EXPERIMENTAL DETERMINATION OF THE VALUES OF THE FUNCTIONS OF THE POSITION OF THE WORKING BODIES OF CHAIN STITCH MACHINES OF TYPE 101 AND CONSTRUCTION OF THEIR SYNCHROGRAMS

Abstract

The paper investigates the process of forming a single-thread chain stitch of type 101 under conditions of variable
technological parameters. For the GK-9-2 type sewing machine, the functions of the position of the working bodies - the needle
S(), the gear rack T(), the expander L() and Z(), the thread feeder U(), as well as the functions of the actual P(φ) and the
required P′(φ) thread feed per one cycle of rotation of the main shaft - were experimentally determined. Approximation
polynomials of the 6th order with a high degree of reliability (R² = 0.998÷0.9999) and an error of no more than ±0.25 mm or
±1.5° in angular coordinates were constructed for all functions.
Comparison of the results obtained by graphical and analytical methods allowed us to verify the models and clarify
the key points of interaction between the actuators (gripping the loop and its “stabbing” with the needle). The constructed
functions were used to model the stitching process, taking into account changes in material thickness and stitch length, which
made it possible to form a generalized synchronization of the machine.
The analysis of the functions P(φ) and P′(φ) revealed significant discrepancies: at the minimum material thickness
and short stitch, the excess of the actual thread feed is 64.4%, and at the maximum values, its shortage reaches 6.2%. The reason
is the fixed feed law in the slider mechanism, which does not provide for adjustment.
The obtained results emphasize the feasibility of developing adaptive mechanisms for thread feeding that can change
its value depending on technological parameters. The presented analytical models can be used as a basis for further designing
mechanisms that will ensure reliable connection of layers of multilayer textile compositions.