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คลงสนคา และการบรหารจดการคลงสนคาคลงสนคา และการบรหารจดการคลงสนคาWarehouse Operations and Management
B ff It h ld i t f d t t f th l• Buffer: It holds inventory for downstream stages of the supply chain, in order to allow the entire production / distribution network to deal efficiently with the systematic and random
i ti i th t k ti t l it i ifi tvariation in the network operations, or to exploit significant economies of scale.
• Typical sources/examples of systematic variationyp / p y• product seasonality • cyclical / batched production due to large set‐up costs
• Typical sources of random variationTypical sources of random variation• variations in transportation times due to weather, traffic congestion, bereaucracy, etc.
• variations in production times due to unreliable operations, unreliable suppliers
• Typical economies of scale involved• Price breaks in bulk purchasing
C lid i l d lid d• Consolidation center: accumulates and consolidates products from various points of manufacture within a single firm, or several firms, for combined shipment to common customers. , p
• Consolidation allows to control the overheads of transportation operations by:– allowing the operation of the carriers to their capacity, and therefore,
the more effective amortizing of the fixed transportation costs– reducing the number of shipping and receiving operations
V l Add d P i (VAP) I i l h• Value‐Added‐Processing (VAP): Increasingly, warehouses are required to undertake some value‐added‐processing tasks like:– pricing and labeling– kitting (i.e., repackaging items to form a new item; e.g., “beauty”
products)products)– light final assembly (e.g., assembly of a computer unit from its
constituent components, delivered by different suppliers)– invoicing
• In general, this development is aligned to and suggested by the idea/policy of postponement of product differentiation,the idea/policy of postponement of product differentiation,which allows for customized product configuration, while maintaining a small number of generic product components.
Receivingreceipt of all materials coming into the warehouse; 2) Providing the assurance that the quantity and quality of such materials are as ordered; 3) Disbursing materials to storage or to other
10%organizational functions requiring them.
The act of placing merchandise to storage; it includes 15%Put‐away
p g g ;1) determining and registering the actual storage location(s), 2) transportation and 3) placement
กจกรรมโลจสตกสในคลงสนคากจกรรมโลจสตกสในคลงสนคาThis set of activities includes•checking that the requested material is available to
Processing customer orders
•checking that the requested material is available to ship;•if necessary, coordinating order fulfillment with other facilities of the distribution network;•producing the “pick” lists to guide the order picking
‐•producing the pick lists to guide the order picking and the necessary shipping documentation;•scheduling the order picking and the shipping activity.
Order‐picking
The collection of activities involved in 1) Order receipt of all materials coming into the warehouse; 2) Providing the assurance that the quantity and quality of such materials are as ordered 3) 55%p g quality of such materials are as ordered; 3) Disbursing materials to storage or to other organizational functions requiring them.
h k Checking orders for completeness (and quality 15%Checking Checking orders for completeness (and quality of product) 15%
g g pp pshipping containers, and attaching the necessary documentation / labels.
•preparing the shipping documents (packing
‐
Shipping
p epa g t e s pp g docu e ts (pac glist, address label, bill of lading);•accumulating orders to outbound carrier;•loading trucks (although, in many instances, thi b th i ’ ibilit )
‐
Handling returns, and performing the additional value added processing supported
this may be the carrier’s responsibility).
Others additional value‐added‐processing supported by contemporary warehouses, as discussed in a previous slide
An excellent tool – Receiving and Shipping Analysis Chart (RSAC)
Columns 1‐5: define what is to be received or shippedColumn 6: size of shipmentColumn 6: size of shipmentColumn 7: when the receipts and shipments will occurColumns 8‐9: list the types of carriersC l 10 11 h dli h d & i i d f l di / l di
Columns 10‐11: handling methods & time required for loading/unloading
Determine Dock RequirementsDetermine Dock Requirements
D t i i th i t f th• Determining the requirements for the receiving and shipping dock baysH d k b i d?• How many dock bays are required? Frequency of activity Carrier inter‐arrival time and service time Guessing Waiting‐line analysis Simulation
• How should the dock bays be configured? Types of vehicle at the dock bay
1. Defining materials to be stored2. Choosing a storage philosophy2. Choosing a storage philosophy 3. Space requirements for alternative storagemethods
• Fixed location storage• each individual SKU is always stored in a specific location, and• no other SKU may be stored in that location, even though that location may
be empty
• Random location storage• Random location storage • any SKU may be assigned to any available storage location
Cl b d t• Class‐based storage • SKU’s are grouped into classes. Each class is assigned a dedicated
storage area but SKU’s within a class are stored according tostorage area, but SKU s within a class are stored according to randomized storage logic
• Major Criteria driving the decision‐making process:Enhance the throughput of your storage and retrieval operations by reducing the travel time <=> reducing the travel distance
• How? By allocating the most “active” units to the most “convenient” locations...
