1.1 Why have a warehouse?
Why have a warehouse at all? A warehouse requires labor, capital (land and storage-and-handling equipment) and information systems, all of which are expensive. Is there some way to avoid the expense? For most operations the answer is no. Warehouses,or their various cousins, provide useful services that are unlikely to vanish under the current economic scene. Here are some of their uses:
To better match supply with customer demand:
One of the major challenges in managing a supply chain is that demand can change quickly, but supply takes longer to change. Surges in demand, such as seasonalities strain the capacity of a supply chain. Retail stores in particular face seasonalities that are so severe that it would be impossible to respond without having stockpiled product. For example, Toys R Us does, by far, most of its business in November and December. During this time, their warehouses ship product at a prodigious rate (some conveyors within their warehouses move at up to 35 miles per hour). After the selling season their warehouses spend most of their time building inventory again for the following year. Similarly, warehouses can buffer the supply chain against collapsing demand by providing space in which to slow or hold inventory back from the market.
In both cases, warehouses allow us to respond quickly when demand changes. Response-time may also be a problem when transportation is unreliable. In many parts of the world, the transportation infrastructure is relatively undeveloped or congested. Imagine, for example,sourcing product from a factory in Wuhan, China for retail sale within the US. After manufacture, the product may travel by truck, then by rail, by truck again, and then be loaded at a busy port; and it may repeat the sequence of steps (in reverse order) within the US. At each stage the schedule may be delayed by congestion, bureaucracy, weather, road conditions, and so on. The result is that lead time is long and variable. If product could be warehoused in Los Angeles, closer to the customer, it could be shipped more quickly, with less variance in lead time, and so provide better customer service.Warehouses can also buffer against sudden changes in supply. Vendors may give a price break to bulk purchases and the savings may offset the expense of storing the product. Similarly, the economics of manufacturing may dictate large batch sizes to amortize large setup costs, so that excess product must be stored. Similarly, warehouses provide a place to store a buffer against unreliable demand or price increases.
To co solidate product to reduce transportation costs and to provide customer service.
There is a fixed cost any time product is transported. This is especially high when the carrier is ship or plane or train; and to amortize this fixed cost it is necessary to fill the carrier to capacity. Consequently, a distributor may consolidate ship- ments from vendors into large shipments for downstream customers. Similarly, when shipments are consolidated, then it is easier to receive downstream. Trucks can be scheduled into a limited number of dock doors and so drivers do not have to wait. The results are savings for everyone.Consider, for example, Home Depot, where more than a thousand stores are sup- plied by several thousands of vendors. Because shipments are frequent, no one vendor ships very much volume to any one store. If shipments were sent direct, each vendor would have to send hundreds of trailers, each one mostly empty; or else the freight would have to travel by less-than-truckload (LTL) carrier, which is relatively expensive (Figure 1.1). But there is enough volume leaving each vendor to fill trailers to an intermediate crossdock. And each crossdock receives product from many vendors, sorts it, and prepares loads for each store, so that the total freight bound for each store is typically sufficient to fill a trailer. The result is that vendors send fewer shipments and stores receive fewer shipments. Moreover, the freight is more likely to travel by full truck-load (TL) and so pay significantly less transportation costs (Figure 1.2).
A warehouse also provides opportunities to postpone product differentiation by enabling generic
product to be configured close to the customer. Manufactur- ers of consumer electronics are
especially adept at this. Country-specific parts, such as keyboards, plugs, and documentation, are
held at a warehouse and as- sembled quickly in response to customer order. This enables the
manufacturer to satisfy many types of customer demand from a limited set of generic items, which
therefore experience a greater aggregate demand, which can be forecast more accurately.
Consequently safety stocks can be lower. In addition, overall inventory levels are lower because
each item moves faster.
Another example is in pricing and labeling. The state of New York requires that all drug stores
label each individual item with a price. It is more economical to do this in a few warehouses,
where the product must be handled anyway, than in a thousand retail stores, where this could
distract the workers from serving the customer.
Figure 1.1: With m vendors and n stores the transportation plan consists of mn direct shipments, each relatively small and likely subject to the higher, less-than-truckload rates.
