Tag: ink chamber

Corrugated Converters at the Crossroads Blog Series Part 2 “Necessity is the Mother of Ink Delivery Innovation”

The first blog post in our Corrugated Converters at the Crossroads series looked at how new consumer buying behaviors are changing what is expected of corrugated packaging printers. Converters are being asked to step up their game, and how they do it will define their future.

But how can they get the most innovation bang for their buck? Ink delivery system innovations are a good place to start. Adding ease, automation and better control over the application of ink will improve press efficiency and enhance graphics quality.

Doctor blade chamber systems

Once made of aluminum, chambers are now constructed from strong polymer and composite materials which resist pitting and corroding and maintain their strength without warping or twisting. Newer models have simplified loading and mounting designs that allow for easier installation and consistent blade contact angles with minimal pressure. Also, the new equipment is engineered to accommodate multiple blade thicknesses without modifications or shim stock, so printers are not limited to only the doctor blade materials that the chamber will hold.

Doctor blade materials

UHMW is the longstanding traditional blade material used in corrugated applications. But as the demand for higher quality graphics creeps into the market (and anilox line screens rise), the blade material can’t effectively control the volume of ink delivered to the plate. As the blade edge wears, its contact area quickly becomes too large to effectively meter the roll – ink film thickness grows, ink mileage declines and blade wear accelerates, all driving the price of the box up.

Some newer chamber designs can hold thinner materials, such as polyacetal, steel and TruPoint Orange® with MicroTip®, without a shim or modification. But many of the early chambers were designed to hold only a specific UHMW blade thickness such as .060” (1.6mm) or .080” (2mm). In these cases, a next-generation polymer blade, TruPoint Green®, is a good solution. It can be made in .060” and .080” thicknesses, has 3 times better spring memory than UHMW and is about 20% stiffer – all while having an equal or longer blade life.

Anilox rolls

Until recently, about 85% of corrugated anilox engravings have been under 300 lpi (120 L/cm) and 60° angle. Like other flexo printers have done, corrugated printers are beginning to take advantage of complex anilox surface configurations, cell shapes and higher line screens. New technologies such as elongated cells, tri-helical cells and wave style engravings give printers more control over their ink delivery, so they can create eye-catching POP displays and other attractive packaging.

Plate materials and plate carriers

New performance-grade cushion mounting material is made from higher durometer foam that resists compression set and reduces plate make-ready time. Superior impact and deflection during the print run allows for stable print reproduction and a reduction in fluting or “washboard” phenomenon. Great advancements are being made with patterned photopolymer plates (often referred to as “plate on a plate” technology) to help the printer manage ink delivery volume and distribution from the plate.

Ink temperature control systems

Water-based inks run best between 66°-74° F. This is typically well-below the ambient temperature of the plant, so ink will often go to press above its optimal temperature. There is more energy (and heat) added to the ink as it is pumped through the hoses and chambers and transported by the anilox roll.

As ink temperature rises, pH levels drop and viscosity increases – impacting ink tack levels and flow characteristics – and affects print quality and making for tricky anilox and plate clean-up.

By installing an ink temperature control system, printers can maintain steady command over all the ink properties without using additives. They also enjoy better imaging, easier wash-ups and quicker job changes.

There is no question that basic market pressures are challenging today’s corrugated printers. But industry suppliers have responded with skill in refining their technology to help their customers meet these demands. As an integral part of the printing process – from blades, to chambers, to anilox rolls, to plate, to cushion, to temperature, to viscosity, to pH – the ink delivery system is a good place to start.

