Facilitator's Question: What are the deciding factors for adopting conveyor (as shown in your Blog) instead of other material handling equipment (MHE) in a warehouse/distribution centre? Explain.
Factors like controls, noise levels and energy efficiency are other deciding factors for adopting conveyors.
Controls have a direct impact on how the conveyor will operate. Firstly, they provide direction to the conveyors. It acts as a traffic cop for data coming from other conveyors, the warehouse management system, and related warehouse components. Both programmable logic controllers and PC-based controls are commonly used. Two other conveyor options to consider are plug-and-play capabilities and modular designs. Plug-and-play units possesses their own power, drives, and controls within each major section of the conveyor. This allows the system to be re-routed and physically relocated with minimal effort.
Secondly, noise reduction is also a common criteria in conveyor selection. Many facilities order conveyors with high precision bearings that surpass safety and health requirements for noise. Cost would increase but it also reduces worker fatigue.
Lastly, energy-efficient motors may be a consideration especially with energy prices in flux.
Unit load formation equipment used to restrict materials so that they maintain their integrity when handled a single load during transport and for storage. The major types of unit load formation equipment are :
-Self-restraining(no equipment)
-Pallets
-Skids
-Slipsheets
-Tote pans
-Pallet boxes/skid boxes
1. Self-Restraining (No Equipment)Self-restraining means one or more items that can maintain their integrity when handled as a single item (e.g., a single part or interlocking parts)
2. Pallets
-Platform with enough clearance beneath its top surface (or face) to enable the insertion of forks for subsequent lifting purposes.
-Most common materials for pallets is wood but paper, plastic, rubber and metal can also be used.
-Size of pallet is specified by its depth (i.e., length of its stringers or stringer boards) and its width (i.e., length its deckboards)—pallet height (typically 5 in.) is usually not specified.
3. Skids
-Platform (typically metal) with enough clearance beneath its top surface to enable a platform truck to move underneath for subsequent lifting purposes
-Forks can also be used to handle skids since the clearance of a skid is greater than that of a pallet
-Compared to a pallet, a skid is usually used for heavier loads and when stacking is not required; a metal skid can lift heavier loads than an equal-weight metal pallet because it enables a platform truck to be used for the lifting, with the platform providing a greater lifting surface to support the skid as compared to the forks used to support the pallet
4. Slipsheets
-Thick piece of paper, corrugated fiber, or plastic upon which a load is placed
-Handling method: tabs on the sheet are grabbed by a special push/pull lift truck attachment
5. Tote Pans
-Tote pans are reusable container used to unitize and protect loose discrete items
-People typically used for in-process handling
-Returnable totes provide alternative to cartons for distribution
-Pallet boxes are reusable container used to unitize and protect loose items for fork/platform truck handling
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Transport equipment is used to move material from one location to another within a facility or at a site.
The major subcategories of transport equipment are:
-Industrial truck
-Cranes
-Conveyors
-No Equipment
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Industrial trucks are used to move materials over variable paths, with no restrictions on the area covered by the movement. The major types of industrial trucks are:
1. Hand truck
a)Two-wheeled hand truck
b)Dolly
c)Floor hand truck
2.Pallet jack
a)Manual pallet jack
b)Powered pallet jack
3.Walkie stacker
a)Manual walkie stacker
b)Powered walkie stacker
4.Pallet truck
5.Platform truck
a)Walkie platform truck
b)Rider platform truck
6. Counterbalanced lift truck
a) Sit-down counterbalanced lift truck
b) Stand-up counterbalanced lift truck
7. Narrow-aisle straddle truck
8. Narrow-aisle reach truck
9. Turret truck
a) Operator-down turret truck
b) Operator-up turret truck
10. Order picker
11. Sideloader
12. Tractor-trailer
13. Personnel and burden carrier
14. Automatic guided vehicle (AGV)
a) Tow AGV
b) Unit load AGV
c) Assembly AGV
d) Light load AGV
e) Fork AGV
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Cranes are used to move materials over variable paths within a restricted area. The major types of cranes are:
1.Jib crane
2.Bridge crane
3.Gantry crane
4.Stacker crane
1. Jib Crane
-It operates like an arm in a work area, where it can function as a manipulator for positioning tasks
-A hoist is attached to the arm for lifting
-Arm mounted on the wall or attached to a floor mounted support
