Chapter 11 Heragu

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Materials Handling: 

Materials Handling Chapter 11

Materials Handling: 

Materials Handling Material handling is an activity that uses the right method to provide the right amount of the right material at the right place, at the right time, in the right sequence, in the right position and at the right cost

Materials Handling (Cont): 

Materials Handling (Cont) Systems perspective 20-70% of product cost attributed to material handling

Materials Handling Principles: 

Materials Handling Principles

Materials Handling Principles (Cont): 

Materials Handling Principles (Cont)

Materials Handling Equation: 

Materials Handling Equation Material Handling Equation (see Fig 11.3)

Unit Load: 

Unit Load Unit load - number of items or bulk material arranged so they can be picked up and delivered as one load Large or small? If large, cost/unit handled decreases But, depending upon cost of unitizing, de-unitizing

Unit Load (Cont): 

Unit Load (Cont) space required for material handling material handling carrier payload work-in-process inventory costs storage and return of empty pallets or containers used to hold the unit load smaller unit load may be desired

Unit Load (Cont): 

Unit Load (Cont) Seven steps to design a unit load Unit load concept applicable? Select the unit load type Identify most remote source of load Determine farthest practicable destination for load

Unit Load (Cont): 

Unit Load (Cont) Establish unit load size Determine unit load configuration Determine how to build unit load

Material Handling Device Types: 

Material Handling Device Types Conveyors Palletizers Pallet Lifting Devices Trucks Robots

Material Handling Device Types (Cont): 

Material Handling Device Types (Cont) AGVs Jibs, Cranes and Hoists Warehouse MHSs

Conveyors: 

Conveyors Accumulation Belt Bucket Can Chain

Conveyors (Cont): 

Conveyors (Cont) Chute Gravity Pneumatic or vacuum Power and free Roller

Conveyors (Cont): 

Conveyors (Cont) Screw Skid Slat Tow line Trolley Wheel

Palletizers: 

Palletizers

Pallet lifting devices: 

Pallet lifting devices

Trucks: 

Trucks Hand truck Fork-lift truck Pallet truck Platform truck Counterbalanced truck Tractor-trailer truck AGV

Robots: 

Robots Point-to-point Contouring or continuous path Walkthrough or teach Lead through or teach pendant Hydraulic Servo-controlled

AGVs: 

AGVs

Hoists, Cranes and Jibs: 

Hoists, Cranes and Jibs

Warehouse MHSs: 

Warehouse MHSs Discussed in Chapter 12

MHSs in Action: 

MHSs in Action Europe Combined Terminals (ECT) ECT - one of largest in world and largest in Europe Goods shipped from and to Europe Built on reclaimed land in the North Sea Large and Small containers

MHSs in Action (Cont): 

MHSs in Action (Cont) Trucks wait to be off-loaded by straddle carrier Carrier takes container to holding area Shipped in approximately 2 days Mobile gantry cranes on tracks deposit containers in forward area

MHSs in Action (Cont): 

MHSs in Action (Cont) Mobile gantry cranes hold containers in top four corners and deposit on waiting AGVs Fleet of AGVs in forward area take containers to tower cranes Tower cranes deposit load on ship bed Procedure reversed for off-loading ship

AGVs: 

AGVs Classification of MHS Synchronous systems Asynchronous systems Synchronous systems, e.g. conveyors, used in continuous processes or heavy traffic, discrete parts environments

AGVs (Cont): 

AGVs (Cont) Asynchronous systems, e.g., AGV, AS/RS, fork-lift trucks, monorails, cranes and hoists used in light traffic, discrete parts environments when material handling flexibility desired

Design and Control Problems in AGVSs: 

Design and Control Problems in AGVSs Material flow network Location of pick-up/drop-off (P/D) points Number and type of AGVs AGV Assignments to material transfer requests AGV routing and dispatching

Design and Control Problems in AGVSs (Cont): 

Design and Control Problems in AGVSs (Cont) Strategies for resolving route conflicts, so AGV throughput rate is maximized, and other costs (purchase, maintenance and operating costs of AGVs, computer control devices, and the material flow network, as well as inventory costs and production equipment idle costs incurred due to excessive material transfer and wait times), are minimized

MHD Selection and Assignment Model: 

MHD Selection and Assignment Model Minimizes operating and annualized investment costs of MHD Variables and parameters i part type index, i=1,2,...,p j machine type index, j=1,2,...,m l MHD type index, l=1,2,...,n Li set of MHDs that can transport part i H length of planning period

MHD Selection and Assignment Model (Cont): 

MHD Selection and Assignment Model (Cont) Di # of units of part type i to be produced Kij set of machines to which part type i can be sent from machine j for next process Mij set of machines from which part type i can be sent to machine j for next process Ai set of machine types required for the first operation on part type I Bi set of machine types required for last operation on part type I

