Cool and in control1 March 2007
Merobel brakes and clutches offer cost effective tension control on narrow web machines
An extensive range of cooling systems - a necessary component when achieving higher linear speeds - is the key feature of Merobel's latest brakes. Together with a new digital tension controller, they are offered as a cost effective way of improving tension control to refurbish existing machines or improve the performance of new equipment.
The company claims its EMP technology is the best option for applying variable torque in tension control, because the brakes and clutches are “more reliable, they will not wear out, and are easier to implement than friction systems”. The brakes are also said to be more cost effective and easier to maintain than shaftless systems.
The new EMP range of brakes and clutches is said to be the widest available. “Because the versatility of narrow web label machinery is increasingly important,” explains Merobel, “the available global range of torque - from 2-1,000Nm - is also becoming increasingly crucial when considering an application's needs. “Firstly, the web diameter ratio between full and empty is usually about 1:10, while the width ratio can be 1:4. Secondly, the material range that can be processed on the same machine leads to a wide product tension variation. For example, in order to print from 12 micron BOPP to 600 micron cartonboard on the same press requires a typical material tension variation of 1:20.”
The EMP range is said to offer the widest choice of cooling systems: fins, axial and radial fans, and water jackets. The most innovative of these is the radial fan. More compact, this system is easy to implement, ranging from 125-2,000W of heat dissipation power.
The brakes and clutches are also said to be kinder to the environment. They are “dustless by design, as there is no way to accept any loss of magnetic powder outside of the internal working areas“. In accordance with ISO14000, the seal quality was a “100 per cent reliability target“ for Merobel's designers. Particular attention has also been paid to customer needs for quiet operation, the company emphasizes.
In addition to the brakes, the DGT300 tension control system is claimed to offer all the features necessary to deal with application parameter variations: web elasticity, bobbin rotational inertia, continuous or stop and go running process, and range of diameter variation. Designed for both closed and open loop tension control, the DGT family of controllers is suitable for unwinding, rewinding and intermediate tension control applications.
Allowing 100 per cent set-up through their user friendly Windows PC interface or through the front panel keyboard, these devices are said to include all the necessary web tension control specific functions, such as E-stop proportional to the set point, soft start, hold and release, taper tension and no-stop splice turrets.
Advanced regulation features are also offered, such as automatic PID coefficient variation, open loop and closed loop control combined, inertia compensation, smooth start-up with programmable slope, as well as motors and drive specific algorithms. Compatible with any basic position sensors, US sensors and any type of loadcell technology, the design of this range of controllers provides the benefits of fully digital calibration procedures, according to Merobel.
In addition, direct control of EMP brakes and clutches is available through the built-in power amplifier, while drive control can be effected with standard analogue output. The company says this system offers the advantage of easy tuning through a simple Windows PC interface and a greater degree of flexibility to change production batches.
It stresses: “This is crucial for maintenance staff, wherever they are in the world, to be able to read and modify all the parameters and to make data records for easier troubleshooting".