Keep on rolling

Keeping the ironer line running at the optimum performance point is fundamental to maintaining production and achieving targets so it surprising to learn that in many organisations the ironer line is only working at 60-70% of design performance. Replacing clothing on the ironer rolls is a specialist operation that can pay real dividends.

Maintaining the ironer rolls

The rolls are supposed to be perfectly cylindrical, with a diameter which exactly matches the semi-circular cross-section of the beds in which they turn. Getting the diameter exactly right requires careful specification of the ironer cladding or ‘clothing’ and it might vary for each roll. Many ironers are made with the roll diameter increasing slightly, going from front to back. It is generally preferable to use two turns of strong, slightly thicker clothing, rather than three turns of the older traditional material. This usually gives better porosity of clothing and greater strength and stability in use.

When renewing the clothing, a careful check should be made of the underlying springs, because it these which gives the roll its main resilience to accommodate different thicknesses of textile items and to maintain perfect bed contact. The springing should be free of rust, with no broken springs or flattened areas of poor contact. Damaged springing should be replaced. The clothing thickness and resilience then allows fine tuning of roll diameter and roll-to-bed contact. Too great a diameter and the roll with ‘bridge’ the bed, touching only at the upper parts. Too small a diameter and the roll will ‘bottom, with a narrow arc of contact at its lowest point. Both are disastrous for output.

Vacuum suction

As the moisture is evaporated it is drawn by vacuum through the porous clothing into the centre of the hollow roll (via small holes drilled into the metal cylinder) and away to atmosphere. This is a vital part of the entire operation. If the vacuum is inadequate, then drying of the textiles slows noticeably and they will come out damp, with ‘roughdried’ patches. Even more seriously, the leading edge will not be taken cleanly into each nip and the consequent ‘stutter’ will create a leading corner crease and spoil a perfect finish. The reason for the ‘stutter’ is failure of the vacuum to dry the roll surface, lowering the coefficient of friction between this and the textile so that the fabric is not grabbed cleanly into the nip.

The target suction force for the vacuum is between 30 and 90 Pascal (Pa), with the strongest vacuum being delivered to the first roll, where most evaporation occurs. The vacuum should be checked with a properly calibrated vacuum gauge, checking for uniform vacuum across the entire width of each roll. Poor vacuum can result from build-up of wax in the vacuum pump and in the ductwork downstream of this. Curing poor vacuum will result in better drying and better finished quality.

If the problem is blinding of the clothing surface with either starch or wax, then further action is required before the clothing is replaced. Starch blinding is caused by incorrect starching in the washing machine. The starch solution should be added at the manufacturer’s recommended dosage and in liquor at the right temperature. This is 50C for some starches, although more modern types are designed for cold absorption. The starching time should be long enough for the starch to build into the cloth, rather than sitting on the surface. Too much starch for too short a time at the wrong temperature will produce starch residues on the leading edge of the first bed of the ironer, with consequent blinding.

If the rolls are being blinded by wax, then the special waxing cloth should be run once every eight hours with the correct amount of wax sprinkled evenly across the width of the cloth, under the trailing flap. The cloth should then be re-run every two hours with no further wax additions. If the ironer is being waxed by hand-scattering of wax directly onto the beds, then the required minimal application will be exceeded and wax blinding of the clothing inevitable, the vacuum will be stifled and work still damp.