Use of Altshuller’s Matrix for Solving Slag Problems Related to Steering
Knuckle (Part I of II)
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Use of Altshuller’s Matrix for Solving Slag Problems Related
to Steering Knuckle (Part I of II)
TRIZ case study in the process industry
Edgardo CORDOVA LOPEZ
INSTITUT NATIONAL POLYTECHNIQUE DE TOULOUSE-ENSIACET
Laboratoire de Génie chimique, UMR-CNRS 5503
Edgardo.CordovaLopez@ensigct.fr
INPT tel. (+33) 05 62 88 58 42, fax 05 62 88 57 85
Germain LACOSTE
Directeur de l’ECOLE NATIONALE D’INGENIEURS DE TARBES
Laboratoire de Génie Chimique, UMR-CNRS 5503
Germain.Lacoste@enit.fr
ENIT Tel. (+33) 05 62 44 27 01, fax (+33) 05 62 44 27 27
Jean-Marc LE LANN
JeanMarc.LeLann@ensigct.fr
Responsable du Département Genie Industriel
Laboratoire de Génie Chimique, UMR-CNRS 5503
ECOLE NATIONALE SUPERIEURE DES INGENIEURS EN ARTS CHIMIQUES ET
TECHNOLOGIQUES (INPT-ENSIACET)
ENSIACET tel. (+33) 05 62 88 58 33, fax (+33) 05 62 88 57 85
ABSTRACT
Volkswagen of Mexico S.A. de C.V, the well-known german
automotive industry has become the first company in Mexico and perhaps in Latin
America using the TRIZ methodology in order to improve its processes of
production. The line of foundry manufacture for one of its pieces of safety,
namely the steering knuckle, has presented from the beginning various quality
and operation problems. It is a strategic piece for the security of the
passengers in cars since it is closely interacting with the direction, the shock
absorbers, and with the front wheels. Two great problems have been accurately
identified: one is the slag and the other one is referring to the sand system
for the manufacture of molds. The matrix of Altshuller, a key milestone in the
TRIZ methodology for innovation technology has allowed to help for proposals of
valuable and sustainable solutions to solve these great problems that originate
scrap causes, such as “solidification shrinkage”, “sand rain” or “ porosity”.
All of these cause a high percentage of scraps or reworks. In this paper,
the first of them, namely the slag problem will be analyzed.
Key words: TRIZ methodology, steering knuckle,
contradictions, ideal solution, Altshuller’s matrix, Inventing principles, slag
1. INTRODUCTION
TRIZ is a new methodology born in Russia (called
Theory of Inventive Problem Solving). TRIZ is a knowledge-based
technology for speed-up development of design concepts. The power of this
methodology is based in the evolution of successful products, ways to overcome
psychological barriers, and generalization of the ways used to solve several
problems in the most innovative inventions. TRIZ is able to analyze products or
process functions in order to best use its resources and identify the best
opportunities for its development. Many papers about TRIZ have been published in
difference international revues, the most important and dedicated is the
triz-journal. ( www.triz-journal.com ) [4]
1.1 Overview of the Company.
The Volkswagen firm in Mexico is one of the most important
automotive industries around the country. It is conformed to a great amount of
industrial ships and various processes of production that conform everything in
an industrial system that makes the manufacture possible of the different
automobiles which, at the present time, are sold in the country. The
macro-industry of more than 15000 workers has just produced its unit number 5
million in more than 30 years of existence. It uses the most modern methods of
production and the most advanced management quality systems. It is located in
Puebla next to mountains and only 80 miles from Mexico City. [1]
