Abstract
Analysis of literature described in the dissertation showed the complexity of phenomena of machine stitch creation processes. The reference to the lockstitch proves particularly difficult working conditions of needle thread. Tools forming the stitch (needle, bobbin, needle thread take-up, thread tensioner, transporter of the textile package) cause the weakening of thread inserted into the seam structure, what can lead to thread breakage. Hence, a great attention is paid to the action on thread of stitch forming mechanisms in the sewing machines.
A particular role of thread take-up mechanism was stressed during discussing the process of thread control conditions by the take-up in the lockstitch machines. Characteristic working phases of the take-up were distinguished i.e., supplying by the thread and drawing of thread end during the stitch tightening. One has paid the attention to the conditions of interlacement location in the material and the possibility of correcting them by the improving the structure of the thread take-up mechanism. Changing the stitch tightening modelling process was to achieve this aim. So, a physical model, and next a mathematical model of the zone of stitch creation were elaborated. Due to the possibility of configuration of multibarrier take-ups creation a model of the stitch tightening considering the take-up disc was built.
The presented results of model research required the experimental verification. The dynamic tensions in threads and the thread strength decrease after the sewing through process as well as a reaction of the take-up to changes thread length in the link of the stitch were studied. Carrying out the experimental analysis required the building the take-up disc installed on the chosen machine. Thus, there is a need for elaboration of the methodology of the take-ups disc designing using genetic algorithms as well as a classical programming in Fortan and C++ languages. The determination of requirement take-up disc configuration was preceded by a definition of the curve of the thread controlled by the take-up disc. Next, one made an estimation of defined curve of the thread controlled by take-up disc with a software called “Take-up disc 2.0” elaborated on the basis of genetic algorithm.
The designed and built thread take-up disc allow decreasing peaks of strength of the stitch tightening over twice of the basic value, which is the significant achievement from a technical-technological point of view. Moreover, it causes the decrease of thread breaking strength losses. In the case of the takeup disc, holding the position of the interlacement in the stitch link on the set level requires the extending the part of machine working cycle corresponding to the stitch tightening in comparison to the generally used take-ups.
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