Tissue and Towel Converting Line Automation

At the start of the line the parent roll is unwound; the unwinder drive holds web tension with a dancer arm or tension measurement, because tissue is thin and weak and tension swings mean breaks or wrinkles. The web passes through embossing rolls and the lamination unit, where two-ply products are glued together. The speeds of these sections are tied by ratio to the line's master axis (virtual master); when the line speeds up, they all speed up by the same ratio.

In the perforation unit a cylinder with rotating blades cuts the line of holes between sheets. Perforation spacing (sheet length) is set by the ratio of the perforation cylinder to web speed; this ratio is set with an electronic gear, taking the number of blades into account. While the rewinder winds the paper onto the core, the log diameter grows; winding roll speeds change with the growing diameter to hold winding firmness at the target. When the log reaches the set sheet count the paper is torn off, a new core is inserted and winding moves to the new log without stopping (non-stop). For the paper to tear at the same place every time, at the perforation line, the tear moment is calculated not only from length but also from the perforation cylinder angle.

The finished log goes through the tail sealer, which glues down the last sheet, and on to the log accumulator. The log saw cuts the logs into roll widths with a rotating, self-sharpening circular blade; the axis that feeds the log and the blade motion run in sync, the first and last pieces are rejected as trim, and sharpening and blade cooling run every set number of cuts. The core maker winds cardboard strips spirally with glue to make the core and cuts it to length; when core stock runs low the rewinder is slowed or stopped automatically.

In the ONX architecture the line is controlled by CODESYS running on an industrial PC or panel PC. Unwinder, embossing, perforation and winding sections are coupled to a virtual master axis with electronic gears; servo axes run on EtherCAT and roll and conveyor motors on AC drives. Sensors, glue level and web break signals connect to Crevis EtherCAT I/O modules; alarms are shown on the operator panel and logged.

Sheet count, sheet length, log diameter and winding profile are stored as product recipes. The rewinder, log saw and core maker know each other's state within the same line: when cores run out or the log saw cannot keep up, the rewinder slows and the line balances without stopping. The operator screen is multilingual; on lines abroad, alarms and menus are shown in the local language or English.

Since 2018 ONX Control has done the control of toilet tissue and kitchen towel rewinders, log saws and core makers for a tissue machine builder. These projects were done for plants in Ankara, Kayseri and Konya and for lines in Qatar, Ukraine, Libya and Kenya.

On the Kenya line a non-stop rewinder, log saw and core maker were commissioned together. During commissioning the tear moment was changed to be calculated from the perforation angle as well as length, so the paper tears at the perforation line every time; log length was made definable by sheet count instead of length; and web break and glue level sensors and door safety switches were added to the alarm system. The video below shows field footage from this line.

A typical picture on older tissue lines: perforation spacing set with mechanical gearboxes, gear changes at every product change, paper tearing off the perforation line, drives with no spare parts and a single-language panel with limited alarms. In a retrofit the machine frame and rolls are kept; perforation and winding move to servo axes and sheet length and sheet count are changed from a recipe on the screen.