1 material handling systems design applied basics of queuing

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Material Handling Systems Material Handling Systems DesignDesign

Applied Basics of QueuingApplied Basics of Queuing

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MATERIAL HANDLINGMATERIAL HANDLING

Twenty principles of material handlingTwenty principles of material handling Selecting material handling methodsSelecting material handling methods Simplifying/eliminating material handlingSimplifying/eliminating material handling Simple analysis techniquesSimple analysis techniques

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Material HandlingMaterial Handling

Material handling adds COST, but not Material handling adds COST, but not VALUE.VALUE. as much as 60% of total production costas much as 60% of total production cost 20%-30% of direct labor costs20%-30% of direct labor costs 50%-70% of indirect labor costs50%-70% of indirect labor costs

What’s the best way to handle materials?What’s the best way to handle materials?DON’T!!DON’T!!

Goal: MINIMIZE COSTS OF MATERIAL Goal: MINIMIZE COSTS OF MATERIAL HANDLINGHANDLING

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Muther’s Material Handling Muther’s Material Handling EquationEquation

WHY?

WHAT WHERE WHEN HOW WHO

No MAT’L MOVE METHOD

Q

P

etc.

Type,Qty,Characteristics

Sink, Source Flow;Direction Flow, VolumeType of Move, etc.

UnitManpowerEquipment

+ +Yes

A

B

C

D

E

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Muther’s Material Handling Muther’s Material Handling EquationEquation

Use to analyze flow within and between:Use to analyze flow within and between: ReceivingReceiving StorageStorage ProductionProduction WarehousingWarehousing ShippingShipping

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The Twenty Principles of Material The Twenty Principles of Material HandlingHandling

1.1. Orientation PrincipleOrientation Principle: Study the system relationships : Study the system relationships thoroughly prior to preliminary planning in order to thoroughly prior to preliminary planning in order to identify existing methods and problems, physical and identify existing methods and problems, physical and economic constraints, and to establish future economic constraints, and to establish future requirements and goals.requirements and goals.

2.2. Planning PrinciplePlanning Principle: Establish a plan to include basic : Establish a plan to include basic requirements, desirable options, and the consideration of requirements, desirable options, and the consideration of contingencies for all material handling and storage contingencies for all material handling and storage activities.activities.

3.3. Systems PrincipleSystems Principle: Integrate those handling and : Integrate those handling and storage activities which are economically viable into a storage activities which are economically viable into a coordinated system of operation including receiving, coordinated system of operation including receiving, inspection, storage, production, assembly, packaging, inspection, storage, production, assembly, packaging, warehousing, shipping and transportation.warehousing, shipping and transportation.

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4.4. Unit Load PrincipleUnit Load Principle: Handle product in as large a unit : Handle product in as large a unit load as practical.load as practical.

5.5. Space Utilization PrincipleSpace Utilization Principle: Make effective utilization of : Make effective utilization of all cubic space.all cubic space.

6.6. Standardization PrincipleStandardization Principle: Standardize handling : Standardize handling methods and equipment wherever possible.methods and equipment wherever possible.

7.7. Ergonomic PrincipleErgonomic Principle: Recognize human capabilities and : Recognize human capabilities and limitations by designing MH equipment and procedures limitations by designing MH equipment and procedures for effective interaction with the people using the system.for effective interaction with the people using the system.

8.8. Energy PrincipleEnergy Principle: Include energy consumption of the MH : Include energy consumption of the MH systems and material handling procedures when making systems and material handling procedures when making comparisons or preparing economic justification.comparisons or preparing economic justification.

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9.9. Ecology PrincipleEcology Principle: Minimize adverse affects on the : Minimize adverse affects on the environment when selecting MH equipment and environment when selecting MH equipment and procedures.procedures.

10.10. Mechanization PrincipleMechanization Principle: Mechanize the handling : Mechanize the handling process where feasible to increase efficiency and process where feasible to increase efficiency and economy in the handling of materials.economy in the handling of materials.

