Inventory control

Types of Inventories

Raw material
• Components (sub-assemblies)
• Work-in-process: waiting in the system for processing
or being processed (JIT reduces WIP to a minimum).
• Finished goods (products): also known as end items.
Reasons for holding Inventories
Economies of Scale: savings in large orders
• Uncertainty in delivery lead times: lost customers
• Speculation: changing costs over time
• Transportation: large investments in pipelines
• Smoothing: dealing with demand variations
• Inventory Control costs: increase with lower levels of inventory.
Characteristics of Inventory Systems
• May Be Known or Uncertain (random)
• Rate may be constant or variable
Lead Times (τ):
• Time that elapses from placement of order until it’s arrival.
Internally, it’s the time required to produce an item.
Review Time:
• Is system reviewed periodically or is system state known at
all times?
Excess demand:
• Is either back-ordered or lost Inventory Costs
Holding Costs (h):
• Costs proportional to the quantity of inventory physically
on hand.
• Includes: Physical Cost of Space, Taxes and Insurance, Breakage
Spoilage and Deterioration , and Opportunity Cost of alternative
• Convenient to express holding cost in terms of dollars
per unit per year.
• If c is the dollar value of the inventory unit, and I is the
annual interest rate, then h = Ic.


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Material Handling Equipment

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:

[li]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.[/li][/ol][ol]
[li]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.[/li][/ol][ol]
[li]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.[/li][/ol][ol]
[li]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.[/li][/ol][ol]
[li]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.[/li][/ol]

| Top | About MHE Taxonomy |

I. Transport Equipment

A. Conveyors

[li]Chute conveyor[/li][li]Wheel conveyor[/li][li]Roller conveyor[/li][li]Chain conveyor[/li][li]Slat conveyor[/li][li]Flat belt conveyor[/li][li]Magnetic belt conveyor[/li][li]Troughed belt conveyor[/li][li]Bucket conveyor[/li][li]Vibrating conveyor[/li][/ol][ol]
[li]Screw conveyor[/li][li]Pneumatic conveyor[/li][li]Vertical conveyor[/li][li]Cart-on-track conveyor[/li][li]Tow conveyor[/li][li]Trolley conveyor[/li][li]Power-and-free conveyor[/li][li]Monorail[/li][li]Sortation conveyor[/li][/ol]
B. Cranes

[li]Jib crane[/li][li]Bridge crane[/li][li]Gantry crane[/li][li]Stacker crane[/li][/ol]
C. Industrial Trucks

[li]Hand truck[/li][li]Pallet jack[/li][li]Walkie stacker[/li][li]Pallet truck[/li][li]Platform truck[/li][li]Counterbalanced lift truck[/li][li]Narrow-aisle straddle truck[/li][/ol][ol]
[li]Narrow-aisle reach truck[/li][li]Turret truck[/li][li]Order picker[/li][li]Sideloader[/li][li]Tractor-trailer[/li][li]Personnel and burden carrier[/li][li]Automatic guided vehicle (AGV)[/li][/ol]
D. No Equipment

II. Positioning Equipment

[li]Manual (no equipment)[/li][li]Lift/tilt/turn table[/li][li]Dock leveler[/li][li]Ball transfer table[/li][li]Rotary index table[/li][li]Parts feeder[/li][/ol][ol]
[li]Air film device[/li][li]Hoist[/li][li]Balancer[/li][li]Manipulator[/li][li]Industrial robot[/li][/ol]
III. Unit Load Formation Equipment

[li]Self-restraining (no equipment)[/li][li]Pallets[/li][li]Skids[/li][li]Slipsheets[/li][li]Tote pans[/li][li]Pallet boxes/skid boxes[/li][li]Bins/baskets/racks[/li][li]Cartons[/li][/ol][ol]
[li]Bags[/li][li]Bulk load containers[/li][li]Crates[/li][li]Intermodal containers[/li][li]Strapping/tape/glue[/li][li]Shrink-wrap/stretch-wrap[/li][li]Palletizers[/li][/ol]
IV. Storage Equipment

[li]Block stacking (no equipment)[/li][li]Selective pallet rack[/li][li]Drive-through rack[/li][li]Drive-in rack[/li][li]Flow-through rack[/li][li]Push-back rack[/li][li]Sliding rack[/li][/ol][ol]
[li]Cantilever rack[/li][li]Stacking frame[/li][li]Shelves/bins/drawers[/li][li]Storage carousel[/li][li]Automatic storage/retrieval systems (AS/RS)[/li][li]Split case order picking system[/li][li]Mezzanine[/li][/ol]
V. Identification and Communication Equipment

[li]Manual (no equipment)[/li][li]Bar codes[/li][li]Radio frequency (RF) tag[/li][li]Magnetic stripe[/li][/ol][ol]
[li]Machine vision[/li][li]Portable data terminal[/li][li]Electronic data interchange (EDI)/Internet[/li][/ol]