WAREHOUSES OVERVIEW Flashcards
A distribution network is conformed by:
- transport
- warehouses
Warehouses, part of a DN, have 3 characteristics:
- Functions
- Types
- Functional areas
- Functions
What are they?
a) Storage: static.
Decoupling point, leverage of unpredictability of demand and LT.
b) Transformation and sort the flows: dynamic
Flows management
- Types
What are the main types of nodes?
a) Warehouses:
Inventories are present.
Safety and Cycle stocks
Materials planning and management needed. down and upstream flows.
Static +Dynamic functions
b) Transit points
Inventories absent, goods stored only to sort them.
In transit stocks.
Re-packing, cross docking, delivery
Dynamic functions only
- Activities:
What are the main activities (5)
- Receiving
- Put-Away
- Storage
- Picking
- Shipping
1-3 Inbound
3-5 outbound
What warehousing activity is characterised by:
Schedule carrier
Unload vehicle
Inspect for damage
Compare to P/O
- Receiving
What warehousing activity is characterised by:
Identify the product
Identify the storage location
Move products
Update records
- Put-away
What warehousing activity is characterised by:
physically maintaining the products in the designated or random area of the WH
- Storing
What warehousing activity is characterised by:
Managing order info
Picking goods
Moving goods
Labelling package
- Picking
What warehousing activity is characterised by:
Scheduling carrier
Loading vehicle
Bill of landing
Recording update
- Shipping
When we talk about designing a WH, what are we defining? (2)
Handling system & layout
3 Handling storage parameters:
- Design parameters
- Descriptive parameters
- Cost Parameters
Handling storage parameter,
Design 1/2 :
Number of UL locations (UL)
SC: Storage Capacity
Handling storage parameter,
Design 2/2 :
Flow of UL. (UL/h)
Input Capacity
Output Capacity
TC: Throughput capacity
Handling storage parameter,
Descriptive 1/3 :
Number of units I can store per m2 (UL/m2)
SC / WH Area
AUR: Area Utilisation Rate
Handling storage parameter,
Descriptive 2 /3 :
Directly accessible UL locations / SC
Ratio <= 1
Selectivity
Handling storage parameter,
Descriptive 3 /3 :
UL stored / SC
Ratio <= 1
Saturation
Handling storage parameter
What are the 2 Cost parameters
Storage cost per UL
[ € / UL*year ]
Handling Cost per UL handled
[ € / UL]
What are:
Block stacking
Rail Racks
Selective pallet racks
Flow racks
Storage Systems for big size UL
What are:
Miniload
Carousels
Vertical AS/RA
Systems for small size UL
OR
Picking Systems
Mainly used to move pallets both horizontally and vertically
- Counterbalance forklift (sit)
- Straddle reach (standing)
Mainly used to move pallets both horizontally and vertically usually in the aisles
Expensive
- side loaders
- turret trucks
Used to move horizontally and unload trucks
walkie stackers
You storage in the floor
No racks
UL must be stackable (3/4)
Low selectivity
LIFO
Low AUR
High Inventory level
Block stacking
Racks
UL non or stackable
better selectivity
Special trucks 1m
LIFO
High AUR
High Inventory level
Drive in/through
Storage system that enables gravity-based moving with inclined roll conveyors
Low selectivity
Low retrieval
Medium to high stock level
High cost
Paet/case flow rack system
amount of time it takes to locate, pick, and retrieve a specific item from the warehouse once it has been requested.
retrieval time
Couple of racks separated by working aisles
uprights and beams
High selectivity (1 if 1 dept)
Cost is low 20 € / UL
Selective Pallet Rack system
2 solution we could distinguish when designing a storage system with trucks:
- Traditional + truck
- Storage system + AS/RS
What are:
1. Management of Operative cycles
2. Space Allocation
Warehouses Management policies
- Management of Operative cycles:
- Single Command Cycle to store or retrieve. 1UL
- Dual Command cycle to store or retrieve. 2UL
How Single Command Cycles time is conformed:
Variable time:
Related to distances horizontal (transfer) & vertical (lifting).
With or without the load.
Fixed time:
Wait for data transfer
Curves
Positioning
Load / Unload
Compare Dual vs Single cycles in terms of:
Efficiency
Cycle length
Fixed time incidences
Requirements
Efficiency:
2 instead of 1 UL per cycle.
Cycle length:
Longer but in proportion to 1UL shorter.
Fixed time incidences:
Lower
Requirements:
The UL has to be ready for storage and retrieval.
- Space allocation
What is it?
Criteria to decide where to placate UL of an article and the space subdivision criteria
Number of ULi RETRIEVED from the storage system during a time window T
Retrieval Index
Retrieval Index of i,T divided the number of locations assigned to I during T.
Access Index
(how visited is a location)
What happens when I have different items with different Access index
I wan to place the items that I visit most (higher AI) closer to the I/O to decrease operative cycles.
Dedicated space or classes needed for this approach.
What are the main allocation policies?
a) Random storage:
location shared
b) class based storage:
Locations assigned to class of Items
c) Dedicated storage
Locations are assigned to specific Items
Rank the three allocation policies in terms of:
Efficiency of cycle time, complexity and storage capacity.
0 is low
1 is high
0 Random storage
.5 class based storage
1 Dedicated storage
If I take a Dedicated storage policy, how do I calculate the capacity of the system?
As it is dedicated I need to make sure that the max qty of each of the scheduled items, in a year for example, will have a place in the WH.
Take the highest qty among items and sum it up.
If I take a Random storage policy, how do I calculate the capacity of the system?
Random the location is shared, so I need to make sure that the highest period qty will fit in the WH.
monthly sum and I take the max as the capacity needed.
