Drives up productivity for tobacco industry
20 February 2008
A new cigarette making machine, capable of producing 8,000 cigarettes per minute, has been developed by Molins. The machine is driven by servo technology from Lenze with L-force servo drives and synchronous servo motors.
Demand for tobacco products generates a total world market for 5,500 billion cigarettes per year and is still growing by about 3.4% in the developing world despite ever increasing regulation. However, the evolving marketplace is compelling cigarette manufacturers to re-examine their production strategy in order to meet demands for new niche brand types such as Superslims and Lights whilst controlling manufacturing cost. In addition they are recognizing the critical need to introduce flexible and reactive manufacturing resource to grow their global market share.
Molins’ latest cigarette making machine, the Octave, was specifically designed to target these increasingly diverse markets. Its manufacturing speed provides flexible and responsive production capabilities. The on board cigarette inspection system measures many parameters associated with individual cigarette quality, such as rod diameter, ventilation and pressure drop. Weight analysis is further enhanced with rod scanning microwave technology. All inspection, ejection and sampling functions are carried out by using Molins’ High Speed Controller, satisfying the demand for high quality cigarette production.
At the start of the Octave project, Molins engineers looked at the existing machines and tried to strip out as many parts as possible without compromising performance. Questioning the necessity of every component, the company managed to decrease the number of parts by 66 per cent, minimising opportunities for malfunctions and reducing the number of spares that a customer would have to stock. Building a machine with fewer parts is easier and shortens the build time. Importantly in today’s competitive market, it is more cost effective. Improvements to the hopper allow optimisation of tobacco handling in line with the characteristics of modern tobacco brands.
By using independent drives, rather than gear linkages, many mechanical parts are removed. High degrees of accuracy and minimal downtime are paramount in the tobacco industry and the use of servo drives creates further opportunities to reduce complexity.
A key part of the new Octave machine is a six axis servo system using the Lenze 9400 servo drives. A single power supply module mounted side-by-side with the six drive units saves panel space and ensures maximum output for minimum machine footprint. Build times are reduced too. The 9400 drives have a separate backplate which can be easily handled and mounted into the panel. The electronics module is clicked into place later. Once the backplates are mounted, sliding rails connect the DC bus from one drive to the next in seconds. They are locked in place by a screwdriver. No external DC bus cables are required.
The six machine modules of the Octave, each controlled by a servo drive, are synchronised electronically. The drives communicate by CANbus, which is integrated as a standard feature. When a stop is needed, the drives hold synchronisation, which is important for example to maintain tension in the paper feed module. If the operators then need to make machine adjustments, safety legislation demands that any unexpected machine motions must be prevented. Rather than isolate the drives and the motors, Molins selected the Lenze safety option SM100 for the 9400 drives. This gives Safe Torque Off meeting the EN954-1, SIL4 standard. So once the machine has made a controlled stop and is stationary, Safe Torque Off is engaged and the operators can work on adjustments to the process.
On restart there is no delay as the drive capacitors remain charged and control settings remain live. A synchronised start means minimum wastage – a very important factor as tax has to be paid even on cigarettes that are scrapped in production.
The plug-in modularity extends further than the SM100 safety modules. The 9400 servo drives have a plug-in memory module, which holds all the drive parameters. In the event of a drive needing to be changed, perhaps on the far side of the world, skilled engineers with laptops are not needed. It is simply a matter of unplugging the cables and removing the memory module. Then the drive electronics can be unplugged from the backplate and a new drive clicked into place followed by the plug-in memory module and cables.
By introducing a servo system into the Octave, Molins has reduced the cigarette manufacturers production downtime. Previous machines were mechanically driven and required numerous adjustments to a variety of different parameters, however the new system is easily adjusted via the Control PLC on the face of the machine. For example, if the machine operator wanted to change the length of each cigarette he would need to adjust the ratio between the knife and cigarette rod manually. Now, they can be moved by selecting different preferences using the control PLC. Molins also selected Lenze’s MCS range of servo motors with electronic nameplates to further reduce the commissioning time and cost.
Each of the servo drives controls a separate function of the machine; from the supply of the tobacco and paper, through to printing. Whilst the integrated CANBUS system ensures synchronisation within the drives, PROFIBUS is used to communicate between the Control PLC and an 11kW 8200 vector, which acts as the master axis.
Mike Kent, senior systems engineer at Molins commented: ‘Having built a successful partnership over many years with Lenze we were keen to use their systems on our new machine. We saw the new 9400 servo and liked its modularity, the optional safety modules and ease of end user operation it offered’.
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