Avoiding ironer creasing

A good wash process and, more importantly, thorough rinsing will remove wash chemicals and other residues from the cloth and offer the best chance of a smooth flow through the ironer. Greater care is required for starched work because getting starching right at the end of the wash is only half of the process.

Starching should be carried out from a low dip at around 50°C and it is vital that sufficient time is given to the starching stage to build starch right into the cloth rather than just leaving it sticking on the surface. This calls for the correct concentration of an appropriate starch and for this you need the advice of a reputable supplier—there is no point in penny-pinching this stage.

When the work is spun or pressed it is important to reduce the moisture retention for cotton goods to 55% or below. For polyester cotton, you need to strike a compromise between maximum water removal for efficient drying while avoiding potential problems with static that can arise through over-drying of polyester cotton. Unless you have an ironer line specifically set up for polyester you may wish to allow more moisture retention by reducing spin time or spin speed (or press time or press speed).

Ironer information

Preparation for ironing: the tumble dryer after a continuous batch washer provides an ideal shake-out stage and should leave the sheets or table linen ready for ironer feeding with no tangling or roping. Otherwise, you need to vary the height at which the tumble dryer is discharging and the programming of forward and reverse rotation so as to correct this.

Ironer feeding: to minimise creasing, flatwork needs to be fed centrally to the ironer or to its appropriate lane. Lateral tension must be applied to the leading edge and some back tension is needed along the trailing part so that the item is presented in a flat and uniform manner. The leading edge must be absolutely parallel to the ironer roll and should be crease-free with no curling or rucking.

The feed belts should be set at a speed 10%-15% slower than that of the ironer so that a little additional tension is created when the ironer feed belts pull the work off the feeder belts. This setting differential is essential and should be maintained over the full range of ironer speeds.

The ironer is fitted with tapes that are designed to transport work cleanly over the correct flow path. For these to function properly the tape tension must be even and correct and you can check these with a glance at the tape tension arms usually visible at the front of the machine. It is equally vital that all the tapes are in position and in good repair—trying to run with several missing is asking for trouble.

Troubleshooting

Roll and bed problems: steam used to heat the ironer beds and the rolls on some installations must be dry and at a uniform pressure in excess of 6.5 bar, ideally 8 bar. Water droplets in the steam create an insulating blanket of water over the inside of the bed which slows down heat transfer and causes a cold spot.

It is equally important that liquid condensate formed when the steam gives up its heat is drained properly from the bed and not allowed to back up as the result of a blocked filter, a blocked trap or a trap that is too small for the duty.

Even more important is to ensure that air is properly vented from each bed using air vents at the horns and a trap with an integral air vent at the base. Thermostatic traps and thermodynamic traps generally vent air very well through the main condensate discharge mechanism. Float traps can be specified with a thermostatic air vent (which should be checked whenever the trap is serviced) and inverted bucket traps have a small hole in the top of the bucket, usually with a wiggle wire in it to keep it clear.

As far as creasing is concerned, it is the ironer roll diameter and the uniformity of this which has one of the biggest influences.

An overclothed ironer roll with a diameter greater than that of the bed in which it sits will lead to bridging, and an underclothed roll will lead to bottoming. This is so important that every new ironer is supplied with a special measuring tape for each roll—often a plain metal tape with two marks that match up when placed around a roll of exactly the correct diameter.

Frequently, these measuring tapes fall into disuse and reclothing is carried out simply with the correct number of turns, hoping that this will produce exactly the right diameter.

It is vital that the roll diameter is correct right the way across the width, otherwise there will be a much stronger drag at some places than others and this will cause distortion of the best fed sheet.

It is essential to have some stretch in the ironed work between the rolls and this is achieved by building an ironer so that there is a slight increase in circumferential speed as you go from roll to roll through the machine. This stretch can be measured with the appropriate meter and you should be looking for an increase in speed which gives an extra 50mm of travel in every ten turns of the ironer roll.

It is also important to have the beds precisely aligned so that they are exactly parallel to each other, otherwise there will be a permanent twist and distortion to every piece of linen passing through. It is just as important that the beds are perfectly clean with no traces of wax build-up, rust or corrosion, abrasion or erosion, build-up of starch deposits or anything else that might hinder uniformly smooth passage.

It is interesting to note the improvements in ironer manufacture over the last few years. A modern ironer bed is not only machined much more precisely than its predecessors but is also held in shape much more effectively during treatment to remove fabrication stresses. The end result is a perfectly uniform bed profile across the ironer width with no hint of deviation or twisting.

Finally, the speed of the feeder belts should be set 10%-15% faster than the discharge speed from the final ironer roll to maintain the pulling principle through into the feeder mechanism.

Why does work crease during passage through an ironer, and how can this be avoided?

Wine glass creasing: caused by rolls which are slightly oversize look a little like rows of wine glass outlines and are sometimes referred to as ‘wine glass creases’. There are tight nipping marks where the ironer roll pinches onto the bed. Once the linen has passed through this point it receives relatively little pressure from the clothing to hold it against the heated bed so that wine glass creasing is frequently accompanied by poor drying or slow running.

Diagonal creases: when any component of the ironer is in poor alignment or the roll diameter varies across the width, there is a tendency for the sheet or table linen to be skewed, producing diagonal creasing. When this happens, feeder, rolls, beds, folders and all major parts need to be checked for alignment and adjusted to within a few millimetres. The most difficult cause of diagonal creasing to detect and sort out arises from poor control of roll diameter side to side or from damage or build-up on a bed causing differential drag.

Concertina creasing: if the leading roll in particular does not grab hold of the fed linen cleanly and take it straight into the system there is a tendency for concertina creases to develop as linen is pushed forward without being pulled into the system. This can be caused by seriously undersized ironer rolls bottoming within the bed.

It also happens when poor control of the starching operation at the end of the wash process results in excess loose starch on the fabric surface leading to the progressive build-up of hardening starch deposits at the lip of the front bed.

Concertina creases also occur if the roll to roll differential speed is not properly maintained throughout the ironer’s entire operating range.

If the second roll starts to run fractionally below the speed of the first, then concertina creases will slowly develop over the gap piece or bridge between the first and second rolls. The speed at which these build up depends entirely on the differential speed between the rolls.

Mixed results

Visitors to different laundries have often commented on the enormous variation between ironer production in different plants running nominally identical units.

One plant might be successfully processing1200 sheets/hour from a four-roll 700 mm diameter unit while another sited laundry a few miles away, might be struggling to get 650 sheets/hour from the same model.

It will only be when operators start to realise the importance of attention to the details mentioned in this article, that it will become clear how and why these types of discrepancies occur. It will also enable them to eliminate problems at source.