Laboratory for Machine Tools and Production Engineering · demand, globalization of procurement,...
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Production Management A – Winter Semester 2009/10
Operations Control P. 0
Lecture 08
Production Management A
Lecture 08Operations Control
Organisation:Dipl.-Wirt.-Ing. Niklas HeringPontdriesch 14/16Room 211Tel.: [email protected]
Laboratory for Machine Tools and Production Engineering
Chair of Production EngineeringProf. Dr.-Ing. Dipl.-Wirt. Ing. G. Schuh
Chair of Production ManagementProf. Dr.-Ing. A. Kampker
Production Management A – Winter Semester 2009/10
Operations Control P. 1
Lecture 08
Index:
Index Page 1
Schedule Page 2
Glossary Page 3
Target of this lecture Page 4
LectureBasics and challenges of operations control Page 5
Tasks of operation control following the Aachen PPC-Model Page 15
Questions Page 36
Bibliography Page 37
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Operations Control P. 2
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Schedule:
No. Date Responsible
V1 19./20.10.2009 Mr. Haag 0241 89 04275
V2 26./27.10.2009 Mr. Nollau 0241 89 04271
V3 02./03.11.2009 Ms. Maletz 0241 80 28019
V4 09./10.11.2009 Mr. Jung 0241 80 27392
V5 16./17.11.2009 Mr. Bartoscheck 0241 80 28203
V6 23./24.11.2009 Mr. Pulz 0241 80 27388
V7 30.11/01.12.2009 Mr. Ivanescu 0241 80 20394
V8 07./08.12.2009 Mr. Hering (fir) 0241 47705-428
V9 14./15.12.2009 Mr. Kompa (fir) 0241 47705-426
V10 11./12.01.2010 Mr. Deutskens 0241 80 27380
V11 18./19.01.2010 Mr. Kuhlmann 0241 80 28197
V12 25./26.01.2010 Mr. Ziskoven 0241 80 27378
V13 01./02.02.2010 Ms. Völker 0241 80 28477
Materials Management
Lean Production - Production Systems
Production Strategies
Frontloading in Innovation Processes
Variant Management
Process Planning
Planning for Manufacture & Assembly
Operations Management
Technology Management II
Topic
Technology Management I
Product Planning & Engineering
Business and Process Modelling
The Industrial History: From Taylorism To Virtual Factory
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Lecture landscape
Facility planning
• Tooling planning• Storage- & Transport planning• Employee planning
Production-oriented- andAssembly-oriented Construction
• Construction tasks in small groups• Construction examples• Constructions guidelines
Production management II
• IT in Production management + Dig. Fab.• Customer Relations Management• Enterprise Resource Planning• Supply Chain Management• Product Lifecycle Management
V1 Technology Management IV2 Technology management IIV3 Frontloading in Innovation ProcessesV4 Product planning / ConstructionV5 Variant ManagementV6 Work planningV7 Planning of Manufacturing & AssemblyV8 Operations controlV9 Material ManagementV10 Lean Production - Production SystemsV11 Production strategies V12 Business and Process modellingV13 Industrial history
Capital budgetingBusiness Engineering
Production management I
• Integrated management tasks• Product- and product program planning• Organization and behavior of employees
• Strategies & Management• Business & production processes• Financial statements & capital budgeting
• Tooling planning• Technology planning• Cost calculation
Innovation Management
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Glossary:
Kanban Kanban is a production control methodusing the pull control principle thatmakes permanent intrusions of a centralcontrol unit unnecessary. It is solelyoriented at the customer demand.
Lead time scheduling Lead time scheduling establishes thechronological coherence betweenproduction orders. By stringing togetherall production orders that correlate due totheir bill of materials, a time schedule isdrawn to express these correlations.
Load-dependent order release Load-dependent order release (BoA) isbased on a rough-cut scheduling andavailability check. A separation of urgentand not urgent production orders resultsfrom rough-cut scheduling. It is further-more checked for every urgent order iftheir dispatching would lead to anoverload of necessary resources.
Operations control Operations control includes thearrangement monitoring and guaranteeingof quantity, deadline, quality and costs.
Production Planning & Control Production Planning & Control (PPC)comprises the whole technical orderprocessing going from quotation toconsignment. Its planning and controlfunctions thereby touch the departmentssales, engineering, purchasing,production, assembly and consignment.
Throughput time The throughput time of an order is definedas the sum of machining-, transport-,control-, and queuing times.
