Static Electricity: Causes and Cures in Web Converting Presented By: Matt Fyffe

Transcription

1 Static Electricity: Causes and Cures in Web Converting Presented By: Matt Fyffe Product shown in this document may be covered by one or more patents, patents applied for and/or registered designs and/or trade marks. For further information please refer to our Head Office or visit Meech international UK: Hungary: USA: China: Belgium: web: Meech Static Eliminators Ltd 2010

2 What is Static Electricity? Electrical imbalance of charge can exist on insulators & isolated conductors. Insulator Isolated Conductor

3 What Causes Static? Friction between materials: Separation of materials:

4 Not +ve or ve... but size does matter! The Polarity of the charge is not very important. You can not tell the difference. It is the size of the static charge that is important. The larger the charge the greater the problem it will cause.

5 What factors affect the size? Force/Speed faster, harder processes increase the charge Repetition causes further build-up Heat - heating and cooling can leave an object charged Humidity low humidity allows high charges to remain for long periods Type of Material some materials charge very easily (i.e.: PVC film)

6 Triboelectric Series Materials above the arrow will naturally charge positive. The materials below the arrow will naturally charge negative. When contact and friction is generated between different materials the central point shown by the arrow may change relevant to the type of materials

7 Triboelectric Series This example shows polyester film contacting a silicon coated roller. When measured immediately before and after the silicon roller the negative charge on the polyester will reduce or change to positive. Polyester Film Silicon coated roller ( + ) ( - )

8 Problems Caused by Static in Industry Problems with static electricity in the converting industries are numerous. Processes where static can be an issue include film sheeting and slitting, wind and rewind stations as well as printing. The primary problems resulting from high static charge are: Process Control and Quality Problems Dust Attraction and Contamination Operator/Personnel Shocks Possible Fires and Explosions

9 Methods of Elimination Passive Eliminators Nuclear Eliminators Polonium 210 AC Eliminators Pulsed DC Eliminators and Static Generation

10 Passive Eliminators

11 Nuclear Eliminators Polonium 210

12 AC Eliminators

13 Pulsed DC Eliminators (Mid & Long Range)

14 Static Eliminators - Comparison Passive Eliminators Advantages Disadvantages Low Cost Limited Capabilities No External Power Source Wear Part/Flaking Low Maintenance Nuclear Eliminators - Polonium 210 Advantages Disadvantages Perfectly Balanced Annual Lease/Cost Ideal for Hazardous Locations Paperwork Requirements No External Power Source Low Maintenance Ease of Installation AC Eliminators Advantages Disadvantages Low Cost Limited Range w/o Air Power/Performance Limited Load Capability Ease of Installation Maintenance Required Multiple Bars on Power Supply Pulsed DC Eliminators Advantages Disadvantages Long Range w/o Air Requires Education Reliability Longer Set Up Low Maintenance Increased Cost Adjustability/Customization Feedback Capabilities Internal or External Power Supply Very Flexible

15 Operating Distances Compressed Air Driven Static Control Close Range Static Control Mid Range Static Control DC Nozzle AC Air Curtain Standard AC Bar Long-Range AC Bar Mid Range DC Bar Pulsed DC Bar Long Range Static Control Pulsed DC Bar with Air Boost AC Blower Install at optimal distance where possible ¼ * Not to scale. Actual positioning will depend on the type of application.

16 Positioning Free air is required on opposite sides of the target material, not a roller or solid object

17 Positioning Avoid proximity to grounded parts of machinery as this will distort the corona and reduce its efficiency If bars are needed on both sides of the material, they should be staggered

18 Measuring Static Meters measure actual surface charge Ion Sensors maintenance tools for testing ionizers Charge Decay Monitors measure decay times of ionizers Benchtop & Handheld Surface Resistance Meters measure capability to hold a charge AC Sensor Pen down and dirty way to test for voltage

19 Applications Winding Short Range

20 Applications Winding Mid Range

21 Applications Winding Long Range

22 Applications Turret Winder

23 Applications Slitting

24 Applications Laminating

25 Applications Coating

26 Static Generation Static generation describes a method for creating a controlled static charge on a non-conductive material that will allow a sound, but temporary adhesion between surfaces with charges of opposite polarity.

27 Applications Static Generation Film on to Roll Cores

28 Applications Static Generation Sheet Lamination

29 Web Cleaning Systems Web cleaning systems provide effective solutions to problems such as: Dirty webs causing loss of profit and customer dissatisfaction Excessive downtime on printing presses Frequent blanket washing High reject rates in laminating or coating processes Unacceptable quality in pharmaceutical or food packaging Poor print quality

30 Web Cleaning Systems Tacky Roll Cleaner Contact Web Cleaner Non Contact Web Cleaner

31 Tacky Roll Contact Web Cleaners How it works Elastomer cleaning rollers contact the full width of the web with even pressure. Dry, unbonded contamination is lifted from the web surface. Pneumatics hold the adhesive roller in contact with the elastomer roller. Contamination is transferred from the surface of the elastomer roller to the adhesive roller where it is trapped. Any static charge present on the web is neutralised on exit from the web cleaner; minimising the risk of statically attracted recontamination.

32 Vacuum Based Contact Web Cleaners How it works Static Neutralization Breaks the bond between dust particles and web, leaving the web neutral after cleaning. Breaking boundary layer Brushes destroy boundary layer on fast moving webs and dislodge any physically attached particles. Powerful Vacuum Extremely high speed airflow through faceplate is very turbulent. The turbulence allows removal of very small particles.

33 Non-Contact Web Cleaners How it works The web passes through a cloud of ionization on entry to the cleaning, which neutralizes any static charges. The web is then subject to a force of turbulent air created by the blowing and vacuum airflows within the head unit. High frequency micro-movements of the web are created by the turbulent air. The combination of the high frequency micro-movements and turbulent air shatters the web boundary air layer, releasing the contamination into the vacuum airflows. As the web exits the head, it passes through a second cloud of ionization to prevent recontamination of the web.

34 Web Cleaners - Comparison Tacky Roll Contact System Advantages Disadvantages Low Cost 750'/min max speed Proven to 0.5 micron Not suited for heavy contamination Compact Size Ongoing consumable cost Ease of install Suitable for sensitive materials Vacuum Based Contact System Advantages Disadvantages Excellent for high contamination Not suitable for sensitive materials Suited for high speed applications Requires installation space for fan Suited for paper and board Ease of installation Proven to 5 micron cleaning Suitable for wide webs Non-Contact System Advantages Disadvantages Suitable for all materials Double sided only Proven to 0.5 micron 120" max web width Compact size Ducting requirements Low and high end applications Initial Installation Time

35 Thank you