度很高的物品如钢材 Two-dimension Three-dimension NP-hard 故一般用算法.,仓库规划-微观Pieces: Geometry of slotting装箱,直接转运站台是高速的仓库（Crossdocks are high speed warehouses）. 如果一个到达的物品已经有了最终的需求，那么就没有必要进行存储而应该直接从收货区运到发货区。这样该物品经过该仓库的速度就加快了，这样仓库操作的人力成本就大大减少了。 In a high

35、-volume crossdock the turnover times may be measured in hours. To support this velocity of movement, a crossdock may be nothing more than a slab of concrete with a roof and walls punctuated with doors for trailers. Freight is pulled off arriving trailers, sorted and loaded onto departing trailers wi

36、thout intermediate storage.,直接转运（Cross-docking）,为什么直接转运? The biggest reason to have a crossdock is to reduce transportation costs. This can be achieved by consolidating multiple shipments so that full truck loads can be sent 。,直接转运的原因,一般而言，卸货比装货要容易，通常后者所花的时间是前者的两倍。 为了使物品流动的更通畅，流入流出直接转运站台的容量应该合理设计。比如

37、, one should plan to have twice as many outgoing doors as incoming doors. Alternatively, one can balance the rates of flow by assignment or workers. More doors not necessarily means efficiency, rather, the long distance may increase the travel time and the consequently the labor cost.,直接转运中心的设计,北美 m

38、ass consumption. allows fewer, more centralized and therefore larger distribution centers.,世界各地的仓库简介（Warehousing around the world）,东亚 The most active economic areas are separated by lots of water, which means lots of product conveyed by air (for high-value or time-sensitive products) or ship (for bu

39、lky items or commodities). For both air and sea cargo, the large fixed costs increase incentives to consolidate freight Consequently, one expects to see the emergence of strong regional hubs, such as Singapore and Hong Kong, to support this consolidation.,世界各地的仓库简介（Warehousing around the world）,印度In

40、dia Capital costs are relatively high in relation to the cost of labor and so there is less pressure to install specialized storage, even pallet rack. And because labor costs are low there is less incentive to increase efficiency. For example, it is not an attractive proposition to reduce labor cost

41、s by picking from flow rack: The labor savings cannot justify the cost of the rack or the forklift trucks.,世界各地的仓库简介（Warehousing around the world）,In addition, warehouses in India distribute mainly to the local economy and so supply a market that is not wealthy. Consequently, the skus are not likely

42、 to be high cost items and so there is not much savings available from reducing inventories by precise timing. Consequently information technologies cannot generate much savings. Finally, inefficiencies in transport make India in effect a collection of smaller markets. These inefficiencies include t

43、he physical, such as roads in less-than-ideal condition, as well as the administrative.,世界各地的仓库简介（Warehousing around the world）,For example, each state within India levies customs duties on freight transported across the border (different from China). This slows interstate commerce and increases the

44、 expense. Such factors increase the costs of transportation and so favor a strategy of having more, smaller distribution centers rather than fewer, larger ones, where the volume of activity could better justify capital investment,世界各地的仓库简介（Warehousing around the world）,China A distinctive feature of

45、 the logistics scene in China is the seemingly boundless supply of very low cost of labor together with relatively inexpensive land. Consequently warehouses tend to be large, low buildings as in North America; but with some striking differences.,合适的就是最好的,世界各地的仓库简介（Warehousing around the world）,Despite cheap labor, China does have some capital-intensive warehouses, with the latest information technology and storage equipment. Such warehouses are most likely devoted to the distribution of high-value goods for export. Because such goods, such as consume