Kraev's Korner: Inventive Principles - Lesson 7

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  • By Val Kraev

    Editor's note: Kraev's Korner was first published in the newsletter of the Altshuller Institute in 2005. Our thanks to the Altshuller Institute and the Technical Innovation Center for letting us reprint this educational series. Previous lessons can be found by searching the TRIZ Journal's archives.

    At the beginning of the last century different lists of inventors' recommendations were published. Each author suggested the strongest inventive rules in his personal opinion. As a result, these lists included recommendations concerning technical systems (i.e., "segmentation principle"), and advice concerning psychological aspects (i.e., "personal analogy principle") published together. The subjective character of such lists made the solving of engineering problems less efficient. They also did not allow for a formalized process of solution development. These first inventors' lists of recommendations were, therefore, limited in practical application and did not have wide circulation.
    Genrikh Altshuller offered another approach to the development of inventive principles in the late 1950s. He and his colleagues selected the most often occurring strong principles based on the analysis of a large number of the patents – more than 400,000. Each of these principles efficiently "worked" in at least 80-100 inventions. As a result, 40 most often used inventor's principles were published (see following table).

    40 Inventive Principles
    1. Segmentation
    2. Extraction
    3. Localized characteristics
    4. Asymmetry
    5. Consolidation
    6. Universality
    7. Nesting principle
    8. Counterweight
    9. Prior counter-action
    10. Prior action
    11. Be prepared
    12. Equipotentiality
    13. Reverse
    14. Spheroidality
    15. Dynamicity
    16. Partial or satiated action
    17. Move to a new dimension
    18. Mechanical vibration
    19. Periodic action
    20. Continuity of useful action
    21. Rush through
    22. Convert harm into benefit
    23. Feedback
    24. Mediator
    25. Self-service
    26. Copying
    27. Inexpensive and short-term instead of expensive and durable
    28. Replacement of a mechanical system
    29. Pneumatic or hydraulic construction
    30. Flexible film or thin membrane
    31. Porous material
    32. Changing color
    33. Homogeneity
    34. Rejecting and regenerating parts
    35. Transformation of the physical-chemical properties of the system or parts
    36. Phase transition
    37. Application of heat expansion
    38. Using strong oxidizers
    39. Inert environment
    40. Composite materials

    The principles are the simplest TRIZ tool for resolving technical contradictions and solving problems. Their application does not require any special knowledge – children as well as professionals may use them. Nevertheless, utilization of this TRIZ tool does require some practical skills.
    The contradiction table of the 40 principles was designed to formalize and to facilitate the usage of this TRIZ tool in practical activity. This table is called Altshuller's contradiction matrix. The matrix presents you with 39 system characteristics. The pairs of contradictory characteristics form a matrix. The first item in the pair is located in the left column of matrix and called the improving feature. The other item of the pair is placed in the top row of the matrix and called the worsening feature. (Not every contradictory pair of features has a set of principles associated with them.)

    In practical activities, several methods of applying the principles are used during the problem solving process.

    1. The first method is also the simplest – enumeration of principles. This method reviews each of the principles while trying to apply each (or their combinations) to solving the technical contradiction in the specific problem.
    2. The second way is the formulation of a technical contradiction and use of Altshuller's matrix in order to get a set of recommended principles (as a rule, just two-four principles) for solving the problem.
    3. The third method is the formulation of the direct and reversed technical contradiction for the problem and using the matrix for both of these formulations. Both of these formulations can make sense and the matrix may suggest additional effective principles since it is not symmetrical. Principles for reversed contradiction also may be useful in eliminating both contradictions. For instance, consider the direct contradiction, "improving the characteristic of reliability of the system (row 27) leads to worsening the characteristic of force (column 10)." From the matrix we can get for this conflict the principles 8, 28, 10 and 3. If we formulate the reversed contradiction, "improving the characteristic of force (row 10) leads to worsening of reliability (column 27)," then we get principles: 3, 35, 13 and 21. Both of these contradictions can potentially improve the system. It is useful to try all of the principles to solve the problem.
    4. The fourth way is the formulation of two or more different contradictions for the problem, solving the contradictions with the matrix. When using this method, identify the common principles from the different sets. These common principles may provide extra benefit – because they may be useful for solving several technical contradictions simultaneously.

    We will use examples to test each of these methods. There are two simple steps for using the inventive principles and matrix for problem solving:

    1. Formulate the problem through the technical contradiction. This step is devoted to exploring the features of the system that need to be improved and the features that are worsening due to the improvement.
    2. Solve the problem by removing the technical contradiction. This step implies the development of solutions for the problem adapting principles from a list or recommended specific principles from the matrix that are determined with help of contradictory features.

    First, we will apply the simplest method for solving problems using the inventive principles. This method is accomplished by scanning each principle and selecting one – or a combination of – principles, the most appropriated for solving the problem.