1.2 The Piece.
The steering knuckle is an important part of the vehicle that
allows fixing the front wheel brakes, the motion of direction, the fixation of
the shock absorber, and the axis of impulsion. This piece is of safety
importance whereas it is subject to diverse types of strengths in different
directions and must strictly fulfill the design-required parameters. (Fig.1)
1.3
The Material
This piece is made with ductile iron. After a magnesium-based
reaction, the iron is impregnated with a large amount of nodules that present,
at the microscopic level, the appearance of spherical bubbles. These
particularities allow for ductility and resistance to the tensions. It induces
an extraordinary resistance to the breakage and/or the flexion. For that reason,
it is necessary in this process of reaction to introduce certain substances such
as carbon, silicon and others in order to give the required properties to the
piece. [1]
1.4 The Process.
The production in the foundry manufacturing line begins with
the induction furnaces that are fed mainly with new raw material, recycled
material, and scrap pieces. These furnaces melt and mix the material with other
necessary substances for the casting process (temperature>1400°C). Later, the
iron-base is put under a reaction process using magnesium in order to form
nodules that allow it to acquire certain physical properties of ductility. It
allows for the manufacturing of a piece whose function is associated to diverse
efforts and tensions that cause their critical parameters and its meticulous
control. Then the casting process is performed. A casting is a metal part formed
by pouring molten metal into a sand mold. The mold is composed with two halves
that form a cavity into which the molten metal is poured. The mold forms the
external surface of the casting. If an internal cavity is required in the
casting, a core is placed inside the mold cavity, as in the case for our piece.
After the metal solidifies, the mold is broken, the core
removed and the part is ready for finishing operations. The sand is then
remolded, prepared and used again in a cyclic process.
Then, there is a cooling process that strips the two pieces
which are then drained: a right and a left one, totally symmetrical that
separated by a ‘branch’ that serves as a joint between both pieces (which is
known as recycled or returned material). At the same time, the sand is recovered
in order to be reused through a transportation band until the sand tower, where
the sand has already been treated with water in order to fulfill the required
humidity. Some pre-mixed substances that give the sand agglutinates properties
have also been added. The pieces, cold and clean, are tested in laboratories in
order to avoid out of specification pieces, arriving at the machine process.
Finally the pieces are re-assembled.
1.5 The Basic Problem.
The manufacturing line in its first foundry step for the
steering knuckle has been recently started. It was implemented less than a year
ago and since then a lot of problems have had to be surpassed, reflected in the
high percentage of scraps and reworks considerably increasing the operating
costs. The main causes of these scraps are the ‘solidification shrinkage’, that
is a deformation of the piece because of the metal in fusion does not fill the
mold in certain points due to a premature cooling. The ‘sand rain’ attributed to
that the molds do not have the properties with required humidity or
agglutination and thus they are deformed at the moment of the casting. In
addition to these two reasons that cause 90 % of scraps, there are also the
porosity, the struck piece, and others which causes are attributed to diverse
reasons. Nevertheless, most of those problems may be eliminated or diminished if
two great fundamental problems can be solved: the slag and the recycle sand
quality.
The excess of sand deposited in the hopper feeding the
induction furnaces, impregnated in the return material is certainly the main
cause. Using the Altshuller’s matrix we will able to analyze these two great
problems and we will try to propose a solution for each of them. In this paper
we will analyze only the first problem.
2. ANALYSIS OF THE PROBLEM
The slag is one of the most persistent problems; it is the
impurities that are detected in the metal before the casting process. This
problem is originated mainly in the material of return or the scrap pieces that
are impregnated with an important amount of sand, as product of strips, which
cannot be easily eliminated. The slag represents a contaminant element that is
necessary to eliminate or to diminish before the casting process to avoid
scraps. From the point of view of the Altshuller’s matrix, we want to improve
the adaptability of the metal, since the slag causes the metal to not fulfill
the desired conditions for fluidity. Nevertheless, the main challenge is the
natural effect of the high temperature and conditions of the process that
prevent or make difficult any effective remedial action. The ideal solution
is that the scrap pieces or the material of return do not contain sand at all
[5], but it is a difficult task by the inherent conditions of the process. If we
consulted the Altshuller’s matrix in line 35 related to Adaptability and
column 17 referring to Temperature, we find the numbers 2, 27, 3, 35 that
correspond to the inventive principles suggested by the matrix. (The matrix can
be consulted and used in http://www.inp.nsk.su/~dolgash/triz/index.html
). Each of them has been analyzed carefully in
order to give the right answers.
