Abstract : This article mainly introduces the application of frequency converters, PLCs, and human-machine interfaces in the electrical control of the CLMA445G denim pre-shrinking and finishing machine, making the CLMA445G a new generation of denim pre-shrinking and finishing machine that meets market requirements. Keywords : pre-shrinking machine; frequency converter; PLC; human-machine interface; position feedback 1 Introduction The denim pre-shrinking and finishing machine is mainly used for sizing, padding, skewing, drying, pre-shrinking, and finishing of flat-width indigo fabrics (denim) with a weight of about 200-500 g/m2, in order to reduce fabric shrinkage, stabilize fabric dimensions, and improve fabric hand feel. As early as the 1970s, our factory developed and produced denim pre-shrinking machines. At the beginning of this century, with the increasing demand for diverse denim fabrics in domestic and international markets, we promptly redesigned our previous denim production equipment to adapt to the production of new denim varieties. 2. Key Control Points of Denim Pre-shrink Finishing Machine During weaving and dyeing processes, the fabric experiences significant radial tension, resulting in weft shrinkage and radial elongation. Garments made from this fabric shrink in length after washing, causing deformation. Therefore, anti-shrinkage finishing is added as the final step in dyeing and finishing. To maintain the fabric width, the radial tension is increased after washing and padding to elongate the fabric radially, ensuring the width remains unchanged after pre-shrinking. To ensure a stable pre-shrinkage rate and allow the radial yarns to shrink back, the fabric must be in a near-tension-free state during pre-shrinking, with a certain speed difference between units to allow for free fabric shrinkage. Therefore, ensuring a stable pre-shrinkage rate requires precise proportional synchronization coefficients between units, while maintaining stable process parameters affecting the pre-shrinkage rate, such as temperature and humidity. Traditional denim pre-shrink finishing machines use a relay-controlled DC speed regulation system, implemented through a "side shaft + PIV continuously variable transmission." The pre-shrinking machine section consists of three units driven by a DC motor. The DC motor directly drives the rubber blanket pre-shrinking unit after passing through a reducer, while the other two units are driven via side shafts after passing through a reducer. Both of these side shafts are equipped with continuously variable transmissions (CVTs) to fine-tune the speed of the two units and ensure synchronization of the pre-shrinking machine. Although this transmission method can meet the synchronization requirements, the system has a complex structure, large footprint, and control accuracy of less than 2‰. Furthermore, when the fabric tension changes, adjusting the PIV on the machine is both time-delayed and difficult to control, requiring experienced operators. This can easily lead to asynchrony between the two preceding and following units and the pre-shrinking unit, making it difficult to achieve dynamic accuracy and causing fabric tension fluctuations, thus affecting the stability of the pre-shrinking rate. Now, an electronic side shaft is used. Through the proportional setting of a frequency converter, programmable logic controller (PLC), and human-machine interface, and the closed-loop control formed by encoders for each unit motor of the pre-shrinking machine, the electronic side shaft replaces the mechanical side shaft, achieving tension-free transmission and precise proportional synchronization with a synchronization accuracy of 0.5‰, ensuring the stability of the pre-shrinking rate. The drying drum section has also been upgraded from DC speed control to AC frequency conversion speed control. Simultaneously, the tension slack frame not only ensures synchronization between the rolling mill and each drying drum column, but also controls the denim fabric width by changing the tension of the slack frame, thus bringing the denim pre-shrinking equipment in line with the world's advanced standards. [b][align=center]For details, please click: Electrical Control of CLMA445G Denim Pre-shrinking Finishing Machine[/align][/b]