Optimising the layout of the converting line

Increased line productivity in the Tissue Industry

Massimo Franzaroli – Pulsar Srl

Pulsar would like to share this experience in the field of conveying systems with those companies that are facing investments in converting, to help them optimize the space available in their plant and to make the line operator-friendly through the use of intelligent exchanging and conveying systems.

PRELIMINARY CHOICES FOR A CONVERTING LINE. In the planning and design of a system there are some important aspects to be considered, as these determine the final layout of the line: the processing machines, the packaging and wrapping machines, the palletizing robots and the laser-guided vehicles. The processing machines (rewinders, embossing machines, log saws) play a strategic role in the choice as they affect the productivity and the overall quality of the roll expected by the customer. The packaging and wrapping machines are of fundamental importance for brand policy: the product’s packaging. For this reason much attention is given to the study of the packagings and to the performances of the machines involved. As to the palletizing robots and the laser-guided vehicles, the aim is to find optimized solutions to save space and to reduce the number of operators involved in the process.

POSSIBLE CONSEQUENCES OF CHOOSING AN INAPPROPRIATE CONVEYING SYSTEM. The first problem could arise when the company chooses a cheap conveying system, saving on materials or using unsuitable ones. A typical example is to use belt conveyors, which easily become dirty with glue and are not easy to clean, or to use long conveyors with a very long distance between motors. This choice negatively affects line productivity: the poor quality of the materials used requires a higher level of maintenance, with frequent anti-economic line stops.

In other cases, the company chooses a layout which is not ergonomic, for example ceiling conveying systems, particularly difficult to control by the operators, that require very long maintenance times and also pose many problems as far as the operators’ safety is concerned.

A third problem may come from the choice of a system which is too flexible and which can turn out to be unsuitable for the machines of the line. Such system calls for frequent adjustments according to production needs: the efficiency and productivity of the line largely depend on the technical skills of the operators.

TRADITIONAL SYSTEMS. In traditional tissue lines in Europe, each log saw normally feeds 2 or 3 wrappers: this is necessary in order to avoid stopping the log saw and the rewinder when one wrapper stops, because this would lead to economic and production losses. The old dividers need a very high conveyor speed (80 mt/min), which is 3 times greater than the linear cutting speed of the log saw. For this reason, rolls are often spaced out and this increases the risk of roll overturning, whereas, during accumulation, a high back pressure on the rolls could cause damages. To sort the rolls among the different wrappers it is common to use pneumatic or electromechanical diverters or dividers, 4-6 meter long, which need a 5-meter long conveyor upstream and downstream to accumulate the rolls. These dividers stop the rolls with mechanical clamps, which often damage them. They accumulate and exchange the rolls to the wrappers of the line. On the whole, the total length of the line between the log saw and the diverter, including the conveyor for roll accumulation, is of at least 14 meters.

FIRST PULSAR INNOVATION: THE R.E.D.S. DIVIDER. In 1998, Pulsar engineered the R.E.D.S. divider (Rolls Exchange Divider System), an extremely compact divider for toilet rolls and kitchen towel rolls, in close cooperation with a leading Italian Tissue producer.

Thanks to its small dimensions and position in the line, the R.E.D.S. divider introduces significant innovations in this industry. R.E.D.S. can exchange at a rate of 300 rolls per minute per lane, making full use of the highest operating speed of the fastest log saws (1200 rolls per minute for a 4-lane log saw) and allows continuous sorting of the rolls, without stoppages and at a constant speed of 25 mt/min. It reduces the risk of roll overturning and back pressure on the rolls and also increases the system’s life-span which becomes 3 times longer (at the same production rates).

SECOND INNOVATION BY PULSAR: THE REDS SYSTEM SUPERVISING SOFTWARE. In 1999 Pulsar introduced another absolute innovation in this industry: the REDS System software which can control and manage the entire converting line from one single unit, thus integrating the processing machines with the conveying system.

With the REDS System it is possible to obtain the electronic and mechanical synchronization of the machines comprising the line (log saw, wrapper, bundler, palletizer) with the conveying system. The main resulting advantage is that, in case of machine stoppages, the REDS System automatically changes the speed of the other machines in “just in time” fashion, thus conferring maximum productivity to the line in any case.

Thanks to the REDS System it is possible to plan production according to the different product types, organize a database with the characteristics of the single machines (remote control and speed optimization), to obtain production event controls and collect data from the machines (production records, emergencies, machine stops).

Increased line productivity, substantial reduction in the line’s ordinary and extraordinary maintenance, management cost reduction – these are the reasons of the success of the REDS System. •

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