In the next post in our Corrugated Converters at the Crossroads blog series, we will continue to look at how the industry is responding to these big changes and evolving with new technology. Watch for Part 3 – ” This Is Not Your Father’s Pressroom“

Click on the link below to view the first post in the series:

Part 1: “The Consumer Is King” – Read about the forces behind the corrugated package printing renaissance
The Right End Seals Will Prevent Leaks in Your Doctor Blade Chamber System
In an enclosed doctor blade chamber system, the job of the end seals is to keep the coating or ink from leaking out of the ends of the chamber. Selecting the right end seals for your application is critical to achieve proper doctor blade seating and prevent leaks. If used correctly, these inexpensive consumables will ensure graphic quality and save a printer thousands of dollars in waste, downtime and replacement of other press parts due to premature wear.

Problems That Result from Failed End Seals
- Chamber leaks and mess
- Poor graphic quality and ink/coating waste
- Excessive doctor blade wear
- Premature anilox roller wear and scoring
- Press downtime
Why Chamber Leaks Occur

While there are other causes of chamber leaks, failed end seals are responsible for the lion’s share. It is important to use an end seal material that is compatible with the type of ink or coating being used, the length of the run and the press speed. Good seal design for a proper fit is also critical to ensure that end seals contain the liquid within the confines of the chamber. Incorrect end seal size and shape will leave gaps for fluid to leak out of the ends. If the seals aren’t sufficiently lubricated, the increased friction against the anilox roller will cause buildup and leaking. Enlist the help of your end seal supplier to work through these issues and make sure that you are using the correct end seals for your application.

When a chamber is leaking, a press operator will often try to fix the problem by increasing the load pressure instead of looking for the cause of the leak. End seal leaks should never be resolved by increasing chamber pressure. The additional pressure increases friction between the doctor blade and the anilox roll and causes both to wear prematurely. Paying a little extra attention when installing doctor blades and end seals can prevent many leaks from occurring in the first place. After installing new end seals, a press operator should evaluate the chamber and confirm that there is a snug end seal fit with no gaps or distortion. The doctor blade should have some upward pressure to form an adequate seal, but not so much that it requires extra loading pressure to make contact with the anilox roller in the middle of the blade.

End Seal Materials for Chamber Systems

There are various end seal materials which range in abrasion resistance, durability and solvent resistance. Again, your end seal supplier is a good resource to help you determine the best material for your application:
1. 1. Foam seals are the most common and the least expensive type of end seals. This material generally does not perform as well as other materials and may not be a good choice for long runs, higher press speeds and certain fluid chemistries. There can also be a lot of variation in the density of the material which can range from super firm to more malleable.
1. 1. Neoprene or rubber seals offer longer life compared to foam seals. They are compatible with aqueous and UV coatings & inks so they don’t have to be changed out between jobs. However, these seals do not seat well due to the coefficient of friction between the material and the anilox roller surface.
1. Pre-soaked felt end seals are a superior solution for resolving leaks. These end seals are oversized for a snug fit and pre-soaked in petroleum to reduce friction and prevent buildup. Felt end seals are compatible with all ink and coating types, provide a tighter seal and typically last longer than rubber and foam seals. Keeping felt seals lubricated with seal grease is key to their superior performance and longer life. Felt end seals tend to dry out after the anilox system is flushed with detergents and water. Applying seal grease to the radius portion of the seals after flushing the system will ensure a tight fit and extend the life of the seals by reducing friction.
Choosing the right seal material and design for your application and replacing end seals when necessary will help ensure that they do their job of keeping inks and coatings from leaking out of the chamber. Better yet, the right seals will allow for proper doctor blade seating and a predictable and even transfer of fluid from the anilox roller to the blanket. Despite their small cost, end seals have the power to save thousands of dollars in waste and downtime.
Corrugated Ink Delivery Systems: Two-Roll or Doctor Blade?
The flexographic ink delivery process has come a long way since the days when “Fragile – Do Not Drop” and “This End Up” were the only requirements of box printers. New press designs are able to achieve the quality of work that has traditionally been done by litho lamination, and corrugated printers have to produce a consistently high level of quality to compete. The evolution of the ink delivery process from a two-roll ink metering system to the enclosed doctor blade chamber has made this possible.

