+ ·If Indian Journal of Fibre & Textile Research Vol. 28, September 2003, pp. 239-245 Mechanics of IxI rib loop formation on a dial and cylinder machine: Part II-Measurement of cam force Sadhan Chandra Ray" & P K Banerjee Department of Textile Technology, Indian In stitute of Technology, New Delhi 110 016, India Received 16 July 2001: revised received and accepted 28 June 2002 The cam force, i.e. the yarn tension, inside the knitting zone for a complete loop forming cycle has been measured on a dial and cylinder machine equipped with I x I rib gating to validate the model developed for the purpose and to understa nd the mechanics of loop formation. A separate cam track has been designed for running the isolated measuring needl e a nd other necessary modifications have been made on the cam jacket for in stallation of the quartz force link. The cam force signals generated by the quartz force link fitted on the stitch ca m are recorded in computer through analog- to-digi tal convertor. The recorded digital va lu es are then plotted with the help of available software for ge tting cam force curves which have, in general, four peaks. Keywords : Analog-to-digital co nv ertor, Cam force, Knitting force, Quartz force link, Transducer 1 Introduction For understanding the mechanics of loop formation in weft knitting, it is necessary to record and analyze the knitting force, i.e, yarn tension, inside the knitting zone for a complete loop forming cycle. The main aim of this measurement is to study the stress to which a yarn segment is subjected to during its passage across the knitting elements and to evaluate the performance of needles and cam for higher production and product developments. The critical analysis of these aspects helps to optimize knitting conditions as well as redesign the machine components. Various knitting tension and force measuring methods (direct and indirect) have already been developed J - 8 . Knitting tension was first measured by Henshaw 4 using pointed and flat bottomed stitch cams on single-jersey machine. He actually measured the needle butt reaction force on cam by fitting the stitch cam to a force measuring transducer. A typical cam force curve, as obtained by him, has three peaks. Peat and Spicer5 used the same experimental set-up as designed Henshaw and obtained good matching between theoretical and experimental curves at high cam setting values. Aisaka et a/. J measured the ·To whom all the correspondence should be addressed. Present address: Institute of Jute Techno logy, 35 8allygunge Circular Road, Kolkata 700 019, India Phone : 24751985/24765299 : Fax: 0091-033-24750996 ; E-mail: ijt@ca I2. vsnl.net. in knitting tension with the help of knitting simulator. Black and Munden 3 measured the cam impact force as a function of increasing machine speed. Wray and Burns 8 measured the yarn tension by fitting transducer on verge and needle shank and measured the cam force and cam impact force by fitting transducer on stitch cam. For measuring various loop formjng forces on needle, Pietikaeinen 6 attached a transducer on partly recessed needle shank. She studied the effect of yarn properties on stitch forming forces for both negative and positive feeding arrangements. The effect of positive and negative feeds with varying cam setting on needle force was studied by Pietikaeinen and Valkama 7 . The foregoing experiments were carried out on circular single-jersey machines only. Measurement of cam force on double-jersey machine was first attempted by Araujo et aL. 2. To evaluate the performance of different needles and cam, they fitted transducers to both cylinder and dial stitch cams (combined with clearing cam) of an interlock machine. The objective of the study was to find out the ways and means of increasing production rate. As direct measurement of yarn tension involves interference with the normal knitting process, it has been decided to measure the needle butt-cam interactive force on a dial and cylinder machine and to compare the same with the predicted cam force (output of the model) translated from yarn tension