Flexibility and reliability are key
Bar Graphic Machinery has implemented an efficient solution to control the unwind tension of its rewinders. The solution is based on web-tension specialist Merobel's brakes and power supplies.
Bar Graphic Machinery, founded in 1992, specialises in the manufacture of narrow web slitter rewinders, inspection slitter rewinders, rotary die cutting rewinders, re-register die cutting, re-register flexo converting and finishing equipment. Chairman Bill Rhodes explains: "Keys to our success compared to other manufacturers is the ability to offer flexible solutions. This means we are able to meet our customers' specific demands. Our engineering experience and capabilities are second to none, thus enabling us to customise our machinery where necessary, making sure our solutions still offer maximum accuracy."
One of the main technical issues concerning rewinders is to be able to maintain constant torque on the reel especially when the diameter is low and the torque is small. To do this, Bar Graphic has implemented Merobel's EMP brakes and PowerBlock. Their main advantage is that they enable constant torque, even at very low levels.
The operating principle of the electromagnetic brake is that a change in the magnetic field alters the viscosity of the EMP powder, controlling the mechanical coupling between the inner and outer rotors. With this technique, the torque is proportional to the current that produces the magnetic field and is independent of the rotation speed. The torque/size ratio is better than for a friction-based mechanical solution and better than a servo motor which will be less reliable for small torques. The torque is reliable and reproducible, without shocks, and the response time is rapid. Wear is also very low, ensuring a long maintenance-free lifetime. In addition, Bar Graphic has implemented Merobel's PowerBlock2 power supply. This ensures very precise electrical control thanks to a closed-loop-controlled output current, based on microcontroller technology. PowerBlock2 has a high level of protection against transients (short circuits and circuit openings) and is very easy to set up.
Another key point is that the EMP brake and clutch range is eco-friendly. It is dust-free by design as there is no loss of magnetic powder outside of the internal working areas. Recently, particular attention has also been paid to quiet operation. Specific surface treatment characteristics as well as the exact powder composition help to improve the natural noiseless trend of EMP technology. "We are really involved in our product maintenance and after sales service, so we didn't want any pollution from this system," explains Rhodes.
Bar Graphic Machinery has just shown its latest digital finishing and converting line at Label Expo. The BGM Elite FDTR Flexo Die Cut is able to start and stop, producing little if any waste. Other standard features include the ability to print to re-register, die-cut to print re-register and print to print re-register; the servo-driven print stations are equipped with self-positioning print cylinders enabling automatic print registration set up. Other models exhibited from the Elite Range were a filmic inspection slitter rewinder, inspection slitter rewinder, rotary die-cutting rewinder and die-cut to register slitter rewinder. Bar Graphic sells its machines throughout Europe mainly, via a network of international resellers.
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