There are currently three types of ink metering systems used in corrugated printing applications: the two-roll system, the single blade system and the enclosed doctor blade chamber system. All three systems rely on an anilox roll to transfer ink to the plate. The difference lies in how the ink is applied to the anilox roll.

Two roll corrugated inking system

The Two-Roll Ink Delivery System

In the original two-roll ink metering system, a fountain roll rotates partially submerged in an open ink pan, picking up ink and applying it to the anilox roll. The anilox roll transfers the ink to the plate cylinder which then lays it down on the sheet. Though still widely used in the industry, there is a lot of variability in the two-roll system which results in a lack of control over the amount of ink transferred to the plate:

Imprecise wipe of the anilox roll leads to inconsistent volume of ink delivered to the sheet.

Color strength fluctuation and ink slinging can occur at higher press speeds due to the hydraulic force between the rubber roll and the anilox roll.

Transfer characteristics vary according to the hardness or “durometer” of the rubber roll.

Ink viscosity is subject to evaporation, dust and surface skimming due to the open tray design.

Single blade corrugated inking system

Single Doctor Blade Ink Delivery System

The addition of a reverse angle doctor blade added precision to the ink metering process. In the single blade ink metering system, a doctor blade made from steel, plastic or a composite material is used to replace the rubber roll. The blade is installed just beyond the ink metering nip to shear ink from the anilox roll surface. Doctor blade ink metering systems give the printer better control over the volume of ink being delivered to the plate. Where a rubber roll often leaves an additional ink film on the surface, a doctor blade shears ink cleanly from the roll. The inks perform better on press and a printer can achieve a more consistent ink film thickness. Ink consumption is reduced, and color application is consistent across the sheet even at higher press speeds.

Chamber doctor blade corrugated ink delivery system

Enclosed Chamber Doctor Blade System

The most recent development in the flexographic inking process is the enclosed chamber doctor blade system. In this system, two doctor blades are used along with an enclosed chamber to dispense the ink to the anilox roll. The reverse angle blade acts as the metering blade and wipes excess ink from the anilox roll. The trailing blade acts as a capture or containment blade and holds the ink within the chamber. Foam, rubber or felt gaskets seal both ends of the chamber and keep ink from leaking out. The ink is delivered through a closed loop from the ink pump to the doctor blade system and then back to the pump.

With this method, a printer can maintain ink viscosity because the enclosed design provides protection from evaporation of solvents or amines from the ink, depending on whether the ink is solvent or water-based. Also, dust, slinging and skimming are minimized. Better control over ink usage means lower ink consumption by as much as 15% per year. The system holds less ink than open pans, so there is not as much leftover ink at the end of a press run and ink can be removed and stored for future use.

Due to a more efficient cleaning process, a smaller amount of cleaning solution is needed to clean up a chamber so cleaning solution waste and disposal costs are also reduced. Color changes are quick, speeding up changeover and setup time on a run. The enclosed chamber system is more eco-friendly because of reduced ink consumption and disposal of waste ink as well as a lower volume of cleaning solution and water required to wash-up the station for a color change.

After years of being relegated to jobs with low graphics requirements, flexography now rivals other printing methods for quality. Today’s corrugated printers are able to produce products that are highly attractive and eye-catching to the consumer due to advances in the ink delivery process. Whether they opt for a single doctor blade system or see the benefits in investing in a dual blade enclosed chamber, printers gain clear advantages by using doctor blades in terms of controlling ink film thickness and maintaining color consistency.

Request a Free TruPoint Doctor Blade Sample
Take Care of Your Doctor Blade Chamber and It Will Take Care of You!

Carbon fiber chamber system by Celmacch

The job of a doctor blade chamber is to help deliver a precise, consistent ink film thickness to the substrate.  Like other parts of the press, the doctor blade chamber needs to be maintained and inspected on a regular basis to ensure its peak performance. Taking the time to do this is a smart way to maximize press uptime and minimize costs.

