How to Brush Up a 40-Year-Old Gravure Printing Machine
Significantly reduced waste and higher printing quality in combination with improved user-friendliness and freedom in development of new designs – Forbo Novilon has used mechanical retrofit and state-of-the-art automation technology to raise the performance of its 40-year-old gravure printing machine for PVC flooring to a new level. Moreover, for the safety of the employees, it also proved possible to improve and adapt the press to today’s needs. In addition to BST eltromat International as the leading partner of the company, the companies Interflex, Jansen Antriebstechnik, and Siemens also participated in this sophisticated retrofitting project.
“For reasons of cost alone, investment in a new gravure printing machine never was an option for us,” explains André Wachtmeester. Together with the Styling/Printing Manager of Forbo Flooring Systems in Coevorden in the Netherlands, we are standing in the control center of the Erwepa machine that was installed in 1977. We are looking at the four-meter-wide, completely printed and embossed web of a grey-brown flooring made of 0.6 mm PVC composite that is running through the “command center” at the end of the printing machine, finally leaving the machine in the direction of the reel.
“This machine also offers some special features e.g. its extra-wide web. We did not even check whether there is still a manufacturer who is able to deliver a gravure printing machine that meets our requirements,” points out André Wachtmeester, stating that there had never been an alternative to the retrofitting of the existing machine at Forbo Flooring Systems. In addition to this, an increased number of vinyl floorings are set to be manufactured by digital printing in Coevorden in the future; today, just over ten percent of the floorings are produced using this method. Currently, large-format digital printing is not able to compete with gravure printing in terms of speed and repetition accuracy. However, it will surely catch up in the near future. Thus, everything pointed to completing the modernization of the present technology.
“Above all, we wanted to reduce our waste and improve printing quality. Furthermore, we hoped to be able to break new ground in the manufacturing of floorings when completing a retrofit,” says André Wachtmeester, looking back to the end of 2013. At that time, Forbo Flooring Systems contacted BST eltromat International to discuss the possibilities regarding the modernization of the gravure printing machine that is almost 40 years old. “The machine with the eltromat register control DGC-650 has been in operation since 1999. Furthermore, we knew that the automation department of this company has the required practical know-how as it has successfully completed a multitude of sophisticated projects in the past.”
The Main Shaft Had to Be Discarded
In March 2013, BST eltromat proposed to remove the main shaft, i.e. to discard the previous main drive of the gravure printing machine, and to replace it with individual drives for each of the six printing units – with all the benefits offered by such a configuration for the more flexible control of the machine. This means that, in addition to the modernization of the automation technology and register control, the necessity for a larger mechanical intervention already became apparent at the beginning of the project. For the professional completion of such an intervention, the experts of BST eltromat recommended involving the company Jansen Antriebstechnik GmbH from Viersen and the company Interflex from Bielefeld, which specialize on mechanical retrofits, because they had previously cooperated with them successfully in several projects. However, the technical service of Forbo Flooring Systems insisted on using the latest TIA-based (Totally Integrated Automation) Siemens technology for the drives. Thus, the project consisted of employees from five companies, who would complete the concept by May 2014.
After the general approval of the concept, BST eltromat prepared a test design including new drive technology and register control, providing a practical visualization of the mode of operation of the new automation technology. In July 2014, twelve employees of Forbo Flooring Systems attended a technical training day at Ostwestfalen-Lippe. “That day we got to see the technical benefits of the planned modernization. It was clear by then that we would be able to meet our expectations with a comparably low investment,” shares André Wachtmeester.
Every Printing Unit with Its Own Drive
Before the retrofit, the main motor not only operated the six printing cylinders, but also the doctor blades, via a special gearing and chains. This was not possible any more after the retrofit, because the removal of the main shaft also removed the mechanical system and the inherent drive train for the doctor blades. Instead, the concept for the doctor blades provided small frequency converter motors made by Siemens that were intended to replace the gearing. This was also able to reduce the required cabling because the motors are only required to receive the control signals from the control cabinet via a bus and the 400V power supply via a second cable.
This concept offers Forbo Flooring Systems a range of benefits in the two-layer production of PVC flooring using the gravure printing machine. As any printing unit is equipped with a controlled drive for the doctor blade, the blade speed can now be individually pre-selected. This enables the machine operators to accelerate the doctor blades in the case of a possible development of streaks. In André Wachtmeester’s words, “All it will take is the touch of a button.” In the past, the doctor blades had a fixed transmission ratio due to the rigid connection to the gearing so that their speed was always identical to the machine speed.
The good accessibility of the whole technology represents another benefit, enabling a simple and quick replacement if needed. “We now have more space for movement within the machine. This also enables faster access,” explains the manager, while we change sides between two printing units via an aisle approx. 1.5 meters wide. “In the past this would not have been possible because the main shaft would have blocked our way. Furthermore, the drives are installed in an upright position so that they do not extend into the walkway,” says André Wachtmeester, pointing at one of the motors that are installed in a vertical position directly in the printing units. “This is also a very convenient feature for our machine operators.” In the case of malfunction, they can access the corresponding site faster than ever. Last but not least, the new technology is also cost-efficient.
