Tuesday, July 9, 2019

Corrugated Post-Print Best Practices

Today, all manufacturing industries face challenges that require changes from past business practices. Twenty, even ten, years ago the consumer was a passive actor who accepted market proposals. Now the end-user is an informed and sophisticated consumer who seeks differentiation, personalization. Today’s consumer has a clear understanding of the supply chain and the value it brings to key aspects of packaging, such as the environment and sustainability. Companies seek greater efficiencies and more productive use of resources. Because of this, Consumer Packaged Goods (CPG) companies must produce better packaging while controlling their manufacturing costs and minimizing time loss and materials.

Flexo's Evolution
The flexographic industry is no stranger to this “new” reality and strives to reduce response times and provide packaging with greater shelf impact at competitive prices. All this PLUS the trend towards shorter runs as CPGs require their brand identity be maintained regardless of the region, the printing method, or the substrate. Successful converters have adapted to this new reality, by increasing production by establishing standard procedures, assuring adequate tools are available and providing constant training to their production staff. This allows successful converters to increase production with minimal cost increases.
Why change what has been done for so many years? Because the needs of customers are changing!

Evolution of the Box
The corrugated box has also evolved from a means of product protection in shipping to an important sales tool. Even the simplest, one color box requires adequate legibility with barcodes or QR codes that are fundamental to the organization of inventories, selection, and distribution. With the great e-commerce boom, companies are forced to respond with customized boxes, while continuing to ensure highly efficient operations.

Considering the above, we will discuss some practices for the press floor that can be implemented to improve efficiency and reduce errors for the post-print corrugated market.

Before going to press
After proper plate processing (liquid resin, analog sheet, or digital sheet), it is necessary to inspect for defects and measure the plate with a micrometer to ensure the gauge and relief tolerances are within specification (Image 2). Any low point will cause printing failures and over-printing which affects the printed result AND the strength of the box. Additionally, the more consistent the gauge, the longer the life of the plate on press. The use of a Shore A calibrator will confirm that the hardness of the material is ideal for both the graphics to be printed and the substrate used (Image 3). Corrugated materials require low durometer from 25 to 40 Shore A. All instruments used must be properly maintained and calibrated following the manufacturer’s recommendations to ensure accurate and precise measurements.

Image 2. Digital micrometer for reading the thickness of the plates. The plate should be supported on a table perfectly parallel to the floor and with a sufficient area to prevent movement. Source: FLEXOGRAPHY Principles & Practices. 5th Edition.
Image 3. The Shore A gauge of durometer measures the penetration of its cone on a soft material. Source: FLEXOGRAPHY Principles & Practices. 5th Edition.

Prior to mounting the plate, check the work order to confirm measurements of the box design, number of colors, plates per color, and other specs. Cutting the plates, whether manual or automated, must be precise, clean, and without burrs that impair adhesion to the carrier. Beveling the edges of the plate is highly recommended (Image 4). Beveled edges improve the contact area with the sealant and reduce the risks of the plate lifting during the production run. The polyester backing, as well as, the carrier must be thoroughly cleaned to remove any traces of dirt that may affect the application of the rigid mounting tape. Typically, when there is poor adhesion between these components, there are high areas that print with more pressure on the cardboard. After the placement of each plate on the plate roll, it is important that constant pressure is exerted with a rubber roller to improve adhesion and avoid bubbles. The plate mounting must not only guarantee an exact registration but also an even impression of each color.

Image 4. Beveled edges and cut corners of a plate. 

There are different targets available for manual or automatic evaluation. The designer, mounting operator, and printer must agree with the type and location of the registration marks (Image 5) Everyone involved must understand how to use the marks to clearly communicate if a registration problem arises from design, mounting, or printing. Flexographic Image Reproduction Specifications & Tolerances (FIRST) supports the use of the Railroad Track Target which contains implicit measurements for lateral and circumferential adjustment thus avoiding the use of a measuring tape reducing the time required to achieve aligned images. The goal is to place the colored triangle on the centerline. These targets along with the traditional crosses should be placed in the four corners of the sheet.

