Production Management A – Winter Semester 2008/09
Operations Control P. 0
Lecture 07
Laboratory for Machine Tools and Production Engineering
Chair of Production EngineeringProf. Dr.-Ing. Dipl.-Wirt. Ing. G. Schuh
Production Management A
Lecture 07
Operations Control
Organisation:
Dipl.-Ing. oec. Jerome Quick
Pontdriesch 14/16Room 210
Tel.: [email protected]
Production Management A – Winter Semester 2008/09
Operations Control P. 1
Lecture 07
Index:
Index Page 1
Schedule Page 2
Glossary Page 3
Target of this lecture Page 4
Lecture
Introduction of the tasks of operations control Page 5
Challenges of operations control Page 11
Methods and strategies of operations control Page 16
Questions Page 38
Bibliography Page 39
Production Management A – Winter Semester 2008/09
Operations Control P. 2
Lecture 07
Schedule:
No. Date Responsible
V1 20./21.10.2008Mr. Haag
� 0241 89 04275
V2 27./28.10.2008Mr. Nollau
� 0241 89 04271
V3 03./04.11.2008Mr. Jung
� 0241 80 27392
V4 10./11.11.2008Mr. Bartoscheck
� 0241 80 28203
V5 17./18.11.2008Mr. Pulz
� 0241 80 27388
V6 24./25.11.2008Mr. Ivanescu
� 0241 80 20394
V7 01./02.12.2008Mr. Quick (fir)
� 0241 47705-425
V8 08./09.12.2008Mr. Helmig (fir)
� 0241 47705-435
V9 15./16.12.2008Mr. Deutskens
� 0241 80 27380
V10 05./06.01.2009Mr. Kuhlmann
� 0241 80 28197
V11 12./13.01.2009Mr. Baumann
� 0241 80 28398
V12 19./20.01.2009Mr. Ziskoven
� 0241 80 27378
V13 26./27.01.2009Mr. Gaus
� 0241 80 28477
Technology Management II
Variant Management
Process Planning
Topic
Technology Management I
Product Planning & Engineering
Planning for Manufacture & Assembly
Production Strategies
Prozess Modelling
Operations Management
Materials Management
Lean Production - Production Systems
The Industrial History: From Taylorism To Virtual Factory
Buisness Modelling
Production Management A – Winter Semester 2008/09
Operations Control P. 3
Lecture 07
Glossary:
Kanban 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.
Lead time scheduling Lead time scheduling establishes the
chronological coherence between
production orders. By stringing together
all production orders that correlate due to
their bill of materials, a time schedule is
drawn to express these correlations.
Load-dependent order release Load-dependent order release (BoA) is
based on a rough-cut scheduling and
availability check. A separation of urgent
and not urgent production orders results
from rough-cut scheduling. It is further-
more checked for every urgent order if
their dispatching would lead to an
overload of necessary resources.
Operations control Operations control includes the
arrangement monitoring and guaranteeing
of quantity, deadline, quality and costs.
Production Planning & Control Production Planning & Control (PPC)
comprises the whole technical order
processing going from quotation to
consignment. Its planning and control
functions thereby touchthe departments
sales, engineering, purchasing,
production, assembly and consignment.
Throughput time The throughput time of an order is defined
as the sum of machining-, transport-,
control-, and queuing times.
Production Management A – Winter Semester 2008/09
Operations Control P. 4
Lecture 07
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
Introduction of the tasks of operations control1
Challenges of operations control2
Methods and strategies of operations control3
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Operations Control P. 6
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Short content of the lecture
� Introduction of the tasks of operations control– Tasks and objectives of operations control will be defined and classified in the context
of production planning and control (PPC).
� Challenges of operations control– The basic challenges of operations control will be specified and clarified with case studies.
� Methods and strategies of operations control– In the main part methods and strategies of operations control will be introduced.
– Focus:� Push and pull order release� Flow scheduling� Capacity balancing and capacity smoothing� Load-dependent order release (BOA)� Priority rules for order release� Kanban� Dimension of time in operations control
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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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Operations Control P. 8
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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
co
ord
inati
on
Inven
tory
Man
ag
em
en
t
PP
C-C
on
tro
llin
g
(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, globalisation of procurement, sales markets, substitution of goods and the increasing
process of globalisation, 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 Aachener PPS 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 optimise the production planning and control.