MHD Selection and Assignment Model (Cont): 

MHD Selection and Assignment Model (Cont) Vl purchase cost of MHD Hl Tijkl time required to move one unit of part type i from machine type j to k using MHD l Cijkl unit transportation cost to move part type i from machine j to k using MHD l Xijkl number of units of part type i to be transported from machine j to k using MHD l Yl number of units of MHD type l selected

MHD Selection and Assignment Model (Cont): 

MHD Selection and Assignment Model (Cont)

MHD Selection and Assignment Model (Cont): 

MHD Selection and Assignment Model (Cont)

Example for MHS Selection and Assignment: 

Example for MHS Selection and Assignment Small manufacturing system Processes two high volume parts P1 and P2- 50 and 60 units, respectively Part P1 processed first on machine M1, and on machines M2 or M4 for second step and to machine M3 for final step

Example for MHS Selection and Assignment (Cont): 

Example for MHS Selection and Assignment (Cont) Of the 60 units of part P2, 30 are processed first on machine M1 and then on machine M2. The remaining 30 units of part P2 are processed first on machine M3 and then sent to machine M2 for final processing

Example for MHS Selection and Assignment (Cont): 

Example for MHS Selection and Assignment (Cont) Two candidate MHDs - H1 and H2 with purchase costs of $100,000 and $140,000 available Unit cost for transporting P1 and P2 on each of the MHDs as well as transportation times given

Example for MHS Selection and Assignment (Cont): 

Example for MHS Selection and Assignment (Cont) Assume there are 7150 seconds in the planning period Each handling device is expected to make empty trips 30% of the time Determine the required MHDs and assign departmental moves to them

Example for MHS Selection and Assignment (Cont): 

Example for MHS Selection and Assignment (Cont)

Example for MHS Selection and Assignment (Cont): 

Example for MHS Selection and Assignment (Cont)

Models for Conveyor Performance Analysis: 

Models for Conveyor Performance Analysis There are m stations which load or unload n carriers Amount of material loaded on the jth carrier as it passes station i is fij If material unloaded, assign a negative value to fij Load/unload cycle is a period of length p

Models for Conveyor Performance Analysis (Cont): 

Models for Conveyor Performance Analysis (Cont) Construct a set Fi = {fi1, fi2, ..., fip} including load/unload activities carried out in p successive carriers For eg., if add one load to one carrier at the first station, unload two from the next and let the third one go by without loading or unloading and repeat, cycle has a period of length 3 F1 = {1, -2, 0}

Models for Conveyor Performance Analysis (Cont): 

Models for Conveyor Performance Analysis (Cont) p need not be equal to n. In a cycle, total material loaded must be equal to total unloaded

Models for Conveyor Performance Analysis (Cont): 

Models for Conveyor Performance Analysis (Cont)

Models for Conveyor Performance Analysis (Cont): 

Models for Conveyor Performance Analysis (Cont) One round completed when all m carriers have gone around the conveyor once So, m/p load and unload cycles in the first round

Models for Conveyor Performance Analysis (Cont): 

Models for Conveyor Performance Analysis (Cont) If carrier j is in some position of the load/unload sequence (with respect to station i) during one round, it need not be in same position in subsequent rounds

Models for Conveyor Performance Analysis (Cont): 

Models for Conveyor Performance Analysis (Cont) It can be shown that if n mod p is not equal to 0, load picked up or dropped off will change from one round to the next, for the same carrier at the same station Let Pijk be the load/unload sequence position of a carrier j, with respect to station i in round k

Models for Conveyor Performance Analysis (Cont): 

Models for Conveyor Performance Analysis (Cont) Given Pij1, Pijk can be determined using the following formula, for k=2, 3, ..., p Pijk = [Pijk-1 + n mod p] mod p After p rounds, the position sequence repeats itself If Pijk=0, set Pijk=p

Models for Conveyor Performance Analysis-Example: 

Models for Conveyor Performance Analysis-Example

Models for Conveyor Performance Analysis-Example: 

Models for Conveyor Performance Analysis-Example Load/unload cycle length has a period 5 F1={2, 0, 0, 2, 3}; F2={-2, 0, 0, -1, -4} Determine the conveyor capacity

Models for Conveyor Performance Analysis-Example: 

Models for Conveyor Performance Analysis-Example

Models for Conveyor Performance Analysis (Cont): 

Models for Conveyor Performance Analysis (Cont) Change conveyor capacity requirement in one of three ways Change number of carriers n. Pijk will change resulting in different cumulative loads and hence, carrier capacity Change load/unload sequence of one or more stations Change the location of one or more stations

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