RETROFIT MECCANICI

Pulling units TR140 / TR240: replacement of the two-rollers dancing roller system with a single-roller system

The replacement of the two-rollers system with a single-roller system, be it on the infeed / outfeed pulling units as well as on the unwinder and rewinder, is useful on all the Cerutti presses equipped with this type of dancing rollers built in the 80s and the 90s. The unwinder / rewinder model is irrelevant; at most, it can require a dedicated study / design for the installation of the new dancing roller system.

Past examples:
  • Job n. 3879 – Modification on job n. 3253, Model R961
  • Intervention: may 2010
  • Job n. 4029 – Modification on job n. 2760, Model R940
  • Intervention: december 2011
  • Job n. 5211 – Modification on job n. 2775, Model R940
  • Intervention: september 2016

 

TR240 with two-rollers dancing system (left); TR240 with single dancing roller (right)

 

The intervention consists in the replacement of the old dancing system (made of two idle rollers with short, double stroke) with the new one, made of a single, long-stroke idle roller.

To execute this upgrade, it is necessary:

  • to remove the old unit (dancing system, levers, rollers, linear potentiometer)
  • to install the new levers, roller, potentiometer
  • to drill the new holes, if and where necessary
  • to align and level the roller
  • to connect the linear potentiometer and to recalibrate the electronic part till a correct and reliable tension control via the pulling unit is obtained

Necessary resources:

  • mechanical assemblage, drilling, etc.: n.1 Cerutti technician per unit (unwinder / rewinder / infeed pulling unit / outfeed pulling unit)
  • pre-wiring:  n.1 Cerutti technician per dancing system
  • test and electronic check: as a function of the number of materials to be tested and of the timing decided by the Client

Performance improvements are remarkable:

1) the new dancing roller, having a longer roller-stroke, allows for a longer recovery time for the material during any sudden variation in tension (for instance, during splice); on the unwinder / rewinder, this allows the motor / the pneumatic cylinder to recover web tension without having the rollers’ mechanical support part touch the mechanical stop strokes, which is a great disturbance for tension and, if longer than a few seconds, causes the press to stop

2) the old, two-rollers system had a short lever arm but four web segments involved in recovery / release, therefore the system, on every linear movement, responded with a minimal angular movement, which nevertheless turned into a big linear movement of the web; this means that the system worked too suddenly, “nervously”, causing difficulties in tension stabilization and, as a consequence, in keeping a good printing register during any variation in the press conditions influencing web tension; similarly, every eccentricity in the unwinding reel caused tension variations quite difficult to stabilize, and on the outfeed pulling unit, or on the rewinder’s tension control unit, such tension variation, when rewinding sensitive materials or particular laminated materials, may cause the formation of uneven reels

Summing up, the new dancing roller gives more stability to web tension through the press, which means a better register and better end reels when processing critical products.