Our Home Page is viewed 
over 6,500 times per month.
Become a Sponsor

asksponsor
Welcome to  ‘Ask The Expert’.  This page is moderated by industry consultant, Steve Wilkinson.  This page features the answers to your questions. Our visitors can also post comments to these questions/answers as well.  You can learn more about Steve’s background and our ‘Ask The Expert’ page by Clicking Here.

If you have a new question to ask, just CLICK HERE to post your question.  Questions and comments will be reviewed by our staff and posted as quickly as possible.  All questions should be non-commercial in nature

As always, thanks for visiting www.nvpublications.com.


 

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.

No Comments

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.

No Comments

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!

No Comments

March 24, 2013

What is the most effective way to improve our bottom line that doesn’t entail a huge capital investment?

In my opinion if you were to improve your general housekeeping of your press room but in particular your anilox, you would be able to :

  • Reduce Down time
  • Reduce Set up time
  • Reduce set up material
  • Reduce ink costs
  • Reduce roll replacement costs
  • Improve print quality

All of which will lead to an improved bottom line, but it takes a real commitment and the use of the right cleaning solution and equipment to achieve more consistent ink transfer from the anilox to the plate to the substrate. Whenever I do plant evaluations I invariably find that housekeeping is a low priority and is not taken seriously by many management teams. They claim that it is important but there seems to be little or no real accountability other than to blame the press operator. So please do take a look at your cleaning procedures and if you are not sure what to use, ask your vendors as they will be pleased to help.

No Comments

March 11, 2013

We are plagued with scoring on our anilox, what are we doing wrong?

After plugging of the anilox cell, scoring of the anilox surface has to be the most common issue that all printers have with their anilox rolls. Unlike plugged cells however, which can be cleaned and in so doing regain their volume, a score line in the surface of an anilox cannot be removed and in effect requires the roll to be reworked.

With this said, it is therefore paramount that everything possible must be done to reduce the possibility of scoring the engraved surface of your anilox. Notice I said “reduce the possibility”, this is because a great deal of scoring comes from contamination within your ink or coating. Even if you have filters and rare earth magnets in your ink lines, it is difficult if not impossible to remove all metal, pigment/resin clumping and paper dust particles all of which can and do get trapped between the anilox and doctor blade. This will drag the particle around the surface of the roll, which can and will cause score lines of varying degrees. The irony is that you do not have to dig a groove into the surface coating to have it show up on your print, just dragging a hard particle across the surface of the anilox will change its surface characteristic, which in turn will be reflected in a different color density in the form of a light or dark line.

Doctor blade pressure and angle are also very critical. Too much pressure and too acute an angle will cause the blade to begin to wipe from the back of the blade, which increases its surface area, compounding the issue of potential scoring of contamination digging into the roll surface. You need to make sure that the blade is parallel to the anilox surface at set up, that there is no dried ink on its edge, and that the roll is inked up adequately before the blade is presented to the roll.

Too much pressure on the doctor blade, particularly plastic blades, can lead to the blade softening, which can trap hardened particles in it that, in turn, can and will lead to scoring of the roll surface. I strongly recommend that on receipt of your newly engraved anilox that you wash it thoroughly to help remove any remaining ceramic particles, and that if you chip the edge of the roll you fill it immediately to help reduce further ceramic particles getting into the ink and again getting dragged around the surface of the roll.

Remember ceramic is inert, cannot be pulled out with magnets and is very difficult to filter out, and other than diamond can cause dramatic damage to the engraved surface of your roll. So, as you can see, there are a lot of potential causes of scoring and while difficult to eliminate can be significantly reduced with a better understanding of its root causes.

No Comments

February 26, 2013

Is XG really the answer to Flexo finally being recognized as an equal to offset and gravure printing?

So far, flexo has tried simply adding more colors to extend its spot color range and for a while has had some success with 7-color printing. This has now been extended into 4-color process printing by running higher density CMYK and has shown some remarkable results for the few that have tried it.

Getting enough ink transfer from many photopolymer plates has proved such an issue that texturization of solid plate surfaces has been used to help it achieve greater densities. Special software programs and new plate materials are helping the process significantly and can be very productive on press with fewer color changes, wash-ups and reduced ink costs. That said, it does not appear so far to replace all spot colors but is producing gamut ranges that are challenging offset and gravure. Will it ever be seen as an equal? It really depends on the buyer and ultimately the consumer’s expectations.

No Comments

January 2, 2013

What are the benefits of LED technology; can they cure my existing UV inks?

