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wilkinson-pic.jpgWelcome to 'Ask The Expert'. This page is moderated by industry consultant, Steve Wilkinson.This page featuresthe answers to your questions.Our visitorscan also post comments to these questions/answers as well. You can learn more about Steve's background and our 'Ask The Expert' pageby Clicking Here.

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ASK-THE-EXPERT


October 20, 2014
We use a variety of Dyne pens to measure the Dyne level of our films. What are the pros and cons of using this method of measurement?

     Most companies use dyne pens as a method to evaluate the treatment ( dyne ) levels of their materials because they are relatively cheap and easy for most operators to use. This does mean that the results can be very subjective dependent on the interpretation of each peron's observations and can vary dependent on the application rate and pressure that is applied.
     Great care must be taken not to contaminate the substrate to be tested or the pen itself with such elements as dust, wax finger prints, water and plasticizers. Water is a particular problem as every surface will have absorbed some water and like all of the other contaminents mentioned will cause incorrect readings.
     All pens have a mix of two liquids to give the different dyne levels so once opened the liquids will begin to evaporate and as one usually evaporates faster
than another if the top is not kept on the pen when not in use it will quickly become inaccurate. On plastic film static electricity can also be a problem as this will also
affect the wettability of the dyne fluid and as a result can result in inaccurate results.
     Surface roughness of a material can and will affect the de-wetting of the pen fluids.
     The truth is all dyne levels are approximations so at least three test lines should be drawn down on the material with the first two usually being ignored to ensure
that any contaminants have been flushed from the prior use of the pen.

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September 25, 2014
What matters more the material that a doctor blade is made from or its thickness?

     There is no doubt that choosing the correct blade material to suit your specific print application is very critical. Choose a material that is too soft and you will have to replace it almost every shift, too hard and it may damage your anilox. And if the material is not resistant to the ink or coatings that you are using then it may be chemically attacked and simply corrode.

     All that said, if your blade is not rigid enough it will fold over the first time your operator applies too much pressure between the blade and the anilox. Blades that are too thin will also have a tendency to develop a wave in them even with careful installation so will be unable to wipe your anilox evenly across the full face of your roll. This is particularly prevelant in wider web machines. Even when the recommended blade thickness is used many need a back-up material to give it further rigidity and support. If a blade bends to the point that you are no longer wiping with its edge
but the back of the blade then you have really lost all control of your wiping action and will potentially cause serious damage to your anilox.

     So to some extent blade thickness may initially have it over the material but if you want consistent wiping of your anilox throughout your entire print run you had better make sure you have the right material as well.

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August 18, 2014
What is the best method to analyze our anilox cells to determine their condition and current volume capacity?

     A quick visual inspection can give you a very good idea of the general condition of any anilox. Look for score lines, dings, chipping around the edge of the roll and of course general contamination.

     Any roll with a significant number of score lines, mechanical impact damage or chipping around its edge is likely to need relacement sooner rather than later. In regard to cell condition and current volume capacity this cannot be done with the naked eye and requires some form of magnification in the form of a roll scope or interferometry device.

     The roll scope is the most common but is dependent very much on the operator skill and can be very subjective. That said, in the hands of an experienced operator it can be reasonably consistent provided the scope is well maintained and calibrated on a  regular basis. It does allow for pictures to be taken of the cells but requires a manual calculation by the operator to determine the cell count and to calculate a theoretical volume.

     There are also a number of liquid volume test methods to help determine volume but they again require considerable operator expertise and can have quite a wide
range of accuracy. Interferometry is probably the most accurate but again requires significant operator training, regular calibration and is a
significant investment but is capable of providing very accurate data and pictures in 3D showing the exact cell structuure, line count and volume. It is up to each printer to determine how much information they require, which will determine the level of investment necessary.

     You can of course ask your roll supplier to carry out a regular inspection of your anilox and provide you with the same information but there is always likely to be some bias in regard to the information given so you should always review the data provided and apply some common sense yourself, particularly when it comes time to replacing your rolls.

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May 20, 2014
Digital printing appears to be making some inroads into short print runs. Is there any way we can combat this with Flexo?

     One of the most interesting developments in Flexo is the use of process colors to create spot colors. While not a new concept, it has really only been the relatively recent introduction of new software packages that can convert spot colors into process files that allow for brand spot colors to be reproduced as a process set instead of the conventional
special spot colors.

