Parameter Settings for Knitted Fabric High-Frequency Embossing

Knitted fabrics, with their stretchable, porous structure, require specialized parameter settings in high-frequency embossing to ensure the pattern adheres well, retains elasticity, and avoids distortion. Unlike woven fabrics, knits (e.g., cotton jersey, polyester spandex,) have loops that can stretch or compress during embossing, making parameters like pressure, power, and dwell time critical for success.

Power setting is the first consideration. Knitted fabrics conduct high-frequency energy differently due to their fiber composition and air pockets. For cotton-rich knits (50%+ cotton), a power range of 3-5 kW is effective, as cotton absorbs energy moderately. Polyester or synthetic knits, which are more conductive, require lower power (2-4 kW) to prevent overheating and melting of the fibers. Overpowering can cause the fabric to harden or shrink, losing its stretch. The power should be adjusted based on fabric thickness: a 2mm-thick fleece knit may need 5-6 kW, while a thin 0.5mm jersey works with 2-3 kW.

Pressure settings must balance pattern definition and fabric elasticity. Too little pressure results in a faint, uneven pattern, while excessive pressure flattens the knit’s loops, reducing stretch and causing the fabric to feel rigid. Ideal pressure ranges from 2-5 bar (29-72.5 psi), with stretchier knits (e.g., those with 10%+ spandex) requiring lower pressure (2-3 bar) to maintain their give. The die should apply pressure evenly, with a silicone pad on the lower platen to cushion the knit and ensure all areas of the pattern make contact.

Dwell time (the duration of high-frequency application) typically ranges from 1.5-3 seconds. Thicker knits or those with high loft (e.g., terry cloth) need longer times (2.5-3 seconds) to allow heat to penetrate the fibers, while thin, lightweight knits (e.g., modal jersey) work with 1.5-2 seconds. Post-embossing cooling time (0.5-1 second under light pressure) helps set the pattern without stretching it as the fabric relaxes.

Additional parameters include the distance between the die and the fabric (gap setting), which should be 0.1-0.3mm larger than the fabric’s thickness to accommodate stretch. For example, a 1mm-thick spandex knit would use a 1.2mm gap. Testing these settings on a swatch ensures the embossed pattern retains clarity even when the fabric is stretched, making it suitable for activewear, loungewear, or accessories where flexibility is key.

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