Flex design for thin walled and scratched sleeves
Every part of a flexo press has to be singing in perfect harmony for the output to please the customer and generate a good profit. Tapes are of course no exception and play a vital role in ensuring the press runs to its full potential. Michal Lodej reports.
Technology advancements in flexo printing continue to hit the market on a regular basis, with anilox rollers, software, presses, plates and screening formats all becoming more advanced. All of these contribute to the capability of flexo to compete with the alternative printing processes – litho, gravure and digital. At the same time, with and more printers using fixed pallet systems the need to improve the transfer/laydown of the ink to the substrate surface is paramount. Take into account the challenges of the extensive variety of substrates to be printed upon and the desire to produce a winning print, and this is indeed a complex challenge.
To keep up and meet these challenges, Lohmann has produced the DuploFLEX plate mounting tape range. The DuploFLEX range was originally created 15 years ago, and has continued to evolve over the years with a new improved adhesive formulation launched at drupa 2016.
The key benefits of this range include high resilience and strong recovery. It is suitable for long and short print runs and has a range of ‘hardness’ to suit all image types and a range of adhesive formulations to suit all challenges.
With the continuing step up from traditional repro to high resolution repro systems being arguably the main driver, the movement to print finer and finer images has increased. Image areas are more detailed with more vignettes being produced and solids being originated from tones.
The key characteristics of the plate mount tape need to embrace all of these variables with consistency/repeatability being paramount. The next time the job is run the new batch of tape needs to produce a repeat performance to ensure that the printed image produced is a replica of the same as last time.
There is also the adhesive to consider, adherence to the sleeve, cylinder (various finishes), adhesion of the plates ensuring the plates stay in position and the edges do not lift, removal of the plates without damage and in many cases re-use of the tape.
Tapes for all seasons
The wide range of BiesSse double-sided adhesive tapes especially designed for the printing industry cover many different applications, such as flexible packaging, labels, cardboard pre-print and post-print.
The BS Firm range features various rubber-based adhesives (wet style), normally with medium/high adhesion levels, balanced on both sides. The BS Print range features a selection of combined acrylic (dry style) and rubber-based (wet style) adhesives, generally with medium adhesion levels differentiated on each side. This product range ensures easy mounting, repositioning and removal.
BiesSse’s range of BS Mount tapes
The BS Mount range offers several features that make them an ideal choice for flexo printing applications, providing an effective cushioning system as well as a high resilience formula for good printing results at very fast speeds.
Its high performance adhesive system gives strong adhesion but allows the tape and plate to be lifted with a clean removal after printing, leaving no adhesive residues.
Also important is its air bubbles repellent liner. The transparent colour makes it easier to identify air bubbles and is especially designed with a structure that allows the exit of air bubbles.
Keeping fit
Within the printing and graphics market, Scapa has developed highly specialised adhesive foam tapes to ensure high quality printing results which are essential to the flexible packaging markets and which assist in achieving superior printing results even at higher machine speeds and during longer print runs.
Today’s flexographic printers are constantly looking to perfect the quality of their printing and to improve their processes. Printing quality, speed and efficiency are essential to meet the growing demands of their customers. Scapa’s Exafit HP gives a reliable bond to the plate/cylinder enabling longer, faster print runs with improved printing definition and reduced dot gain.
The new Exafit High Performance (HP) range includes the addition of five new foam harnesses’. These include soft to hard foam as well as medium soft and medium hard. According to the company it allows for longer, faster print runs with consistently high print definition and reduced dot gain. Contrast and details are kept consistent and colour density is preserved. Its improved surface coverage contributes to superior results from half tone to block printing. Exafit HP also features a new type of PE foam with improved resilience which helps to absorb any tolerances caused by variable substrate thickness and machine vibration.
These products use specialist acrylic adhesive technology that allow a strong contact to be maintained between the tape and the plate during the print process. Scapa’s acrylic adhesive used in the Exafit HP range also have the added benefit of providing great solvent and chemical resistance.
In a growing and dynamic market like flexographic printing, the extent to which a company can participate in this growth depends on the flexibility to react to market trends and offer benefits to the market. One of the main market trends in flexographic printing is the reduction of the length of print runs, and therefore more job changeovers per day.
The right selection of plate mounting tapes consequently becomes more and more crucial to support efficient process steps before, during, and after printing. More efficiency, less waste, less downtime, and less complexity leads to an overall reduction of process costs.
Soft touch
tesa has further developed its Softprint assortment of tapes by introducing the Softprint TP-X in combination with its new product design, Flex. This new development is optimised for lean production processes and maximised efficiency on the shop floor level.
The Softprint TP-X plate side adhesive is based on a new robust chemistry to avoid reactions with ink residues. Meticulous and time consuming plate cleaning procedures before plate mounting therefore become redundant. After printing, plates can be easily removed from the tape, even if ink residues appear on the plates. These would have led to an increased bond between plate and tape if other adhesives had been used, thus increasing the risk of plate damage.
Changes in sleeve circumference due to air mandrel pressure during sleeve mounting can cause the tape bond to break. The Flex product design
offers more flexibility and therefore compensates for the differences in sleeve circumference, ensuring a reliable tape bond at all times. Printers can benefit from a trouble-free print process with minimised press downtime and the highest process efficiency.
Scratched sleeves lead to an inconsistent surface, thus endangering a secure tape bond. This product combines a flexible product design with a specially engineered adhesive on the sleeve side, resulting in a secure bond even on demanding sleeve surfaces. This again allows for the smoothest processes to achieve the necessary output.
Tape reusability depends on various factors. One of them is the perfect balance between the bonding strength to the sleeve and the plate, as you want the tape to remain on the sleeve upon plate demounting. However, once you are ready to remove the tape from the sleeve at a later point of time, easy and residue-free tape demounting is also necessary. This product offers specially engineered adhesives providing this balance to support tape reusability in certain conditions such as short print runs.
Alternatives to tape
Polymount’s self-adhesive Twinlock Sleeves sales have seen a rise in popularity over the last couple of years. These eliminate the need for mounting tapes. Carlos Saya, marketing manager at Polymount, said, ‘A great example of this growth is our home market in the Benelux, where the potential of Twinlock has almost reached its maximum market penetration. 65% of mounting tapes have already been eliminated and the last of the large flexo printers are currently converting their facilities to tape free plate mounting. In two years’ time 85% of the printing plates used in the Benelux will be mounted on self-adhesive Twinlock sleeves. Our largest Twinlock user in the Netherlands does 3000 sleeve changes per week. Since they started using Twinlock sleeves they can no longer imagine going back to using tape.’
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