Innovative Register Control for More Options
The gravure printing machine now uses a regi_star 20 register control made by BST eltromat, developed for inline printing machines of all customary print methods. In addition to the high computing power, this innovative PC-based system is also characterized by the high quality of its sensor system, which is composed of a light conductor system and an integrated camera. Therefore, even poorly visible print marks no longer represent a limiting factor. “Today, we can virtually see the white eagle on the white background,” says André Wachtmeester, with regard to the daily production process. Contrary to “the need to rely on virtual parameters” as in the past, the printing units can now be measured in terms of each other, enabling a fine-tuning of the whole process. This may well make Forbo Flooring Systems the only print shop in the world that is able to emboss over a width of four meters in the register.
This is complemented by a high degree of automation in the case of repeated jobs. The new register control at Forbo Flooring Systems is connected to the machine control via an interface that is used to exchange information between both devices. With every new job, the machine operators adjust the required printing cylinders by sight; they then start the machine and complete the fine adjustment. As soon as the machine is within the register – that is, ready for production – a button for saving the production parameters can be pressed on the main operating console. Then, the positions of the printing cylinders are measured relative to each other. The bracket offset is measured and included in the calculations; the correspondingly calculated value is then assigned to the job and stored in the register control.
In the case of repeated jobs, the appropriate data can be retrieved at the touch of a button. The machine operators only have to insert the cylinders and switch on the machine. Even before the web starts to run, the cylinders automatically move to the required position; here, it is important to know that Forbo Flooring Systems has more than 750 different cylinders available for the production of PVC floorings. This amount makes it clear that the possibility of saving job data is highly important for the company.
Approximately 20% Less Waste
Although the previous register control enabled presetting within certain limits, the new possible settings have significantly reduced the waste generated during the start of operations at Forbo Flooring Systems. As the six printing units are now driven individually, the machine operators can optimize the material throughput and therefore reduce waste. Thus, the generated waste with repeated jobs during full use of the machine is now less than one machine length. Given a rate of six to ten new jobs every day, this means high cost savings when considering the web width of four meters and the high costs for the raw materials. “Altogether, we reduced our waste during start by approximately 20%,” estimates André Wachtmeester. “This particularly applies to the more difficult production work we do using light colors such as white and silver.”
Another benefit is the high availability of the machine thanks to the significantly reduced setup times. Furthermore, the machine operators can now store additional information together with the job data in the control unit, thus further simplifying the setup process. This is used e.g. in the case of deviating cylinder circumferences. The factory owns a multitude of cylinders processed several times during the years so that their circumference is less than 1,500 mm. Thanks to the individual drives, the speed of these cylinders can be set individually and adjusted to the speeds of the other cylinders. The machine operators save the corresponding data in the control unit so that they can be retrieved within seconds at any time in order to set the drives to the required speed.
New Possibilities for the Design of PVC Flooring
At the same time, this possibility means more flexibility regarding the use of the machines at Forbo Flooring Systems, because the company can now insert the cylinders into the gravure printing machine in any order, and may consider the slip via the individually controllable drives. “As we are no longer required to insert the cylinders according to size, but are able to flexibly equip the individual printing units, we now have various possibilities regarding the combination of cylinders and the design of the flooring,” explains André Wachtmeester, with regard to the benefits of the daily business.
The retrofit of the gravure printing machine has also made the whole appearance of the machine more attractive for the machine operators; everything is clearly arranged now. Cables are now installed in trays, which means there is sufficient additional space for further modernizations.
Another important aspect: the retrofit was used to specifically increase safety of the machine operators. For instance, the electro-mechanically locked covers at the drives can only be opened if the machine stops and the web is not moving. Furthermore, safety-checked PLCs and motors with on-board safety were used. Altogether, this represents a good compromise between safety and user-friendliness that ensures the employees comply with certain procedures.
Extremely Tight Timeframe
In addition to the sophisticated technical requirements, the project team also had to deal with a particular challenge. The retrofitting and re-commissioning of the machine had to be performed and completed within the three weeks of the company holidays at Forbo Flooring Systems in July 2014. This meant that the given timeframe was very narrow, thus requiring scrupulous preparation by all of the parties involved. “We were able to finish our work three days ahead of schedule, and even pre-produced some jobs before the end of the summer holidays,” says André Wachtmeester. The involved Forbo employees were so enthusiastic that they did not want to stop working. “Come on, just one more job.”
The new technology has been running on a stable basis since its commissioning. However, the experts at BST eltromat can still use remote maintenance to access and update the whole machine control, including the register control, should this be needed. For example, the latest version of the HMI user interface was installed via remote access. Even in this regard, the 40-year-old gravure printing machine is state of the art.