LEDs (light-emitting diodes) emit light when subjected to an electric current. The light that is generated consumes very little energy, and the diodes have an extremely long working life. One major benefit is they do not generate any ozone, unlike conventional UV lamps with mercury tubes. A typical LED-UV lamp system consists of numerous LED panels across a given press width and have multiple rows. The substrate can be very close to the LED panels since very little direct heat is generated.

Conventional UV lamps requires a warm-up phase before they can operate; LED-UV lamps has no waiting time and are ready to use immediately when they are switched on. LED-UV lamps only produce  a small range of the conventional spectrum of UV lamps and have no high-energy IR radiation or hazardous UV-B and UV-C radiation. LED UV cannot cure conventional UV inks due to the narrow wave length window of the LED-UV lamp, which peaks at 395 nm. It should be noted that being a new technology you will find the LED lamps and inks more expensive than your conventional UV technology. That said, the lower energy consumption (claimed at up to 80%), reduced need for sophisticated air exhaustion systems and their perceived safer operation for the operator and others around the printing press makes it a technology very well worth while considering.

No Comments

December 3, 2012

How many types of print cylinders are there, and which is the most accurate?

Probably the best know print cylinder is the integral shafted cylinder.    

While the most rigid and most accurate over the years has the journal shaft, running completely through the tubular core, it is also much heavier as a result when compared to the stub shafted design. The stub shafted integral roll journals are heat shrunk and often welded for added strength but are more susceptble to deflection, which in turn can lead to a lot more plate bounce. Its major benefit however is that the roll is much lighter and cheaper to build, which makes it more popular.

The next type of plate cylinder is a tubular core with a shaft that it can be mounted on and off. Original designs used tapered cones and lock nuts but have been largely replaced with more modern expandable shafts that use hydraulic or pneumatic expansion of the shaft to lock it to the inner bore of the core.

Finally there is probably the most popular which is the air cylinder. In most cases it looks just like a normal plate cylinder but has a hole drilled usually in the header on one side of the cylinder and 3-4 smaller holes drilled through the outer shell of the core with perhaps one other in the center. Plates are mounted on a sleeve consisting of polyester, fiberglass, carbon fiber or a combination of these materials and is slid onto the outside of the cylinder after air has been pumped into the cylinder from the header air valve. The air escaping from the smaller surface holes on the cylinder creates a cushion of air that the sleeve can slide over and locks into place once the air supply is stopped. Due to the action of sliding the sleeves on and off the cylinder, and the likelihood that dirty, moist air very often is put through unfiltered air lines, these cylinders are prone to scratching and corrosion and as a result will usually need refurishment and even replacement after several years of regular use.

The tubular demountable cylinders can be very accurate but great care needs to be taken to ensure that the shafts are not bent or scratched during installation and removal. Of the two shafted integral designs, the straight through shafted is the most durable and accurate but this often gets overlooked in today’s rush to reduce weight and cost but if you are willing to make the initial investment as well as the right lifting equipment, they will last you a lifetime if properly maintained and looked after.

No Comments

October 24, 2012

What is (ITR) technology, and how can it benefit my company?

“ITR”, otherwise known as “In the round” is the generic term that has been used for a long time to describe any image that has been produced around the circumference of a plate cylinder or sleeve in either a photopolymer or elastomer covering. The technology has been used primarily in Europe for more than thirty years with elastomer coatings being vulcanized, ground and directly laser engraved onto sleeves and integral rolls. While plate material has and still can be exposed in the round and is classified by some as “ITR” , I personally only classify it as true “ITR” if the material has been bonded or vulcanized to the sleeve or roll circumference and engraved or washed out while in a continuous format. As to the benefits of true “ITR” there are many ranging from dramatically increased press speeds, improved print quality, improved registration, more uniform densities, less dot gain, less bounce, reduced waste, improved productivity, improved profitability, less set up time and less make ready.

No Comments

October 11, 2012

We hear so much about best practice being necessary for good quality print but how do we define what is best practice?

This is a very big subject but for me best practice is about eliminating as many variables as possible on and around the press. You need to look at each aspect of the print process and determine what you believe to be the most effective in helping you to achieve consistent results.

This usually starts by measuring and recording what is being done to help to determine if it is repeatable and if the results are acceptable. Generally the use of measuring devices such as spectrophotometers, densitometers, video web inspection, interferometers, viscometers are necessary to help capture the necessary data in an accurate form that can then be repeated and measured accurately each time a job is run.

Always try to get your suppliers involved at the earliest stage possible as they will then be able to assist you in achieving what is best practice for you and your company and more to the point, how to define it.

No Comments