Class based storage,
How do I know how to place the zones.
In a selective storage system served by counterbalance lift there are two arrangements that follow ISO-TIME-CURVES.
In triangle if the II/= is only located in the middle or rectangular if I/O is all along the side.
Always A closer to I/O and normally 2 or 3 classes.
Class based storage:
How do I define the classes
- AVG of all AI
- AI A > AI avg
- AVG remaining AI
- AI B > AI remaining avg
- C remaining (or again)
True or false
The higher the # of classes the higher the managerial complexity of the system
True
Explain the ABC curve:
Access / occupied space
x: occupied space in terms of % UL locations
y: % access
Curves represent the relationship of how the behave when one of them changes.
If I manage to concentrate as much as possible my access in 20 % of my sace…
I get benefits as reduction of the operative cicle VARIABLE time with respect to random storage.
And having +1 class reduces it even more! But increases complexity managerial.
- Clustering the items by storage system
- Required performances (SC-TC)
- Constrains
- Storage system selection
- Area PRE-design
- Modeling and simulation
- Technical - Economical checks
- Design
Main Design Principles
Criteria to cluster items:
Technical features:
dimensions, weight, fragility
Environmental req:
Temperature, humidity
Safety req:}Fire prevention, hazardous, non compatibility
Design constrains:
Urban:
heights, distances
Technical:
Surface and shape of the ground
Safety:
Escape routs
Economical:
Available resources
If we divide the design framework into 3 phases wha are those:
- Identify design parameters SC-TC
- Layout design to cover SC
- Throughput capacity assessment TC
What are the assumptions we make for a conventional manual storage system?
trucks not connected to # aisles
Data exist
Singledeep selective racks
Full pallet loads not mixed
counterweight forklift trucks
No picking activities
Is the analysist that:
Takes into account the values of the flows (hr/day) from storical data
Analysis of phisical flows
Throughput capacity
Throughput Capacity TC
How is TC assesed in terms of handling system for storing and retrieving
If same system:
TC= Fin+Fout
If diferent:
TCin= Fin
TCout=Fout
How can I chose a best storage solution?
Calculating the NPV
NPV=-Io-OCt+TV
Io in NPV
Initial invertion:
Storage (racks)
Land (area)
Handling system (trucks)
The price I pay to get them
TV in NPV
Terminal Values after T period:
Storage (racks)
Land (area)
Handling system (trucks)
What they will value as assets
OCt in NPV
Operative cost:
How much i will pay to handle the pieces of one year during the period T and considering the increase of annual cost capital (K).
True or false
In a Drive in and in a sigle deep rack the pallets are places in the same way the diference is the truck where it take them from
True
U side of my warehouse divided the dimension U side of the UM
Uum= 2*DeepUL+aisle width
Number of aisles
NA
I use dimentions
SC divided how many PL I storage in 1 column
UL per column = 2BayULNA*NL
Number of Columns
NC
I use capacity
The I/O point is in the corner
U=V
P=2*( U/2 + V/2)
a=2
The I/O point is in the midle
U=2V
P=2*( U/4 + V/2)
a=4
The I/O point is all along
U=1.5V
P=2*( U/3 + V/2)
a=3
How to calculate the Time of a single comand cycle
TSCC= FT + VT
FT given
VT=P/Vh + S/Vv
If Access aisle, sum it to P
How you calculate the TC by truck
TCtruck= UF*3600/TSCC
How you calculate needed trucks
SC/SCtruck
Automated Storage Systems
Compare an automated storage system against a standard one on terms of layout:
Height
Aisle Width
Lenght
AUR
Height: higher
Aisle Width: narrower
Lenght: higher
AUR: Strong impact
Automated Storage Systems
Compare an automated storage system against a standard one on terms of Handing system:
AS/RS machines
Automated I/Osystem
Positive impact in TC
Automated Storage Systems
Main choices about system configuration regarding:
Structure
- Standard
- Sunk
- Rack supported
Automated Storage Systems
Main choices about system configuration regarding:
S/R macines / #aisles
=1
diff 1
Automated Storage Systems
Main choices about system configuration regarding:
Rack Depth
- Single Deep
- Double Deep
Automated Storage Systems
Main choices about system configuration regarding:
Telescopic Forks per machine
1
2
Automated Storage Systems
When to select this type of solution
Low vailability / high cost area
High storage capacity
High TC
Specific conditions of the product
Automated Storage Systems
Drawbacks
Low flexibility
Investment
Reliability
Automated Storage Systems
Which type of coordinates can we use?
Spatial or Time
Automated Storage Systems
How can I calculate time coordinates:
Tx=X/Vx
Ty=Y/Vy
The time is the one from the highest between X or Y
Automated Storage Systems
Management policies
1. Operative Cycle types
2. Optimization of dual command
- Operative Cycle types
Single
Dual - Optimization of dual command
NCZ No Cost Zone
MTB Minimum travel between
Automated Storage Systems
VT Variable time depends on pallet location
FT does not
T or F
True
Automated Storage Systems
Why are Dual Command Cycles more efficient than Single Command Cycles?
They can move 2 UL in less than 2 single cycles
Automated Storage Systems
The idea is to couple a storage/retrival in a specific paallet location with a retrival/storage in the closest pallet location.
Minimize the interleave without the load.
MTB
Minimum Travel Between
Automated Storage Systems
Cople a Storage/Retrival in a specific pallet locoation with a retrival/storage withough increasing the Variable time of the cycle.
NCZ
No Cost Zone
Automated Storage Systems
Autonomous Vehicle Storage and Retrieval System
Decouples Vertical and Horizontal movements
Increases SL and reliability