     Of particular interest is that of creating seven instead of four process colors that gives the printer the ability
to reproduce a vast number of pantone colors, which reduces the number of colors needed, the number of plates required, the amount of ink required, and the amount of time required to set up and run. All of this makes for a more affordable, quicker way of producing even very short runs, making flexo just as competitive if not more competitive than digitally printed short runs.

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April 22, 2014
How do we reduce vibration and bounce when printing multiple images across our wide web press?
     This can be a challenge for most printers if you are using a pin registration system or are producing plates with a straight cut across the width of your plate. The solution, while simple, can be a challenge for printers using the above methods of mounting their plates as it entails stepping the image either up and down or stepping the image progressively down as you step and repeat it across the width of your web. This will then require you to cut your plates in the same stepped manner and can make mounting quite a challenge and eliminates the option of using a conventional pinned system.
     The reason for the stepping of the image is to minimize the possibility of a continous gap occuring on any or all of the colors across the web. This means that some part of the image should be in contact with the web, which in turn will be pressed against the impression roll. This in turn will reduce the bounce and hence vibration that can often be seen and even heard at press side when the printed edge finishes in a straight line.
     One method of overcoming these mounting challenges is to have the design engraved as a continous engraving, i.e. ITR, which can be produced in elastomer by direct laser ablation or as thermally ablated or chemically washed continous polymer sleeves.

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March 20, 2014
Our plate supplier has expressed that he is concerned about the amount of ozone in our plant but did not explain why. Can you tell me what this has to do with the plates that he supplies us?
     Ozone is generated by electrical motors and corona treater equipment and is a form of oxygen. The reason your plate supplier is concerned is that ozone will attack all forms of plates and will eventually cause cracking in the plate surface, which will obviously make them unusable. For this reason you should store plates well away from areas that ozone may be generated as well as away from any direct UV such as sunlight, which will have a similar effect.

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February 27, 2014
Our anilox supplier has offered to audit our anilox. What information should we expect from this?
     The first thing to remember about any anilox audit is that it's a "snapshot" in time, in that the moment it is done it is already out of date assuming that you continue to use your anilox.
     Fundamental information that you would expect from any audit would be anilox engraving, volume, and any obvious damage such as scoring, mechanical impact damage, chipping, general cell condition, and overall cleanliness. You will be surprised how many rolls are sent out for refurbishment when they are simply plugged with ink or coatings so if you are advised to replace an anilox that does not have any obvious damage,scoring or chipping please make sure it has been mechanically cleaned and its volume rechecked before making the final decision to have it reworked.
     Remember about the "snapshot" in time comment so you need to act on the audit information immediately. Failure to do so really minimizes the benefit of the audit.

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February 10, 2014
We have recently purchased a new press that uses anilox and plate sleeves, what do we need to do to keep them in good condition?

     The first thing to do is to make sure that every manager, supervisor and operator understands how much they cost to purchase and the cost of replacement. In my experience most personnel at all levels view sleeves as a disposable items, which ultimately they may be, but if properly cared for can give many years of
service.

     You mentioned both types of sleeves, that being anilox and plate sleeve. Both, however, cannot function without the appropriate air mandrel that you will apply compressed air into via an air inlet nipple either through the header of the mandrel or through the journal. The air escapes through a series of small holes that are drilled around the circumference of the mandrel usually at the end nearest the inlet and also in the center of the mandrel face. This will create an air layer that allows the sleeves to be slid onto the mandrel core before being locked in place when the air is stopped and the sleeve contracts back to its original diameter.

     So just as you have recognized the importance keeping the sleeves in good condition it is just as important, if not more, to protect your air mandrel from any form of surface scratches, dings, or contamination. Failure to protect the surface of the mandrel will result in sleeves sticking to the core resulting in the operators inability to push them along the full face of the mandrel or indeed to be able to easily remove them.

     Never use greater air pressure than recommended by the supplier as this can distort thinner walled sleeves and can result in catastrophic failure of the air mandrel. Always ensure the compressed air is dry and oil free as any contamination can cause rusting of the inside of the mandrel, which can leak onto the surface of the mandrel and the inside of the sleeve.This can make removal of the sleeve very difficult if not impossible if moisture or staining does build up on the end of the mandrel.