-Arm can rotate 360°-The hoist can move along the arm
-The hoist can move along the arm
2. Bridge Crane
-Bridge mounted on tracks that are located on opposite walls of the facility
-Enables three-dimensional handling
-Top riding (heavier loads) or underhung (more versatile) versions of the crane
-Underhung crane can transfer loads and interface with other MHS (e.g., monorail systems)
3. Gantry Crane
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-Single leg, double leg, and mobile types of gantry cranes
-Similar to a bridge crane except that it is floor supported at one or both ends instead of overhead (wall) supported
-Used to span a smaller portion of the work area as compared to a bridge crane
-The supports can be fixed in position or they can travel on runways
-Can be used outdoors when "floor" supported at both ends
4. Stacker Crane
-Similar to a bridge crane except that, instead of a hoist, it uses a mast with forks or a platform to handle unit loads
-Considered "fork trucks on a rail"
-Used for storing and retrieving unit loads in storage racks, especially in high-rise applications in which the racks are more than 50 feet high
-Can be controlled remotely or by an operator in a cab on the mast
-Can be rack supported
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Identification and control equipment is used to collect and communicate the information that is used to coordinate the flow of materials within a facility and between a facility and its suppliers and customers.
Bar codes, Radio Frequency(RF) tags, magnetic stripe, Electronic Data Interchange (EDI) and portable data terminal are the major types of identification and communication equipment.
1) BAR CODESThe video above tells us what UPC bar codes are and how does it work.
2) RADIO FREQUENCY (RF) TAGRF tags have greater data storage capability than bar codes. Most of the tags contain at least two parts. One is an integrated circuit for storing and processing information, modulating and demodulating a (RF) signal and can also be used for other specialized functions. The second is an antenna for receiving and transmitting the signal.
3) MAGNETIC STRIPEIt is a data encoded on a magnetic stripe that is readable in almost any environment. It have a greater storage capability and more expensive than bar codes.
4) ELECTRONIC DATA INTERCHANGE (EDI)Electronic data interchange (EDI) provides standards for inter-corporate transfer of purchase orders, invoices, shipping notices, and other frequently used business documents. But it is expensive.
5) PORTABLE DATA TERMINALHandheld, arm-mounted, or vehicle-mounted data storage and communication device.
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Storage equipments are used for holding or buffering materials over a period of time.
The major types of storage equipment include :
- Block stacking (no equipment)
- Pallet Rack - Selective Pallet Rack, Drive-through rack, Drive-in rack, Push-back rack, Cantilever rack, etc.
- Stacking frame
- Shelves/bins/drawers
- Storage carousel
- Automatic storage/retrieval systems (AS/RS)
- Split case order picking system
- Mezzanine
Block Stacking
Block stacking is a palletized storage that does not use any storage equipment. Loaded pallets are placed directly on the floor and built up in stacks on top of one another to a maximum stable height. Warehouse safety is one of the primary concerns in warehousing. Therefore, it is recommended to have a maximum stable height of stacks (e.g. usually not more than six pallets). This aims to prevent accidents of toppling pallets.
Below is a video of which you could easily see how dangerous it is if accidents were to happen.
Ideally, any one row of pallets should contain pallets of the same products to avoid double handling and to simplify records of stock locations (where possible). When setting out the simple block stacking, clearances should be allowed for the movement of forklifts. It is recommended to have lines painted on the floor to help maintain the layout disciple.
Free access to retrieval of these pallets is limited only to pallets on top/ front of each row, or at the sides. Thus difficulties may be encountered in practicing First- In- First- Out (FIFO). This is especially the case for pallets which are situated in the ‘middle’ or ‘bottom’ of the blocks.Block stacking is said to be more suitable for stored products which have only few product lines, each with high inventory level to ensure FIFO movement of inventory. Hence it is a good practice to empty a row completely before replenishing any more products into that row.
With no storage equipments required, it provides flexibility for the warheouse to change the layout of blocks (when necessary). Below is a pictures are taken from a local bearing company, to illustrate bulk stacking in a warehouse. The logo has been blanked out to protect the confidentiality of the company.
