fem modelling of a bellows and a bellows- based micromanipulator

II. Bellow's' dimensionFEM modelling of a bellows and a bellows-based micromanipulator2.2.2 MEASUREMENTSThe parameters to be determined are (figure 7) : the inner and outer radii, respectively r 1 andr 2 , of the convolutions, and the straight length m between the inner and outer curves. Theycan be deducted from the given parameters, but only if symmetricity assumption is made, i.e.r 1 = r 2 . These measurements have to be made to be on the safe side.The first step was to cut carefully the bellows axially into two equal parts, in a way asprecise as possible. If the FE analysis is made with inexact geometrical basis, the results willbe erroneous, and it is useless to proceed.bellowsPower drillwooden maintaining-toolCircular cuttingplatezxFigure 5Overview of the cutting system.The power-drill is fixed andguarantees a non-displacementin Z-direction. The X- and Y-direction movements areperformed by moving thewooden piece, which lays onthe table.Consequently, a small oblong hole was built in a wooden cube, so that the bellows has justenough place to be put in, without moving it too much. A thin circular cutting-tool was fixedon a power drill, and adjusted the elevation so that it will cut the bellows just in its axis, asshowed in figure 5.To study at the imprecision ratio, two bellows are cut in order to compare if similardimensions are obtained, and so that an average value for each needed measurement can beselected. is more accurate in this manner, because there are four different parts to measure.Figure 6Photo taken under a microscope,showing a part of onehalf-bellows. The ruler on theleft side is in millimetres. Itmeans that the picture heightrepresents about 0.9 [mm].The dimensions of the bellows are so tiny, that some photographs had to be taken under amicroscope. A ruler is set on the bottom of the bellows, so that it can be compared it with the8