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Target of this lecture:
The main objectives of the lecture „Operations Control“ are:
• Getting an overview of tasks and goals of operations control
• Understanding problems and challenges regarding operations control
• Becoming acquainted with methods and strategies of operations control
• Push- and pull control
• Production requirement planning
• Lead time order- and capacity-based scheduling
• Capacity management
• Release strategies
• Kanban-method as an example of pull control
• Throughput time reduction
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Structure
Basics and challenges of operations control1
Tasks of operations control following the Aachen PPC-Model2
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Definition of Operations Control
Costs Minimization by Optimization of Production-Economical Objectives
- High Due-Date Reliability- Short Lead Times- High Capacity Utilization- Low Shelf Inventories and Float
Floor Stocks
- High Service Level- High Flexibility- Constant Capacity Load- High Level of Information- ...
Operations control:Operations control includes the arrangement for, the monitoring and
guaranteeing of quantity, deadline, quality, and cost
- Creation of programme and order- Determination of demand- Determination of deadline- Staging and task distribution
- Quantity and deadline- Quality- Budget accounting- Working conditions
- Intervention and modification to planning
- Quality management
Targe
t statusActual
status
Arrangement
Monitoring
Guaranteeing
ObjectivesTasks
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Multi-dilemma of Operations Control
Equal & high workload:
- High inventories
- Low capital
- High order capacity
Low capital commitment:
- Low stock of material
- short lead time
High delivery date reliability:
- High inventories
- High stock of material
- Low workload
Short lead time:
- Low stock of material
- High capacity
- Low workload
Lead time On-time delivery
Workload
Transfer tocapital lockup
Notes: Two challenges must be taken into account within the multi-dilemma of operations control:
• Conformity between workload in production (by customer orders respectively market specific orders) and own capital commitment.
• Adjustment of lead time of production orders with the scheduled delivery date. At this point the waiting within the lead time and the delivery date should be considered.
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Tasks of Production Planning & Control (PPC): The Aachen PPC-Model
In-plant production planning and
control
Procurement planning and
control
Data management
Production program planning
Production requirements planning
Network configuration
Network marketing
Network requirement planning
Network Tasks Cross-sectional tasksCore tasks
Ord
er c
oord
inat
ion
Inve
ntor
y M
anag
emen
t
PPC
-Con
trol
ling
(Source: Schuh 2006)
Notes:The function of the Production Planning and Control (PPC) is the time, capacity and quantitative planning and scheduling of the production and assembly (Eversheim 1989). Whereas the production planning has to organize the content and the single processes of the production and assembly, production control has to organize the operations in the production within the scope of order processing. The production control takes input from the production planning regarding the process sequence and associated logistics objectives.
The focus is on the company internal planning and control processes. Due to diverse customer demand, globalization of procurement, sales markets, substitution of goods and the increasing process of globalization, companies are under immense pressure to strengthen and focus on value adding processes in the whole supply chain. To cater this growing integration in the supply chain, the Aachen PPC Model has introduced in the network to manage the dependence.
The tasks of production planning and control can be divided into core tasks and cross-sectional tasks. While core tasks advance the order processing, cross-sectional tasks aid to integrate and optimize the production planning and control.
Core tasks are long term production program planning, medium term production requirement planning, short term in-plant production planning and control and short term procurementplanning and control. Cross-sectional tasks are order coordination, storage and the controlling of the ERP system itself.
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ERP Workflow (“Aachen PPC-Model”)
Proc
urem
ent
mar
ket
Customer order entry
Sale
s m
arke
t
Forecasting
Production program planning
Production requirements planning
In-plant production planning and control
Procurement planning and control
Procurement program
In-plant production
program
Production program
Requirements program
Dispatch handling Storage
Costing Pay calculation
Quality inspection
Construction/ Work scheduling
Ord
er c
oord
inat
ion
Notes:During the planning process, resources are planned with increasing level of detail and de-creasing planning horizon. The results of a planning step are input for the next step. Planning information is fed forward to the next planning step with the aid of a control loop. The core tasks of PPC can be shown in a flowchart.
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Subdivision of functions of the PPC/ERP
(Source : Luczak, Eversheim, 1997)
Primary requirement planningSales planning
Resource planning
Net secondary requirement determination
Production requirement planningGross secondary requirement determination
Allocation of kind of procurement
Capacity requirement calculationLead time scheduling
Capacity adjustment
Fine scheduling
Self-manufacturing planning and controlLot sizing
Detailed resource planning
Disposability planning Sequence planning
Order enabling
Offer evaluationOrder invoice
Vendor selectionSubscription enabling
Operations planning
Materials management
Production program planning
Procurement planning and control
Notes: Operations Control includes methods which are necessary for the processing of orders accor-ding to the results of work scheduling. One factor that influences operations control is the kind of dissolution of orders. In addition, the tasks of operations control are influenced by products, procurement, workflows in manufacturing and assembly and by customer changing priorities during manufacturing.
