Combating static couldn’t be any easier with the use of static control equipment and a designated static controlled room. There are several accepted methods you can use to combat static during printing and plastics operations – ionisation being one of these. In this article, we will be focusing on ionisation and several other anti-static control methods, exploring how it can help to reduce or eliminate static in the printing and plastics industries.
Static electricity is a problem in many production processes when there are non-conductive materials such as different plastics, types of paper or wood and textile being processed. Especially difficult during the winter months when humidity levels are low, static can cause numerous problems in many processes like printing or a coating process. It is essential for static to be eliminated or, at least, reduced for safety and quality purpose. The removal of static can be of major importance if production processes work with insulative (non-conductive) materials.
A static charge remover can be used to solve the problems. There are many different static eliminators available in the market. The way the static eliminator operates or the place where it can be mounted or put is determinantal on the type you opt for. Bondline has a range of ESD products which are used in order to support any production process where static can be a problem.
The most recommended method of static control, and most widely used, is ionisation. Ionisation is the process by which air molecules are broken down into ions of both positive and negative charges (an ion is an atom or molecule which is electrically unbalanced). Air Ionisation systems work by flooding the atmosphere with positive and negative ions. When the ionised air comes in contact with a charged surface, the surface attracts ions of the opposite polarity. As a result the static electricity that has built up on products and equipment is neutralised.
Ionisers are made up of either a single emitter point (guns) or multiple emitter points (blowers). An emitter point is a metal needle that conducts charge. When the voltage from an electrical power source is applied to an ioniser’s emitter point, it creates an electric field or “corona” around the emitter. This corona of ions then interacts with electrons in nearby gas molecules. With the use of alternating current (AC) or direct current (DC) the ionised air is pushed by the motor in the ioniser towards the surface you are aiming it at.
1) Induction: Ionisation through induction involves bringing electrically grounded sharp metal points, usually made of copper or brass, in close proximity to a moving static-laden surface. An interaction between the electrostatic field, always present with static electricity and the sharp end of the metal points, initiate, and maintain an ionisation process in the surrounding air, thus acting to neutralise the static charges. The most commonly used induction type device is copper static eliminating tinsel. The three most evident limitations of induction type devices are:
a) The device must be kept in close proximity, usually within 1/4“, to the static laden surface in order to be most effective,
b) The inductive device requires a threshold voltage (usually considered to be approximately 2000 volts) to maintain the ionisation process. Below this threshold voltage the induction device will cease to function and, thus, will not reduce the static charge below this point. (Note: Threshold voltages will change with factors such as changes in humidity and temperature),
c) In the case of copper tinsel and similar devices, oxidation, dust, ink, and similar contaminates require it to be replaced periodically. On the other hand, induction devices are a low-cost method of static elimination and in many applications can reduce static charges to an acceptable level.
2) Radioactive: Radioactive static eliminators use low grade radioactive elements, usually polonium 210, to create a static eliminating ion field. As a result of the decaying radioactive elements in the static eliminator, high speed alpha particles are emitted, bombarding surrounding air molecules, creating both positive and negative ions.
Radioactive eliminators are most commonly used where a completely self-contained device (one without external power cables or power supply) is desirable or for explosive atmosphere or for applications that require a light free device (such as photographic film processing).
3) Electrically Activated: Electrically activated static eliminators operate at voltages from about 1500 volts to 18,000 volts. Ionisation is achieved by impressing high voltage on the sharp points of one or more metal emitters that are in close proximity to electrically grounded targets or electrodes. Because of the difference in electrical potential between the emitter and grounded targets, the air surrounding the emitters breaks down into both positive and negative ions.
Electrically activated eliminators can be found in several different configurations including: Static Eliminating Bars, Ionising Air Guns, Air Nozzle, and Static Eliminating Blowers (fans). Although competitively manufactured electrically activated eliminators vary in their performance, a well-designed eliminator should be able to eliminate static charges at any level or speed that is typical in the printing industry. A good criterion for evaluating the performance of an electrical eliminator or radioactive eliminator is its effective gap range (gap is the distance from the emitters to the static laden surface). The higher the gap range the higher the output of the eliminator.
As we can see from above, ionisers are a great solution to static controI. Despite this, ionisers should be used in accordance with the right grounding equipment such as wrist straps, coil cords and table mats to effectively work. Think of ionisers this way – the wrist strap, cord and matting are the layers of the cake (the core components to static control which everyone needs). Then to top these layers off, we add the icing – ionisation! (The final part we need for ultimate ESD protection).
When selecting an ioniser, there are many different factors you will need to consider before choosing one. Remember, there is no right or wrong ioniser to use. The wide variety of ionisers allows you to select one best for your needs.
A few things you should consider before making any decisions:
Depending on the work your operators are doing, one type/configuration of ioniser may have more benefits than another. For example, if your workspace is limited, an overhead ioniser might be the answer. On the other hand, if there is an issue with debris and dust in your operation, then a compressed air ioniser would be better suited.
Does your ioniser need to be made of stainless steel? Does it need to use zero-volt technology? Do you need a cost-effective ioniser with built-in emitter point cleaners? Do activities need to be monitored and recorded with some sort of software? Make a list of what is an absolute must and where you can compromise – see next point.
Even though this one is the last one in this list, it by no means is the least important factor. Quite contrary, it’s generally one of the main considerations when investing in an ioniser. However, it kind of goes hand in hand with the previous 2 points. So, you may have to make compromises, e.g. on the features, depending on what monies are available.
Uncontrolled static electricity has been, and is, a costly problem in many industries, including the printing and plastics industries. A problem that printers, engineers, and management need to be aware of. And once recognised, steps should be taken to incorporate proven methods of static control, if the goals of higher quality, production, and profits are to be achieved. We hope this article has shed some light on the solutions and methods to reduce or eliminate this static-related issue.
If you are looking to control static in your printing / plastics business, Bondline has everything you need to establish your static-free area. From ionisation to grounding solutions, Bondline’s products can help to mitigate the risk of static effects and damage.
Get in touch today with one of our expert sales members who can discuss the best ionisation solutions for you. You can call us on 01793 511000 or even leave us an email at firstname.lastname@example.org.
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