Image 5. The orientation of the register targets on the sheet. Source: Cordes Porcher 

On press
On press, organization and cleanliness are fundamental and necessary. A lean manufacturing mentality must be maintained following the basic principle of the 5s which focuses on how best to organize the workspace to maximize efficiency: sort, set in order, shine, standardize, and sustain. The tools and supplies should be easy to see, easy to obtain, and easy to return, guaranteeing only the materials needed for the print run will be on the press.

A program of preventive maintenance should be agreed upon for the press with the personnel dedicated to this task: inking systems prepared and adjusted to provide the thickness of the desired ink film to the plate; rollers under concentricity, conicity and parallelism tolerances confirmed by the manufacturer; bearings and bushings in perfect condition and properly greased; register and material guidance controls; and drying units operating efficiently with the airflow itself. Negligence in maintaining these items and delayed replacement of worn items will result in problems of quality and productivity.

As for the ink film thickness, it is essential that the pressman knows their anilox. They must know the linescreen and volume, and the condition of the anilox. Although the change of anilox in a corrugated printing machine is relatively infrequent, a routine cleaning program must be carried out. Equipment that incorporates the recommended cleaning chemical is available to complete the cleaning on the machine. Likewise, an inventory audit must be carried out, relying on the manufacturer expertise.

Another critical element to control on press is the ink. Those used in the corrugated industry are water-based and require an alkaline pH (pH> 7.0) to keep the resin in solution. This is achieved through the incorporation of chemical substances such as amines that tend to evaporate during the run which reduces the pH and increases the viscosity. This causes variation in the color density, dirty impression as the ink accumulates on the plate due to a poor redisolubility, excessive generation of foam, and accumulation of paper fibers on the surface of the plate. To maintain consistency in the control of the color during printing, both pH and viscosity should be measured frequently and pH corrective solutions should be added to maintain stable ink properties. The addition of water reduces the pH and should be used with great care as the color strength can also be affected. Before making an adjustment in the viscosity, one must ensure that the pH is in the range recommended by the supplier (pH 8.5-9.5) (Image 6). Any measurement carried out must have adequate and regularly calibrated equipment and the ink temperature recorded.

Image 6. The pH should be maintained in a range of +/- 0.3 during the print run to ensure a stable behavior of the ink. Source: Flexographic Image Reproduction Specifications & Tolerances

Once the plates are placed in the press, the next step is to confirm adequate inking through the appropriate adjustment of the pressures: anilox-to-plate and plate-to-substrate. First, verify the ink flow to the anilox is at its optimum level, the printing plate must be completely inked without excesses through the slow approach of the anilox. Then move the whole assembly towards the cardboard substrate. Confirm that the substrate has printed the entire plate and stop the adjustment at that moment. The anilox adjustment should be done first and last to avoid excess ink on the plate. The objective is to apply the lowest possible pressure that allows a consistent impression; excessive pressure will cause greater dot gain, premature wear of the plate, and considerable crushing of the board. Drag Targets can be useful to visually evaluate excess pressure depending on the pattern shown in each one (Image 7). If a more objective evaluation is desired, the inclusion of control strips with different dot percentages will allow the reading of the dot gain experienced by each: a minimum point patch, quarter-tone, halftone, shadows, and solid block would be a good sample for process control. Regardless of the target used, they must be placed on both sides of the press to ensure the parallelism of the rolls. The values must be correlated with those established during the press fingerprint test to confirm if a certain value read with the densitometer confirms or rules out an over impression.

Image 7. Impression targets: circular (anilox/plate) and hexagonal (plate/substrate). Source: Flexographic Image Reproduction Specifications & Tolerances.