L ti ith th ll t di t d j t th I/O• Locations with the smallest distance d_j to the I/O point!
• In case that the material transfer is performed throughIn case that the material transfer is performed through a forklift truck (or a similar type of material handling equipment), a proper distance metric is the, so‐called,
tili M h tt t i ( L1 )rectilinear or Manhattan metric (or L1 norm): d_j = |x(j)‐x(I/O)| + |y(j)‐y(I/O)|
• For an AS/RS type of storage mode where the S/R unitFor an AS/RS type of storage mode, where the S/R unit can move simultaneously in both axes, with uniform speed, the most appropriate distance metric is the, so‐ll d T h b h i ( L )called Tchebychev metric (or L norm):
SKU’ h l f ffi ไ • SKU’s that cause a lot of traffic. (สนคาทมการเคลอนไหวมาก‐รบเขา จายออก
สมาเสมอ)
I t d t t th i t “ ti it ” f i• In steady state, the appropriate “activity” measure for a given SKU i:
Average visits per storage location = (number of units handled per unit ofAverage visits per storage location = (number of units handled per unit of time) / (number of allocated storage locations) = TH_i / N_i
A fast solution algorithmA fast solution algorithm
• Rank all the available storage locations in increasing distance from the I/O point, d_j.
• Rank all SKU’s in decreasing “turns”, TH_i/N_i.• Move down the two lists, assigning to the next mostMove down the two lists, assigning to the next most highly ranked SKU i, the next N_i locations.
• Consider that classes are established in such a way that SKU’s with comparable ratios of TH_i/N_i belong to the same class.F th ith l i t t titi• Furthermore, with every class c associate two quantities
– N_c = a*i N_i where a
– TH_c = i TH_i• Then the logic developed for the location assignment underThen, the logic developed for the location assignment under
dedicated storage applies immediately when replacing the set of SKU’s i by the set of classes c.
The trade‐offs behind the establishment of a “forward pick” area• A forward pick area increases the pick density by
concentrating a large number of SKU’s within a small physical spacespace.
• On the other hand, it introduces the activity of restocking.• Also in general a forward pick area concerns the picking of• Also, in general, a forward pick area concerns the picking of
smaller quantities and involves more sophisticated equipment than the picking activity taking place in the reserves area. So, p g y g p ,its deployment requires some capital investment in equipment and (extra) space.
Selecting the SKU’s to be accommodated in the fast‐pick area and the corresponding volumes
• W d t tif th “ t b fit” f h i th SKU i th f t• We need to quantify the “net benefit” of having the SKU in the fast‐pick area vs. doing all the picking from the reserve.
• This is done as follows: Let– V: Volume of entire forward‐pick storage area (e.g., in cubic ft)– f_i: Flow of SKU i, (e.g., in cubic ft / year)– c_r: cost of each restock trip ($/trip)– s: the saving realized when a pick is done from the forward area
rather than the reserve ($/pick)– p_i: the expected annual picks for SKU i (picks/year)
i l b ll d SKU i i 1 ( bi f )– u_i: storage volume to be allocated to SKU i, i=1,…,n (cubic ft)Then, the net annual benefit of allocating fast‐pick storage u_i to SKU i, is:
CrossdockingCrossdockingSeeks to eliminate the expensiveSeeks to eliminate the expensive functions of inventory STORAGEand ORDER PICKING from
d di t ib ti t bmodern distribution centers by taking advantage of the information system infrastructure in modern supply chains.Hence, at a crossdock, ReceivingGoods is already assigned to a Shipping, and therefore, the only required functions are qconsolidation and shipping.