FLEXIBLE CAST EXTRUSION SYSTEMSIN MODULAR UNITS

CAST Flex . . . productivity, flexibility

A cast line involves not only the assem-bly of components, but also requires implementation of specific design skills, technologies, electrical and mechani-cal engineering expertise. Experience needs to be fielded in collaboration with qualified users.

Macchi possess the resources and the experiences gained in over forty years of activity, that allows to maximise in any line production efficiency, energy saving, ergonomics and ease of opera-tions. This, in short, is what Macchi offers: its Know-how.

The production of cast film offers sev-eral benefits over that of blown film:

the system offers a greater yield interms of the width and thickness of the film

providesmoreversatilityinthechoiceof polymers

great dimensional tolerance controlof the product

a filmof outstandingoptical proper-ties

The materials normally transformed on cast systems mainly belong to the family of Polyolefins; the cast proc-ess causes fast crystallization, exalting their physical and chemical properties. The primary materials used include:

polyethylenes especially linear(Ziegler - Natta) and Metallocene resins which are used in the produc-tion of stretch film

polypropylenes Homopolymers,Co-polymers and Terapolymers, gen-erally used to make flexible packag-ing in the food and technical sectors, both directly and as components of various films for lamination

resins that are used for barrier andpackaging film that resist oxygen transmission, control flavour for longer

product shelf life as well as various cooking methods such as nylon (PA6, PA6-66)andethylenevinylalcohol(EVOH)

resinswith special sealing or struc-tural properties Ionomer resins,bonding resins, resins boasting par-ticular thermal or mechanical resist-ance, PET/PS

Macchi offers a range of cast film products from small polyvalent, mono-layer or co-extruded systems able to handle film 1500/1600 mm in useful width, through to typical systems for co-extruded polypropylene films, also in specific versions for high barrier film up to 5 and 7 layers and 1600-2100 mm in width. Lastly, there are the large systems for stretch film, with an output of 1000/1200 kg/h at a width of 2000 mm, and more than 1800 kg/h at a width of 3000 mm.

All Macchis systems are extremely modular in design and we are particu-larly proud of this achievement.This means the systems are highly rationalized, integrated and evenly dis-tributed, allowing for ease of handling, installation and maintenance. They are also very user-friendly and easy to service, ensuring a good level of safety at the workplace.Each unit is devised as a standalone module or can interface mechanically or electrically with the machines other modules.

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10 Trim suction and conveying11 Fluff de-dusting and conveying12 Operator panel13 Containerized electrical plant14 Core feeding unit15 Shaft handling and recoring16 Reel handling system17 Water chilling plant18 Pumping and temperature control units

1 Main extruder2 Coextruders3 Fluff re-feed extruder4 Feed block5 Flat die6 Chill roll unit7 Thickness scanner8 Web gauge randomizer9 Winder

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In the same vein as the blown systems, the co-extrusion unit is mounted on a single raised technical platform in such a way that the melt can be transferred via extremely short and rectilinear chan-nels to the extrusion head.

At the top, a second service level ensures safe and convenient access to the resin inlet and outlet systems.

At the bottom of the structure sup-porting the hot extrusion section is an insulated and conditioned container representing the technical part of the line; here, too, are installed all the devices and electrical drives servicing the various motors and utilities that can therefore be inspected, connected and tested quickly and easily by the appointed staff.

Special care is taken over the selec-tion of the electrical and mechanical components to ensure the ultimate in reliability, safe operation and minimal noise levels.

The layout of the casting unit, central unit and winding unit has been devised in such a way that it can be optimized and customized according to specific needs in terms of type of product and available space.At the end of the day, we aim to ensure a machine that is ergonomic, user-friendly and extremely secure, also with regard to the required peripheral and end-of-line accessories.

For example, the extrusion waste treat-ment and recovery unit and the large cooling units required for this type of system can be installed in a room other than that in which is installed the extru-sion line.This makes it all much easier to clean and ensures a higher technical output.

There is a main remote control so the operator can control the unit at a safe distance and at any time.

Film inlet winder

The Plastex extruders come with:

extrusioncylinderswithspecialwear-resistant centrifugal bimetallic sur-face

screws with special barrier proper-ties polyvalent ones and custom-ized ones. These too are made of wear-resistant materials and those intended for the treatment of particu-larly aggressive materials are fully chromed

multi-zone heating/cooling systemswith shielded ceramic heating ele-ments for precise heat configuration according to the selected resins

digitally-controlled maintenance-freeliquid-cooled AC motors

The hydraulic sliding-plate filter units facilitate changeover and are extremely compact to eliminate the risk of the material stagnating. For specific appli-cations there are also cartridge-type elements with large filtering areas to enable long production runs without the need for downtime to change the filters.The channels that transfer the polymer from the filter-changers to the feed-blocks or extrusion head are the hall-marks of quality design. They feature

sturdy metal sections guaranteeing excellent thermal stability and the inter-nal channels are carefully designed to ensure optimal melt flow.