In spite of the different characteristics of the specific factors in different companies, core tasks and cross-sectional tasks of operations management can be identified in a universal concept. Core tasks are production program planning, production requirements planning, in-plant production planning and control and procurement planning and control.
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Co-Ordination Materials Management / Assembly Control
100 %
(Example company)(Source: Stolz)
70 %
17 %27 %
56 %
17 %13 %≤ 2
months
> 5months
2 - 5months
Quantity of object numbers
Inventoryvalue
100 %
91 %
Troubles in total
Missing parts58 %
Production faults19 %
Engineering faults14 %
Wrong parts4.5 %
Pre-assembly faults3 %
Other faults1.5 %
material
Total number: 13,944
Breakdowns in assembly Structure of inventory
Inventoryrange
Other troubles: 9 %
Notes: Operations Control and Materials Management can not be separated in the handling process of production assignments. The coordination of the non-physical information flow with the associa-ted physical flow of material is the core challenge of an effective production planning and scheduling.
A lack of coordination between materials management and production & assembly scheduling will result in a disturbance of the assembly even though high stock levels are available. These disturbances increase with an increase of variety and complexity of the products in combination with variation of demand.
In the graph is shown that 91% of production disturbances are caused by material problems, despite of the high inventory level (the stock suffices for 70% of the code numbers for more than 5 month). It is significant that 53% of the material conditional disturbances are due to missing parts. A better coordination between inventory management and assembly control can therefore reduce both the disturbance quota and inventory.
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Rough planning
shor
t
med
ium
lon
g
low
m
ediu
m
h
igh
Creation of production
order
BOM explosion and
material planning
Detailed capacity planning
Work distribution
Throughput and capacity scheduling
Creation of shop-floor
order
Program planning
Order planning
Production order
Shop-floor order
Planning horizon
Planning intensity
Customer order
Detailed planningMedium-term planning
„Information Gap“
„EffectivityGap“
t
Planning Tasks and Levels of Operations Control
(Source: Brankamp)
Operations Control
Notes: Production control is taking charge of the results of the production program plan as well as pro-duction requirement planning. Manufacturing orders as well as primary and secondary needs are available and contributed during the first step of job processing control, lead time and capa-city scheduling.
The planning process is carried out on several levels in order to keep the large volume of data under control. For planning on higher levels, aggregated data is used; planning on higher levels has a longer planning horizon. In contrast, planning on lower levels is short-term planning, but uses detailed data.
Two basic planning problems arise. The "information gap" exists in early planning phases since enough information for a more intensive and therefore more detailed planning is not available yet. The "effectivity gap" during the later fine planning expresses that detailed data for the planning is existing but the intervention possibilities are restricted due to the temporal closeness to the start of production.
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Characteristics of order types for Operations Control
Order types
Customer-anonymous
• Delivery ex stock
• Customer-anonymous production and assembly of lots for stock
• No customer demands
Customer-specific
• Delivery after running through engineering, operations planning, production, and assembly
• Nearly no stock or lot production
• All customer demands
Mixed
• Delivery determined by assembly time
• Production of basic components for stock, customer-specific production and assembly of variants
• Customer demands within the framework of combination
(Source: Wiendahl) see also PMA L8 „Material Management“
Notes: Based on the product and the present market situation, there are different types of solutions for an order. A producing company that needs to provide its goods on a continuous basis, will standardize its products and keep a high stock level. This results in a high level of capital costs. With an increasing customer orientation, the demand of time and capacity planning rises. The companies focus is to meet the delivery date on time.
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Types & framework of orders for a mechanical engineering company
(Source: Traub, 1991)
~~~
Customer order
120,000 / year100Assembly processes:
18,000 / year15Assembly orders:
1.2 mio. / year1,000In-house production parts:
3 mio. / year2,500Outsourced parts:
Yearly requirements:Framework of orders for one machine:
Production order
Shop-floor orderParts production
Shop-floor orderAssembly
1,200 Customer orders / yr.350 Machine types / yr.
Purchase order
Notes: The difficulties of operations control are caused by a high number of different parts to be pro-duced and obtained. A high number of orders which must be coordinated with regard to her completion appointments and capacity requirements results from it.
This problem is found particularly with complex products and customer-specific production. Normally there are so many operations necessary that even a mid-sized company needs the support of a PPC-system for its operations control.