     Each sleeve type has its own unique features and weaknesses but both are prone to premature failure due to mis-handling and lack of good housekeeping. In the case of the anilox sleeve they are generally the more complex structure with an inner composite tube, flexible inner core and an outer aluminum shell. It is the outer shell that is ceramic coated and laser engraved. The key to remember is that while ceramic is very abrasive resistant, they are very susceptable
to impact damage. For this reason great care must be taken not to bump the sleeve into anything or to drop any heavy or sharp objects onto it as the ceramic will invariably crack and come away from the sleeve's outer core.

     You must store the anilox sleeve carefully at all times and take great care never to allow them to be dropped on the ends or knocked over, which will result in distortion of the sleeve and make it impossible to be slid onto its mandrel. The inside must be kept clean at all times and again great care must be taken to prevent scratching, scoring or any cuts to the inside of the sleeve. This applies to plate sleeves equally as much. You can store both types of sleeves vertically or horizontally but they must not be allowed to rest against another sleeve or rack support and when stored horizontally plastic tubing should be used if you choose to support them through the middle. If you prefer to store them in boxes, you shoud use cones placed in both ends if you choose to so that they again do not rest on the face of the sleeve.

     In the case of plate sleeves, try to minimze the amount of cutting of the backing tape to help reduce cutting of the sleeve outer face, which can case them to split if cut too deeply or at least present a very rough surface to mount future plates onto.
While plate sleeves are a much simpler construction than an anilox sleeve they should always be treated with great care and kept as clean as possible at all times

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January 14, 2014
Not only are there many suppliers of printing plates, the plates also vary in material, durometer and thickness. How do we determine what is best for us?

     Although all plates have the same function, to pick up and transfer your ink or coating to your substrate, you must choose carefully to ensure you achieve a consistent ink or coating transfer for at least the length of your print run.  Some fundamental decisions are easy such as selecting a plate that will suit your ink or coating chemistry i.e. water, UV or solvent.

     Next you need to determine what thickness you need based on the undercut of your print cylinder and thickness of mounting tape you intend to use.

     Determining what durometer you need is a little more subjective, but a general rule of thumb is the smoother your substrate the harder the plate. But this is also affected by the hardness of your mounting tape, as well.

     Another major factor is whether you are still using film to expose the image to the plate or using more modern direct laser imaging. If you are purchasing your plates this is not really a factor, but whether you purchase or make your own, choosing a plate that is water, solvent or thermal development clearly has a potential environmental impact and should be considered carefully.

     While less of a consideration today the plate material can also be molded rubber, although the majority of choices are varieties of photopolymer materials. So what works best for you? The decision is obviously helped by consulting with a variety of suppliers but is only really determined from experimentation by yourself with various plates on various substrates under a variety of conditions. A final choice comes from how sophisticated your graphics are, which again your plate material or imaged plate supplier can help you with.

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November 25, 2013
My prepress supplier said he could enhance our color gamut with GCR , what is this?

     G.C.R. is an acronym for Gray Component Replacement and when applied by an experienced prepress provider can greatly increase the gamut of color and hue that a printer can achieve. This removes most of the gray type areas from each color and adds it to the black plate, which will help maintain the definition of the original image and at the same time gives the operator much wider latitude to achieve strong vibrant colors. This in effect removes neutrals that were once three colors and puts them all onto the black printer, which will help maintain hues and color throughout the run.

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October 29, 2013
What are the benefits of helical and spur gears?

      The majority of gears you generally see are spur gears. They are easy to identify as the teeth of the spur gear project radially and are parallel to the axis of the gear, with the teeth being exactly perpendicular to its flat faces. They are simple to make and are actually more efficient if compared to a helical gear of the same size. The efficiency of the helical gear is less because helical gear trains have sliding contacts between the teeth that in turn produces axial thrust of the gear shaft and generates more heat, which causes it to lose some of its efficiency. The teeth of helical gears are not parallel to the axis of the gear, and are set at an angle. Since the surface that the teeth are made is cylindrical the teeth create a helix shape. Because the teeth of helical gears engage a little at a time they create much less noise and can be used to transfer power between non parallel shafts. Helical gears can handle more load than spur gears because a helical tooth is larger due to its diagonal position. When you need a simple design, where speeds are lower and noise does not matter, then spur gears are ideal. If you want a quieter machine, with higher speeds and accept a more complex design then helical is the better choice.

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October 18, 2013
What can we do to reduce pollution from our Flexo facility?