What Can Go Wrong

1. The chamber needs cleaning – The doctor blade chamber requires regular cleaning to make sure it functions properly. Dried ink and coating particles can interfere with doctor blade seating in the blade holder and cause the chamber to go out of alignment.

2. The doctor blade chamber is not aligned properly – The doctor blade and anilox roll work best together when there is light, consistent contact between the two. If the blade does not have even contact with the roll due to chamber misalignment, it will not shear the ink cleanly and consistently from the anilox roll surface.

Doctor blade chamber corrosion

3. There is corrosion or pitting in the chamber components – Over time, regular exposure to harsh cleaning chemicals can cause corrosion and pitting in parts of the chamber. This can create recesses in the metal that prevent the blade from lying flat in the holder. Pitting also makes cleaning difficult, and particles from a corroded chamber can dislodge, settle into the ink and score anilox rolls.

4. The chamber is bowed or warped – Due to the length of the doctor blade chamber, it can bow and become warped from being mishandled. When bowing or warping occur, the blade will not lay flat along the full surface of the blade holder and contact the anilox roll uniformly when engaged.

Oftentimes, the press operator may try to correct some of these issues by increasing pressure to force contact between the anilox roll and doctor blade. While this may fix the problem temporarily, it often makes it worse. The added friction from excessive blade-anilox contact can cause chamber leaks and accelerated wear on the blade and roll.

What To Do

1. Clean the chamber – A cleaning routine involves wiping down the chamber with a cloth and flushing with approved cleaning solutions every day to remove ink deposits and particles from the doctor blade and blade clamp.  (This can take place when the press is shut down to clean the anilox roll which is also recommended on a daily basis.)

2. Verify chamber alignment – Operators should take the time to make sure the system is properly aligned and parallel on a regular basis. This will prevent early and excessive doctor blade and anilox wear and ink leaks.  If aligned properly, the system will remain stable even at increasing press speeds.

3. Inspect the chamber for defects – Chamber bodies should be flat and straight. This should be confirmed periodically (such as when other scheduled maintenance is taking place). To check, take a long straight edge and lay it along the full length of the doctor blade. Look for gaps which indicate that the chamber is bowed or warped. Also, examine the blade mounting surface and holder for corrosion and pitting. The chamber should be replaced if any of these conditions are evident.

4. Replace consumable parts – It is important to replace doctor blades and end seals when needed. Skimping on these inexpensive consumables is penny-wise and pound-foolish! Using new blades and seals to ensure a good contact area with the anilox roll and a tight chamber seal will prevent chamber leaks and anilox roll damage.

5. Standardize a cleaning and maintenance routine – Establish a recommended schedule of cleaning and maintenance for the doctor blade chamber. Make sure that procedures are documented and press operators are properly trained and evaluated.

Tresu’s carbon fiber E-Line chamber

6. Convert to a carbon fiber chamber system – In addition to other benefits, carbon fiber chamber constructions, such as the ones pictured here by Celmacch and Tresu, offer superior resistance to corrosion and pitting.

The doctor blade chamber is a precision tool that plays a vital role in producing a consistent product, and a regular routine of cleaning and maintenance will ensure its peak performance. A small investment here will go a long way to guarantee that this press component does its part in keeping your bottom line healthy and your customers happy!
Cut-to-Length Doctor Blades Can Reduce Ink Chamber Leaks
Doctor blade chamber leaks are costly in terms of downtime and waste. While failed end seals are responsible for a large number of chamber leaks, ill-fitting doctor blades can also contribute to leaks. Ordering cut-to-length doctor blades from your supplier is a smart way to reduce leaks, maximize doctor blade and end seal performance and save a printer thousands of dollars every year.

