Second Hand Stitching Machine - vssewingmachine
Needle penetration. Considering again the high sewing speeds that occur, problems with needle penetration can arise due to the mechanical and thermal interaction between needle and fabric. Fabric yarns may be torn by the forces acting during needle penetration or they may fuse due to the high needle penetration produced by friction. Systems to monitor needle penetration forces during the process to detect defects and off-line systems to support the choice of needles and fine-tune fabric structures and finishing to avoid these problems, would be of high value to the industry.
Stitch formation/Thread tensions. The interlacing of the threads itself, which constitutes the actual stitch formation, cannot be dissociated from the processes of material feeding and needle penetration. However, there are two variables directly linked to the thread that most intimately represent it: Thread tensions and thread consumption. The relationships between fabrics, machine set-up and stitch formation in lockstitch machines have already been studied in . Methods for defect detection have been developed for overlock machines and presented in . However, an automatic system for setting thread tensions online is still missing describe thread tension control in embroidery machines, but the work only tackles the issues associated to the control of the actuator. Setting of the correct references for the controllers to produce a high-quality product in varying conditions is the key issue, and this has to be further tackled. Read More
This paper describes current work on the behavior of thread tensions in an industrial lockstitch sewing machine using a new measurement set-up. Methods previously investigated for monitoring of thread tensions and establishing the correct variable references are being ported and/or re-evaluated. The first step is the study of the relations between material properties and thread tensions. Some aspects are still not clear in this regard. In [13], for instance, the authors state that the thickness of fabric plies does not affect the needle thread tension. This is one of the aspects to be studied in this work.
The sensor (custom-designed by Petr Skop) is a cantilever beam with semiconductor strain gauges at the base, configured as a complete Wheatstone bridge. A glass sphere with a rounded slot allows a low-friction interface with the sewing thread. A thread guide with two ceramic O-rings has been designed to guide the thread around the thread sensor. The thread pulling force produces deformation on the cantilever sensor that is picked up by the strain gauges. Click Here
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