Inventive principle 2. Taking out
A. Separate an interfering part or property from an
object, or single out the only necessary part (or property) of an object.
Locate a noisy compressor outside the building where
compressed air is used.
Use fiber optics or a light pipe to separate the hot
light source from the location where light is needed.
Use the sound of a barking dog, without the dog, as a
burglar alarm. [2]
Interpretation: The separation of the polluting
elements that are accumulated in the superior part of the hoppers (Slag) must
make with some special devices in the same way one takes off the cream from a
glass of milk. This solution is in fact already practiced each day in order to
controlling the excess of slag. Although it is only a partial fix and it does
not represent a solution to the problem.
Inventive principle 27. Cheap short-living objects
A. Replace an expensive object with a multiple of
inexpensive objects, comprising certain qualities (such as service life, for
instance).
Use disposable paper objects to avoid the cost of
cleaning and storing durable objects. Plastic cups in motels, disposable
diapers many kinds of medical supplies. [2]
Interpretation: the addition of some components could neutralize the
injurious effect of the slag, for example the use of salts or saline solutions
that have a neutralizer effect and make easier the operation of extraction. This
method is already considered and practiced in a regular way within the process,
obtaining a significant decreasing of the problem.
Inventive Principle 3. Local quality
A. Change an object's structure from uniform to
non-uniform, change an external environment (or external influence) from
uniform to non-uniform.
Use a temperature, density, or pressure gradient
instead of constant temperature, density or pressure.
B. Make each part of an object function in conditions
most suitable for its operation.
Lunch box with special compartments for hot and cold
solid foods and for liquids
C. Make each part of an object fulfil a different and
useful function.
Pencil with eraser
Hammer with nail puller
Multi-function tool that scales fish, acts as a
pliers, a wire stripper, a flat-blade screwdriver, a Phillips
screwdriver, manicure set, etc. [2]
Interpretation. This principle suggests to avoid that
the sand arrives at the furnaces or at least, it does not arrive in excess or,
if it arrives that some reaction process is possible in order that the slag
becomes operational or its effect is unnoticed.
Perhaps to obtain some external agent allows avoiding the
excess of sand in the furnaces.
This problem will be analyzed in section 3 like one more contradiction.
Inventive principle 35. Parameter changes
A. Change an object's physical state (e.g. to a gas,
liquid, or solid).
Freeze the liquid centers of filled candies, then dip
in melted chocolate, instead of handling the messy, gooey, hot liquid.
Transport oxygen or nitrogen or petroleum gas as a
liquid, instead of a gas, to reduce volume.
B. Change the concentration or consistency.
Liquid hand soap is concentrated and more viscous
than bar soap at the point of use, making it easier to dispense in the
correct amount and more sanitary when shared by several people. [2]
C. Change the degree of flexibility.
Use adjustable dampers to reduce the noise of parts
falling into a container by restricting the motion of the walls of the
container.
Vulcanize rubber to change its flexibility and
durability.
D. Change the temperature.
Raise the temperature above the Curie point to change
a ferromagnetic substance to a paramagnetic substance.
Raise the temperature of food to cook it. (Changes
taste, aroma, texture, chemical properties, etc.)
Lower the temperature of medical specimens to
preserve them for later analysis. [2]
Interpretation. To make the undesired material become
more evident and manipulable in order to eliminate it more easily. To use the
effect of some chemical reaction to cause all the impurities that cause problems
to ascend to the surface and make its recovery easier. This operation would be
unnecessary if we managed to avoid that the sand arrives at the furnaces in
excess.