    It is impossible to climb painted wooden stairs leading to a second floor until the paint dries. How can we access the second story during the painting process?
    Formulate the technical contradiction: if we paint stairs we improve its protection from outside harmful influences (scratch, water, wear and tear) but we worsen the time to use the stairs. After reviewing the principles, principle 1 is selected as the most appropriate for this situation.
    Principle 1: Segmentation. Recommendations for this principle are:

    • Divide an object into independent part
    • Make an object sectional
    • Increase the degree of an object's segmentation

    Paint every other step and once those steps are dry, paint the remaining steps. This allows us to use the stairs without having to wait for all of them to dry.


    When a vacuum cleaner is working in an enclosed space an unpleasant smell may occur. Increasing the thickness and number of external air filters in vacuum cleaner are options for avoiding the unpleasant smells. This solution, however, is not efficient because the consumption of energy increases dramatically with an increased number of filters. How can we avoid creating an unpleasant smell when vacuuming?
    Now formulate the technical contradiction. If we reduce unpleasant smell (improve parameter "harmful action developed by vacuum cleaner"), then the parameter of "spent energy" of vacuum gets worse. For solving this contradiction and problem, the combination of two principles was selected:
    Principle 9: Prior counteraction

    • Understand what might go wrong in advance and take action to eliminate, reduce, or prevent its occurrence

    Principle 6: Universality (Multifunctionality)

    • An object can perform several different functions; therefore, other elements can be removed

    The best way to develop these ideas is to use the simplest and cheapest "home resource" that is always available. Before vacuuming, put a coffee bag or some other good smelling home substance (e.g., cinnamon in a bag) as an external vacuum filter. This serves as an air freshener at the same time as a filter.

    The second way to utilize the inventive principles is to use the contradiction matrix to identify a set of recommended principles to formulate a technical contradiction for the problem. The most appropriate contradictory characteristics are defined at the intersection of the horizontal rows (improving feature) and the vertical columns (worsening feature) of the matrix. The improving feature list is the concept that best describes improving the objective. The worsening feature list is the concept that best describes the corresponding deterioration in reaching the objective. In case you cannot find an exact match between the stated objective and one of the features, try finding a feature that is closely related to the objective. The description of each principle and additional hints provides clues to a solution.
    The important feature of this method is determining and applying 2-4 of the recommended principles to resolve a specific technical contradiction.

    Consider the scattered non-magnetic graphite, or magnesium powder, that needs to be cleaned. A remained after trying to use a brush. A vacuum cleaner was used, but we could not easily collect the powder from the vacuum pipe and filter after cleaning. How can this problem be fixed?
    The technical contradiction is: we can use a vacuum cleaner to quickly gather scattered non-magnetic powder but some amount of powder is lost in the vacuum pipes and filter.
    The improving feature that goes with "to quickly gather" is "productivity" (39). The worsening feature is "loss of substance" (23). At the intersection of this row and column there are four recommended principles for resolving the indicated contradiction:
    Principle 28: Replacement of mechanical system

    • Replace a mechanical system with an optical, acoustical, thermal or olfactory system
    • Use an electric, magnetic or electromagnetic field to interact with an object
    • Replace field from static to movable, from unstructured fields to those having structure
    • Use fields in conjunction with ferromagnetic particles

    Principle 10: Prior action

    • Perform required changes to an object completely or partially in advance
    • Place objects in advance so that they can go into action immediately from the most convenient location

    Principle 35. Transformation properties

    • Change the physical state of the system
    • Change the concentration or density
    • Change the degree of flexibility
    • Change the temperature or volume

    Principle 23. Feedback

    • Introduce feedback
    • If feedback already exists, change it

    Principle 10 is the most appropriate for solving our problem. The scattered non-magnetic powder can be gathered with a vacuum after a piece of cloth is placed on the end of the vacuum pipe. Powder will adhere to the cloth when the vacuum is on. When the vacuum cleaner is off the powder falls onto a plate readied in advance. This solution satisfies both parts of the contradiction.

    The third method of using the inventive principles is formulating (in advance) two reversed technical contradictions. The unique feature of this method is the use of the principles for direct and reversed contradictions to find an improved solution concept. This is reasonable because both of the reversed formulations make sense and the matrix may suggest additional effective principles for solving the problem. 



    A washing machine works pretty well for cleaning small articles of clothing. Similarly, cleaning bulky items, such as blankets, window curtains or a thick downy jacket is difficult in a standard washing machine. To clean these bulkier items, we have to use several washing cycles. This solution is imperfect because we lose time and energy without guaranteed success. What can we do to improve this situation?
    The direct contradiction is: if we increase the size of the articles in the washing machine, then we have to allot more time for their cleaning. The reversed contradiction is: if we do not want to take extra time to wash larger articles, then we can only clean smaller clothing.
    The next step is using the matrix to find the features that are closely related to the real conflicting parameters. "Volume of mobile object" (7) is the improving characteristic and "loss of time" (25) is the worsening characteristic. At their intersection there are four recommended principles for resolving the indicated contradiction: 2, 6, 34 and 10.
    The matrix's reversed contradiction is: "loss of time" (25) as an improving characteristic vs. "volume of mobile object" (7) as the worsening characteristic. At their intersection there are four recommended principles for resolving the contradiction: principles 2, 5, 34 and 10.
    The principles 10 and 34 are associated with proposals for solving the problem.
    Principle 10: Prior action

    • Perform required changes to an object completely or partially in advance
    • Place objects in advance so that they can go into action immediately from the most convenient location

    Principle 34. Rejecting and regenerating parts

    • After completing its function, or becoming useless, an element of an object is rejected (discarded, dissolved, evaporated, etc.) or modified during its work process
    • Used-up parts of an object should be restored during its work

    Both of these principles suggest using in advance new, additional object or objects that should be removed after the washing process. Before washing, put some tennis balls into the washing machine with the thick downy jacket. The tennis balls serve as mobile activators, which dynamically collide with the jacket and provide better cleaning without requiring extra washing time.

