Saturday, January 17, 2009

Why do we need layout design?

The goal of warehouse layout design is to optimize your warehousing functions and achieve maximum efficiency and space utilization.

A warehouse is typically divided into areas to support your every day processes. These areas include: reserve storage, forward pick, cross docking, shipping, receiving, assembly/special handling lines, and quality/inspection area.
Designing a new facility starts with analyzing your current and projected data on the activities in each of these areas, including the receiving, shipping and inventory levels. This data should be supported by other considerations such as process flows, material handling equipment, type and styles of racking equipment, special handling requirements, and personnel.

When considering the layout and operation of any warehouse system, there are fundamental principles that embody a general philisophy of good practice.The principles are:

1) Using the most suitable unit load

2) Making the best use of space

3) Minimizing movement

4) Controlling movement and location

5) Providing safe, secure and environmentally sound conditions

6) Maintaining at minimum overall operating cost

Successful warehouse layouts must adhere to the principles, regardless of material being stored to:

i) maximize the use of space

ii) maximize the use of equipment

iii) maximize the use of labor

iv) maximize accessibility to all items

v) and maximize protection of all items

Although the objectives of warehouse layout and operation are easily recognized, warehouse layout problems are often complicated by large varieties of products needing storage, varying areas of required storage space and drastic fluctuations in product demand.

Therefore, an effective layout design of the warehouse is required to address these problems and accomplish the objectives.

Taken from:

Space Requirements Planning

The first step in laying out a warehouse is to determine the overall space requirements for all warehouse processes. The space requirements for each process should be computed and summarized to estimate the overall building requirements. Effective space utilization makes good use of total building volume and not merely the floor area.

For example, when calculating the space required for the receiving and shipping staging area, the number of receiving and shipping dock doors and the turnaround time for each dock would be considered. A common practice is to allocate enough staging space behind each dock door to accommodate a truckload’s worth of material.

Some other processes that would be considered in the space requirement planning include case picking, pallet storage, broken case picking, packing and unitizing, customizing, cross docking and more.

Warehouses should also be designed based on current and future needs to:

  • Facilitate changes in business/agency growth, and size/population of office and warehouse spaces within the building. Warehouse space should be easily adapted to new functions such as office (on ground or upper levels), computer centers, or light industrial/fabrication.

  • Accommodate need for future loading docks, truck space, and car parking spaces if space configuration changes through effective site design.

  • Address material handling technologies and business practice, such as "just-in-time" storage, which have fundamentally changed operation of warehouses and distribution centers, and will continue to do so.

  • Include roof design with built-in extra structural capacity to handle addition of future rooftop equipment.

  • Be designed with fire protection capacity to accommodate storage of materials with a greater fire hazard, especially needed with high plastic product content or packaging, and plastic shrink-wrapped pallets.
It should also be able to maximize utilization of space while providing adequate circulation paths for personnel and material handling equipment such as forklift trucks. We should also use higher bays to take advantage of height allowances in the space.

Alternative material handling methods will determine other building aspects, such as aisle widths, lighting design, need for mezzanine space, fire protection, and egress design. Businesses will often use different methods of storage handling simultaneously for different products.

Taken from:

Factors affecting warehouse layout & planning

Outside Factors

Various external factors influence the design and layout of a warehouse operation. These factors have to be taken into considerations to achieve an optimum overall system.
  • Size & configuration of site: must be adequate to accommodate the required equipments

  • Site access: must be adequate for the types of vehicle and volume of traffic using that particular site

  • Local authority plans: the proposed warehouse can be greatly affected by the government development plan

  • Site details: characteristics of the facilities found in the site such as drainage and ground.

  • Financial considerations: consider about the rents, costs of ownership, investments grants

  • Building factors: existing building to be use as a warehouse.

Inside Factors

These factors has a dominant influence on how effectively a warehouse can be operated.
  • Flow of goods in the warehouse: ‘U’ flow or through flow

  • Movement of people and equipments

  • Access to stock and minimize congestion

  • Identification of stock and codes

  • Stock location, rotation( FIFO)

  • Stock checking requirements

  • Stock replenishment

  • Handling of goods in and out of the warehouse

  • Supervision, safety, stock security

Warehouse aisles and gangways need to be properly design in order to achieve one of the warehouse objectives, which is maximizing effective use of space. The widths in between should be adequate enough for movement of people and equipment. It is ideal to have separate doors for people on foot and for forklift trucks.

