CASE STUDY Nicole KYNCL - metal 2013

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IDENTIFICATION OF BOTTLENECKS IN IRONFOUNDRY PRODUCTION – CASE STUDY
Nicole KYNCL
Komerční slévárna šedé a tvárné litiny Turnov a.s., Přepeře 326, CZ 512 61, kyncln@slevarna-turnov.cz
Abstract
The Theory of Constraints (TOC) presupposes that every enterprise has one constraint (bottleneck) limiting
its profit, at least. In order to attain a higher profit by earning more money and to reach a higher degree of
efficiency, such an enterprise has to find its constraint and take necessary measures, how to put it in best
use.
Article introduces possible ways to identifying constraints (bottlenecks) in the manufacturing process. It
focuses primarily on identifying bottleneck by capacity calculations utilization of production resources. A case
study is solved in Komercni slevarna sede a tvarne litiny Turnov a.s. during February 2013.
Identification of bottleneck is the first step in the application of principles and methods of TOC. If plant marks
real constraint incorrectly, taken measures and improvements will not bring the expected result. For enhance
the output of the plant is not necessary to have utilized all production resources at 100%. The idea is not to
waste any of constrained resource.
Key words: TOC, bottleneck, constraint, throughput, source
1. INTRODUCTION
The Theory of Constraints (TOC) was introduce in 1984 in The Goal, written by Eliahu M. Goldratt and Jeff
Cox. Now, this phylosophy belongs to successfully booming methods, which offering new approach to
manage and permanent improving all processes in organizations. The Theory of Constraints presents
unconventional way how to solve problems and way of thinking, which is based on common sense.
The core idea in TOC is that every system such as a profit-making enterprise must have at least one
constraint. If it were not true, then the system would produce an infinite amount of whatever it strives for. In
the case of a profit-making enterprise, it would be infinite profits. Constraint limits the system from getting
more whatever it strives for. [1]
Most businesses cases can be viewed as a linked sequence of processes that transform inputs into saleable
outputs. In TOC, an analogy often is drawn between such a system and a chain. The chain is as strong as
strong is the weakest link. If someone wants to improve the strength of a chain, he must identify the weakest
link and then concentrate efforts on strengthening this single link. The weakest link (bottleneck) sets the
pace for entire system. [2]
Following article contains case study in Komercni slevarna sede a tvarne litiny Turnov a.s. (in futher text
Komercni slevarna). This iron foundry is a traditional producer of glass moulds, grey-cast iron and ductilecast
iron castings. Over 120 employees produce almost 2000 tons per year.
As many other iron foundries has Komercni slevarna sede a tvarne litiny Turnov a.s. problems with keeping
of confirmed terms, lot of defects during producing process, frequent changes in a production plan, and
management have to solve operating problems and they do not have time for strategic decisions.
The purpose of this article is to show ways how to find bottleneck in iron foundry production as a first step to
improving production process by focusing on the constraints. Subsequent application TOC principles and
rules stabilizate operations in iron foudry and simultaneously increase throughput, decrease work-in-process

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inventory and decrease operating expenses. Production managers are suddenly able to make a good plan,
which is realistic, productive and immune against collapse.
2. THEORETICAL BASIS
The constraints will determine the output of the system whether they are acknowledged and managed or not.
Either we manage constraints or they manage us. [4]
2.1 Managing constraints – the process of ongoing improvement
Ironfoundries and industrial enterprises at all have their primary constraints in production. Constraint is
usually a recourse with least capacity – it could be for example a machine, workplace or worker. Constraint
significant affects material flow and utilization of resource’s capacity. If production managers effectively
implement ideas from TOC, constraints usually shift outside of the factory. Suddenly is a constraint demand
or unreliable supplier.
The Theory of Constraints presents instructions for the management of a constraint in the form of five basic
steps:
1. Identify the system’s constraint (bottlenecks)
2. Decide, how to exploit the system’s constraint(s)
3. Anything else must be subordinated to this decision
4. Elimination of the constriction (if steps 2 and 3 do not help to remove the bottleneck, increase the
output of the bottleneck by means of more decisive measures)
5. After elimination of the bottleneck, repeat the cycle by returning to the step No. 1
2.2 Identification of bottleneck
The term bottleneck is taken from the 'assets are water' metaphor. As water is poured out of a bottle, the rate
of outflow is limited by the width of the conduit of exit—that is, bottleneck. By increasing the width of the
bottleneck one can increase the rate at which the water flows out of the neck at different frequencies.
A constraint in a system is anything that limits the system from achieving its objective. Any real system must
have at least one constraint that prevents it from making more profits. If a system did not have a constraint,
its output would be unlimited.
Ironfoundries and industrial enterprises at all have their primary constraints in production. The source with
the least capacity ordinarily will be the bottleneck. The identification of a bottleneck limiting the production
process as a whole can be carried out in three possible ways:
by keeping under observation and on the base of one´s own experience – looking for the place of
inventories accumulation
capacity calculations – determination of capacity requirements for the given assortment and
comparison with the capacity being available
simulation
3. CASE STUDY
In a well-run factory, the constraint can be identified easily by the location of work-in-process inventories. If
the factory is well managed, they will be concentrated in front of the constraint. In a poorly run factory, workin-process
inventories will be scattered all over, and identification of the real constraint is initially more

