Static Control & Web Cleaning
Static charges: production mishaps and product misbehaviour
R
educing downtime and maximising productivity is a key aim for any converter, but the generation of static
on production lines poses a major threat to this. With today’s high-speed webs, fast- paced operations and a variety of lightweight materials being processed, it’s important to understand why this phenomenon happens, and how to prevent it from impacting on business operations. In many cases static charges will slowly
decrease over a period of time, but in fast- moving business environments this is less than ideal. Some materials, such as plastic, have very high resistivities which allows them to maintain static charges for long periods of time. Static charges are generated when an
external force causes an electrical charge to move from one material to another, leaving one positively charged and the other negatively charged. If one of the materials is conductive, it won’t hold the charge, but if the material is non-conductive, the charge is unable to move across the surface, creating a static “pool” of electrical charges. The size of the charge is determined by
the force of the friction, speed, pressure and separation, with increased force and faster processes leading to larger charges. The type of material involved, humidity levels in the facility, repetition of actions (friction or separation, for example), and changes in temperature can all influence the generation and maintenance of a static charge. The impact of uncontrolled static can
result in distorted finished products, out of register printed products or damaged extruded films – this can lead to increased product rejections and wastage. Machinery on the production line can also be affected – dust attraction can lead to blockages – increasing downtime and maintenance costs. These issues are of particular significance when product cleanliness is essential to the end use for the web material: food packaging for example, or packaging for medical supplies. Static control technology has advanced rapidly in recent years and the latest static control and web cleaning systems play a vital role in ensuring that converters have fluid and uninterrupted production.
32 March 2020
STATIC CONTROL SOLUTIONS Active static control provides the most effective means of neutralising charges. This technology uses ionisation, or ionised air, whereby a voltage is fed to an array of emitter pins mounted on an ionising bar, creating a high-energy “cloud” of positive and negative ions. Any statically-charged surface, of either polarity, passing close to the cloud is quickly neutralised. Today’s pulsed DC systems come in a
variety of forms to suit short, medium and long range applications. Built to last, ionisation bars found across many converting lines are now more resilient to build up and even provide feedback on their performance – in fact, the most advanced static control technology now incorporates automation, allowing operators to see the performance information of the static control devices on a local user-friendly display, such as a mobile phone, tablet, touch screen or monitor, and make
instantaneous
amends to the operating settings. These devices can be connected to static bar
controllers, which
alter the level of ionisation supplied from the static bar. While static control can help deter
issues surrounding product quality and staff safety, these devices alone will not solve all problems associated with a statically charged web.
WEB CLEANERS The introduction of effective web cleaning systems alongside static control increases productivity by reducing maintenance downtime and minimising the waste caused by sub-quality product. A contact cleaning system, such as
Meech’s TakCleanTM (tacky roller), is employed mostly in the print and label printing sectors. The design of the system allows operators
to see the contamination being collected on a second adhesive roll, which removes debris from the first roll that makes contact with the web surface. Due to the limited life- span of adhesive rolls, contact web cleaning may not be suitable for more heavily contaminated substrate materials. Non-contact or vacuum contact cleaners are unaffected by contamination levels. These systems are suitable for a variety of surfaces and with no consumables required for operation, running costs are reduced. CyCleanTM, Meech’s non-contact web cleaning system, is capable of removing contamination to below 1 micron and incorporates fluid dynamic principles to deliver higher levels of cleanliness. Using a blow-and-vacuum system, the CyCleanTM produces a powerful blowing airflow on either side of the web to strip the boundary layer and all traces of contamination from the web’s surface. The presence of vacuum airflows ensure that turbulent air is captured and subsequently removed.
CONCLUSION Determining which types of static control and web cleaning equipment is most appropriate will require an assessment of current converting machinery and production demands. It is vital that any ionisation bars and web cleaners are able to fit seamlessly into the production line, keep up the speed of production and be fitting with the budget available. Assessments should also be performed first to help determine the levels of static and contamination that are currently being generated on the line – only then can the appropriate equipment be selected.
meech.com
convertermag.com
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