Figure 1.2: There are only m + n shipments through an intermediate aggregator, such as a distribution center or crossdock. Furthermore, each shipment is larger and more likely to qualify for the lower, full-truckload rates.
2 回答
为什么要有仓库?仓库需要劳动力、资金(土地、储存和搬运设备)和信息系统,所有这些都很昂贵。有什么办法可以避免这笔费用吗?对大多数企业来说,答案都是否定的。仓库或它们的各种兄弟公司提供的有用服务在当前的经济形势下不太可能消失。以下是它们的一些用途:
为了更好地满足客户的需求:
管理供应链的一个主要挑战是需求变化很快,但供应变化需要更长的时间。需求激增,如季节性调味品会使供应链的能力紧张。尤其是零售店面临的季节性变化非常严重,如果没有库存产品,就不可能做出反应。例如,玩具反斗城目前的大部分业务都在11月和12月进行。在这段时间里,他们的仓库以惊人的速度运送产品(他们仓库中的一些输送机以每小时35英里的速度移动)。销售旺季过后,他们的仓库将大部分时间用于为下一年重新建立库存。类似地,仓库可以通过提供空间来减缓或抑制市场库存,从而缓冲供应链的需求崩溃。
在这两种情况下,仓库使我们能够在需求变化时迅速作出反应。当运输不可靠时,响应时间也可能是一个问题。在世界许多地方,交通基础设施相对落后或拥挤。例如,想象一下,从中国武汉的一家工厂采购产品,在美国进行零售。产品制造完成后,可以通过卡车、铁路、卡车再次运输,然后在繁忙的港口装货;并且可以在美国境内重复步骤(以相反的顺序)。在每一个阶段,时间表可能会因交通堵塞、官僚主义、天气、路况等而延迟。其结果是交货期长且多变。如果产品能在离客户较近的洛杉矶仓库,则可以更快地发货,交货期差异更小,从而为客户提供更好的服务服务仓库也可以缓冲供应的突然变化。供应商可能会对批量采购给予价格折扣,而节省下来的费用可以抵消储存产品的费用。类似地,制造业的经济性可能要求大批量生产来分摊大量的安装成本,因此多余的产品必须储存起来。类似地,仓库提供了一个储存缓冲区,以应对不可靠的需求或价格上涨。
联合产品以降低运输成本并提供客户服务。
任何时候运输产品都有固定成本。当承运人是船舶、飞机或火车时,这一比例尤其高;为了分摊这一固定成本,有必要使承运人满载。因此,分销商可以将供应商的发货合并为面向下游客户的大宗货物。类似地,当货物被合并后,下游的接收就更容易了。卡车可以安排在有限数量的码头门,因此司机不必等待。结果是节省了所有人。考虑一下例如,家得宝(homedepot),那里有一千多家商店由数千家供应商提供服务。因为发货频繁,没有一家供应商会将大量货物运往任何一家商店。如果货物是直接发送的,每个供应商将不得不发送数百辆拖车,每辆拖车大部分都是空的;否则,货物将不得不由低于卡车(LTL)的承运人运输,这是相对昂贵的(图1.1)。但是每个供应商都有足够的数量来填充拖车到中间的交叉口。每个crossdock从许多供应商那里接收产品,对其进行分类,并为每个商店准备货物,这样每个商店的总运费通常足以装满一辆拖车。结果是供应商发送的货物更少,而商店收到的货物更少。此外,货物更可能通过满载卡车(TL)运输,因此支付的运输成本显著降低(图1.2)。
仓库还提供了通过启用泛型来推迟产品差异化的机会
靠近客户配置的产品。消费电子产品制造商
尤其擅长这个。特定国家的部件,如键盘、插头和文档
存放在仓库中,根据客户订单快速组装。这将启用
制造商从有限的一组通用项目中满足多种类型的客户需求
因此经历了更大的总需求,可以更准确地预测。
因此,安全库存可以降低。此外,由于库存水平较低
每件物品移动速度更快。
另一个例子是定价和标签。纽约州要求所有的药店
给每件商品贴上价格标签。在一些仓库里这样做比较经济,
不管怎么说,产品必须在那里处理,而不是在一千个零售店,在那里可以
分散工人的注意力,使他们不能为顾客服务。