Plate Cleaning
During the press run and at the end of the run, cleaning processes must be carried out on the plates which can extend their useful life. Immediately after the production ends, clean the plates to prevent the ink from drying completely. A brush with soft and fine bristles (nylon or natural fiber) or a suitable sponge must be used for this operation; never use brushes with metal bristles or rough cloths. Moisten the plate with a cleaning solution prior to brushing it; a solution of lukewarm water with an alkaline pH (> 9.0) works well to remove the ink from the surface. When in doubt contact the supplier to develop a swell test under the established protocols and determine the variation of caliber and hardness using a small sample of the plate. It is not necessary to aggressively brush the plate as excess pressure can damage the surface. During brushing, apply generous amounts of the cleaning solution to keep the surface moist and avoid scratching. Improperly cleaned plates can stick together, develop surface cracks, and become more difficult to clean for reuse. After cleaning, dry the plate with an absorbent soft paper or forced air to remove residual water.

Plate Storage
Finally, store the plates vertically. The storage area should not exceed 100°F (38°C) and should be located away from ozone generating sources such as motors that generate electrical discharges and energy sources. Keep the plates in an environment free of dust, keep them dry, and at room temperature. Protect plates from exposure to direct light sources that can cause softening, brittleness, and discoloration.

Image 8. The protection of the plates to UV light will prolong their useful life. Avoid direct exposure using filters.

Undoubtedly, there are more areas that can be considered but the most important thing is to understand the variables, control them, and rely on suppliers to define standard operating parameters in each of their areas of responsibility. Knowing the capabilities of the printing system is critical through press fingerprint tests to make consistent designs. However, the capacities of the personnel of each area and the processes that are carried out day after day must also be reviewed. The best printing equipment may not provide the expected results if employees are neither properly trained nor empowered to implement procedures to make their work more efficient. The objective is not to work harder but to work smarter, and this is where the company that adapts best manufacturing practices will maintain a differentiated position in the market.

To learn more contact MacDermid Graphics Solutions. Email us today.

Written By: Ivan Rozo, Business Development Manager, MGS Latin America

Ivan Rozo is the Business Development Manager for Latin America. Ivan is a Chemical Engineer with a Master Degree in Business Administration with an emphasis in marketing. He has more than ten years of experience in the Flexographic industry working in roles of sales and technical support in which he has led optimization projects. Ivan's is responsible for attracting new business and consolidating strategic accounts at MacDermid in Latin America.

Wednesday, June 26, 2019

Quality Control in Flexo Platemaking

Flexographic printing is continuously evolving, and the platemaking process is seeing this exponentially. Platemaking is evolving not only in the development of new and innovative materials but also in the technological improvements of imaging and processing equipment. Together these make a more efficient and consistent workflow to deliver high-quality plate that can consistently reproduce the information of a digital file in its finished structure. All of us have been familiarizing ourselves with terms such as high definition, high resolution, surface screening pattern, and flat-top dot, among others. The reality is that ALL suppliers in this field have achieved a synergy, bringing about a complete revolution making the flexo printing process more competitive compared to other technologies such as rotogravure and offset. However, in an environment that tends to become more automated, there are still uncertainties in the manufacture of the plates and even returns of the finished product. In this post, we will review the procedures, tools, and criteria that can be used to maintain an adequate environment in ​​digital platemaking based on the golden rule...“What cannot be measured cannot be controlled". What to measure? How to measure it? How often? Are some of the questions that will serve as a starting point to deliver a finished product that meets the user's expectations.

Quality Control
Broadly speaking, quality control includes a combination of procedures designed to monitor and validate effective "acceptance/rejection" criteria in key stages of a process:
  1. First, identify the variables that have the greatest impact on the process or workflow. These will then become the key control points for the process.
    • By finding the key control points we can ensure quality at critical stages in the workflow and reduce the opportunity for defects downstream in the process.
  2. Define standards to use "acceptance / rejection" criteria.
    • Due to the physical limitations of the process involved, tolerances must be established for these standards.
  3. Measurements are taken at these key control points to verify the process and conformity of the product to these standards.
A benefit of establishing measurement standards is the increased opportunity for a consistent and successful process or product. In addition, the key control points ensure that any defective product is identified in the earliest stages of the workflow.