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Basics and challenges of operations control
Tasks of operations control following the Aachen PPC-Model
Structure
1
2
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Principles and characteristics of Push-Pull-Control
Storing of components
Job progress
Push
Push
Storing of customer-independent products,
sale ex stock
Sale of customer-specific products
Sale of customer-specific products
Material procurement according to production
program
Customer-specific material procurement
Material procurement according to production
program
Legend:
Direction of flow transferred by operations management
Push
Pull
Pull
Delivery time Capital tie-up
Notes: The application of various methods depends on the product and/or order structure. The different types of the order triggering require different mechanisms of operations control. One distinguishes basically in Pull and Push control (Wiendahl):
1. Pull control (Pull)
Objective: Guarantee the availability of a certain quantity within one time period
Characteristics: Order release triggered by a customer demand towards the material flow; orders without closing date and job number; synchronization of input and output
2. Push control (Push)
Objective: Focus on completion on schedule
Characteristics: Order release triggered by a superior planning level; orders with closing date as well as job number; no synchronization of input and output
The limits of Pull and Push control circles have to be established specifically for every enterprise in dependence of capital relationship and desired delivery time. The structuring of products into assemblies and components without variant influence (neutral assemblies) supports the specification of these limits. Superordinated planning functions for long and short term planning are frequently affected by the push-principle and with approaching the start of production they are supplemented with control systems based on the pull principle.
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Effects of Push Control
(Example company)
Control flow (push control)
Control flow (pull control)
Market
Forecast
Order management
Purchasing
Supplier
Production
High inventories in case of bad availability of material
Inventory
Assembly
Order
PUSH
CONTROL
Notes: The application of the Push control principle means that a high inventory is necessary to make a custom-designed final assembly possible. This inventory grows with the increase of the diver-sity of variants since all variants must be on stock to meet the customer requirements.
Since the planned inventory depends strongly on the quality of the forecast of the customer demand, an overestimation of the demand causes a very high inventory level. If the forecast values are below the actual demand, a low inventory leads to low material availability. Therefore the choice of the right forecasting method for the respective products is of great importance (compare PMA L8 “Material management").
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Expansion of Pull-controlled production volume (example)
JIT = Just in time
Control flow (pull control)
Assembly
Pre-assembly
Final assembly
Order
Market
Forecast
Purchasing
JIT
Reduction of inventory of up to 30% with
simultaneous increase of availability of material
PUSH
CONTROL
PULL
CONTROL
Control flow (push control)
DEMAND-ACTUATED
CONSUMPTION-DRIVEN
Supplier / Cost centre Pre-assembly
Synchronized inventory
Notes:A synchronized assembly increases the planning flexibility in production and results in lower stock levels in the assembly area. It is useful to implement this measure if the assembly requires time and if high part value and/or part volume is involved.For example: air plane production: Supply of jet engines as late as possible
The assemblies and components which are necessary for the assembly are divided up into stock classes. They are manufactured (push controlled) without any direct relation to a customer order but according to there different use frequency. The corresponding variants are produced custom-designed (pull controlled) in the assembly from the stored assemblies and parts. The pull controlled assembly makes a lower inventory possible since only assemblies and parts must be stored.
The interface between pull and push control is called order penetration point.
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Tasks of the Production Requirement Planning
Production Program
Secondary demand planning
Gross secondary demand
Net secondary demand In stock components
Flow scheduling
Product structure Effective date for capacities
Technological requirements
Capacity demand Balancing/AdaptationCapacity
availability
Capacity planning
Requirement Program
70x
210x
50x
80x
20h Sawing
6h Drilling
10h Millcuttling
2h Sawing
6h Drilling
12h Millcutting
Materials management
Notes:The input information for the production requirement planning is the production plan. The production plan is the result of the production program planning. For a certain planning horizon for example a year the monthly lot size of the products or product parts are listed (planning pattern). The task of the production requirement planning is to secure the production program with adequate procurement programs. The considered resources (production factors) are production facilities, material (secondary demand), personal, transportation devices etc. that means everything that a production process incorporates.
Secondary demand planning calculates the actually needed amount of raw materials, parts and groups and matches them with the appropriate procurement type (in house production/outside supply). Finally the classical tasks of time management (lead time scheduling and medium range capacity planning) occur. These are the basic tasks of operations control and are the basis for the short term planning of in house production.
