Using TRIZ to Improve Pem-nut Production

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    "Identify the IFR...then identify the resources available ...identify the contradictions that prevent the achievement of each IFR. If there are overlapping contradictions and resources that exist, that's the place to focus the TRIZ problem solving."

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    By Jaewook Lee and Byoungkon Roh

    Project Summary

    Pem-nuts are used to attach circuits to a chassis-base, but they are too expensive for regular use because of the numerous processes required to produce them using a traditional machining process. The authors used TRIZ (Theory of Inventive Problem Solving) tools and the application of the 40 inventive principles to design a mold-form to improve production and reduce the cost of pem-nuts. Figure 1 shows the circuit components used in the pem-nut production process (PDP).

     Figure 1: Circuit Components Used in PDP

    Standoff nuts are used for printed circuit boards (PCB) and other assemblies. They are manufactured in various shapes and formed in a variety of ways based on how they will be used. Most standoff nuts are built using a machining style and are called pem-nuts after the developers – the Penn Engineering and Manufacturing Company (PEM). Pem-nuts are made from free-cutting steel that improves machining ability. Automatic lathes form the pem-nuts through a machining process and the cutting tools are changed as necessary to get the proper shape.

     Figure 2: Standoff Nuts Built Using a Machining Process

     Figure 3: Standoff Nuts – Cross Section and Actual Object


    There are several forming methods – the use of an injection mold, stamping and forging. This project's inventors did not include the injection mold method on the target techniques list, because the injections affect the electric conductivity of the components. The stamping and forging methods, however, maintain the key properties of the raw material. Stamping is the best forming method for productivity.

    The goal was to reduce costs and improve the productivity of nut manufacturing by implementing a stamping method of forming the nuts instead of machining standoff nuts, so they applied TRIZ to stimulate idea generation for solutions on the best forming method for shaping parts for this project.

    Problem Statement

    System Analysis and Structure

    During the system analysis stage the researchers referred to the system as the "nut injection process." The nut injection process includes adding nuts to the main base chassis to fix the PDP circuit to the panel and requires the use of nuts and the chassis. The system structure is shown in Figure 4. The function of each component is as follows:

     Figure 4: System Structure

    Current Injection Structure

    The under-cut is important functionally. The base chassis moves to this groove, and the nut and the base chassis are mechanically joined. Figure 5 represents the "before nut injection."

     Figure 5: The Before Nut Injection

    The "after nut injection" is shown in Figure 6. Because the base chassis is deformed in volume due to its plasticity, it rushes into the head of the nut at point A. The nut is fixed firmly against both the upward and downward forces to separate it from the base chassis.

     Figure 6: The After Nut Injection

    Problem Definition

    When using the current stamping method, it is impossible to form the groove. But, it is also necessary because the groove is key to the injection function. Therefore, the authors formulated a contradiction – the groove must not exist for stamping but rather for strength.

    Contradiction Definitions

    Ideal Final Result

    The ideal final result (IFR) was a reliable nut structure that would be superior to the existing manufactured nuts based on the injection effect and press forming. The system must make grooves for the machining style nuts and maintain the current shape of the nuts in the manufacturing process.

    Function Diagram

    The function diagram made it evident that the injection groove met the desired function – holding the nut and base chassis simultaneously.

     Figure 7: Component Name

     Figure 8: Function Diagram

    Contradiction Definition

     Figure 9: Contradiction Definition

    Generate Solution

    Generate Ideas from the Physical Contradiction

    Separation principles were applied to determine the physical contradictions. In this case "separation in time" could be done – the groove does not exist at the press forming stage, but does exist at the nut injection stage. Separation in time is shown in Figures 10 and 11. Before the injection there is no groove, but after the nut is injected the energy generated forms a nut-groove.

     Figure 10: Before Injection

     Figure 11: After Injection

    Generate Ideas from the Technical Contradiction

    The second technical contradiction was taken from the 40 inventive principles. The researchers generated ideas to produce the nuts by forming them without grooves and improving the effects of the injection.

    The researchers also used the contradiction matrix to select four inventive principles: 30, flexible membranes and thin films; 14, spherical shapes; 10, preliminary action; and 40, composite materials.

     Figure 12: Contradiction Matrix and Technical Contradiction

    Among the four recommended principles, number 10 (preliminary action) provided feasible ideas. Instead of grooves, small bores could be made prior to injection. If the small bores worked like grooves, the contradiction could be overcome.

    Final Solution

    The final solution was derived using the inventive principles (10, preliminary action) and the separation principles (time). The following stages are based on the separation principles and 40 inventive principles.

    1. In advance, the bores are formed in the nut head.
    2. Manufacture nuts without grooves using the stamping method.
    3. The bores in the nut head gently form grooves.

    The injection process provides the natural pressure to change the grooves.

     Figure 13: Injection Process Improvement


    By utilizing TRIZ tools and principles of innovation these inventors developed and implemented an idea that increased productivity and reduced costs by more than 20 percent. The basic idea for improvement was derived from the separation principles and the 40 inventive principles of TRIZ. This project served as another example of how TRIZ offers unique and creative ideas for problem solving.

     Figure 14: Process Before and After Use of TRIZ

    About the Authors:

    Jaewook Lee has been working for Samsung SDI as an innovator in the manufacturing process. Mr. Lee is using Value Engineering, Six Sigma and TRIZ to lead innovation at Samsung SDI.

    Byoungkon Roh has been working for Samsung SDI as an innovator in the manufacturing process. Mr. Roh is using Value Engineering, Six Sigma and TRIZ to lead innovation at Samsung SDI. Contact Byoungkon Roh at bk_roh (at)

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