3. ANALYSIS OF THE PROBLEM OF THE NON-ADHERED SAND ON
THE RECYCLED MATERIAL
Since the problem of the slag is mainly attributed to the
high sand content, the problem must be presented in such a way that the
possibility that the sand arrives at the furnaces does not exist or it arrives
only with a minimal amount. The recycled material as well as the scrap pieces
are transported in freight elevators that in addition to the material cannot
avoid to transport a great amount of sand non-adhering to the material. Let us
say that the sand adhered to the material will require other methods of solution
(section 4), but it is possible to avoid that the loose sand arrives at the
storage zone of the recovery pieces, making it very difficult to eliminate
without increasing the cost of the processing. Therefore, the following
situation exists: we would like to eliminate the undesired material during the
transport process but the amount of material to transport prevents it; that is
to say, the parameters are: line 33, Ease of operation and column 1,
Weight of a Mobil object. The precognized inventive principles suggested by
the matrix are: 25, 2, 13 and 15. Let us analyze carefully these principles and
try to find answers adapted to our problem.
Inventive principle 25. Self-service
A. Make an object serve itself by performing auxiliary
helpful functions
-
A soda fountain pump that runs on the pressure of the
carbon dioxide that is used to "fizz" the drinks. This assures that
drinks will not be flat, and eliminates the need for sensors.
-
Halogen lamps regenerate the filament during
use--evaporated material is redeposited.
To weld steel to aluminum, create an interface from
alternating thin strips of the 2 materials. Cold weld the surface into a
single unit with steel on one face and copper on the other, then use
normal welding techniques to attach the steel object to the interface,
and the interface to the aluminum. (This concept also has elements of
Principle 24, Intermediary, and Principle 4, Asymmetry.)
B. Use waste resources, energy, or substances.
-
Use heat from a process to generate electricity:
"Co-generation".
-
Use animal waste as fertilizer.
-
Use food and lawn waste to create compost. [2]
Interpretation in the context of our problem: The
freight elevator must clean the return material during the transportation; that
is to say, not only should it transport but also it should be able to clean it.
This can be performed through some device of suction (aspiration) using its own
calorific or electric power energy to avoid extra costs.
Inventive principle 2. Taking out
A. Separate an interfering part or property from an
object, or single out the only necessary part (or property) of an object.
Locate a noisy compressor outside the building where
compressed air is used.
Use fiber optics or a light pipe to separate the hot
light source from the location where light is needed.
Use the sound of a barking dog, without the dog, as a
burglar alarm. [2]
Interpretation: The extraction of the sand is confirmed
with this principle as it was settled in the previous principle.
Inventive principle 13. 'The other way round'
A. Invert the action(s) used to solve the problem (e.g.
instead of cooling an object, heat it).
To loosen stuck parts, cool the inner part instead of
heating the outer part.
Bring the mountain to Mohammed, instead of bringing
Mohammed to the mountain.
B. Make movable parts (or the external environment) fixed,
and fixed parts movable).
Rotate the part instead of the tool.
Moving sidewalk with standing people
Treadmill (for walking or running in place)
C. Turn the object (or process) 'upside down'.
Turn an assembly upside down to insert fasteners
(especially screws).
Empty grain from containers (ship or railroad) by
inverting them. [2]
Interpretation: This principle suggests to undo the
leftover sand before the material is unloaded and not later, inverting the
deposit, previously covered by a very resistant mesh that can load all the
material, so that only the sand drains. Later the material without the
protective mesh could be unloaded in the corresponding area.
Inventive principle 15. Dynamics
A. Allow (or design) the characteristics of an object,
external environment, or process to change to be optimal or to find an
optimal operating condition.
Adjustable steering wheel (or seat, or back support,
or mirror position...)
B. Divide an object into parts capable of movement
relative to each other.
The "butterfly" computer keyboard, (also demonstrates
Principle 7, "Nested doll".)
C. If an object (or process) is rigid or inflexible, make
it movable or adaptive.
The flexible boroscope for examining engines
The flexible sigmoidoscope, for medical examination
[2]
Interpretation:
A double bottom of the return material deposit could be a
good solution.
The first bottom is a solid surface with innumerable
perforations so that the sand filters to a second bottom.
