A Method of Inspecting Non-woven Basis Weight Using the Exponential Law of Absorption and Image Processing

Abstract

Fabric quality analysis [7,8,9] is important in textile engineering. Inspecting the non-woven basis weight on-line is a significant target toward improving the quality of the nonwoven material [3]. The discrepancy among various manufacturing processes affects the distribution of fiber, and also causes changes to non-woven basis weight. The short-distance deviation represents the quality of fiber carding, the long-distance deviation reflects the non-uniform quantity of product material, and the periodic deviation indicates flaws in manufacturing processes. Therefore, inspecting the non-woven basis weight on-line to monitor the quality during the production process, to avoid production flaws and to reduce the production costs are the major issues of the textile industry. 1The methods used for inspecting non-woven, web basis weight or uniformity can be either contact or non-contact methods. Usually the contact methods cause damage to the material. Owing to the direct contact of non-woven fabrics in the measurement process, the method of using floating pressurized rollers [17] to measure the non-woven thickness for converting into non-woven weight can easily damage or change the physical nature of the original nonAbstract This article explores a method of inspecting the non-woven basis weight on-line, by combining the exponential law of absorption and image processing technique. In the experiment, a theoretic equation for the charge-coupled device image-capture transmittance and non-woven basis weight was acquired through the exponential law of absorption. By using light source compensation and the least-squares approximation, the best approximate equations of transmittance and basis weight were acquired. According to the experimental results, the method of inspecting non-woven basis weight by image processing as proposed in this paper can reduce the uniformity of image gray scale from a coefficient of variation (C.V.) of 5.5 to 0.7%, raise the R 2 of basis weight and transmittance to 0.998, and decrease the basis weight inspection error to 0.33%. The proposed method effectively enhances the accuracy and stability of non-contact inspection of non-woven basis weight. The result acquired herein can also be applied to the on-line uniformity inspection system with web as the basic material.

Characterization of the Formation of Filter Paper Using the Bartlett Spectrum of the Fiber Structure

“…As a consequence, there is a close relationship between weight distribution and formation and, in fact, often one does not distinguish between both. See Van den Akker (1949), McDonald et al (1986) and Lien and Liu (2006) for the computation of the grammage from the absorption of visible light. The use of soft X-radiation is suggested in Farrington (1988), and the influence of the choice of radiation on transmittance is investigated for nonwoven fabrics in Boeckerman (1992) and for paper in Norman and Wahren (1976) and Bergeron et al (1988).…”

“…The use of Fourier transform for an identification of periodic patterns in paper and board traces back to I'Anson (1995). In Sara (1978), Norman (1986), Cresson (1988), Provatas et al (1996), Cherkassky (1998) and Lien and Liu (2006), the correlation function and the power spectrum are also suggested as characteristics for cloudiness of (non-periodic but macroscopically homogeneous) nonwovens and paper formation, respectively (Section 2.2 in Alava and Niskanen, 2006). Sometimes the range of interaction , i.e., integral of the correlation function (also known as the integral range), is used as a formation index.…”

“…In the present article we use Gaussian Random Fields (GRFs) for modeling paper formation and, following the suggestion made in Xu (1996) and Lien and Liu (2006), a Fourier approach is applied for computing characteristics of paper formation. More precisely, we show that the formation of the investigated filter papers can be characterized by the density of the Bartlett spectrum, i.e., a spectral representation of the correlation function, which can be estimated by the method of Koch et al (2003).…”

Basis weight uniformity analysis in nonwovens

“…Here also, when the nonwoven fabrics were uniformly illuminated through transmitted light, the intensity of the image collected by the camera directly related to optical density of samples and its basis weight (Pourdeyhimi & Kohel, 2002). Similarly, optical density measurements have been used for online-basis weight measurement (Lien & Liu, 2006). In almost all these cases, the uniformity index was based on CV% of the optical density.…”

“…Another defect based on uniformity analysis is reported by Lien and Liu (2006). This method also used coefficient of variation of the randomly selected region which carries the same inherent problems indicated before with respect to size dependence.…”