Key Control Points
Image 1. Digital Plate Construction
A digital plate is processed without the use of a negative film. On the surface of the sheet material is a thin carbon layer that is removed using a laser ablation technique in conjunction with a 1-Bit TIFF file. After ablation, the carbon layer acts as a negative or mask, blocking ultraviolet light during the exposure process. The processing stages of a digital plate are back exposure, image ablation, main exposure, processing (solvent or thermal), drying (solvent), and post-exposure/finished plate which can be grouped into three key control points:
  1. Ripped Digital File
  2. Imaging (mask ablation)
  3. Processed/Finished Plate
Ripped Digital file
Once the digital file is ripped, it becomes the digital negative and cannot be manipulated. All information of the image, tone curve, and metadata is contained within the file and is used directly by the imaging device. Therefore, when reviewing this type of file, it is important to consider:
  • Image resolution
  • Orientation of the image (right reading/wrong reading)
  • Linescreen, angle, and dot shape
  • Screen configuration (halftones and solids)
  • Compensation (bump and printing curves)
  • Dimensional accuracy (distortion)
  • Registration marks or guides
All elements of the ripped file must be verified and certified that they correctly adapt to the standards defined by both: the basic workflow and those unique to the job. The use of an application, such as a bit-map viewer software (Image 2), for the visualization of this type of file is an excellent process control tool.

Image 2. Esko Grapholas visualization tool

Imaging (mask ablation)
The quality of the image ablation on the carbon mask of the plate is a function of the raw material and the adjustments of the imaging device and its condition. The plate manufacturer must ensure a uniform and consistent application of this layer to avoid problems during ablation and/or exposure. Before and after ablation, the mask should be checked for visible marks, scratches or abrasions. Remember, at this stage, the plate is more susceptible to damage because it has yet to be cured.

Measurements must be obtained during this stage by a transmission densitometer, the following apply:
  1. Fidelity of the image (focus adjustment)
  2. Density of the mask from 3.5 to 4.3
  3. Stain level of the plate after the device removes carbon mask (Dmin) <0.07
  4. 50% Density on 0.30 +/- 0.02
It is important to maintain a consistent ablation on any digital imaging device with any digital plate. Ensure the laser is properly focused on the carbon mask to concentrate its energy in the smallest possible area and achieve a clean removal. Defects due to poor focus are seen as visual lines in areas that have been removed or malformed dots (Image 3).

Image 3. Out of focus ablated image 

A weekly ablation test should be carried out to monitor that both the device and the material do not vary from their original setting parameters. Using a transmission densitometer (Image 4), standardized targets are measured; these consist of 100% and 50% removed areas which are compared to the material with the mask removed manually. (NOTE: Calibrate the transmission densitometer with the control strip supplied by the manufacturer to confirm the correct amount of transmitted light is consistent with the amount transmitted when the unit was manufactured.) If the readings are below recommended targets, then there is too much energy being applied by the laser and the physical size of the dots will be larger than desired. On the contrary, if they are higher, then very little energy is acting on the plate to remove the carbon mask, resulting in lines present in solid areas and smaller than the desirable dot size affecting the applied bump curve. In either case, the energy (mJ/cm2) applied to the plate must be adjusted by modifying the RPM or power.

Image 4. Transmission densitometer

Finished plate
After the plate is processed, it is necessary to carry out measurements to ensure specification compliance. These results are dependent on the condition of the platemaking equipment and adequate monitoring of the processing conditions found during optimization. You should consider the following control points:
  • Caliber
  • Relief
  • Dot formation
  • Tackiness
  • Cleaning

Both the caliper and the relief can be measured with an analog or digital reading micrometer
Image 5: Micrometer
(Image 5). (NOTE: Calibrate a micrometer using a precision block placed between the surface to ensure the readings are accurate.) The test area must be at least 1" x 1", and multiple measurements throughout the plate are necessary to determine uniformity. The caliper of the plate is one of the most important factors when controlling the impression setting on the press machine; any low spot will not print or will cause overprinting for the remainder of the printing plate. All areas must be at full print height including solids and halftones. Flexographic Image Reproduction Specifications & Tolerances (FIRST) specifies variations for raw material thickness of digitally-imaged photopolymer plates and sleeves as follows:

        Within the same plate: +/- 0.0005" (0.0127 mm)
        Within a set of plates:  +/- 0.001" (0.0025 mm)

The flatness of the finished plate depends on the platemaking process; however, any variation will be accumulated with those of other variables, so the lower the better.