11.11. Flexibility PrincipleFlexibility Principle: Use methods and equipment : Use methods and equipment which can perform a variety of tasks under a variety of which can perform a variety of tasks under a variety of operating conditions.operating conditions.

12.12. Simplification PrincipleSimplification Principle: Simplify handling by : Simplify handling by eliminating, reducing, or combining unnecessary eliminating, reducing, or combining unnecessary movements and/or equipment.movements and/or equipment.

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13.13. Gravity PrincipleGravity Principle: Utilize gravity to move material : Utilize gravity to move material wherever possible, while respecting limitations wherever possible, while respecting limitations concerning safety, product damage and loss.concerning safety, product damage and loss.

14.14. Safety PrincipleSafety Principle: Provide safe MH equipment and : Provide safe MH equipment and methods which follow existing safety codes and methods which follow existing safety codes and regulations in addition to accrued experience.regulations in addition to accrued experience.

15.15. Computerization PrincipleComputerization Principle: Consider computerization : Consider computerization in MH&S systems, when circumstances warrant, for in MH&S systems, when circumstances warrant, for improved material and information control.improved material and information control.

16.16. System Flow PrincipleSystem Flow Principle: Integrate data flow with the : Integrate data flow with the physical material flow in handling and storage.physical material flow in handling and storage.

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17.17. Layout PrincipleLayout Principle: Prepare an operational sequence : Prepare an operational sequence and equipment layout for all viable system solutions, and equipment layout for all viable system solutions, then select the alternative system which best then select the alternative system which best integrates efficiency and effectiveness.integrates efficiency and effectiveness.

18.18. Cost PrincipleCost Principle: Compare the economic justification : Compare the economic justification of alternate solutions in equipment and methods on of alternate solutions in equipment and methods on the basis of economic effectiveness as measured by the basis of economic effectiveness as measured by expense per unit handled.expense per unit handled.

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19.19. Maintenance PrincipleMaintenance Principle: Prepare a plan for PM and : Prepare a plan for PM and scheduled repairs on all material handling equipment.scheduled repairs on all material handling equipment.

20.20. Obsolescence PrincipleObsolescence Principle: Prepare a long range and : Prepare a long range and economically sound policy for replacement of economically sound policy for replacement of obsolete equipment and methods with special obsolete equipment and methods with special consideration to after-tax life cycle costs.consideration to after-tax life cycle costs.

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Unit Load PrincipleUnit Load Principle Follows traditional thinkingFollows traditional thinking

The greater the amount moved per trip,the less the cost per unit moved

Maximize Unit Load

$/unit

Quantity

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Unit Load PrincipleUnit Load Principle

ButBut:: Creates more inventoryCreates more inventory Requires expensive, heavy-duty material Requires expensive, heavy-duty material

handling equipmenthandling equipment Increases lag time between operationsIncreases lag time between operations

poor process communication, slower poor process communication, slower reaction to quality problemsreaction to quality problems

Requires more floor spaceRequires more floor space

WASTE!WASTE!

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Selecting Material Handling Selecting Material Handling MethodsMethods

Systematic ApproachSystematic Approach

1. Define the problem1. Define the problem

Preliminary Survey Check sheet (see Preliminary Survey Check sheet (see Appendix at end of section)Appendix at end of section)

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2.2. Analyze the problemAnalyze the problemObserve activitiesObserve activitiesObtain layouts, flow patters, schedules, etc.Obtain layouts, flow patters, schedules, etc.Obtain information on existing material handling Obtain information on existing material handling

equipmentequipmentAnalyze situation by material handling equation, Analyze situation by material handling equation,

Twenty Principles of Material Handling, and/or Twenty Principles of Material Handling, and/or forms forms such as Basic Data Form (see insert)such as Basic Data Form (see insert)Can activities be combined, simplified, Can activities be combined, simplified, eliminated???eliminated???

