TRIZ Tutorial #2

Alla Zusman and Boris Zlotin
Ideation International Inc.


The first tutorial contained three problems that readers were encouraged to solve by applying the described principles. Now letís discuss solutions.

Problem 2: Unloading frozen material

Unloading loose, frozen material by first defrosting it can be an expensive procedure. What other method would you recommend?

Because we are talking about frozen material, psychological inertia impels us to look for various ways to thaw the material. But consider the principle of inversion, which recommends doing the opposite of what would usually be attempted. The opposite of heating is freezing -- and indeed, if the temperature of the material is lowered even further (using liquid nitrogen, for example) the material becomes brittle and can be easily loosened for unloading.

Problem 3: Bullet-proof windows

Initially, bullet-proof glass windows used on fighter aircraft had a serious defect: When a bullet hit the window, a "network" of cracks would form in the glass and obstruct the pilotís vision. How might this damage be reduced?

The segmentation principle can help here. This principle recommends that the window be made of smaller panes of glass that are cemented to an acrylic plastic sheet using a transparent adhesive. When a bullet hits the window, the pane that took the hit -- and that pane alone -- fills with cracks (see figure).

Problem 1: Removing layers of insulation

Certain metallic surfaces must be coated with a thick layer of insulating material. Removing this coating later is difficult, however. How might this be accomplished?

Remember the prior action principle in last monthís tutorial? This principal can be applied by placing a steel wire on the metal surface prior to applying the insulation. The insulation layer can be cut by pulling the wire. Itís a good approach -- but the problem is not yet completely solved.

The next step is to select a wire of appropriate diameter. To withstand the pulling force, a relatively thick wire must be used. There are disadvantages to using a thicker wire, however. First, it increases the consumption of material; second, a thicker wire means a heavier wire, which in turn means that more force will be required to cut the insulation. Itís a paradox.

 In TRIZ, this type of situation -- i.e., where two mutually opposite requirements exist -- is called a physical contradiction. In this case, the physical contradiction can be expressed as follows: the wire must be thick in order to withstand the pulling force and the wire must be thin to minimize the cutting force and reduce material consumption.

Most of us do not like dealing with paradoxes. Instead, we try to overcome the situation by compromising, making a trade-off, finding an optimal solution, etc. And in many situations this will work. But often contradictions are "sharp" and compromise is not possible.

Paradoxes produce frustration in humans -- and even animals -- due to the uncertainty that they engender. Ivan Pavlov, the noted physiologist, conducted a group of experiments to study the reactions of dogs to contradictory situations. A dog was trained to expect a positive outcome (food) when viewing a circle, and a negative outcome (mild electroshock) when viewing an ellipse. Because it knew exactly what to expect in each case, the dog was able to handle each situation adequately. Then the experimental conditions were changed: the dog was shown a circle that began to flatten until it looked more and more like an ellipse. Eventually it became impossible to recognize whether the image was a circle or an ellipse -- at which point the frustrated dog suffered a heart attack.

In TRIZ, there is a special tool to handle physical contradictions.

Invention 11. Coating metal workpieces

Metal surfaces are chemically coated as follows: the metal workpiece is placed in a bath filled with a metal salt solution (e.g. nickel, cobalt, etc.). During the ensuing reduction reaction, metal from the solution precipitates onto the surface of the workpiece. The higher the temperature, the faster the process takes place; however, at high temperatures the solution decomposes, and up to 75% of the chemicals are lost by settling on the bottom and sides of the bath. Adding stabilizers is not effective, and conducting the process at a low temperature sharply decreases production.

Letís see how we can use TRIZ to address this problem. The physical contradiction is as follows: The temperature should be high to increase productivity, and it should be low to avoid waste. To resolve physical contradictions, the following separation principles are recommended:

  • Separation in space
  • Separation in time
  • Separation between the whole system and its parts
  • Separation based on different conditions

To apply the principle of separation in space, for example, we should ask ourselves the following question: Do we need this parameter -- temperature, in this case -- to be high (and low) everywhere, or is it necessary in certain places only? If the temperature need not be both high and low everywhere, we can try to separate these opposite requirements in space.

In this case, we need the temperature to be high only near the parts rather than everywhere in the bath. How can this be achieved?

The answer is as follows:

The workpiece is heated to a high temperature before it is immersed in the solution, and the process itself is conducted at a low temperature. The solution is therefore hot near the workpiece but cold everywhere else. (One way to accomplish this is to apply an electric current to the workpiece during the coating process.)

Invention 12. Sterilizing potatoes

A potato can rot due to naturally-occurring bacteria on its surface. Heat kills the bacteria, but too much heat will cook the potato as well.

