Sensorless rewinder regulation system (PatentPending) - Technical article
• Comexi PROSLIT gains inspiration from former regulation models to develop a sensorless rewinder control system.
Author: Jordi Prat, Technical Director Slitting & Rewinding Comexi Proslit– Comexi Group
Trends are inclined to follow a cyclic evolution. What we value and use today will be gone and obsolete tomorrow. However, nowadays there is a growing tendency to recover past trends.
In a society such as ours, ever changing and eager for technological progress, the fact that we travel to the past to recover basic regulation principles from the 1960’s is surprising, given that they may seem obsolete to us today.
In the past when it was only possible to control speed with a direct current motor, most machines offered current control in the rewinder motor. The built-in potentiometer limited the power in the armature while a classic needle indicated the level of the current.
The main problem with this system was the tendency of the motor to maintain the power of the current and increase to its maximum speed when the material broke. In addition, the frictions that were generally high and produced by the mechanic transmission system were eliminated.
Therefore, when the use of electronics spread throughout the industrial world and manufacturers were stricken with the desire to seek out increased precision, standardization began on a feedback regulation system via a voltage sensor in the material. In this way, regardless of the type of control used in the motor, a real and apparent voltage could be established and regulated.
This solution has stayed around for many years thanks to its easy application in any type of mechanics system used. However, systems evolve as new technological advances are made. Thus, the introduction of asynchronous motors allows us to precisely adjust voltage in the rewinder without using external sensors while allowing us to take advantage of all the benefits this has to offer.
All systems with regulation inevitably involve oscillation, which is why feedback systems require a series of adjustments to minimize variations. Therefore achieving precision and finding the optimal point in these systems becomes more difficult as it is limited to the abilities of the personnel in charge of making adjustments. In addition, the obligatory strict transfer of material by means of the rollers that contain the voltage reading element and the need to maintain the angle of wrap allow for improvements in this system.
The invasion on the market of three-phase synchronous motors, designed for applications with high levels of coupling at low revolutions, has led to the recovery of a system based on former sensorless versions. As it does not have voltage reading elements, this system is capable of solving problems from the past in terms of material, offering customized adjustment and oscillations from regulation as well as reducing costs.
The project has become a reality in the ComexiProslit S-Turret slitter rewinder. To develop this concept, we used motors that directly couple the extendible shaft of the rewinder to the shaft of the motor, thus creating a solid assembly completely free of loads.
Thanks to this cutting-edge mechanical set-up, the kinematic chain between motor and load is limited to the bearings that support the shaft. This, in turn, achieves a drastic reduction in frictions and greater stability. If we add the large number of electronic aids adopted by innovative motor control equipment to this mechanical revolution, we can record the bearing torque needed in each revolution. The graph resulting from the torque/revolutions enables us to anticipate the torque limit.
Furthermore, electronics gives us the possibility to synchronize real shafts with virtual shafts (perfect in terms of reactions). This synchronization shows real values for the degree of acceleration of the assembly, which is why it is not difficult to calculate the inertia torque of the mass composing the load we must add at the time of acceleration.
We can calculate the voltage torque needed to tauten the material from the required setpoint and the radius of the roll to wind. At this point, it is crucial to obtain a real and stable diameter of the reel to avoid voltage oscillations and working with a voltage other than the one required. In the S-Turret, the rewind shaft moves lengthwise as the diameter increases by means of the two synchronized servomotors. Thanks to this feature, the current position of the servomotors directly expresses the radius, thus conferring absolute stability to the value.
The sum of these three torque values calculated is sent to the motor regulation equipment as the torque limit. If we add a certain overspeed to the speed reference to have a regulation margin, we obtain what we call “Sensorless rewinder” (patent pending), based on the regulation systems from the 1960’s.
Comexi Group reaffirms its presence in Asian market thanks to the CHINAPRINT Fair (n119/2013)
Girona, April the 18th, 2013.-Comexi Group, a specialist in solutions for the flexible package convertible industry, will be at the CHINAPRINT Fair (Beijing) that will be held from 14th to 18 May. This 8th edition underscores the Fair as the most relevant business
meeting point for the printing industry in Asia.
More than 1000 exhibitors will be present at the Fair and more than 160.000 visitors from the sector are expected to attend to know the last tendencies in the technological and machinery areas.
Comexi Group will showcase its range of products, including an EVO, a laminator that has been designed with state-of-the-art control and adhesive application systems in its booth at the Fair. Its simplicity and ergonomic design make Nexus EVO an ideal machine for short and long runs over a wide variety of materials, such as plastic film, aluminium or paper. The company’s assistance at the fair looks forward to reaffirm its presence in this growing market.
SIRPI acquires a Comexi RG EXCEL (n118/2013)
Girona, April 17th 2013.-Comexi Group, a specialist in solutions for the flexible package convertible industry, has began in march the Comexi RG EXCEL installation at the Italian company Sirpi, which is dedicated to wallpapers’ printing.
The new rotogravure printer is installed at Sirpi’s headquarters in Tribiano, at a production center that stands out for its modernity and efficacy.
Sirpi has evaluated carefully the market’s rotogravure printers and they finally chose the Comexi RG EXCEL due to its production capacity, but also because of Comexi Group’s knowledge in the sector.
Sirpi is one of the oldest and most widely recognized wallpapers’ printing companies in Italy. The Jannelli family owns Sirp and they are manufacturing only in Italy as a cultural and strategic decision. By means of the Jannelli & Volpi brand, Sirpi distributes wallpapers, wall cladding, upholstery and decorations all over the world.
The Comexi FLEXO F2 has won the "Red Dot Design" award for its aesthetic and durable design (n117/2013)
• The award ceremony will be in Essen, Germany, at the beginning of July
Girona, 9th April 2013.-Comexi Group, a specialist in solutions for the flexible package convertible industry, has been awarded with the “Red Dot Design” for the design of its Comexi FLEXO F2 flexographic printer.
The Red Dot Design confers recognition to the best products of the year based on communication and product design criteria. The Comexi FLEXO F2 has won among more than 1.800 manufacturers from 54 countries, thanks to its elaborated aesthetic design and its durability.
The Comexi FLEXO F2 innovative design is the fruit of the machine’s ergonomics perfection. Thanks to the changes applied to the printer’s structure, the accessibility has been improved to provide easier ways to the machine’s operating and maintenance. Besides, the working time has been reduced so the machine is even more productive.
The Comexi FLEXO F2 incorporates 10 new patents that affect on grids, doctor blade, drying screen, Excitink, reels, layout and Cingular modules. Since all these aspects are ergonomic and efficacy-related, the company has named the printer F2 FlexoEfficiency.
The “Red Dot Designed” is given since 1955. The current edition of the award has had the bigger jury of its history in order to evaluate in depth all the candidate products. The award ceremony will be held July the 1st in Essen, Germany.
Approximately 1.200 guests are expected to attend the event, so it will be a good opportunity to make new contacts and to know first-hand innovative developments in the design business.