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For clarification: Electrostatic(ESP) nano, micro-perforations

are statistically irregularly distrib-uted, varying by size by up to 40%,and analogically, under laser ormicro-, macro-mechanical perfora-tions, evenly arranged in diametersof about the same in size, at bestnon-inclined holes and rows ofholes of varied arrangements.

Although invisible to the humaneye, electrostatic – ESP – nano ormicro-perforations may be arrang-ed in areas or zones at specific dist-ances within the web. The sizes ofthe holes can range from 1 to 100microns in diameter and hole se-quences from 1.5 to 16 millionpores per second. Arrangements ofpores in zones are usually producedin widths of 2–6 mm and at poredensities of 15–250 pores per sqcm,however the perforation of pores inareas produces pore densities of up

Micro-perforation ofrunning webs

WERNER GROSSE

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Material webs such as those used for cigarette-, mouthpiece tippingpaper, filter-coated, special, bag or packing paper webs, bonded fab-rics, spun bonded non-woven, technical textiles, fabrics, laminate, etcwith base weights from 20 gsm to up to 150 gsm, up to 10 gsm LPDEcoating films, are perforated electrostatically (ESP) by nano, micro,laser, mechanical micro or macro for different application purposes.

IPM (International Perforation Manage-ment). www.microperforation.com

to 2 million pores per m2. ESP per-forations allow for porosity levelsfrom 80 to 2500 CU (Coresta Unitsml/cm2/min), up to 50 perforationzones across the web, web widthsfrom 100 to 2000 mm at web speedsof up to 500 m/min, depending onthe material porosity and consist-ency in relation to its ability to per-forate (figure 1, 2, 3 and 4).

Laser perforation

It is possible to perforate hole sizesof 60–200 micron at a hole densitytypically of 10–30 holes per cmlength, hole sequences from100.000 to 300.000 holes per sec-ond at a maximum of 16 puncturedperforation rows by laser distrib-uted over the width of the web withtraditional systems or machines onthe market using pulsed or enlargedand focussed laser beams. Porosity

levels range from 100 to 3000 CU,normally with web widths from 100to 300 mm at web speeds of up to600 m/min, depending on the po-rosity and material consistency inrelation to its ability to perforate(figure 5, 6, 7 and 8).

IPM is responsible for the devel-opment of the laser perforationtechnology LPM-1 which is patentprotected and operates with quad-ruple CO2 laser beam inputs of up to8 kW total optical power through toa dual jumbo beam multiplexerwhich can generate up to 200 indi-vidual laser perforation lines/rowsacross the web, combines automaticlaser perforation head positioning,focus setting, web speeds up to 400m/min, web widths up to 2000 mm,up to 4,000.000 holes per second,jumbo-roll-by-roll production, au-tomatic perforation head position-ing, optical online permeability andperforation line control, porosityfeedback and other features. Eachlaser perforation line can rangefrom 100 to 1000 CU.

The concept of a dual jumbolaser beam multiplexer opens upmany possibilities for use in otherindustry applications and process-ing such as cutting, cut-offs, weld-ing, surface finishing, drilling,sharpening, polishing, forming,surface treatment, roughness im-provement, etc. Each of the 200single perforation heads can be po-sitioned across the running web orstatic positioned material. The auto-mated processes, equipment anddevices open up completely newpossibilities in industry, science,military or space laser application.

A new patent pending MicroLaser Line perforation technologyMLL-1 generates sinus waves, zig-zags or other kinds of perforationdesigns as multiple pairs of microlaser lines in the web or materialdirection. This can be used for tip-ping cigarettes, packaging or otherkind of paper webs. These specialfeatures of the micro laser line per-foration technology enables funda-mental new product characteristicsto be achieved in perforationscripts, e.g. for mouthpieces withtipping paper on cigarette filters,product identification with visibleTop row (from left):

Figure 1 and 2.

Bottom row (from left):Figure 3 and 4.

See us in Hall 4 Booth A40

Mumbai – Indiawww.kohli.orge-mail: kohli@kohli.org

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FLEXO & GRAVURE ASIA 1-2008 17

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perforation holes as the brand nameor company logo, anti counterfeit-ing designs, perforation crypto-grams, etc. Also the process can beused in other material, industry andapplication fields (figure 9).