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3.3. Identify possible solutionsIdentify possible solutionsOrganize meeting with:Organize meeting with:material handlersmaterial handlersmachine operatorsmachine operatorssupervisorssupervisorssupport engineerssupport engineers

4.4. Evaluate alternativesEvaluate alternativesMeet again to rate alternatives using Factor Meet again to rate alternatives using Factor

AnalysisAnalysis

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Improvement of MH Improvement of MH SystemsSystems

Cellular ManufacturingCellular Manufacturing Eliminate HandlingEliminate Handling Eliminate StorageEliminate Storage Eliminate InventoryEliminate Inventory Eliminate waste due to poor qualityEliminate waste due to poor quality

KEYS:KEYS: Efficient layout, scheduling, problem Efficient layout, scheduling, problem

preventionprevention

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Conveyor SystemsConveyor Systems

• Reduce handling costs

• Better coordination of product thru processes

• Design WIP level into material handling system

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Simple Analysis TechniquesSimple Analysis Techniques

Queuing AnalysisQueuing Analysis

Mathematical analysis of queues Mathematical analysis of queues (waiting lines which occur whenever the (waiting lines which occur whenever the current demand for service exceeds the current demand for service exceeds the current capacity to provide that service).current capacity to provide that service).

Simple Analysis TechniquesSimple Analysis Techniques

Queuing AnalysisQueuing Analysis Suitable for “quick and dirty” evaluations when a high Suitable for “quick and dirty” evaluations when a high

degree of detail is not necessary.degree of detail is not necessary.

Arrivals Server (s)

System

Departure

Arrival Rate Service Rate

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Simple SystemsSimple Systems

FIFO (FCFS)FIFO (FCFS) Single Server, Single Queue - M/M/1 Single Server, Single Queue - M/M/1

SystemSystem Poisson ArrivalsPoisson Arrivals Exponential Service TimesExponential Service Times

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Simple SystemsSimple Systems

LIMITED:LIMITED: Mathematical complexity becomes Mathematical complexity becomes insurmountable if the above is not trueinsurmountable if the above is not true

Objective

SIMULATION

Wait $ Service $

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Material Handling ApplicationsMaterial Handling Applications

Highway Trailers: Ship/ReceivingHighway Trailers: Ship/Receiving Parts on ConveyorParts on Conveyor Pallets/Mc. Waiting for Fork TrucksPallets/Mc. Waiting for Fork Trucks Orders Waiting at AS/RSOrders Waiting at AS/RS Many MoreMany More

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QUEUING PHENOMENONQUEUING PHENOMENON

ExampleExample

If If > > , why Queues?, why Queues?

LOADINGDOCK

arrive every40 min on avg.

= 1.5/hr.

30 min avg. time to unload

= 2.0/hr.

QUEUEING PHENOMENONQUEUEING PHENOMENON

EVENT Time (min) Truck Being Serviced

Truck in Queue

Truck Wait Time

Truck 1 ArriveTruck 2 ArriveTruck 1 LeaveTruck 3 ArriveTruck 4 ArriveTruck 2 LeaveTruck 3 LeaveTruck 4 Leave

305062638090

125156

1122234--

--2--3

3,44----

----32----406276

156 min4 arrivals

= 39 min. avg.

FORMULAS for M/M/1 ModelFORMULAS for M/M/1 Model = avg. arrival rate

= avg. service rate

U = utilization =

W = avg. wait time in system =

Wq = avg. wait time in queue =

Lq = avg. length of queue =

L = avg. number of “customers” in system =

Pn = probability that there are n customers in the system

Pn =

P0 = 1 -

1

1 -

n

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M/M/1 EXAMPLEM/M/1 EXAMPLE

LOADINGDOCK

arrive every40 min on avg.

= 1.5/hr.

30 min avg. time to unload

= 2.0/hr.