Problems arising from Chamber Leaks:

Ink waste

Substrate waste

Excessive solvent consumption for clean-ups

Downtime for change-overs

Reduced doctor blade life

Scored anilox rolls

Increased end seal consumption

Chamber leaks are a nuisance in the pressroom that cause frustration and reduce press efficiency. When faced with a leaking chamber, a press operator has to stop the press and clean up the mess. Often, he will try to fix the problem by increasing the load pressure instead of looking for the basic cause of the leak. While this may work as a temporary solution, it can lead to other problems such as accelerated doctor blade and anilox wear. The increased pressure may also force ink out of the ends of the chamber, making the situation worse. Paying a little extra attention when installing doctor blades and ends seals can prevent many leaks from occurring in the first place.

Causes of Chamber Leaks:

Improper seal material

Bad seal design

Lack of proper seal lubrication

No dead bands on anilox rolls

Anilox roll chips

Incorrect doctor blade length

Failed end seals account for many chamber leaks. Using an end seal material that is not compatible with the type of ink being used, the length of the run or the press speed will allow ink to escape from the ends of the chamber.  Ink build-ups can result from not using the appropriate lubrication to reduce friction between the anilox roll and end seal. If the seals are not a proper fit, they will not do their job at containing ink within the confines of the chamber. Working with your end seal supplier is a good way to work through these issues and ensure that you are using the correct end seals for your application. (View End Seal Brochure)

The condition of the anilox roll can also play a role in chamber leaks. If the roll lacks a dead band (an unengraved area) at each end, ink will build up there and cause the seals to fail. Chips on the ends of the anilox rolls can also create ink buildup and compromise the integrity of the end seals.

Incorrect Doctor Blade Length can cause Chamber Leaks

In addition to failed end seals and defects in the anilox roll, doctor blades that are too short or too long

Doctor blade is the correct length for the chamber

can be another source of leaks.  When changing a doctor blade, it’s important to make sure that the new blade is the right size for the chamber and installed correctly. If it’s not a perfect fit, the doctor blade provides a gap through which ink can leak out of the chamber.

When properly installed, the doctor blade should have some upward pressure from the end seals to ensure a sufficient seal. A very slight rise in the blade is okay, however, extra loading pressure should not be necessary to get the blade to wipe the center of the anilox roll.

When a blade is too short or too long for the chamber, it prevents the end seals from doing their job. The blade should come to about halfway across the tops of the end seals when placed in the chamber. If the blade does not reach the seals, then the seals can actually prevent contact between the doctor blade and the anilox roll.

Doctor blades are too long for the chamber

On the other hand, if the blade extends beyond the outer edge of the end seal, it may create a small opening between the underside of the blade and the end seal which creates a path for ink to flow out of the chamber. If it’s too long, the blade may also become wavy and not lie flush with the roll, causing uneven metering and leaking.

Installing doctor blades that are a perfect fit for the chamber will eliminate this source of leaks. When ordering doctor blade material by the roll, it is important to confirm the proper blade specifications with your chamber OEM to make sure that press operators are cutting blades to the correct length.  An easier way to ensure the proper size is to order cut-to-length doctor blades from your supplier that are ready to install right out of the box.

Cut-to-length Doctor Blades can Reduce Chamber Leaks

Doctor blades that are the incorrect size for the chamber can be a frustrating source of chamber leaks, downtime and waste. Installing blades correctly and making sure that they are the precise length according to OEM specifications is one way to prevent this problem. Ordering cut-to-length doctor blades from your supplier will not only speed up blade changes but also ensure a perfect fit to maximize blade performance and minimize leaks.
Request a Free TruPoint Doctor Blade Sample
3 Steps to Ensure Proper Doctor Blade Alignment
Proper alignment of your doctor blades(s) to the anilox roll (or any roll being wiped or cleaned) is critical to the performance of any ink or coating metering system. This alignment plays a pivotal role in preventing premature doctor blade and anilox roll wear, reducing leaks, and minimizing downtime. Let’s dive into the key aspects of blade alignment to optimize the performance of your process.