    The fourth method for using the inventive principles is applying the contradiction matrix by getting several sets of principles from different technical contradictions for the problem. They should be tested for solving problem at first because it may give extra benefit and these principles may be useful for solving several technical contradictions at the same time.



    If you are going for a long camping trip, do not forget matches. But matches are unreliable – they do not like moisture and work poorly in the rain. You can use a waterproof plastic bag to keep the matches dry, but how can you strike a match when it is raining?
    The technical contradiction is: if we use a waterproof bag then we improve the protection of matches from harmful actions of moisture, but we cannot use this method when we need to strike a match when it is raining.
    "Harmful factors acting on an object from outside" (30) is the improving characteristic and "adaptability and universality" (35) is the worsening characteristic of the system. At their intersection there are four recommended principles for resolving the contradiction: principles 35, 11, 22 and 31.
    There is also interest in having a single match burn longer when starting a fire. Reliability of a single match flame, especially when it is windy, worsens. The most reliable fire occurs when we have just struck the match, while sulfur on the match top is still burning.
    The second technical contradiction (for the new problem) is: if we want to improve the lifetime of the flame, then another characteristic of the match's flame reliability worsens.

    The most appropriately corresponding parameters are "time of action of a moving object" (15) as the improving parameter and "reliability" (17) as the worsening characteristic of the matches. At their intersection there are three recommended principles for resolving the indicated contradiction: 11, 2 and 13.
    We can analyze all seven principles and try to understand how each of them can help solve contradictions. But principle 11 belongs to both found sets and is recommended for solving both contradictions:
    Principle 11: Be prepared or cushion in advance

    • Compensate for the relatively low reliability of an object with emergency measures prepared in advance.

    This principle, therefore, should be tested first. In my opinion, it is the most appropriate principle for solving both contradictions. Before going on the camping trip, dip the matches in a molten candle paraffin to form a thin protective layer on the matches. The matches with protective layer of paraffin are not endangered by moisture and burn with a higher reliability in any time and weather. Thus, the application of one principle solved two different contradictions.

    As a rule, the principles themselves do not give any ready solutions. They advise and direct the solution's development. It is necessary to work with them without rushing, exploring all offered opportunities and recommendations. Sometimes it may be necessary to reformulate the initial problem to get the best-correlated principles.
    Researchers and inventors thought that the further development of the inventive principles would increase the number of principles and conflicting features, but it is clear that difficult problems are solved by the simultaneous application of combinations of several principles or using the principles with physical effects. The inventive principles remain the primary tool for novice inventors and a simple and efficient TRIZ application.


    The 40 principles are the simplest TRIZ tool for removing technical contradictions and solving the whole problem. The invention level of obtaining solutions, as a rule, is not of the highest order, because the solution is developed on the technical level and principles do not work on the physical level. Due to the simple structure of the contradiction matrix, applying the principles does not require special knowledge; beginners as well as professionals may use them without extensive training. The described four methods of applying the principles and matrix work with technical contradictions and each method has its own features and specific order for obtaining recommended principles. The inventor can select the necessary method, as the specific situation requires.

    Practical Work


    Which inventive principles are used in the problem solving process described below?

    Problem: It is not easy to nail a piece of wood to the end of a board that is not reliably supported from below.
    Answer: Instead of using a hammer we can use a clamp. A clamp helps press a nail into the piece and connects the two.

    Problem: How can we collect tiny splinters of broken glass on the floor? A vacuum cleaner and brush cannot completely clean the glass, because some tiny splinters are heavy and stick in the floor.
    Answer: The tiny splinters of broken glass can be gathered with a piece of plasticine. Roll the piece of plasticine where the glass broke, then plasticine absorbs tiny, and even invisible, splinters.

    Three Home Problems for TRIZ Inventive Principles Application

    Thick Thread Problem

    It is difficult to thread a needle with thick woolen thread. Even if we moisten the thread end, it remains thick and resists going through the needle's eye.

    Swab Problem
    This is not an easy situation related to home problems. When mopping a clean floor, we cannot easily get to the spaces under the chair, table and sofa.


    Hammering Small Nail Problem
    It is hard to hammer a small nail in a hard to access location at a specified angle. It is particularly hard to do the initial hammerings.

    About the Author:

    Val Kraev is the chief TRIZ officer of the Technical Innovation Center in Worcester, MA, USA, and has contributed several very valuable case studies to The TRIZ Journal. Contact Val Kraev at kraev (at) or visit

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