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.
-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
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
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
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 CODES
The video above tells us what UPC bar codes are and how does it work.
2) RADIO FREQUENCY (RF) TAG
RF 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 STRIPE
It 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 TERMINAL
Handheld, arm-mounted, or vehicle-mounted data storage and communication device.
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.
Positioning equipment is used to handle material at a single location so that the material is in the correct position for handling, machining, transport, or storage. Material can also be positioned manually using no equipment. The major types of positioning equipment are:
1) Lift/Tilt/Turn Table
2) Dock Leveller
3) Ball Transfer Table
4) Rotary Index Table
5) Parts Feeder
6) Air Film Device
7) Hoist
8) Balancer
9)Manipulator:a) Rigid-Link Manipulator; b) Articulated Jib Crane Manipulator and c) Vacuum Manipulator
10) Industrial Robot
Manual (No Equipment)
Material can be positioned manually without using equipment.Under ideal circumstances, maximum recommended weight for manual lifting to avoid back injuries is 23kg.
As compared to manual handling, the use of positioning equipment can provide benefits:
- raise the productivity of each worker when the frequency of handling is high
- improve product quality and limit damage to materials and equipment when the item handled is heavy or hard to hold and damage is likely through human error or inattention, and
- reduce fatigue and injuries when the environment is hazardous or inaccessible
Now, let us look at the different functions of the different positioning equipment:
1) Lift/Tilt/Turn Table It is used when positioning involves the lifting, tilting, or turning of a load. Also, it is used to reduce or limit a worker’s lifting and reaching motions.
Pallet load levellers are lift and turn tables used in manual palletizing to reduce the amount of bending and stooping involved with manually loading a pallet by combining a lifting and turning mechanism with a device that lowers the table as each layer is completed so that loading always takes place at the optimal height of 1m.
2) Dock Leveler Used at loading docks to compensate for height differences between a truck bed and the dock.
The ball transfer table is used when products are required to be manually rotated or correctly positioned, such as a work station or other similar operation that requires quick, easy handling of the product. Ball transfer table is also used when more than two conveyor lines converge and packages must be transferred from one line to another.
It is used for the synchronous transfer of small parts from station to station in a single workcenter. The circular table rotates in discrete intermittent steps to advance parts between stations located along its perimeter. However, it is difficult to put buffer between stations since each part moves between stations at the same time.
5) Parts Feeder
For feeding and orienting small identical parts, particularly in automatic assembly operations.
Motion can be imparted through vibration, gravity, centrifugal force, tumbling, or air pressure.
Parts feeders can be used to provide inspection capabilities with respect to the shape and weight of parts (e.g., the coin feeder of a vending machine).
Used to enable precision positioning of heavy loads. It can be used in place of cranes and hoists. It can be used in warehousing as the mechanism to convert stationary racks into sliding racks.
7) Hoist
It is used for the vertical translation (i.e., lifting and lowering) of loads. Frequently attached to cranes and monorails to provide vertical translation capability.
8) Balancer
Mechanism used to support and control loads so that an operator need only guide a balanced ("weightless") load, thus providing precision positioning. It can also be attached to hoist and manipulators.
9) Manipulator
Commonly used for vertical and horizontal translation and rotation of loads. Acting as "muscle multipliers," manipulators counterbalance the weight of a load so that an operator lifts a small portion (1%) of the load’s weight. It can be powered manually, electrically, or pneumatically.
To provide variable programmed motions of loads. It is also used for parts fabrication, inspection, and assembly tasks. It consists of a chain of several rigid links connected in series by revolute or prismatic joints with one end of the chain attached to a supporting base and the other end free and equipped with an end-effector. The end-effector can be equipped with mechanical grippers, vacuum grippers, electromechanical grippers, welding heads, paint spray heads, or any other tooling. It can be powered manually, electrically, or pneumatically.
Here is a video on NACHI, a Japanese company which uses industrial robot to handle material.
Conveyors are used when material is to be moved frequently between specific points; they are used to move material over a fixed path. Depending on the materials to be handled and the move to be performed, a variety of conveyors can be used.
It can be categorized in many ways. The location of the conveyor and the type of product being handled serves as a base for classificationof conveyors.
For bulk materials, it can be conveyed using a chute, belt, bucket or vibrating conveyors. Examples of bulk materials are grain and dry chemicals. Unit materials such as machined parts, cartons and tote boxes can be conveyed using chute, belt, roller, wheel, or tow conveyors. Material can be transported on belt, roller, wheel, vibrating, pneumatic or tow conveyors.
The video below illustrates how flat belt conveyor works.
The chain conveyor consists of one or more endless chains on which loads are carried directly. In transporting bulk materials, a chain is located in the bottom of a trough and pulls the material through the trough. Chain conveyors are often used to transport tote boxes and cartons.
Conveyors are not only use in factories but they are also widely used in restaurants especially in Japanese restaurants. Take a look at the video:
Material Handling Equipment is a crucial procedure which its main objective is to efficiently move large quantities of inventory into the warehouse, as well as specific customer orders out of the warehouse. It facilitates the handling of materials seeking the ideal way to ensure the products arrive and depart the warehouse systematically.
The video shown will better allow you to understand the concept of material handling.
Hyundai's Material Handling
Material handling equipment (MHE) is used for the movement and storage of material within a facility or at a site. MHE can be classified into the following five major categories:
- Transport Equipment. Equipment used to move material from one location to another (e.g., between workplaces, between a loading dock and a storage area, etc.). The major subcategories of transport equipment are conveyors, cranes, and industrial trucks. Material can also be transported manually using no equipment.
- Positioning Equipment. Equipment used to handle material at a single location so that it is in the correct position for subsequent handling, machining, transport, or storage. Unlike transport equipment, positioning equipment is usually used for handling at a single workplace. Material can also be positioned manually using no equipment.
- Unit Load Formation Equipment. Equipment used to restrict materials so that they maintain their integrity when handled a single load during transport and for storage. If materials are self-restraining (e.g., a single part or interlocking parts), then they can be formed into a unit load with no equipment.
- Storage Equipment. Equipment used for holding or buffering materials over a period of time. Some storage equipment may include the transport of materials (e.g., the S/R machines of an AS/RS, or storage carousels). If materials are block stacked directly on the floor, then no storage equipment is required.
- Identification and Control Equipment. Equipment 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. The identification of materials and associated control can be performed manually with no specialized equipment.
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It is used for the vertical translation (i.e., lifting and lowering) of loads. Frequently attached to cranes and monorails to provide vertical translation capability.
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