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Order- and Capacity-based Scheduling
A
B
C
Deadline overview Deadline overview
Phase 1(Focus: work-piece)
Phase 2(Focus: machine)
Order-based scheduling Capacity-based scheduling
Deadline plan
Order 1
1.1, 1.2, 1.3
Deadline plan
Order 1 1.1, 1.2, 1.3Order 2 2.2, 2.3Order 3 3.1, 3.2, 3.3
1.1 (e.g. sawing)
1.2 (e.g. drilling)
1.3 (e.g.milling)
Lead time for order 1
Wor
k sy
stem
s
Deadline
A
B
C
1.1
1.2
1.3
Lead time for order 1
Deadline
3.1
2.2 3.2
2.3 3.3
operation
Notes:When setting the dates for customer-oriented production, the start and completion dates for each step (operation) must be determined with the due date in mind. Various types and methods of date-setting are used.Within order-oriented scheduling, only the data relating to one order is taken into account. The basic scheduling methods (e.g. forward and back-ward scheduling )
Within capacity-oriented scheduling, the mutual dependency between orders and therefore between capacity limits is considered.
As a rule, at first order-oriented then capacity-oriented scheduling is conducted.
The results of lead time scheduling within production requirement planning are basic dates related to capacities respectively capacity groups. Later the actual state of charge can be taken into account (Wiendahl 1989).
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Lead Time Scheduling
Legend: Setup Time Operation Time Transitional Period
Combined SchedulingForward SchedulingBackward Scheduling
Distribution of Schedule Deviations
• Starting point is a fixed final date (e. g. desired delivery date of the customer)
• Calculation of the latest possible start date backwards from the final date
• If the calculated date is situated in the past, methods will be applied to reduce the lead time
• Starting point is a fixed start date• Calculation of the earliest possible final date
forward from the start date• Problem: material will be ordered too early⇒ Forward scheduling is only applied to
calculate the earliest possible delivery date, afterwards the latest start dates (and therefore order dates) are calculated with help of backward scheduling
• Starting point is a fixed centre date• Calculation of the latest possible start
date and the earliest possible final date• If the calculated date is situated in the
past, methods will be applied to reduce the lead time
• Application is useful, if the bottleneck capacities have to be taken into special account
Operations
Start Date (calculated)A100
A90A80
A70A60
A50A40 backwards
Final Date (fix)
Time
Operations
A100A90
A80
A60A50A50
A40
Start Date (fix)
Final Date (calculated)
A70
Timeforwards
Operations
forwardsbackwards
A100A90
A60A50
A40
Start Date (calculated)
Final Date (calculated)
A70A80
Time
Process Date for A90 (fix)
Notes:The (period based) supply orders and particularly the in-house production are planed in the lead time scheduling. Therefore each process step has a fixed date according to the production sequence. The lead time is comprised of the processing time (start up time and operation time) and the waiting time (standby time before and after the processing, control time and transport time). Depending on the planning method limited or unlimited capacities are taken into account for the scheduling. The latter one means that the constraints of available capacities are not yet considered. The planning basis for these tasks are work schedules and transfer matrices. In a transfer matrix planned values of the inter operation time for each transfer from one workstation to another workstation are listed. It can be differentiated between three different types of scheduling:
• Forward scheduling: The earliest due date is calculated based on a fixed start date
• Backward scheduling: The latest start date is calculated to fulfill the contract on time based on a fixed due date
• Combined scheduling: Based on a fixed starting point a forward scheduling into the future and a backward scheduling into the past is done. It is possible to start with any particular process when using the combined scheduling. For this process a fixed date can be planned. This method can be used if additional considerations such as bottleneck machine haves have to be taken into account.
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Load-dependent Order Release (BOA)
customer storage requirements
storage
knownbacklog
urgentbacklog
releasedbacklog
VH
regulative parameter “load limit"(Parameter reading in percentage EPS)
EPS
regulative parameter "deadline"(Parameter anticipation horizon
stock level
planned capacity
scheduling
Notes:Load-dependent order release (“Belastungsorientierte Auftragsfreigabe”, BOA) is a stochastic method. The controlling factor of this period-oriented method is the backlog in front of work stations, which is continuously calculated. Only those orders which have to be finished within a defined deadline are considered part of the urgent backlog. When an order is part of the urgent backlog, it will be checked if its load dues fit within a defined load limit.
Indirect load dues will be considered with a reduced load due according to their reduced arrival probability and their reduced load. If there is no capacity for any production step, the whole order will be retained.
The advantage of the BOA method is the high flexibility in case of varying order numbers.
However, there are problems in controlling orders that consist of many steps.