Some areas should also be set aside for other warehouse activities. These include:

  • Areas for loading and unloading vehicle

  • Staging or temporary storage areas

  • Office space, washroom and lunch rooms

  • Area for repacking, labeling, marking

  • Area for equipment storage and maintenanceHazardous or high-value items

5 main areas of warehouse operation

There are 5 main areas of warehouse operation. They are consisted of the following:

1. Goods in
2. Main store – reserve stock
3. Order picking – forward stock
4. Marshalling
5. Goods out

Each area is briefly categorized as below:

Goods In (Incoming of goods)

• Receipt – unload, temporary hold
• Check – correct goods received, grade, package, quantity, damage or shortages
• Record receipts & discrepancies
• Unpack, repack if necessary
• Decide goods location

Main Store – reserve store

• Locate goods in reserve storage area
• Confirm goods location to control function
• Issue goods to replenish order picking stock

Order Picking – forward store

• Select goods for customer orders
• Pack & check
• Packaging material store

A video of the order picking function is shown below:


• Assemble goods by customer, or by vehicle load

Goods Out – outgoing goods

• Loading facilities for vehicles
• Vehicle despatch schedules

These areas can be illustrated in the image below:

Taken from:
  • Johnny Tan, Oh Hui Ling, Cheryl Wee-Teo, Distribution Centre Management, Fourth Edition (2007)

Throughflow and U flow

Material Flow Planning
Planning the flow of materials is important in a warehouse. This is because with a plan, we would most likely be aware of the location of items in the warehouse and also the status and location of the handling equipments. With these information, better control of the warehouse can be achieved.

There are two main approaches of the plan of material flows. They are the 'U' flow and 'Through' flow.

'U' flow
A 'U' flow occurs when the goods receipt and dispatch functions are located at the same end of a warehouse building.

Products flow in at receiving, move in to storage in the back of the warehouse, and then to shipping, which is located at the adjacent to receiving on the same side of the building.

Items with higher throughput level are located closer to the loading bays. An example of a 'U' flow design can be seen in the diagram below.

Advantages of 'U' Flow

  • Excellent utilization of dock resources because the receiving and shipping processes can share dock doors

  • Facilitating cross-docking because the receiving and shipping docks are adjacent to one another and may be co-mingled
  • Excellent lift truck utilization because put away and retrieval trips are easily combined and because the storage locations closest to the receiving and shipping docks are natural locations to house fast moving items

  • Yields excellent security because there is a single side of the building used for entry and exit

'Through' flow

'Through' flow happens when separate loading bay facilities for outbound and shipping are provided, often at opposite end of warehouse.

Products flow in at receiving, move into storage, picking area and then the marshalling and depatch area in a straight line.

Items with a higher throughput levle are located at the center of the warehouse because the total distance travelled would be shorter. An example of a 'Through' flow layout design is shown on the diagram below.

The major disadvantage of a 'Through' flow layout is goods need to travel the full length of the warehouse, even for goods that have a higher throughput level. It is also harder to control and less flexible.

When is it better to adopt a 'Through' flow?

  • When there is a risk of interference or confusion between goods in and goods out
  • When goods inwards vehicles and dispatch vehicles are very different; for example differences in platform height or nature of unit load

  • When a warehouse is connected to a production plan

Taken from:

  • Edward H. Frazelle, World-class warehousing and material handling (2002)

  • Johnny Tan, Oh Hui Ling, Cheryl Wee-Teo, Distribution Centre Management, Fourth Edition (2007)

Usefulness and Constraints of Layout Design

Usefulness of layout design

1) An effective warehouse layout design can help to optimize the efficiency and space utilization.

With the 5 main areas of operations, goods can move in swiftly from the unloading area, into the main storage; picker can also pick goods from the picking area. Congestions are minimized and these help to increase the efficiency of the different tasks in the warehouse.

