# Quality engineering(QE) 16

Continuing from last week, I talk about "functional window."

Please see the materials → 　QE16

Dynamic characteristics are often drawn by plotting energy on the horizontal axis and characteristic value on the vertical axis. As the A's effect, at the higher the energy area, the characteristic value deviates from the straight line, and as the B's effect, the lower energy causes the problem of poor bonding. The good part(light blue part) becomes the "functional window". We need to find the combination of parameters that widens this window in an orthogonal table. For example, consider energizing and bonding parts together. Bonding strength increases with energy, but if too much energy is applied, burrs (bulges) will be large, and if the energy is too small, bonding will be poor, and in some cases bonding may not be possible. A's effect is the appearance rate of burrs, and B's effect is the defective joint. According to the result of the experiment on the first row of the orthogonal table, the energy at which burr starts to appear was 70 [J]. It is assumed that the bonding failure occurs below 20 [J]. The curve above 70[J] and below the straight line indicates that the characteristics are deteriorated due to the appearance of burrs even though the bonding strength exists. Curves below 20[J] below the straight line indicate insufficient bonding strength or non-bonding. SN ratio is calculated as 10.9 by using the formula on the lower right. Calculate the SN ratio for other rows in the same way.　If the denominator is zero, it will be impossible to calculate, so it is better to enter about 0.01. When trying to find a boundary value such as 20 "J" or 70 "J" above, please measure bonding strength by putting energy under various conditions. If the evaluation is pass(〇), jump energy a little and look for failure(×), and then evaluate the middle of ◯ and ×. Find boundary values efficiently. How is it?　Can you imagine  "functional window" a little? The boundary value (window frame) of the functional window is important.