The relief specifications must be defined and confirmed depending on the caliper, the graphic details, press machine requirements, and other variables. Target relief specifications should be confirmed with the printer.

Dot Formation
The accuracy of the dot and the formation of the minimum dot is inspected with a microscope (100X) and a flexo plate analyzer. Specific characteristics are evaluated and verified to confirm a successful minimum dot; this method ensures that, although the minimum dot is small, it can be used as an effective control point. This may or may not be the dot percentage used in the production job (Image 6).

Image 6: MinDot test with two different screen configurations (stochastic and circular)

Once the smallest stable dot has been determined, the objective in the production of plates is to maintain this stable value by type of plate. Considerable changes in processing conditions can lead to considerable deviations (e.g. changes in UVA light emission intensity, etc.).

Additionally, a control strip must be recorded and processed with each plate for immediate verification of the consistency, not only of the platemaking but also of the compensation curves applied (Image 7). The use of a constant objective provides a single set of standards and tolerances to meet.

Image 7. Prepress scale where the values that must be measured on the plate for each tone are labeled. Source: FIRST

To verify the tonal accuracy of the finished plate, tools such as flexographic plate analyzers are used to measure the size of the halftones. Utilizing this tool improves process control, production efficiency and consistency of print quality. We recommend the BetaFlex Pro and the Plate to Print to create a record of the data collection verifying the specifications of the plate have been met. In any case, whatever the device used, calibration procedures and the process of taking measurements must be clearly documented along with the approval/rejection criteria.

Finally, it is important to consider the following frequency of operations to maintain stable conditions:
  1. Measure and record the lot number, relief, caliper, minimum dot percentage and halftone percentage of at least one color of each job. 
  2. Conduct a weekly "MinDot finder" test when there is a lot change of the photopolymer plate. This weekly test will help establish an appropriate main and back exposure.
  3. Perform a daily "focus test" and a weekly "stain test" every time there is a lot change This testing will confirm adequate mask ablation. Maintenance for cleaning lens optics and changing parts must be programmed with the manufacturer.
  4. Conduct a bi-monthly audit of the intensity of the UV exposure lamps. It is recommended to change lamps when the readings fall below 80% of their original power especially for jobs that incorporate special effects in the highlights or solids.
  5. Weekly measure the Brix degrees or density of the processing solvent and adjust according to the manufacturer's recommendations.
  6. Review the back exposure at each lot change and adjust accordingly.
  7. Only back expose plates that will be used in less than half an hour.
There are many more initiatives that can be incorporated, but a quality control process must aim for continuous improvement based on the customer's needs. The process should detect any defects in the early stages of the manufacturing process where the cost is much lower than having a defective product in the machine. It should also be noted that a quality control program involves raw materials duly certified by the manufacturers. The goal is to reduce waste, decrease reprocessing, and increase consistency.

The return on investment in these types of programs is easily justifiable when packaging is produced consistently, downtime costs are reduced, margins are improved, and time-to-market is reduced. At MacDermid Graphics Solutions, we not only offer quality products under the tightest tolerances, but we also have a team of specialists willing to help you implement this type of initiative to increase your competitiveness.

To learn more contact MacDermid Graphics Solutions. Email us today.

Written By: Ivan Rozo, Business Development Manager, MGS Latin America

Ivan Rozo is the Business Development Manager for Latin America. Ivan is a Chemical Engineer with a Master Degree in Business Administration with an emphasis in marketing. He has more than ten years of experience in the Flexographic industry working in roles of sales and technical support in which he has led optimization projects. Ivan's is responsible for attracting new business and consolidating strategic accounts at MacDermid in Latin America.

