RETROFIT MECCANICI

Model R940 – TANDEM project: high-evolution electronic retrofit

Developed and installed in 2014

Model R940 TANDEM

High-performance. electric-shaft press model R940, “Tandem” version.

The main feature of a “Tandem” press is the possibility to print two different products at the same time, by configuring the press in such a way to obtain, as a matter of fact, two completely independent presses, or to print a single product with all of the available colours (in this case, 12).

The press has been designed to print film up to 60 micron, paper in the 30 ÷ 60 g/m2 range, 70 micron LDPE; single production up to 12 colours or two separate productions of all the intermediate combinations (1+11, 2+10, 3+9, … ,11+1); max web width 1220 mm; printing cylinders repeat 450 ÷ 920 mm;  max printing speed 500 m/min.

The case

Actually, the press is the combination of 2 high-performance presses, and is equipped with two different automation platforms:

  • on the unwinders (2) and rewinders (2): Reliance GV3000 drives for AC motors, Reliance Automax CPU PLC, I/O PLC AB 1746 series
  • to control the independent drives on the printing units (electric shaft): Bosch Rexroth (Indramat) drives, version DIAX 3
  • on printing units and the remaining parts: Reliance GV3000 drives for AC motors, Reliance Automax CPU PLC, I/O PLC AB 1746 series

The printing units are equipped with vector- and motion-control AC motors; the press is of the electric shaft type (“shaftless”).

Reliance components are highly obsolete since several years*, therefore a fault in one of these components may cause serious availability problems of spare parts; this is why the Client decided for a retrofitting focused on these parts of the machine. Furthermore, since it is a “Tandem” press, on each side (i.e., upstream and downstream the printing units) there is an unwinder + rewinder group; the two groups are exactly the same, therefore the decision was made to retrofit one group only, as described later, to reduce the installation time (and, as a consequence, the downtime).

* since june 2012 (GV 3000 drives and Automax PLC components); since 2002 (I/O PLC Eurorack series)

The intervention, then, has been a partial retrofitting limited to the Reliance automation part and on a single part of the press.

On the UW1-RW1 group, physically the right-end part of the press, the Reliance GV3000 drives for AC motors have been replaced with the new Rockwell PowerFlex 700 models: on the reel axes, on the infeed and outfeed pulling units, on the pulling unit aboard the Corona treatment unit and on the cooling rollers, which means 9 drives of different sizes.

The Reliance Automax PLC CPUs on the UW1-RW1 group and for the sequence management of the printing units have been replaced with the new Rockwell ControlLogix.

The AB 1746 series I/Os have not been replaced, being still efficient and manageable.

The press, then, has not been completely cleared from the potentially-obsolete parts, since the unwinder + rewinder group on the left side of the press has been left in its original shape; anyway, the Client will keep the materials (drives and PLC components) recovered from the retrofitted parts as spare parts for the untouched units.

A new, dedicated interface has been developed to allow the new ControlLogix and the old Reliance Automax platforms to coexist; furthermore, the whole operation has been planned to leave open the possibility to complete the retrofitting easily, in the future, losing nothing of what has been done in this stage.

Replacing the electric cabinets was not necessary, and works have been performed on the existing ones and on some parts aboard the press directly on site to reduce the installation time (and, as a consequence, the downtime). The materials to be replaced have been accurately prepared and pre-wired at Cerutti HQ to reduce installation time.

Some sequences have been reviewed and improved as well, and some adjustment loops have been optimized, notably the ones for tension management.

The management systems (two, since this press can be split into 2 presses working at the same time) have been replaced and now match the hardware and software state of the art.

Schedule

3-weeks downtime plus one week of assistance during production. The press underwent a complete general test and inspection, as well as the main print tests with the relevant materials, in both configurations (in-line single press and “Tandem” 2-presses configuration).

Targets and improvements

The main goal was to solve the obsolescence of the electronic components; this is why the Client decided for a retrofitting focused on the electric / electronic side of the machine.

Since a “Tandem” press is, basically, the union of two complete and independent presses, but is also able to work with all of the printing units in-line, the retrofitting greatly improved the attribution sequence of each single press unit to one press or the other, also increasing the safety criteria in the process.

Another important feature is the possibility to complete the retrofitting of the remaining parts without having to intervene again on the parts that have been already retrofitted.

Notes

This kind of retrofitting offers the best price / performance ratio, since it makes the press perfectly aligned with the current state of the art in automation. These factors have a positive effect on the return on investment of such a retrofitting, taking into account also the further 10-15 years increase in the obsolescence term of the spare electronic components.