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M/M/1 EXAMPLEM/M/1 EXAMPLE

Lq = = 2.25 trucks in line

L = = 3 trucks in line & being served

also (L = Lq + /)

Lq = Lq/ = 2.25/1.5 = 1.5 hrs/truck

Lq = L/ = 3.0/1.5 = 2.0 hrs/truck

Lq = 1 - = 1 - = .25 25%

1.52.0

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Cost FunctionCost Function

E[TC] = E[WC] + E[SC]

No. of servers

Cost

E[SC]

E[WC]

E[TC]

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WAITING COSTWAITING COSTType I.Type I. Internal CustomersInternal Customers

Example: Forklift truck driversExample: Forklift truck driversCost: Lost productivity of driversCost: Lost productivity of drivers

Type II.Type II. External customersExternal customersExample: People waiting for cabsExample: People waiting for cabsCost: ??Cost: ??

E[WC] = CE[WC] = CWW[E(n)][E(n)]

SERVICE COSTSSERVICE COSTS

Total Cost: S(server cost) = Total Cost: S(server cost) = S(CS(CSS))

THUSTHUS

TC = CTC = CWW[E(n)] + S(C[E(n)] + S(CSS))

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Example #1Example #1

Service Time

50 sec/service

Tool Crib Storage

found by

sampling!Inter-arrival time60 sec/arr.

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= 1/60 = 1 arrivals/min.= 1/60 = 1 arrivals/min. = 1/50 = 1.2 services/min. = 1/50 = 1.2 services/min.

Idle Time of Server = PIdle Time of Server = P00 = 1 - = 1 - // = 1-1/1.2 = 1-1/1.2 16.7%16.7%

Assume:1.Assume:1. Service Attendant Paid $12.00/hourService Attendant Paid $12.00/hour 2. 2. Customers (machine oper) paid Customers (machine oper) paid

$16.00/hour$16.00/hourCost of ServersCost of Servers

E[SC] = 8 hrs/day E[SC] = 8 hrs/day $12.00/hour = $96.00/day $12.00/hour = $96.00/dayCost of Machine OperatorsCost of Machine Operators Waiting for Service plus Waiting for Service plus Service)Service)

L = L = /(/(--) = 1/(1.2-1) = 5) = 1/(1.2-1) = 5E[WC] = $16.00/hr (5 people) (8 hrs/day) = E[WC] = $16.00/hr (5 people) (8 hrs/day) =

$640.00/day$640.00/day


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Number of Servers

$

E[SC]

E[WC]96

640

1

Conclusions? _________

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MH Cost Justification of MH Cost Justification of Cellular ManufacturingCellular Manufacturing

Compare:Compare:

I.I. Functional LayoutFunctional Layout--Fork truck--Fork truck

Maint. Labor:Maint. Labor: $10,000/yr$10,000/yrParts:Parts: $1,000/yr$1,000/yrDriver:Driver: $30,000/yr$30,000/yrTruck Cost:Truck Cost: $4,000/yr ($20,000/5 yrs)$4,000/yr ($20,000/5 yrs)

$45,000/yr$45,000/yr

*1 yr = 2000 hrs*1 yr = 2000 hrs

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MH Cost Justification of MH Cost Justification of Cellular ManufacturingCellular Manufacturing

Compare:Compare:

II.II. Cellular LayoutCellular Layout--Fork truck--Fork truck--Cart/Basket--Cart/BasketCart Cost:Cart Cost: $40/yr ($200/5 yr)$40/yr ($200/5 yr)4 Baskets Cost:4 Baskets Cost: $24/yr ($120/5 yrs)$24/yr ($120/5 yrs)

$64/yr$64/yr

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QuestionsQuestions

1 material handling systems design applied basics of queuing

Documents

material handling procedures

systems principle

safety principle

planning principle

computerization principle

gravity principle

energy principle

system flow principle