Tuesday, May 28, 2019

An EPIC® Journey

Bryce Benson’s introduction to EPIC plate technology

In May 2017, during my first year with MacDermid Graphics Solutions, I visited Miller Graphics in Sunne, Sweden.  While waiting for my meeting, I ran into Jan Viberg, then with Esko, and now the Managing Director of Marvaco Sweden.  Never one to shy away from good conversation, Viberg asked quite frankly, “When’s MacDermid going to bring back the EPIC plate? That was a great plate.” As I replied to many questions in that first year, I simply said, “I don’t know, but I can find out.” First, I had to learn a bit about the EPIC plate, so I called our headquarters in Atlanta, Georgia.
EPIC’s journey began in the early nineties. Flexible film printing struggled to attain a balance of low dot gain with good solid ink density and coverage --- capped plate technology was the solution. For the people who think “baseball cap” when you hear “cap”, the cap we are referring to here is a micro-rough layer on a photopolymer printing plate that aids in the transfer of ink to the substrate. Think of it as something like sandpaper - with peaks, valleys, and crevasses that allow more ink to be picked up by the plate. The cap allows the best of both worlds - a hard plate that gives you good dot reproduction WITH good ink transfer. EPIC quickly became the plate of choice within the label market due to its image reproduction and its excellent ink coverage. BUT ink coverage didn’t limit the plate to labels; it also became widely popular for flexible packaging and pre-print corrugated applications.

EPIC’s appearance was unique, featuring a translucent white non-image area and a capped, green image area – very different from MacDermid’s pink plates. This contrast gave it great quality control properties and made it very simple for plate mounting before the days of camera mounting systems and analog platemaking...oh the things we take for granted. Next came magnificent surface screening technologies, allowing you to build the microcells in the image file, becoming favorable over capped plates. While prepress screening technologies are great, they require a high degree of process control on press. The skills required, combined with the decrease in prepress specialists, made the simplicity of cap technology desirable. 

So now…The Cap is Back! The introduction of new capped plates with inherent flat-top dots (AHEM…our LUX® ITP EPIC®plate) provides the print consistency and high solid ink density needed to produce the finest detail graphics on flexible film. LUX ITP EPIC helps you achieve high solid ink density, excellent ink transfer, superior print consistency, and faster imaging. It’s the photopolymer plate that combines a revolutionary capped surface with award-winning flat-top dot technology…could it get any better? Oh…AND you can eliminate the need for surface screening! Yes, you read that correctly. Say farewell to surface screening.

LUX ITP EPIC is the newest addition to the award-winning technology from MacDermid with the convenience of flat-top dots right out of the box. No additional platemaking steps or equipment are needed to take advantage of the print quality and consistency that LUX flat-top dots provide.
LUX ITP EPIC offers a unique micro-rough surface for excellent ink transfer for challenging flexo printing applications or unique ink requirements. The innovative cap layer, specifically developed for the ITP chemistry, ensures that the plate provides the best tonal range possible. LUX ITP EPIC offers near 1:1 mask-to-plate imaging capability, thus minimizing the need for a bump curve. By reducing the bump curve, printers can expand the available color gamut and print a smaller dot creating…VIVID IMAGES! LUX ITP EPIC is a durable and extremely low tack plate, which is perfectly suited for long and clean running print jobs. Get the same quality from job 1,000 as you do with job 1, no surface screening required. And did I mention it is a 2-in-1 plate designed to be processed in either solvent or LAVA® thermal systems!

So, Jan, I have something EPIC ready for you…LUX ITP EPIC that is!

By: Bryce Benson, Territory Sales Manager - Nordics, Baltics, CIS MacDermid Graphics Solutions 

Corrugated Post-Print Best Practices

Today, all manufacturing industries face challenges that require changes from past business practices. Twenty, even ten, years ago the cons...