If the potatoes are exposed to a flame at 500-850 degrees C for a short duration (4 to 8 seconds), the surface bacteria will be destroyed while the inside of the potato is unaffected.

Now letís consider the separation in time principle:

Invention 13. Needle with dynamic eye

It is difficult to pass a thick thread through the small eye of a needle. We can formulate the following physical contradiction to represent this situation: A needle must have a large eye to facilitate insertion of the thread, and must have a small eye for convenient sewing.

By separating the contradiction in time this problem can be formulated as follows: the eye must be large while the thread is inserted, and must be small during sewing, as follows:

R. Pace of Britain designed a needle made of two thin, spring-like wires of identical length. The wires are welded together at one end, twisted three quarters of a turn, then welded at the opposite end. The resulting needle looks like an ordinary needle, but when slightly unwound, a large slot appears through which a thread can easily pass. When released, the needle returns to its initial shape and grips the thread.

Invention 14. Wire enameling method

In the manufacturing of a particular electronic wire, the wire is first passed through a liquid enamel bath and then through a die that  removes any excess enamel and sizes the wire. The die must be hot to ensure reliable calibration; however, if the wire feed is interrupted for several minutes or more, the enamel in the hot die hardens and firmly grips the wire. The process must then be halted while the wire is cut and the die cleaned.

The contradictory requirements (the enamel should be hot to ensure calibration and should be cold to avoid hardening) are separated in time as follows: 

The die should be in a hot zone while moving and in a cold zone when it stops moving. This is achieved by fixing the die to a spring. When the wire moves, it pulls the die into a zone where it is heated (either by induction or by contact with the hot chamber walls). When the wire stops, the spring pulls the die back into the cold zone.

Invention 15. Gripping workpieces of complex shape

To grip workpieces of complex shape, vice jaws must have a corresponding shape. It is expensive to produce a unique tool for every workpiece, however.

The principle separation between the whole and its parts recommends that we assign one of the contradictory requirements to the whole system and the other to its parts, as follows:

Use a vise with ordinary jaws, but add multiple hard bushings around the workpiece that move horizontally to conform to the workpiece's shape.

The early stages of TRIZ development focused on problems related to technological systems. Later, however, it became evident that contradictions occur in many other areas of human activity -- business, personal interaction, etc. And what's more, the same separation principles can also help resolve these contradictions.

Example: If a successful company is large it will bring in high revenue, have extensive resources, etc. At the same time, large companies often suffer from bureaucratic problems that curtail their flexibility and can eventually become crippling. The contradiction (a company should be both large and small) can be resolved using the principle of separation between the whole and its parts, as follows: Create many relatively small, independent companies that operate under a single corporate "umbrella."

Besides causing frustration, contradictions are frequently responsible for the rejection of good ideas -- that is, ideas that have negative side effects.

Problem 4. Braking of an automatic welder drum

Automatic welding machines use a steel wire rolled onto a drum as an electrode. A special motor in the welding head pulls the wire during the welding process. When welding stops, the drum continues to rotate due to inertia, and the wire becomes entangled as a result.

The idea of using a brake to stop the drum from rotating freely was considered, and rejected, because it necessitated a more powerful pulling motor and thus a heavier welding head. This idea can be reconsidered, however, with respect to the following physical contradiction: Drum rotation should exist in order to unreel the wire, and should not exist to avoid entangling the wire.

Problem 5. Producing pure copper

In the electrolytic process by which pure copper is produced, a small amount of electrolyte liquid remains in the pores on the surface of copper sheets. When the copper is stored the electrolyte evaporates, creating oxide spots on the surface which reduces the value of the copper and results in substantial losses. The best way to solve the problem was to avoid producing the pores in the first place. This approach was immediately rejected, however, because it required substantially lowering the d-c current, which would dramatically reduce productivity. Instead, they decided to reduce the financial losses by washing the sheets of copper prior to storage to remove the electrolyte from the pores. This was not only costly but inadequate, and attempts at improving the washing process continued for over 15 years.

When TRIZ specialists addressed this problem, they asked the copper manufacturers if there was a way to eliminate the pores in the copper sheets. The answer: impossible. It took some effort to understand that there was a contradiction behind this "impossible": The current must be low to avoid creating the pores and must be high to provide the required productivity.

Not every contradiction is resolvable within the present confines of technology -- nonetheless, it is always worth trying. If all known ways to resolve a contradiction fail, the contradiction can often be circumvented altogether by changing the problem statement.


Try to apply the separation principles to resolve the physical contradictions contained in these problems:

  1. The thick/thin wire contradiction in problem 1, removing layers of insulation.

  2. Problem 4, braking of an automatic welder drum.

  3. Problem 5, producing pure copper.


Look for examples of physical contradictions in your work or everyday life, and note how they have been handled.

© 2004 Ideation International Inc.