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Methods of reducing Production Throughput Time
Splitting of operations
Overlapping production
Combination of operations having the
same setting-up
Normal production cycle
t
Machining time
A 20 A 30A 10Order A
Setting-up time Transfer time
A 20/2 A 30A 10
A 20/1
t
t
A 20A 30
A 10
t
A 20A 10
tOrder B
A 30B50
t
t
avoid blocking of production resources
build part families / technology families
Notes:There are different possibilities of reducing the transmission delay of an order. When splitting operations e.g. a work step can be carried out at the same time on two machines instead of only one machine. Another method is overlapping the production, this means the next work step doesn't start after the completion of the whole lot but after the completion of just a part. Furthermore the setting-up of operations with the same set-up process can be added together for saving set-up times so that parts of order A are produced together with parts of order B.The allocation of orders to the individual workplaces results in queues. The sequence in which the orders are to be processed can be determined using priority rules in case the detailed shop-floor plans do not contain any exact specifications. Rules are selected depending on the objective.
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Alternativ
e-
machine optio
ns
Alternativ
e-
machine optio
ns
Load
Time
Technicalcapacity harmonization
Time
Time-based capacity harmonization
Time
Load
Alternativ
e
machine optio
ns
Machine AMachine B
Machine C
Machine AMachine B
Combination of technical and time-based capacity harmonization
Time- and machine-based harmonization of capacity
Notes:Within capacity planning, the distribution of activities among the individual units of capacity is optimized, under consideration of the load limitations. Capacity harmonization and capacity adjustment are possible measures.A further distinction is made between technical (e.g. parallel dispatching of an order on another machine) and time-based capacity harmonization (e.g. the same machine, but later dispatching).
In industrial practice, time-based and technical capacity harmonization operations are usually combined. Normally, the time-based harmonization is first, in order to retain optimum use of capacity in terms of both engineering and cost. Placing an order with an external company (extended work-bench principle) is a further option.
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occupied
free
Handling time
1. Cut within production
2. Cut within production
Transitional period Control periodStart-up of production A
1. Cut within production
2. Cut within production
Control period
Transitional period
Handling timeStart-up of production B
1. Day 2. Day 3. Day
1. Produktions-schnitt fürAuftrag B
2. Produktion-schnitt fürAuftrag B
Belegungdurch
Auftrag A
Belegungdurch
Auftrag C(Spittfaktor0)
FreiFrei1. Produktions-
schnitt fürAuftrag B
2. Produktion-schnitt fürAuftrag B
Belegungdurch
Auftrag A
Belegungdurch
Auftrag C(Spittfaktor0)
FreiFrei
1. cut within production for order B
2. cut within production for
order B
Occupied with order
A
Occupied with order C
(Split factor 0)
FreeFree
Cap
acity
of m
achi
ne 1
Capacity Management (PPC/ERP-system)
Notes: Handling time/ Transitional period/ Control periodHandling and control time mark constant values. Handling time is added before the start-up of a process operation, control time is added after the ending of an operation. Both factors do not occupy any capacity but they heighten the machining time.The transitional period indicates a time exposure that arises from product transport within manufacturing from one workplace to an other or from an effort conditional on production after a process operation (e.g. cooling, drying etc.).
Split factor (cut within production)If the temporal effort of production for one process operation cannot take place on a single work day because of lack of capacity or duration of the production, time has to be spread on one or several days. If such a splitting is not possible or only in parts because of production reasons, the splitting can be managed by depositing the split factor within the process operation.
Capacity factorUsually, the basic capacity of a workplace is deposited within the machine group with 100% of the available time. This available capacity can be reduced because of external factors such as machine's cooling times, breakdown time, frequency and maintenance. Therefore, additional capacity reserves for critical situations can be created.
Production Management A – Winter Semester 2009/10
Operations Control P. 27
Lecture 08
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Measures for adapting the capacity
Selection and execution of measures geared to adapting to capacity
Internal influencing factors
External influencing factors
• effectiveness• duration• internal priority
• external priority• penalty • labour market• economic situation
Internal/ external alternative capacity
Overtime/ short-time working
K1
K2
K
Additional shift
2·K
K
InvestitionenInvestment
KK´
K ?
Notes:When the company-specific parameters change, e.g. expansion, acquisition of a new major customer etc., the capacity harmonization measures are generally not enough and it becomes necessary to adapt capacity to the changed parameters.