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difficult. Some managers are unable to figure out where the bottleneck is because of the chaos that has
resulted from applying conventional shop control techniques over the years.
3.1 Foundry introduction
Komercni slevarna after privatisation in 1997 has been focused on production of commercial castings
deliveries (from one piece to small or middle series) with maximal orientation on the customer, his terms and
quality requirements.
Raw material is melted in induction furnaces (1x 1000 kg, 2x 500 kg, 1x 9000 kg foreheart) and gravity
casted in sand forms. The most of cores are manufactured in two automatic shooting machines by COLD-
BOX technology. Production equipment consist of forming unit FORMTEC Air Impec, mechanical moulding
FOROMAT 20, 40 (2+2) and manual moulding. Final operations by grit blasts, grinders and annealing furnace.
Diverse production – various materials, dimensions, weights and quantity complicate scheduling and
managing of production process. In this case is impossible to identify constraint by observation. We have to
use capacity method to identify the bottleneck.
3.2 Calculation of available capacities
Twenty two production operations are defined in the foundry, i.e. of production sources. The production
operation are registered in production process of the casting in question together with the date giving the
planned requirement rate for the treatment with regard to 1 piece (see Fig. 1)
Figure 1 Example of production process
The information and scheduling system OPTI used in Komercni slevarna plans „from behind“. A required
delivery term (according to the customer´s wish) is put into the system; the system will then calculate the
source capacities step by step, starting from the last production operation and taking into account the
possible time reserve. As soon as it hits the overrun available capacity of a certain source, it will shift the
delivery term by 1 day and start to calculate again. And it goes in such a way as long as it plans all
production operations of the production procedure. Thus the production of all individual orders is planned in

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such a way so that the production operations follow immediately one after the other and with respect to the
production technology.
Tab. 1 Survey of exploitation of available capacities in calendar week 8 / 2013
Production Source Plann.
unit
Shift
model
Work./
Mach.
Output /
hour
Utiliz. Prod.
degree
Avail.
capacity
Exploitation
Hand made core min 3 4 60 80 1 20880 83
Cold Box 1 min 3 1 60 80 3 15660 100
Cold Box 2 min 3 1 60 80 3 15660 81
Shooting AVS-16 min 3 1 60 20 1 1305 0
Shooting V-10 min 1 1 60 60 1 1305 68
Hand moulding min 1 4 60 90 1 7830 88
Moulding F20 min 1 1 60 70 1 1522 57
Moulding FA min 3 1 60 90 0.65 3817 100
Moulding F40 min 1 2 60 95 1 4132 83
Casting kg 2 2 500 100 1 72500 100
Handed discharge kg 1 1 200 100 1 7250 88
Machine discharge kg 3 1 750 100 1 81563 89
Grit blasting min 3 1 60 80 1 5220 100
Inlet removing min 3 5 60 100 1 32625 76
Grounding min 3 4 60 100 1 26100 90
Finish grounding min 2 6 60 100 1 26100 100
Coat kg 1 1 600 100 1 21750 62
Spray coat kg 1 1 600 100 1 21750 0
Annealing kg 1 1 600 100 1 21750 14
Income on stock kg 1 4 600 100 1 87000 34
Cooperation CZK 1 1 20000 100 1 725000 46
Income workpiece kg 1 4 600 100 1 87000 15
In order to calculate the available capacity of the individual sources, it was necessary to define the following
data:
Planned unit - each of the sources operates with a given unit of the work to be done – it can be
weight (kg), time (min), and price (CZK)
%

