Demand for tobacco products generates a total world market amounting to a staggering 5,500 billion cigarettes per year and this market is growing by about 3.4% per annum in the developing world, despite regulation. This evolving marketplace is compelling cigarette manufacturers to re-examine their production strategies in order to meet demands for new niche brand types such as Superslims and Lights, while at the same time controlling manufacturing costs. In addition, they are recognising the critical need to introduce flexible and reactive manufacturing resources to grow their global market shares.
Molins’ latest cigarette making machine, the ‘Octave’, was specifically designed to target these increasingly diverse markets. In addition to its speed and flexibility, the Octave features an integral inspection system that now measures more 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 via a Molins high-speed controller, which ensures a high quality output.
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 no less than 66%, minimising opportunities for malfunctions and reducing the customers’ spares inventory.
Building a machine with fewer parts is not only easier but also shortens the build time – an important factor in today’s competitive and price-sensitive market. Improvements to the hopper system has allowed optimisation of tobacco handling in line with the characteristics of modern tobacco brands, and this, combined with a new and improved interface to the garniture, gives unparalleled rod formation. The result is a truly exceptional machine that is set to have considerable impact on the cigarette industry.
By using independent drives rather than gear linkages, it proved possible to remove many of the mechanical parts that are common in earlier machines. The use of servo drives creates further opportunities to reduce complexity – and thus the chances of a malfunction – as well as introducing very high levels of manufacturing accuracy. Each of the servo drives controls a separate function of the machine; from the supply of the tobacco and paper, through to printing.
Six-axis servo system
A key part of the new Octave machine is a six-axis servo system based on Lenze’s 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 saving time and cost. Molins also selected Lenze’s MCS range of servomotors, which feature ‘electronic nameplates’ to further reduce the commissioning time and cost.
Octave’s six machine modules - each of which are controlled by a separate servo drive - are electronically synchronised. The drives communicate via CANbus, which has been integrated into this machine as a standard feature. When a stop is needed, the drives hold synchronisation – a very useful feature that helps to maintain tension in the paper feed module. Whilst the integrated CANbus system ensures synchronisation between the drives, Profibus is used for communications between the main control device (a PLC) and the 11kW 8200 vector drive, which acts as the master axis.
If, following a routine stop, 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 provides a feature called ‘Safe Torque Off’, which meets 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 start work on their adjustments.
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 also have plug-in memory modules, which hold all the drive parameters. In the event that a drive needs to be changed (possibly on a machine working in a distant part 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. All-in-all, it is an unskilled task that takes few minutes.
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 machine controller. 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, these adjustments can be made simply by selecting from a variety of parameters stored within the PLC memory.
Mike Kent, senior systems engineer at Molin’s summarises:
“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”.