Our specialized polymer flow design engineers now have a well-established method for designing feed-blocks and flat extrusion heads, to optimize poly-mer distribution and production effi-ciency for a wide variety of materials and structure configuration.

The feed block has the task of receiving and superimposing the layers of two or more materials which, during lamina-tion, are conveyed to the extrusion head where this multi-layer sandwich is stretched and thinned before being placed on the surface of the chill roll.All the heads have a flexible upper lip for the actuators to automatically con-trol the output gap and therefore the final thickness of the film.

The restriction to the width of the extruded film one of the few disad-vantagesofthecasttechnologyhasnow been easily eliminated by using systems for internal limitation of the melt flow channel.Called Internal Deckling Systems, fixed

Drawing of flat die with encapsulation

Detail of Internal Deckling System (IDS)

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View of automatic flat die and chill roll from operator side Group of extruders with screenchangers

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Layout of chill roll for the production of polypropylene

that can tend to form and solidify during the extrusion process.To obtain production of exceptional quality at the high speeds involved in the cast process, the products stability has to be ensured during the critical phase between it leaving the extrusion lip and the melt being deposited on the surface of the chill roll.A suction chamber extracts the fumes that are developed during the proc-ess and ensures the counter-pressure required to control correct exhaust evacuation during the quenching proc-

or with sliding inserts, these optimize output by minimizing the width of waste at the sides and therefore the amount of product to be fed back into the line or discarded, as in the case of co-extrud-ed films where there may be chemical-physical incompatibility between the costly resins used.

This device is especially useful in the production of PP film, which is extreme-ly sensitive to the amount of re-used material put back into circulation, usu-ally featuring the formation of gels which cannot be tolerated in the final product.

The chill roll systems come in different geometrical shapes that vary according to the type of film to be made, and their size depends on the systems width and production capacity.

The main chill roll, with cutting edge gearless/torque motor, can have an external diameter of 800, 1000 or 1400 mm to offer cooling capacity and sur-faces suited to the required output. A secondary chill roll, also has dif-ferent diameter requirements based on processing requirements as well as variable positioning for optimized film cooling and stabilization process, which is particularly important in the production of thick film or film made with resins (e.g. PP) that cannot with-stand overly vigorous cooling phases.

Macchi design engineers have paid special attention to the cooling fluid circulation system and its associated heat regulation and pumping circuit. Both are essential to obtain accurate and constant regularity of the surface temperature and therefore even cool-ing which affects the optical character-istics and thickness tolerances of the finished product.A cleaning cylinder removes any traces of wax from the surface of the chill rolls

View of chill roll for the production of stretch

1 Chill roll - main2 Chill roll - secondary3 Suction knife (vacuum box)4 Air knife (optional)5 Cleaning cylinder6 Chill roll height adjustment

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ess. A fully adjustable outlet vent cre-ates the flow of air required to obtain a point of contact between the melt and the chill roll that is perfectly parallel with the axis of the roll.There are also electrostatic loaders at the edges that control the viscous-elastic contraction of the melt at outlet, the so-called neck-in.The movement and positioning of the air vents and their respective air capac-ity settings are automated and control-led by means of recipes memorized on the machines supervision PC.

The typical output of a cast line demands a winding technology that is best suited to the required production. This involves not only the typical phys-ical-mechanical properties for forming a well-produced reel that can then be successfully used for processing the film, but also important economic con-siderations also associated with prod-uct distribution.

Macchi has devised its line of cast wind-ers using three winding systems, con-tact, centre and centre-peripheral that can also be used in tandem according

windingqualityforallproductsmadedirectly into commercial reels

There are three machine versions, all specifically for cast film -so are espe-cially stable and sturdy- and featuring the latest generation of motors and electronic controls:

BoPlus Axialwindingmachinewithreel on swing arms generally intend-ed for polyvalent lines where the needs for winding thin adhesive and stretch films are combined with the need to wind delicate, strong or slip-pery films. The option for pure gap-winding makes the machine ideal for barrier cast film configurations or for lamination

BoPlus HS windingmachinewithflat-bed generally used for the pro-duction of stretch film and intended for in-line production of large jumbo reels for conversion, as well as reels for direct use on automatic palletiza-tion units

BoPlus HS Fast Matic the latestin Macchis range and the first in the world,withindexingturretfourspin-dlesandextremelyfastchangeoverpermitting the creation of all stretch products in their various commercial forms. From jumbo reels to reels for automatic applications, and reels for manual applications produced on both standard 3 spindles and light 2 ones

With reel changeover time in less than 30 seconds, automatic control of the spindles, winding devices and reels produced becomes essential. Macchi proposes different versions determined by the winder model, each featuring different approaches to the varying product requirements.The classic Easy Load manipulators, equipped with their respective Module

to the type of winder required by the product processed on the line.

