headband

The headband is a thin strip of iron, typically 1 to 2 inches wide, that runs across the top edge of the tympan on a platen or cylinder printing press. Its purpose is structural: it reinforces the tympan against the considerable mechanical stress that builds up during repeated impression cycles, where the platen strikes the paper and inked form thousands of times per hour.

On a platen press, the tympan is a flat steel or composition plate that sits between the platen and the printing form, cushioning the blow and distributing impression force evenly. The headband is bolted or riveted to the tympan's top surface, running parallel to the direction of the platen's stroke. Without this reinforcement, the tympan would flex excessively, creating uneven impression and accelerating wear at its edges, where stresses concentrate.

Construction and placement

The headband is made from bar stock iron, sometimes mild steel, hardened enough to resist deflection but not so brittle that it cracks under impact. It sits at the leading edge of the tympan, the point that strikes first during the impression stroke. Some presses use a matching tailband at the rear edge. The headband can be removed and replaced as a wearing part when it becomes bent or fatigued; replacing the entire tympan is a much costlier job.

Improper headband tension or alignment will cause the tympan to rock or chatter during impression, resulting in slur, double-strike, or spotty inking. A bent headband may create a high spot that triggers premature impression in one area, ruining registration. Printers check headband condition during routine tympan inspection, particularly after a press has been idle or after a hard set of forms.

The headband is distinct from the underlay or make-ready system built up beneath the tympan to control impression depth in different zones. Its role is purely mechanical reinforcement, making it an unglamorous but essential component of platen press longevity and print consistency.