Advantages of block stacking :
- lower capital cost
- no storage equipment needed
- good utilization of area/space in warehouse
- easy control
- suitable for throughputs
Disadvantages of block stacking :
- increase in material handling costs as FIFO is practised in warehouses and additional costs are incurred
- limits on stack heights which can restrict the use of building height
- honeycombing which reduces storage capacity
- no strict FIFO
- free access is only to pallets at the top of each row
- risk of fire as pallets are located very close to each other
Pallet Rack
A pallet rack, also referred to as “pallet racking,” is for stocking inventory that sits on pallets (or “skids”) that are stored in horizontal rows with multiple levels; pallet racks allow warehouse inventory to be stored more efficiently (called maximum storage density). The pallet racks link together to create a pallet rack system. Forklift trucks are usually required to place the loaded pallets onto the racks for storage because of their size and weight. Pallet racks are essential and ubiquitous to modern warehouses, retail centers, and other facilities.
Selective Pallet Rack
Selective pallet rack systems are the most commonly used rack system because they are inexpensive and quick and easy to assemble. Selective pallet racks typically come in two configurations: a teardrop, or clip-in configuration, and a 
structural bolt-together configuration. The nickname “teardrop” comes from the fact that the holes on the column of the upright are shaped like a teardrop. Pallets then rest on the horizontal beams that are held in place by mounting clips.
Because the clips on teardrop configurations can be quickly moved, the shelves can be easily adjusted to different heights to accommodate various load sizes. This is convenient for a warehouse that needs to store a wide variety of product sizes. Another advantage of selective pallet rack systems is the easy accessibility they provide to all products at all times. Such accessibility is important if the inventory is rapidly depleted and restocked (called quick turnover). A selective pallet rack system is commonly used in a “big-box” distribution application, as well as in retail store inventory rooms, cold storage applications, wholesale stores, etc.
Drive-In & Drive Through Rack
Drive-in and Drive-through (sometimes spelled Drive-thru) are storage rack configurations that allow the forklift to drive directly into the lane of stacked rows (called a bay). The difference between a drive-in and a drive-thru pallet rack system is simply whether the bays have an entry at only one end, or at both ends. Drive-in rack systems use a common 
entry and exit, while drive-thru systems have entry points at either end of the bay. Because a drive-in racking system has only one entrance, it uses what is called a “Last In, First Out” (LIFO) storage method. With only one entrance, the last pallet put into a row is necessarily the first one to be taken out. A drive-thru storage system, with two different entry points, can also use a “First-In, First-Out” (FIFO) storage method. With a FIFO system, pallets are loaded in one end and are pushed back to the other end, where they are then at the front of the row on the opposite side. The first pallet put into such a row is the first one taken out at the other end. This system is advantageous for material with an expiration date or wherever shelf life is a major concern.
Advantages of Drive-In / Drive-Through rack Systems:
- Eliminate conventional traffic aisles
- High density storage
- Floor -to-ceiling palletized storage
- Lower costs
- Greater Throughput
- FIFO & LIFO inventory management
Push-Back Rack
Push-back pallet rack systems are designed around the principle of organizing space by depth rather than width. This depth arrangement greatly reduces aisle space and increases storage density. In this configuration, each row is multiple pallets deep, and often has wheeled carts that fit onto rails to take advantage of gravity, saving enormous amounts of energy for moving heavy pallets. When a forklift sets the pallet onto the cart, it drives forward and causes the pallet to bump the next pallet, causing the entire row of pallets to roll backwards. When removing a pallet from the front position the remaining pallets immediately stage themselves forward so that the next available pallet can be accessed.
Here is a video to give you a better understanding of push-back racks.
Pushback rack increases product storage by 75% verses a selective rack system. Pushback rack system provides high density pallet storage, safer operation, less rack damage, more throughput, and higher productivity. Configurations for Pushback systems range from 2 to 6 pallet positions deep and up to 4 or more levels high. Pushback rack can greatly increase the number or pallet positions in an existing warehouse.
Cantilever Rack
Cantilever Racks allow full selectivity. They can hold long and irregular loads & standard or specialized handling equipment. With how its structured, it enables floor space savings.
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