Core tasks are long term production programme planning, medium term production
requirement planning, short term in-plant production planning and control and short term
procurement planning and control. Cross-sectional tasks are order coordination, storage and
the controlling of the ERP system itself.
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ERP Workflow (“Aachener PPC-Modell”)
Pro
cu
rem
en
t m
ark
et
Customer order entry
Sa
les
ma
rke
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
CostingPay
calculationQuality
inspection
Construction/ Work scheduling
Ord
er
co
ord
inati
on
Notes:
During the planning process, resources are planned with increasing level of detail and
decreasing 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 planning
Sales planning
Resource planning
Net secondary requirement determination
Production requirement planning
Gross secondary requirement determination
Allocation of kind of procurement
Capacity requirement calculation
Lead time scheduling
Capacity adjustment
Fine scheduling
Self-manufacturing planning and control
Lot sizing
Detailed resource planning
Disposability planning
Sequence planning
Order enabling
Offer evaluation
Order invoice
Vendor selection
Subscription 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
according 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.
Inspite 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 programme planning, production requirements planning, in-plant
production planning and control and procurement planning and control.
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Structure
Introduction of the tasks of operations control1
Challenges of operations control2
Methods and strategies of operations control3
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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 date of delivery loyalty:
- 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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Co-Ordination Materials Management / Assembly Control
100 %
(Example company)(source: Stolz)
70 %
17 %
27 %
56 %
17 %13 %
≤≤≤≤ 2months
> 5months
2 - 5months
Quantity of object numbers
Inventory value
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
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
associated 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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Operations Control P. 14
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Rough planning
short
m
ediu
m lo
ng
low
m
ed
ium
hig
h
Creation of
production
order
Requirements
explosion and
material
planning
Detailed capacity
planning
Work
distribution
Throughput
and capacity
scheduling
Creation of
shop-floor
order
Programme planning
Order planning
Production
order
Shop-floor
order
Planning horizon
Planning intensity
Customer
order
Detailed planningMedium-term planning
„Informational 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
production 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
capacity scheduling.
Graded planning 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 "effectiveness 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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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
produced 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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Structure
Introduction of the tasks of operations control1
Challenges of operations control2
Methods and strategies of operations control3
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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
standardise 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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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
programme
Customer-specific
material procurement
Material procurement
according to production
programme
Legend:
Direction of flow transferred by operations management
Push
Pull
Pull
Delivery period 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)
Aim: Guarantee of the availability of a certain quantity within one period of time
Features: Order release triggered by a customer demand in direction of the material flow; Orders without closing date and job number; Synchronization of input and output
2. Push control (Push)
Aim: Focus on completion on schedule
Features: 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
diversity 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
Synchronised inventory
Notes:A synchronised 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, 1.3
Order 2 2.2, 2.3
Order 3 3.1, 3.2, 3.3
1.1
1.2
1.3
Lead time for order 1
Work
sys
tem
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
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
A90
A80
A70
A60
A50
A40 backwards
Final Date (fix)
Time
Operations
A100
A90
A80
A60
A50A50
A40
Start Date (fix)
Final Date (calculated)
A70
Timeforwards
Operations
forwardsbackwards
A100
A90
A60
A50
A40
Start Date (calculated)
Final Date (calculated)
A70
A80
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 fulfil 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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Altern
ative-
mac
hine o
ptions
Altern
ative-
mac
hine o
ptions
Lo
ad
Time
Technicalcapacity harmonisation
Time
Time-based capacity harmonisation
Time
Lo
ad
Altern
ative
mac
hine o
ptions
Machine A
Machine B
Machine C
Machine A
Machine B
Combination of technical and
time-based capacity harmonisation
Time- and machine-based harmonisation of capacity
Notes:Within capacity planning, the distribution of activities among the individual units of capacity is
optimised, under consideration of the load limitations. Capacity harmonisation 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 harmonisation (e.g. the same machine, but later
dispatching).