     Preventing pollution in and around any manufacturing facility is a legal requirement, so trying to prevent it occurring in the first place should be your first goal. You should emphasize the importance to your operators and managers alike that keeping all work areas clean by minimizing spillages and making sure they are cleaned up immediately is a simple but effective way of reducing a great deal of pollution in the immediate area of the press room.

     Always calculate as accurately as possible the amount of materials you will need to produce a job as leftovers often end up not getting used, all of which must be disposed of at some point. There are many less toxic solutions available and if you are not sure, ask your supplier.

     When using any materials, try to use the oldest first so that they do not become obsolete again, resulting in the need to dispose of them. For product that has specific disposal requirements, always consult your supplier or local Environmental department. Always store materials and solutions and provide adequate containment to ensure that any leakage or other waste cannot get into the environment.

     Washable rags are a simple way of reducing waste paper having to be disposed of and, where possible, using water or UV inks will dramatically reduce your solvent emissions. For any waste that you do generate at least take the time to segregate them to make them easier to recycle.

     So bottom line: prevention is far better than treating or disposing of hazardous waste so try to determine if you can use an alternative, less hazardous, product or at least limit the use of more hazardous items that you have no option to use because of their unique features. Even if it is customer specified, if you can find a safer, less hazardous, product they may be willing to allow this to be used. The most critical factor is to involve everyone in your company, your suppliers and as just mentioned even your customers if you are to reduce your potential environmental impact.

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September 12, 2013
We seem to be hearing more about LED UV cured inks being the future for many markets. Do you agree with this and what are its pros and cons verses conventional UV inks?

     There is no doubt that LED UV curing systems offer some tremendous advantages with their ability to switch on and off and hence no need to warm up or cool down, giving the printer tremendous productivity advantages. This in turn leads to much longer lamp life, (Potentially 10 x longer than typical mercury lamps), and considerable less maintenance needs, as they do not need shutters or fans.  LED cured inks do have to be specially formulated and just like the conversion from water to UV will take time for the variety and volume to become available on a global basis.

     Another major advantage of LED technology is its much lower energy requirements so much so that it is at least 50% less than conventional UV.  Environmentally, LED also leads the way not just with less power consumption, but it also does not use mercury and being cool does not generate any plasma. From a safety perspective the lamps are always cool to the touch and do not create a short wave, meaning less risk to the eyes and skin of the operator. As with all new technologies it does presently cost significantly more to purchase but based on its many benefits its payback could be in less than 12 months for most printers.

 

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April 19, 2013
We have recently installed a Flexo press but my prepress department is telling me I cannot use our existing gravure separations to make Flexo plates from. Why not?

     This is a common dilemma for many companies and designers alike wanting to move into the flexographic field.  There is no doubt that Flexo has come a long way and is capable of producing some very high quality print but it does have certain limitations that have to be taken into account at the design and color separation stage.

     Unlike gravure Flexo does have some dot gain that can create problems in creating soft gradients, vignettes and it does have a limit to the size of dot it can hold. This means that an allowance has to be built into the screening of artwork separations for a Flexo plate to be able to hold it up and to allow for the dot gain that is inevitable even with the best press and operator.

     Registration is another challenge, and inevitably means more trapping is needed than for the same gravure printed image. All this said, Flexo’s ability to print on any substrate, its speed of interchangeability of plates and variety of ink systems, all at an acceptable price even with short runs, is what I am sure led you to add Flexo to your  product offering.

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April 3, 2013
How essential is daily/weekly cleaning of a press and how much does it really affect our bottom line?

     It is this sort of question that probably answers why I see so many presses in such a run down and poorly functional condition. If you are running your equipment continuously, as most companies do, the gradual build-up of ink, paper dust, grease and other contaminates will eventually overwhelm most key components on your press such as gears, bearings, drive shafts, belts, and pulleys. The problem is this can take a while and causes the operator to have to make daily adjusts to the operation of your machine. This will lead to slower speeds, more make ready, reduced print quality and higher waste, all of which will affect your bottom line.

     It is vital to make time each day and every week for proper maintenance and cleaning of your equipment and its key components. It is the responsibility of management to understand that good housekeeping practice is essential to maintaining a consistly profitable business and is not something that can be overlooked or ignored. Sooner or later it will, as they say, “stop the press” and instead of a few minutes or hours to make a repair it could take several hours or even days if the fatigue and wear is serious enough. So, how much does it affect your bottom line? In every way and then some!

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