Servo Control Improves Flexibility of Mimi (Tosa Group) Shrink Wrapping Machine

One of Italy’s leading manufacturers of packaging machinery, MIMI s.r.l., has incorporated high accuracy servo-drives from Control Techniques for its latest ‘MITO’ shrink wrapper.

Based in Canelli in northern Italy, Mimi is part of the Tosa Group, famous for making wine bottling machines.  Its MITO automatic shrink wrapping machine is designed as an end-of-line machine for the wrapping of different configurations and pack sizes of bottles, cartons, cans or tubs and its key selling point is its flexibility.  The incorporation of highly accurate and synchronised Digitax ST servo drives into three critical areas of the machine – speed of throughput, the cutting of the film and control of the wrapping action – have resulted in an increase in throughput and versatility to the process in this new machine.

Control Techniques Italy worked closely with MIMI to produce a machine that can quickly and easily be set-up for different bundle / pack sizes and different configurations and even different products.  For example, it can be changed in seconds from a format for wrapping 6 x 1.5 litre bottles of mineral water to 24 x 0.5 litre packs – at a throughput of up to 40 packs per minute.  The machine can also be supplied with a carton pad dispenser or with a tray-maker.
Bottles or other containers are fed into the machine by conveyor and marshalled by a pneumatic separator into blocks of the specified number.  At this point, a chain driven by a brushless motor conveys the bundle into the wrapping area.  The heat-shrinkable plastic film is unwound under controlled tension from a roll; the film is cut from underneath into pre-determined lengths using a rotary cutter mechanism driven by brushless motor.  The cut edge is drawn forward and held precisely in place by toothed suction belts – a bar lifts the leading edge of the film up, over and behind the advancing bundle of products – and it moves into the shrink tunnel, where it shrinks into a secure package, and on to the after-cooler.  This wrapping action is also controlled by brushless motor.
Each of these actions requires high precision, highly repeatable movements.  The advancing bundle of products must synchronise with the cutting stroke and the cut film must meet the advancing bundle at exactly the right moment. 

The trajectory described by the film when looped up and over the bar of the wrapping section must be co-ordinated precisely with the speed of the bundle in order to meet the film at the correct point.  Each of these movements is critical to the machine quality of the packaging, eliminating bubbles, swelling or creases and also ensures the correct placement of the end-user’s logo and copy, so that the finished pack can be merchandised correctly and attractively.

For the control of the three brushless motors in the MITO shrink wrapper, MIMI engineers selected Digitax ST servo drives, which not only provide precision control, but also allow fast and straightforward re-configuring of each of the brushless motors, to accommodate different configurations of product.  Each drive incorporates an SM-Application module that provides PLC functionality at drive level.  For instance, the CAM-profiles required for different products are all stored in the wrapper drive and changing product configuration is as simple as selecting a different recipe on board the drive.  All of the characteristics of each drive – distances, axes, motion control and cam profiles are stored on board, reducing the overall level of PLC control and giving the end user maximum versatility of control.  This also gives the machine designer flexibility in choosing the communication bus to suit the client’s needs as the drives operate down-stream of the bus.

The Digitax ST range encompasses four models, each with industry-leading features, extremely compact in size and having full compatibility with Control Techniques’ existing range of function and communication modules.  It is optimised for servo applications requiring high peak torque, exceptional dynamic response, faster installation and start-up as well as ease of integration.  Four product variants make up the range– Base, Indexer, EZ Motion and Digitax ST Plus chosen for the MITO shrink wrapper.

Digital ST will operate successfully with all makes and types of AC servomotors as well as linear motors and with almost any type of feedback device.  However it has perfect partners in the Control Techniques range of servo motors including the Unimotor fm and hd. 

Unimotor fm is a high performance brushless AC servo motor range,  fm’ stands for flexible motor, designed to accommodate a wide range of applications; The motors are available in seven frame sizes with various mounting arrangements and motor lengths. Unimotor fm provides high-precision over an extended duration requiring lower acceleration and deceleration rates. The motor is optimized for high stability in precision profiling applications
Unimotor hd is Control Techniques’ high dynamic brushless AC servo motor range, designed for high dynamic applications requiring hard accelerations and decelerations.  Unimotor hd is suitable for a wide range of industrial applications, due to its extensive features whilst being exceptionally compact.

The MITO’s shrink tunnel is available in different sizes to suit the application and the machine can be supplied with an in-feed gating system, a twin-film feed unit, print centring unit, anti-stick bars and pneumatic discharge of the pack.