Once this has happened, a sliding device will cause the
perforations to be obstructed so that to the deposited, material created by
inverting, the sand remains intercepted between the two bottoms of the deposit.
A system of aspiration using the same energy of the freight
elevator (calorific, mechanical or electrical) will drain the sand content to
the corresponding area or, by inverting. (Fig.2)
Fig.2 Deposit of return material with double bottom
4. ANALYSIS OF THE PROBLEM OF THE ADHERED SAND ON THE RECYCLED
MATERIAL
The problem of the adhered sand to the return material is one
of most seriousness. There is not a method that allows eliminating the sand that
contaminates the induction furnaces and therefore, increases the amount of slag
that prevents the process as a whole.
The ideal solution would be that the premix* that
is added to the sand had the property to maintain in hot conditions its
properties of adhesion or agglutination but in cold conditions, these properties
were lost. As this solution is not sustainable (that rather corresponds to the
sand supplier), it will be necessary to consider other solutions. We will settle
this problem like a contradiction of the following way: What we want is to clean
to the surface of a movable object that is the material that is transferred to
the recovery area. Nevertheless, a resistance exists because the sand is
compacted to the material and therefore the cleaning work becomes difficult.
Consulting the Altshuller’s matrix, in line 18 (Brightness)
and in column 14 (Strength) we find the numbers 35 and 19 as the inventive
principles to be applied to solve this problem.
Let us analyze each of them.
Inventive principle 35. Parameter changes
A. Change an object's physical state (e.g. to a gas,
liquid, or solid).
Freeze the liquid centers of filled candies, then dip
in melted chocolate, instead of handling the messy, gooey, hot liquid.
Transport oxygen or nitrogen or petroleum gas as a
liquid, instead of a gas, to reduce volume.
B. Change the concentration or consistency.
Liquid hand soap is concentrated and more viscous
than bar soap at the point of use, making it easier to dispense in the
correct amount and more sanitary when shared by several people.
C. Change the degree of flexibility.
Use adjustable dampers to reduce the noise of parts
falling into a container by restricting the motion of the walls of the
container.
Vulcanize rubber to change its flexibility and
durability.
D. Change the temperature.
Raise the temperature above the Curie point to change
a ferromagnetic substance to a paramagnetic substance.
Raise the temperature of food to cook it. (Changes
taste, aroma, texture, chemical properties, etc.)
Lower the temperature of medical specimens to
preserve them for later analysis [2]
Interpretation: this principle suggests to react the sand
adhered to the material, submerging it in an acid or an alkaline liquid of a
certain concentration so when reacting, the sand becomes loose. Exactly like it
happens with grease when reacting it with liquid stove cleaner, this acquires a
favorable consistency for its cleaning without affecting the surface of the
material. This operation can be conducted by those who make the separation of
the pieces with the call “ branch” (material of return) without wasting a lot of
time or effort.
Inventive principle 19. Periodic action
A. Instead of continuous action, use periodic or
pulsating actions.
Hitting something repeatedly with a hammer
Replace a continuous siren with a pulsed sound.
B. If an action is already periodic, change the periodic
magnitude or frequency.
Use Frequency Modulation to convey information,
instead of Morse code.
Replace a continuous siren with sound that changes
amplitude and frequency.
C. Use pauses between impulses to perform a different
action.
In cardio-pulmonary respiration (CPR) breathe after
every 5 chest compressions. [2]
Interpretation: this principle is complemented with
the previous one, because once the cleaning liquid has been applied to the
material, a movement of oscillation or periodic impulses can be applied to the
deposit in order that the return material is undone of the sand that previously
has been treated. These impulses can be made in a more efficient way during
their transfer using the same energy the freight elevator does. The sand can be
eliminated by suction or by inverting the deposit with a mesh that it prevents
the material from falling. This solution is similar to the proposal for the
loosened sand, therefore, the two could be conjugated and consequently any type
of sand, either the released or the adhered one, does not arrive.