Production Management A – Winter Semester 2009/10
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Lecture 08
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Comparison of Order Release Strategies
Release strategy
Inventory
Date
Push control principlePull control principlePrinciple
Parameter
• Progress rate system (FZS)
• KANBAN
• Load-dependent order release (BOA)
• Material Requirement Planning (MRP I)
• Management Resource Planning (MRP II)
• Optimized Production Technology (OPT)
Notes:Different control strategies can be compared on the basis of control principle during the materials allocation on one hand and the control parameters on the other hand. Detailing of different release strategies will be discussed to a large extent in production management II.
Production Management A – Winter Semester 2009/10
Operations Control P. 29
Lecture 08
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Use of the pull principle: Kanban method
KanbanCost center:Grindery
Part-Nr.
Partdescription
Container
Containercapacity
5135 - 371 Model-Typ
Appearance
Process(operation)
grindingbolt
Box
500 pieces
Storage depot-Nr. P371-3450
371
Kanban is a production control method using the pull control principle that makes permanent intrusions of a central control unit unnecessary. It is solely oriented at the customer demand.
Definition Kanban:
kan bannote, card
Notes: The Kanban method is based on decentralized, self-controlled loops. It is characterized by the following aspects:• Production starts as a reaction to a requirement notice from the next production level.• Flexible use of production facilities and personal balances fluctuation of requirement rate.• Buffer storage between production levels.• Kanban cards as information device between communicating sites.
Use:Introduced by Toyota the Kanban principle is used for the communication between different production levels in operations control. For example the supply of an assembly line with small parts or self produced components can be accomplished without the central PPC system.
Production Management A – Winter Semester 2009/10
Operations Control P. 30
Lecture 08
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One card control circuit - sketch
Production kanban
5
1
2
34
6
7
Source Drain
Production kanban-collecting box
Buffer storage
Notes:To obtain the needed parts for the production, a worker from the drain moves with the empty containers to the buffer storage of the control circuit. He will place the empty containers in their intended places.
1. He takes the needed amount of full containers out of the buffer storage.
2. After the removal of the attached Kanban he places the Kanban Card in the Kanban collecting box.
3. Then he moves with the full containers to his work place and starts production.
4. A worker of the source takes a Kanban out of the Kanban collecting box. This Kanban is a production order for the source.
5. The worker of the source retrieves the container that is listed on the Kanban out of the buffer storage and moves to his workplace where he starts producing the needed parts.
6. The finished parts will be put in the empty container. Then he attaches a Kanban to the full container and delivers the container to the buffer storage where he places the container on the intended place that is mentioned on the Kanban.
Production Management A – Winter Semester 2009/10
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Lecture 08
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Advantages and disadvantages of Kanban
A small amount of buffer stock leads to a break in production of the following levels if a disruption occurs.
Highly fluctuating amounts are not controllable
Small multiplicity of variants/high amount of constant components
Disadvantages
Kanban
Advantages
Small amount of stocks
High service level and punctuality
Reduction of lead time
High transparency of flow of material
Low control costs
Low data management and production data collecting costs
Higher responsibility of the employees
Low stocks result in an accurateness of the employees
Production Management A – Winter Semester 2009/10
Operations Control P. 32
Lecture 08
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Tasks of In-house Production Planning and Control
In-House Production Program
Lot Size Calculation
Shop Floor Program
Large Inventory,Non Flexibility
High Setup-Timesand Costs
Economical Manufacturing Lots for all Operations
Finite Operation Scheduling
OperationsOperation Timesand Transitional
Periods
Lead Time
Sequence PlanningQueue of Operations
Capacity or Capacity Group
Optimised Sequenceof Operations
130 13x10
th tnSawingDrillingMillcut.
15s 6s11s 8s14s 12s
SawingDrillingMillcutting
Operations planning
Notes:The planning result of the manufacturing orders based on the production requirement planning assures that the resources are available. The planned orders contain operations that are executed in different manufacturing sectors. Trough a finite resource planning the availability of the needed capacities can be secured. Capacity planning relies heavily on material management to provide the raw materials as planned in production.The internal production planning and scheduling particularizes the guidelines of the available material planning tolerance and the conversion is controlled. Manufacturing orders can be split into different lots. The calculation of the optional lot size is another task of the operations control (see PMA L8). The material planning tolerance is the difference between earliest and latest start date of the production and the allocation of the quantities to the manufacturing orders.
At the end of this planning the key task is to assign manufacturing orders to machines. The final order release can occur in a variety of possible algorithms.