In industrial practice, time-based and technical capacity harmonisation operations are usually
combined. Normally, the time-based harmonisation 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 period
Start-up of production A
1. Cut within production
2. Cut within production
Control period
Transitional period
Handling time
Start-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)
Frei
Frei1. Produktions-schnitt fürAuftrag B
2. Produktion-schnitt fürAuftrag B
Belegungdurch
Auftrag A
Belegungdurch
Auftrag C(Spittfaktor0)
Frei
Frei1. cut within production for order B
2. cut within production for
order B
Occupied with order
A
Occupied with order C
(Split factor 0)
Free
Free
Cap
acit
y o
f m
ac
hin
e 1
Capacity management (PPC/ERP-system)
Notes:Handling time/ Transitional period/ Control period
Handling 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 factor
Usually, 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.
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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
K
K´
K?
Notes:When the company-specific parameters change, e.g. expansion, acquisition of a new major
customer etc., the capacity harmonisation measures are generally not enough and it becomes
necessary to adapt capacity to the changed parameters.
Production Management A – Winter Semester 2008/09
Operations Control P. 27
Lecture 07
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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-Times
and Costs
Economical
Manufacturing Lots
for all Operations
Finite Operation Scheduling
Operations
Operation Times
and Transitional
Periods
Lead Time
Sequence Planning
Queue of
OperationsCapacity or
Capacity Group Optimised Sequence
of Operations
130 13x10
th tn
Sawing
Drilling
Millcut.
15s 6s
11s 8s
14s 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 particularises the guidelines of the available
material planning tolerance and the conversion is controlled. Manufacturing orders can be
splitted 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 2008/09
Operations Control P. 28
Lecture 07
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Comparison of order release strategies
Release strategy
Inventory
Date
Push control principlePull control principle
Principle
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 2008/09
Operations Control P. 29
Lecture 07
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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.
Production Management A – Winter Semester 2008/09
Operations Control P. 30
Lecture 07
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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 2008/09
Operations Control P. 31
Lecture 07
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Use of the pull principle: kanban method
Kanban
Cost center:
Grindery
Part-Nr.
Part
description
Container
Container
capacity
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 ban
note, 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 2008/09
Operations Control P. 32
Lecture 07
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One card control circuit: sketch
Production kanban
5
1
2
3
4
6
7
Source Drain
Production kanban-collecting box
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 2008/09
Operations Control P. 33
Lecture 07
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Advantages and disadvantages of kanban
l A small amount of buffer stock leads to a break in production of the following levels if a disruption occurs.
l Highly fluctuating amounts are not controllable
l Small multiplicity of variants/high amount of constant components
Disadvantages
Kanban
Advantages
l Small amount of stocks
l High service level and punctuality
l Reduction of lead time
l High transparency of flow of material
l Low control costs
l Low data management and production data collecting costs
l Higher responsibility of the employees
l Low stocks result in an accurateness of the employees
Notes:
Production Management A – Winter Semester 2008/09
Operations Control P. 34
Lecture 07
page 34© WZL/FIR
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 interruptions
Queuing 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 2008/09
Operations Control P. 35
Lecture 07
page 35© WZL/FIR
Share in Throughput Time of Lots and Units
time
Quantity
Setting-up
Machining xQueuing time
(after machining)Transport
Queuing time (before
machining)
Machin-ing y
S
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 2008/09
Operations Control P. 36
Lecture 07
page 36© WZL/FIR
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 10
Order ASetting-up time Transfer time
A 20/2 A 30A 10
A 20/1
t
t
A 20
A 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 joined together
for saving make-ready times so that parts of the order A are produced together with parts of the
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.
Production Management A – Winter Semester 2008/09
Operations Control P. 37
Lecture 07
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 2008/09
Operations Control P. 38
Lecture 07
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 medthods do you know? What are the
differences?
• How would you describe the load-dependent order release strategy?
• Of which elements does an one-card kanban control circuit consist of?
Production Management A – Winter Semester 2008/09
Operations Control P. 39
Lecture 07
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: Fertigung
und 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