Fig.3 The hopper with the perforation and the sand collector
5. CONCLUSIONS
The least expensive and fastest solution to implement is to
make an extraction by inverting the deposit, holding onto the pieces by using a
resistant mesh to unload the excess of sand. Although the most efficient
solution is to use the deposit with a bottom, which has multiple perforations,
so the sand falls into a second bottom to be inhaled or drained in a later
operation to discharge the material. This solution implies an adaptation to the
deposits of the material. If the ideal solution cannot be reached, the amount of
slag could at least be reduced in a high percentage that is generated for sand
reasons. A complementary action to assure minimum sand in the induction furnaces
that also can operate in case that the previous operations are not possible is
as follows: To modify the hopper that spills the material to the furnaces adding
a great amount of circular perforations in the base of the hopper. At the moment
it has only these perforations in a small area that is not sufficient to collect
all the sand that already is loosened in the hopper. Thus, once the scraps or
return material is deposited in the hopper, this one will be vibrated in order
to obtain an effect of sifting and eliminate portions of sand, a sand collector
will be adapted (see fig 3 and 4). This solution has been recommended and
implemented with excellent results and without investment managing to reduce the
scraps and reworks pieces from more than 10% to less than 3%.
This demonstrates how using TRIZ methodology is interesting
and how applying these concepts up to the revamping of a manufacturing chemical
process may lead to significant improvements.
It also demonstrates how a based theory approach may be
efficient for help and may be used in manufacturing industry in order to improve
end-user product, process, and processing.
6. BIBLIOGRAPHY
- [1] Gerhard Schreiber. Eine Geschichte Ohne Ende. A Never-Ending Story. una
historia sin fin. First edition 1998. Volkswagen de Mexico, S.A. de C.V.
[2] Format for the 40 Inventive Principles and the accompanying examples,
developed by Karen Tate and Ellen D.
http://www.triz-journal.com/archives/1997/07/b/index.html
[3] Zinovy Royzen, http://www.trizconsulting.com/ Case Study: TRIZ Solves a
Hard Drive Reliability Problem
[4] Terninko, John/Zusman, Alla/Zlotin, Boris
Step-by-step TRIZ, Creating Innovating solution Concepts
3th edition, 1996/responsible Management Inc. Nottinham, New Hampshire
[5] Altshuller, Genrich. And suddenly the inventor Appeared, TRIZ, The Theory
of inventive problem solving/ 2nd edition, published by Technical Innovation
Center, Inc Worcester, MA/ 1996
[6] V. Souchkov 1996/ Cav 1997 /K Tate/E. Domb, 1997 V. Souchkov 1996 http://www.triz-journal.com
[7] Córdova-López, Edgardo/ TRIZ: Une manière innovante de
résoudre les problèmes d’Ingénierie/ Mémoire presented on sept 10th. 1999 in the
Institut National Polytechnique de Toulouse, Francia.
[8] KOWALICK, James TRIZ-Journal, Nov. 1996, (
http://www.triz-journal.com )
17 Secrets of an Inventive Mind : How to conceive World Class Products
Rapidly Using TRIZ and Other Leading Edge Tools
[9] KOWALICK, James TRIZ-Journal, Juin1998, (
http://www.triz-journal.com )
TRIADS : Their Relationship to TRIZ. Elaboration on the Use of Triads and
TRIZ solve Impossible Problems and Creat Next-Generation, Breakthrough Desings.
[10] LEONCIO Jiménez Candia TRIZ-Journal, Nov/01 (
http://www.triz-journal.com )
The Altshuller’s Contradiction Matrix in the Knowledge
Creation of Innovation Case Study : The Honda City/ Institut National
Polytechnique de Toulouse - France
http://www.triz-journal.com/archives/1997/07/b/index.html
__________
Endnotes
- Correspondance to whom should be adressed
- Correspondance to whom should be adressed
* the premix is elaborated with different adhesive substances
like sodium and calcium benzonites, and carbon in order to give at the sand some
adhesion proprieties.
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