Controlled ventilationof filter cigarettes

Electrostatic perforation has beenused for more then 25 years for ven-tilation of non-filter or filter ciga-rettes to create a direct and guidedair bypass. For this purpose, ciga-rette paper for some non filter ciga-rettes and almost every kind of filtercigarettes and their tipping papersare electrostaticaly perforated off-line by ESP in zones from 2.0–6.0mm or with online or offline laserperforation rows in order to reducethe harmful substances such asnicotine and condensates to allow-ed values. Another effect is the pos-sibility of guiding and controllingthe ventilation degree of cigarettes.

New product propertieswith ESPnano sub-micro perforation

One of the most important conceptswhich can be applied to many appli-cations and products containingbonded fabrics, bag or packagingpapers, non-woven, etc with gas orsteam permeability but water im-permeability can be found at theapplication stage of the electrostaticnano micro-perforation technol-ogy.

This means that pore sizes from0.2 up to 10 micron diameter by upto 5 million/m2 are required. This isbecause of the greater surface ten-sion of water which impedes per-meation through the relativelysmall nano or micro pores. Theseand other physical advantages ofthe relatively small pores requiresthe application of the ESP perfora-tion method because alternativeperforation or processes would notbe feasible, too expensive or simplyuneconomical and would not leadto a successful application.

To meet the new ESP require-ments, IPM has developed and pat-ented electronic switching circuitswhich work as upward converterswith IGBT (insulated-gate bipolartransistor), MOSFET (metal–oxide–semiconductor field-effect transis-tor) or HVFET (high-voltage field

effect transistor) to produce powerpulses from 1 up to 15 micro-sec-onds, high current peaks up to 300Amps, base frequencies up to 200kHz on ferrite transformers to gen-erate up to 50 kVss at each sparkingelectrode.

Optical online permeabilityor porosity control

Since naturally porous web materi-als or web materials to be perforatedare processed at speeds up to 600 m/min and web widths up to 2000 mm,

using a pneumatic porosity measur-ing device, taking measurementswhilst touching the web are verydifficult. Further difficulties of thissystem include the disadvantages ofincreasing web tension, materialabrasion, folding, leakage at themeasuring head, impurities, non-

Figure 9 (left),figure 10 (right).

From left:Figure 5, 6, 7 and 8.

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18 FLEXO & GRAVURE ASIA 1-2008

linear processing and calibrationproblems.

Thus, optical measurement tech-niques offer a better way for meas-uring the pneumatic static perme-ability of naturally porous or nano-,micro- or macro-perforated webs.The conditions mentioned abovecan be easily met by using opticalporosity measuring technologythanks to the previously mentionedprocessing and online control, ex-tremely small pore dimensions,relatively high track speeds and ahigh rate of repetition. Completelyindependent from the basic mate-rial information such as consist-ency, thickness, weight, colouring,formation, smoothness, brightness,opacity and other influences can bemeasured.

IPM has developed a number ofnew, patent pending, stationaryand transverse optical measure-ment processes and systems whichwork with multiple colour sensors,precision line lasers, at scanningspeeds from 20–200 mm/second,

porosity ranges from 80 up to 3000CU, perforation line detection of 0.1mm, nano micro holes from 0.5 upto 200 micron in diameter and up to250 holes/cm2 to determine data inreal time. An internal sensor DSPcontroller unit determines each po-rosity level integrally in order toidentify each perforation profileand their colour envelope curves.

Thus direct feedback into the

perforation system makes it possi-ble to compensate for any changesin porosity and perforation locationso that each jumbo production rollup to 25,000 meters as well single orquadruple bobbin sets can be pro-duced and quality controlled with-out intermediate stops and certifi-cated for quantity and quality (fig-ure 10).

Future prospects

The electrostatic ESP nano- ormicro-perforation is usually useddepending on the quality of finepaper, packaging webs, bondedfabrics, non-woven, filter paper,bag or force paper as well as specialpaper webs of most varied types. Itis also used especially for addition-ally treating coarse materials whenaiming for achieving special char-acteristics which for physical orprocess reasons cannot be achievedby other process technologies.

Our highly modern, industriallyapproved ESP perforation technol-ogy operating reliably 24/7 is ableto be integrated into existing re-winding systems or other produc-tion processes or lines. Also, theycan be used as completely inde-pendent perforation units. Newranges of applications will be madeavailable as new products with spe-cial features are developed (figure11 and 12). ■

Figure 11 (left),figure 12 (right).

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Meet withFLEXO & GRAVURE ASIA

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• Compact design• Quick Change pull-out / push-in cartridge • Single-sided or double-sided treatment• Treating width from 0.5-8 metres• Easy film thread-up, maintenance and cleaning

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