Production Management A – Winter Semester 2009/10
Operations Control P. 33
Lecture 08
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Composition of Throughput Time
(Source: Stommel)
Throughput time
Machining time (including setting-up)
Transport time
Control time
Queuing time
100 %
10 %
2 %
3 %
85 %
Queuing time caused by work process
Storing time
Queuing time caused by interruptionsQueuing time caused by persons
75 %
5 %
3 %
2 %
oa
Notes:Analyzing preferably job shop production organized manufacturing sectors shows, that the main part of lead times is not participate in productive progress. A big rationalization potential is lying in control of procedures by reducing high queuing times.
Production Management A – Winter Semester 2009/10
Operations Control P. 34
Lecture 08
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Share in Throughput Time of lots and units
time
Quantity
Setting-up Machining x Queuing time
(after machining) TransportQueuing time
(before machining)
Machin-ing yS
Throughput time (order)
Part I
Part II
Assembly
Machining time (Order) Transfer time
Throughput time (work process, lot)
Part n
Part 2
Part 1
Lot size
Transfer time (unit)Average throughput time (unit)
Machining time (unit)
(Source: Heinemeyer)
Notes:In the case of lot manufacturing, the actual proportion of unproductive time within the throughput time rises with increasing lot-size. In addition to the transition times between two operations, lot-size related waiting times within an operation can also be reduced.On the one hand a large lot size causes a short changeover time, but on the other hand all work pieces have to wait on each other. The determination of optimal lot size is not trivial.
See also PMA L8: Determination of the optimal lot size
Production Management A – Winter Semester 2009/10
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Lecture 08
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Use of Priority Rules for Sequence Planning
FCFS First come, first served
SPT Shortest processing time
RAN Random number per operation
RAND Random number per order
SROT Shortest remaining operation time
TERM Finish date
SLACK Slack time
LPT Longest processing time
OP/RE Operation time / remaining machining time
STRUN Shortest processing time with limitation of waiting time
S-SL SPT if slack time sufficient, otherwise SLACK
Queue of shop-floor orders Priority rules
Shop-floor order in
machining
Notes:Queues arise from the allocation of orders to the individual jobs/machines. The order of the orders to be worked on can be defined with the help of priority rules if the fine planning of the workshop doesn't find any exact specifications. The priority rules should be selected according to the aim.
Production Management A – Winter Semester 2009/10
Operations Control P. 36
Lecture 08
Final statement:
The objective of this lecture was to provide an overview regarding the following topics:
• Tasks and goals of operations control
• Functions of production planning and control
• Problems and challenges of operations control
• Characteristics and differences between pull- and push-control
• Functions of capacity- and order-based lead time scheduling
• Capacity planning in the framework of operations control
• Types and functions of release strategies
• Application of Kanban
Production Management A – Winter Semester 2009/10
Operations Control P. 37
Lecture 08
Questions:
• What are the main differences between push- and pull-control?
• What are the main objectives of operations control? Why are these objectives in competition?
• What types of lead time scheduling methods do you know? What are the differences?
• How would you describe the load-dependent order release strategy?
• Which elements does an one-card Kanban control circuit consist of?
Production Management A – Winter Semester 2009/10
Operations Control P. 38
Lecture 08
Bibliography:
Dangelmaier, W.; Warnecke, H.-J.: Fertigungslenkung: Planung und Steuerung des Ablaufs der diskreten Fertigung; Springer-Verlag; Berlin, 1997.
Eversheim, W.: Organisation in der Produktionstechnik, Band 4: Fertigungund Montage; VDI-Verlag; Düsseldorf, 1989.
Eversheim, W.: Organisation in der Produktionstechnik, Band 3: Arbeits-vorbereitung; Springer-Verlag; Berlin, 2002.
Eversheim, W.; Schuh, G.: Betriebshütte – Produktion und Management; Berlin; Springer-Verlag, 1996.
Hackstein, R.: Produktionsplanung und -steuerung (PPS); VDI-Verlag; Düsseldorf, 1989.
Lödding, H.: Verfahren der Fertigungssteuerung; Springer-Verlag; Berlin, Heidelberg, 2008.
Luczak, H.: Rationalisierung und Reorganisation (Skript zur Vorlesung); Eigendruck; Aachen, 2004.
REFA: Methodenlehre der Planung und Steuerung, Teil 3; Hanser-Verlag; München, 1985.
Schuh, G.: Produktionsplanung und -steuerung – Grundlagen, Gestaltung, Konzepte; 3. Auflage; Springer-Verlag; Berlin, 2006.
Wiendahl, H.-P.: Betriebsorganisation für Ingenieure; Hanser-Verlag; München, Wien, 2008.
Wiendahl, H.-P.: Fertigungsregelung – logistische Beherrschung von Fertigungsabläufen auf Basis des Trichtermodells; Hanser-Verlag; München, 1997.