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Week model of shifts - it may have values 1, 2 or 3, depending on the one-shift, two-shift or threeshift
operation in the given source
Number of workers / machines - working in the given source
Output in one hour - gives the maximum value per 1 hour of work (its value depends on the unit
being used)
Utilization of the working time - the value in % of the real work output of the source – if it is
necessary to take into consideration idle time, defects, intervals for hygiene, maintenance, etc.
Productivity degree - further limiting factor for individual setting up the source capacity
The available capacity equals the factor of all values multiplied by working days per week (5) and the length
of the working time without legislative interruptions (7.25) – vide Table 1.
3.3 Exploitation of the production sources
By comparison of the capacity demands of the contemporaneous assortment and the calculated available
capacity, the following production sources result as the critical ones:
core shooting Cold Box 1
automatic moulding line (moulding FA)
casting
finish grounding
grit blasting
At first sight, it seemingly could look like the different structure of the assortment to be produced in the
foundry according to customer´s orders causes the existence of floating bottlenecks. However, all indicates
that the bottleneck in the Komercni slevarna is the Automatic moulding line. 88% of the produced assortment
influencing directly all the critical sources pass through this line - the casting with complicated shape need a
high number of cores and also a long time for finish grounding, heavy and large pieces need a lot of meltdown
metal and do not exploit the full capacity of the pendant blast barrel. This is just this workplace which is
critical for the efficiency of the entire foundry.
4. CONCLUSION
Five critical sources were ascertained by means of capacity calculations. By observing the production
process and according to the accumulation of the work-in-process inventory, it is possible to certify just this
conclusion. After taking the measures aiming to a higher utilization of these overloaded workplaces, it will be
possible to decrease the number of critical sources and eliminate the mobility of constraints depending on
the assortment to be produced.
If identification of bottleneck by capacity calculations expose more than one constraint, foundries have to
check these critical resources one by one to eliminate individual constraints. After accomplishment of
capacity improvements on critical resources is necessary to check exploitation again. For application
methods and tools of TOC to increase production process is finding right bottleneck the most important step.
When the initial guess at the location of the constraint is incorrect, the system eventually let us know by the
presence of unplanned work-in-process inventory accumalating in front of the real constraint.
It is also necessary to realize that capacity of bottlenecks that are influenced by human work can be
influenced without big problems. Quite simply, the number of workers should be accommodated in such a
way that the workplace does not represent a bottleneck of the whole system. However, a problem occurs in

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the machinery workplace where there is not possible to increase the capacity in such an easy way. Possible
measures aiming to the elimination of critical sources and proposals for increasing the efficiency of a
bottleneck will be described in further research works.
ACKNOWLEDGEMENT
I would like to acknowledge the support of the logistics manager and the master of production at
Komerční slévárna šedé a tvárné litiny Turnov a.s. who gave me generous acces to their annual
reports. I am also grateful to my supervisor doc. Ing. Radim Lenort, Ph.D. who encouraged me to
pursue this topic.
REFERENCES
[1] NOREEN E., SMITH D., MACKEY J. T., The Theory of Constraints and its implications for management
accounting, The North River Press, 1995.
[2] BASL J., MAJER P., ŠMÍRA M., Teorie omezení v podnikové praxi. Zvyšování výkonnosti podniku nástroji TOC,
Grada Publishing, 2003.
[3] GOLDRATT E. M., Cox J., The Goal, The North River Press, 2 Revised edition, 1992.
[4] GOLDRATT E. M., Itś not Luck, The North River Press, 1994.
[5] GOLDRATT E. M., Critical Chain, The North River Press, 1997.
[6] LENORT R., SAMOLEJOVÁ A. Analysis and Identification of Floating Capacity Bottlenecks in Metallurgical
Production. Metalurgija, January-March 2007, vol. 46, no. 1, s. 61-66.
[7] LENORT R., KRAUSOVÁ E., Offer and Inquiry Management in Logistics of Metallurgical Enterprise. In Modernity
of industry and services – new challenges, Vol. II. Katovice: Scientific Society for Organization and Management,
2004, p. 13-20.