b'are engineered so that they are lessAs impact tough than the Yankee and wearwear preferentially.increases, we see a The wear occurs in two discretedegradation areas.Sliding wear takes placein tissue against the Yankee, and impactsoftness wear is created by the tissue on topropertiesFigure 2. the top surface of the blade. (figureand anComparison of crepe quality 1).Yes, thats right; fire a piece ofincrease inbetween unworn tissue paper at 100km/hr at steel orbulk. and worn crepe ceramic for long enough and it willblade.wear a hole in it!IMPACT OF WEAR ON TISSUE MAKING OPERATIONSAs impact wear increases, we see a degradation in tissue softness properties and an increase in bulk, as crepe count decreases and crepeFigure 3. Effect of sliding wear amplitude increases.This is partiallyon coating due to effective pocket angle closurerefreshment.via the trailing edge of the impact wear area. (figure 2)Our other consideration is the cleaning effect of the blade on the Yankee coating layer.Here, it is the sliding wear which is predominant.The worn blade is simply less sharp, so removes less coating. (figure 3).A reduced rate of coating refreshment can allow the coating to harden on the hot Yankee, and this in turn can lead to pinholes, high crepe ratio, web breaks and even blade chatter. 2MEASURING BLADE WEARWhilst several field methods are possible, this study uses lab measured wear.The technique is to section the blade, without distortion, and then optically map the resulting section.Image analysis applies the angles and dimensions. (figure 4) Figure 4. Optical plot of worn crepe blade tip. TISSUE TECHNOLOGY INTERNATIONAL39'