By storing goods with a plan to locate them neatly; more space can be utilized; either horizontally or vertically.

2) There would also be higher labor efficiency and lesser errors.

A layout plan would minimize the movement of the employees and the time used for moving can be used to do other operations or work; thus increasing labor efficiency.

A neatly planned warehouse would have lesser errors such as picking the wrong item or storing the wrong goods in wrong place.

3) Safety and security of a warehouse would most likely be enhanced through an effective layout because employees would know where the walking spaces are and no goods would be left lying around.

Constraints of layout design

Space Constraint
It is very important that when you plan the design layout of the warehouse, you need to think how to make it that the use of space is at the optimum level. It is because that by making the best use of space, you will be able to have a higher amount of inventory storage. Making the best use of space does not only mean the floor areas which is horizontally but also vertically. By maximising the use of space can also help to reduce the total cost of the warehouse therefore it important to take note of the usage of space when designing the warehouse layout.

Constraint of the 5 main areas
Beside making best use of the space, when we design the layout, we should also consider where are we going to locate the different areas of the warehouse. (Goods in, Main storage, order picking, marshalling, goods out) It is because by considering this factors, you will be able to minimize the movement and congestion in the warehouse and therefore, the rate of accident in the warehouse would also decrease. One example is the separation of the main storage and the order picking area.

Some questions asked by other groups:

Bernice's group
Q: U- flow is always preferred for cross-docking.Then May I know how cross-docking works with through flow?

A: Cross docking is preferred in a U flow because the total distance travelled is shorter compared to the through flow where every product needs to travel through the whole warehouse.

In a through flow layout, cross docking can be done by moving the product in the center of the warehouse; directly from the unloading area to the loading area in a straight line.

As you can see from the diagram of the through flow, moving in the center of the warehouse minimizes the total distance travelled compared to moving to the left or right of the warehouse.

Therefore, cross docking can also be done in a through flow layout but the total distance travelled would still be more than a U flow layout.

Jessica's group
Q: Can you give me more examples of how to use of space at the optimum level?

A: One example is to minimize the width and number of gangways or aisles.

Having a large number of aisles take up a lot of space that can be used to store inventories.

However, aisles is a necessary to have a safe warehouse movement, it cannot be completely removed, therefore, what we can do is to minimize them, and carefully positioning them to make the best use of space.

Careful positioning of pipes is also another example of how designing an effective layout can help to utilize the best space.

A warehouse with pipes obstructing the space where it can be used to store more inventory is not utilizing the space at its optimal level.

Another example could be by using racking system.

Using this system, you will be able to make use of the space between the ground and the ceiling of the warehouse. This would enable you to store more goods and also make the use of space at it optimum level.

Hope we answered your enquires =)

Thursday, December 18, 2008

Aishah's field trip reflection

The educational field trip to Army Logistic Base (ALB) in Old Choa Chu Kang Road which I went on the 28th November was such an eye-opener for me, as I got to take a look at how do logistic warehouses works and operates. It was a great experience to start with, as it has impart me with more knowledge and see the real life processes that was mentioned during the E-Lectures.

When we reached, we attended a talk which introduced us more to the company. After which, we were brought around the warehouse to see their operations and practices. ABL had stored a wide range of goods but mostly is for the Army. They had a few different storage system installed such as Mobile Racking System, Pallet ASRS, Bin ASRS, Vertical Carousel System(VCS). The person in-charge of our group during the tour explained how each storage system works and some of his colleagues showed us how each of them works. This made me understand more about what i had read in the text book and also the lectures.

ALB adopted a through flow layout; the loading and unloading bays are at the opposite ends. The main areas are Unloading Bay, Main Area (reserve)- where we saw the Laser Guided Vehicle, Order Picking (forward)- where we the VCS, Marshalling and Loading Bay. The main aspect which is important is Safety. Safety is greatly emphasized in the warehouse to prevent accidents to workers and damage to the goods.

All in all, I think it was a fruitful trip for all of us. It was helpful to aid us in understanding better how warehouses operates in reality. Just by reading and knowing from books and notes is not enough, seeing how they work physically is such a great and meaningful experience.

By Aishah