This production and associated work conditions pose several problems, however: filmtensioncontroluponarrivalfrom

the line and at the reel that needs to be carefully monitored during the production of film such as PP that is particularly slippery and can shrink back

winding stability during the produc-tion of stretch film at speeds over 500 metres per minute

View of turret type winder

C automation, allow Macchi to provide industrial logistic solutions for manag-ing the finished product ranging from the palletization of the finished reels to more complete product collection and boxing systems, all controlled by a dedicated PC to optimize the associ-ated functions.

Mandrel extraction unitMandrel extraction clamp

Winder inlet cutting knives and automatic trim recovery system

As previously noted, the electrical equi-pment is installed in a specially desi-gned controls container that serves to optimize the space required for the control devices, as well as provide a controlled environment temperature for the control systems.

The control system is based on the same approach to the distributed elec-tronics, with serial communication

centralized on the supervision system within the controls container which greatly reduces the risk of downtime due to complicated cabling and inter-connections between the electrical and electronic boards and machine units.

Macchi prides itself on the control of the machines functions and qualitative control of the end product.Operators can often be intimidated by

Line management and thickness control panel

computerized systems not best sui-ted to industrial environments; Macchi however provides two man-machine interfaces with touch-screens that are both simple and easy to understand.There is the screen for the EASY CONTROL Plus system that displays and controls all the machine functions from gravimetric feed to heat regulation and recipes. There is also the monitor that interfaces with the thickness sen-

sor, dedicated to the products profile and management of the extrusion lip.

A heavy emphasis is also, of course, put on the electronics and associated dedicated software for controlling the production transition, from the lines acceleration and deceleration ramping to maintaining product quality control in the process, to management of potential faults or emergency situations.

Gravimetric dosing system and loaders

Thickness meter screen page Screen pages of EASY CONTROL plus system menu

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09The cast film must inevitably be trimmed to remove those edges affected by neck-in proc-ess as well as the bleed trim process in some applications. Quantity-wise, the trim represents a considerable percentage of production and must be recovered in line by means of a closed loop circuit that will not cause contamination and allow the trim scrap material to be recovered and recycled back into the production process as soon as possible. Trim is always recovered in line, except in certain cases involving the pro-duction of film comprising 5 and 7 layer barrier film, when the incompatibility of some materials does not permit in-line scrap recovery. Although there are alternative methods available, such as barrier layer encapsulation which can allow for some in line scrap recovery.

The fluff is processed by a mill and then conveyed via a special pneumatic system for removal of any dust and separation of finer dust particles a potential source of gels inthefinishedproductandthenontorecovery.The system comprises a side extrusion/injec-tion device that compacts the fluff and puts it in the plasticizer screw for extruding (normally the central screw in the case of co-extruders). The re-feed position is selected in such a way as to minimize the risk of overheating the reclaim materials and designed to provide consistent re-feed rate to avoid output variations in the primary extruders production capacity, so the melt temperature and pressure, and therefore the quality of the finished product, remain unaf-fected. Trim recovery systems are available in certain cases and on request.

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Soundproof box for trims suction and grinding

TECHNICAL SHEETExruder diameter range from diameter 55mm to 160mm L/D1/30Feed Blocks and die from 1 to 7 layer automatic and tith IDSProduction capacity range from 200 to 1800 Kg/hFilm gauge range from 10 to 300 micronwinding speed maximum 200 Mt/min for PP 500 Mt/min for stretch

1 Main extruder section

2 Extruder/injector fluff screw

3 Antistatic hopper for fluff

4 Barrel cooling device

5 Screw cooling device

Schematic of fluff extruder/injector

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Macchi S.p.A. - 21040 Venegono Inferiore (VA) Italy - via Papa Paolo VI, 5 - Tel. +39 0331 827.717 - Fax. +39 0331 827.750ServiceHotline+390331866.427-email:macchi@macchi.it-www.macchi.it