Stenters, Heat Setting and Overfeed: What a Buyer Needs to Specify

The line before the stenter: opening and squeezing knit tubes

Fabric from circular knitting is dyed as a tube. Before it can be pinned, it has to be untwisted, opened or slit along a marked line, de-watered and fed flat. These machines are sold separately or within a combined dyeing and finishing range.

Two directory listings show how much the package can vary. Kanglide's B-type opening and squeezing series combines opening, slitting, lint removal and squeezing for open-width or tubular cotton knits, and its parameter image defines a 38 kW arrangement with a 6 m overall height; a softening line shown separately is a different package (see the Kanglide profile). Jinpei's ZXJP919 is described across two pages, one covering the oven and one following spreading, squeezing, pin entry and delivery; its 100 m/min mechanical maximum is listed separately from a 10–90 m/min process range. Ask which stages are in the price, and do not read a mechanical top speed as a production speed. Our note on comparing configurations gives a method for this.

Pins, clips, or both

The chain is the part that touches every metre. Erhardt+Leimer, which supplies stenter infeed and guiding equipment, describes the stenter as a dryer with a revolving chain fitted with pin carriers, clips or a combination, adjustable to the fabric width. Pins pierce the selvedge and allow the fabric to be fed onto them with extra length; clips grip the edge without piercing it. Combined chains let one line handle both. The choice depends on your fabrics and whether selvedge pin holes are acceptable. Pins, clips and chain links wear, so price them as consumables under your spare parts terms.

Overfeed: why it changes shrinkage and width

Overfeed means feeding fabric onto the chain faster than the chain moves, so more fabric length sits on each metre of chain. Erhardt+Leimer explains that this extra length lets the textile relax and shrink in the dryer, improving dimensional stability after washing; for its own overfeed device it claims up to 50 % more fabric pinned per metre of chain. Treat that as a maker's figure, not a target.

Overfeed does not act alone. A study at National Textile University, Faisalabad (Nazir et al., *JTATM*, 2015) heat-set a 95/5 cotton/elastane single jersey on a laboratory stenter, varying temperature (160–200 °C), time (50–130 s), width extension (6–18 %) and overfeed (2.5–52.5 %). All four had a significant effect on dimensional stability. At high width extension, more overfeed reduced lengthwise shrinkage after laundering; its effect on widthwise shrinkage was smaller. Width extension and overfeed also changed the fabric's areal density after relaxation. For a buyer, overfeed range, width setting and their control accuracy are process tools; the line must hold the combination your fabric needs, metre after metre.

Heat setting: what the machine must deliver

Heat setting stabilises fabrics containing thermoplastic fibres. The same paper describes setting cotton/elastane above the glass transition and below the melting temperature of elastane for a suitable time, and reports that shrinkage fell sharply once the setting temperature exceeded the elastane softening range, which it gives as 175–180 °C; temperature had a stronger effect than time. Those figures belong to that fabric and laboratory set-up, not to your production. Recipes come from your fibre and chemical suppliers and your own trials. What the machine owes you is the ability to reach and hold the set temperature evenly across the width and along each chamber at the speed that gives the dwell time the recipe calls for. Put temperature uniformity and its measurement method in the contract.

Chambers, heating media and exhaust

Heating can be direct gas burners, thermal oil, steam, electricity or combinations. Brückner, for instance, said in 2023 that it had developed ways to combine gas, steam, oil or electricity on its Power-Frame stenter, offered burners that could later run on hydrogen, and sold heat-recovery and exhaust-air cleaning systems that can be retrofitted to older lines. The choice depends on your site: gas supply and price, an existing thermal-oil boiler, local emission rules. Ask for fuel and electrical consumption at a defined fabric and speed, and compare it against installed power and real energy use.

Directory listings point to the details worth questioning. Yonglitong's hot-air stenter family is a configurable family that separates knitted, pile and woven duties and publishes sheets on overfeed and edge handling, the oven air path and burners (Yonglitong profile). Jiuyi's JY-2025 is described with a smaller oven volume, 150 mm insulation panels, a lower exhaust arrangement, air-cushion nozzles and hot-air curtains at the end chambers, without a full dimensional or operating-range table (Jiuyi profile). Tie features like these to measured results in your trial.

Weft straightening

Woven and knitted fabrics can arrive with weft distortion, known as skew and bow. Optical weft straighteners mounted ahead of the chain correct it with skew and bow rollers. Mahlo, a specialist in these systems, notes that distortion on knits can change abruptly at the seams between rolls, and that scanning only at the straightener's outlet detects such a change late. Specify whether a straightener is included, its correction range and where its scanners sit.

Safety

ISO 11111-7 sets safety requirements for dyeing and finishing machinery, to be used with the common requirements of ISO 11111-1; the EN ISO version carries amendments from 2009 and 2016. Pin chains, nip points at the infeed, hot surfaces, burner controls and exhaust ducts are all hazards to check at acceptance. Conformity with your local machinery law is a separate document from any acceptance test.

How to run an acceptance trial

1. Send enough of each target fabric, in its real incoming condition, as described in our guide to trials with your own material.
2. Agree targets before the trial: finished width, weight per square metre, shrinkage after a named wash test, skew/bow tolerance.
3. Run at your intended speed, overfeed and temperature; log chamber temperatures, speed and fuel use.
4. Measure finished width and weight on line, and send samples to a laboratory for shrinkage testing.
5. Check selvedge marks and the delivered roll; our page on inspection and rolling machines covers what follows.
6. Repeat the key measurements at site, as set out in factory and site acceptance testing.

If elastane is part of your fabric programme, our note on covered elastic yarns explains the yarn side, and the guide to reading a manufacturer profile helps you judge whether a supplier has built comparable lines.

Sources

1. Nazir, A., Hussain, T., Rehman, A., Abid, A., "Modelling Heat-Setting of Cotton/Elastane Knitted Fabrics for Optimum Dimensional Stability", *Journal of Textile and Apparel, Technology and Management* 9(2), 2015, NC State University Wilson College of Textiles, accessed 2026-11-04. View source
2. "Stenter", Erhardt+Leimer GmbH, accessed 2026-11-04. View source
3. "Brückner ready for ITMA 2023", Knitting Industry (16 May 2023), accessed 2026-11-04. View source
4. "Mahlo Presents A New Straightening Concept – Orthopac RXVMC-20 In A League Of Its Own", Textile World (10 October 2023), accessed 2026-11-04. View source
5. "EVS-EN ISO 11111-7:2005 – Textile machinery – Safety requirements – Part 7: Dyeing and finishing machinery", Estonian Centre for Standardisation and Accreditation (EVS), accessed 2026-11-04. View source