Doctor Blade Functionality

Doctor blades are designed to remove excess ink from the surface of the anilox roll. To achieve this, it’s imperative to maintain consistent, light contact between the doctor blade and the anilox roll along its entire face. Variation from this ideal contact can lead to problems including inconsistent transfer of ink or coating to the substrate and premature anilox roll wear.

Causes of Incorrect Contact

Several factors contribute to inconsistent contact between the doctor blade and the anilox roll:

Blade / Blade Holder Alignment: Ensure the blade is not skewed, offset, or misaligned with the centerline of the anilox roll.

Poor Blade Installation: Properly seat the blade in the holder and avoid overtightening to eliminate ripples or buckling of the blade.

Inconsistent Pressure: Maintain even pressure across the blade holder to prevent variations in blade contact.

Consequences of Incorrect Alignment

Deviation from proper alignment often shows up as uneven ink or coating thickness. Frequently operators try to overcome this problem by increasing blade pressure to compensate for the underlying issue.

This quick fix may temporarily address ink or coating problems but will eventually cause accelerated wear of both the doctor blade and anilox roll. Accelerated blade wear means more frequent blade changes and increased downtime. Accelerated wear of the anilox roll can lead to uneven or inconsistent ink or coating density.

How to Check Doctor Blade Alignment

Start with a clean blade doctor blade chamber (dual blade) or doctor blade holder (single blade) and make sure blades are installed firmly against stops, with no buckling.

Slowly engage the blades against the anilox roll, and verify the blade-to-anilox contact occurs simultaneously across the blade face.

For dual-blade systems, there are (4) checkpoints; top and bottom blades at both ends of the doctor blade chamber.

For single-blade systems, there are (2) checkpoints at the left and right ends of the blade holder.

The goal is to make sure all checkpoints contact the anilox or coating roll at the same time.

Adjust if necessary to achieve uniform simultaneous contact.

Pro tips: When aligning a doctor blade chamber (dual blade), remove end seals to create an unobstructed view of blade and anilox contact.

A feeler gauge (or business card!) is a great tool to help compare blade to anilox pressure.

Maintaining proper doctor blade to roller alignment is fundamental to optimizing your ink or coating metering system. Avoid the temptation to increase blade pressure to overcome misalignment as this can lead to shortened blade life and accelerated anilox roll wear.

By investing a few minutes in checking your setup, you’ll reap long-term benefits in terms of time, cost savings, and reduced waste. Remember, a well-aligned chamber ensures your doctor blade performs at its best, delivering exceptional results.

For detailed instructions on doctor blade installation and visual guides, download our 3 Keys to Success Infographic.

Download Infographic

Tag: ink chamber

Corrugated Converters at the Crossroads Blog Series Part 2 “Necessity is the Mother of Ink Delivery Innovation”

Doctor blade chamber systems

Doctor blade materials

Anilox rolls

Plate materials and plate carriers

Ink temperature control systems

The Right End Seals Will Prevent Leaks in Your Doctor Blade Chamber System

Problems That Result from Failed End Seals

Why Chamber Leaks Occur

End Seal Materials for Chamber Systems

Corrugated Ink Delivery Systems: Two-Roll or Doctor Blade?

The Two-Roll Ink Delivery System

Single Doctor Blade Ink Delivery System

Enclosed Chamber Doctor Blade System

Take Care of Your Doctor Blade Chamber and It Will Take Care of You!

What Can Go Wrong

What To Do

Cut-to-Length Doctor Blades Can Reduce Ink Chamber Leaks

Problems arising from Chamber Leaks:

Causes of Chamber Leaks:

Incorrect Doctor Blade Length can cause Chamber Leaks

Cut-to-length Doctor Blades can Reduce Chamber Leaks

3 Steps to Ensure Proper Doctor Blade Alignment

Doctor Blade Functionality

Causes of Incorrect Contact

Consequences of Incorrect Alignment

How to Check Doctor Blade Alignment

For detailed instructions on doctor blade installation and visual guides, download our 3 Keys to Success Infographic.