Category: Blogs

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.

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Optimizing Your Doctor Blade Trialing Process

Testing a new doctor blade in your printing operation should be a collaboration with your suppler that boosts performance while avoiding costly guesswork. Instead of randomly ordering samples, follow a systematic, data-driven approach.

Collaborate
Start by sharing key details about your press—dimensions, machine model, blade holder type, ink specifics, and any pain points you are experiencing. This information lets your supplier recommend tailored doctor blades rather than generic samples. There are a lot of options in terms of material type, thickness, and edge configuration.

Run Your Trial
Your supplier will likely send you one or more blades based on your provided data. Appreciate what these are and take care when testing them. They’re designed for your specific needs and should be used in a controlled production run.

Crawl, Walk, Run

Install and test the blades under normal operating conditions. Consider starting on a single print/coating station if the blade is new to you. Contact your supplier with any questions related to setup or installation and alignment. Clean the blade holder or chamber, using minimal blade pressure.

Provide Feedback

Complete any surveys your supplier has seeking feedback on the sample performance. Record important details and observations made during the testing related to blade longevity, metering quality, and any anomalies. Feedback is especially important if the blade fails as this can help your supplier make alternative recommendations by changing blade material, thickness, or edge configuration.

The Takeaway
An iterative, collaborative testing process is more efficient than random sampling. By working closely with your supplier—starting with detailed information, running controlled trials, carefully documenting results, and refining based on feedback—you achieve optimal performance and a long-term printing solution. Embrace this method to streamline your doctor blade selection and keep your press running at peak efficiency.

Trial a TruPoint Doctor Blade
Three Reasons Why Sheetfed Offset Printers Should Replace Their Steel Doctor Blades with Plastic

The goal of a sheetfed offset printer, like every printer, is to produce printed pieces efficiently and economically. In sheetfed offset coating applications, selecting the right doctor blade will help keep presses running and minimize costs while maintaining a safe pressroom environment. By replacing steel with non-metallic doctor blades, a printer can reduce pressroom injuries, eliminate anilox roller scoring and extend blade life.

Three reasons to replace your steel blades with non-metallic doctor blades:

1. Pressroom Safety

Steel doctor blades are responsible for a large number of pressroom injuries each year. As the blades wear, their edges become honed through contact with the anilox roller. This leaves razor-sharp tips that can cause serious cuts. Press operators need to be extremely careful and wear protective gloves when removing the worn blades from the press to avoid injuries. Due to their material composition, non-metallic doctor blades are safer to handle even when worn. Switching to non-metallic doctor blades will reduce lost-time accidents and can save a printer a lot of money in terms of workman’s compensation insurance rates, medical bills, labor replacement expenses and press downtime.

2. Anilox Roll Scoring

Steel blades are also to blame for many cases of anilox roll scoring. Incorrect blade installation or too much blade pressure can cause small fragments of metal to break away, become trapped against the roller and destroy rows of anilox cells as the roller turns. The score line appears as a thick band which runs around the circumference of the roller and affects the corresponding area of coating coverage. The printer wastes substrate and coating and has to have the roller resurfaced or replaced at a significant cost. In addition to scoring, steel blades accelerate wear on the surface of the anilox roller. The friction between the blade and roller erodes the anilox cell walls. As a result, the cell volume is reduced and the anilox roller can no longer carry the precise volume of coating that it was designed to deliver. Non-metallic blades are non-abrasive and will neither score rollers nor cause accelerated wear on the anilox roller.

3. Blade Life

Steel blades wear quickly and need to be replaced frequently. Non-metallic blades, on the other hand, have a long, slow wear period and deliver a consistent application of coating for the duration of the print job. They have a low coefficient of friction which means they need to be changed out less often. By switching from steel blades, a printer can minimize press disruptions and keep presses running longer.

For sheetfed offset printers using in-line tower coating units, there is a non-metallic blade available for every application. Tresu and Harris & Bruno chamber users can opt for the TruPoint Orange® blade with MicroTip® edge – a blade capable of effective metering with the added advantages of improved safety, reduced anilox roller scoring and longer blade life.

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!
New Polymers Meter Like Steel Doctor Blades

Steel doctor blades used to be a printer’s only option to produce high-end graphics. It wasn’t because he didn’t want longer blade life and the safety benefits that came with using plastic, steel was simply the only material that could sufficiently meter a high line screen roll. Not anymore! Today’s next generation polymers and advanced tip engineering have at last resulted in a non-metallic doctor blade with the metering quality of steel. This blade can replace steel doctor blades in a full range of flexo printing applications from solids and lines, to reverses and fine print, to screens and process work. Here’s why.

Steel Doctor Blades vs. Traditional Plastic

Due to its thinness and stiffness, steel has been the only blade material that could achieve a fine point of contact sufficient to execute a clean wipe on a high line screen anilox roll. By comparison, the characteristics of traditional plastic doctor blades require them to be thicker to provide the same rigidity. While they have other benefits in terms of safety and blade life, their thickness prevents them from maintaining a fine contact area with the anilox. As they wear and their contact area with the anilox roll grows, plastic blades produce changes in tonal value and dot gain when metering high line screens. For this reason, they have historically been limited to jobs with low to modest graphics requirements.

Next Generation Polymers

Now, specially formulated polymer doctor blades can compete with steel in the most demanding graphics applications. Unlike traditional plastic, the stiffness of the next generation material with a precisely engineered MicroTip™ edge allows the TruPoint Orange doctor blade to achieve and maintain a fine contact area with the anilox roll. Orange can deliver effective metering on line screens up to 2,000 lpi (785 L/cm) and produce graphics of the highest quality. The following diagrams compare the contact areas of traditional plastic, steel and next generation polymer blades:

Doctor Blade Contact Area Comparison

As shown, the contact area of a worn traditional plastic blade grows to .060″ (1.52mm) compared to a contact area of .016″ (.40mm), for a worn steel blade. The next generation polymer is able to maintain a contact area of .012″ (.305mm), equal to or smaller than that of most steel doctor blades, throughout the life of the blade due to the edge design. The engineered tip wears slowly and evenly and delivers consistent ink film thickness for the duration of the print job.

Today’s innovations in polymer doctor blades offer printers a viable alternative to steel. A combination of advanced materials and new tip technology has yielded a blade that meters as well as steel on the highest line screens yet retains the benefits of traditional plastic. Printers no longer have to compromise on anilox scoring, blade life, and safety to fulfill the most demanding graphics requirements!

Request a Free TruPoint Doctor Blade Sample
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
UV Ink Spitting is a Dirty Habit

As competition for shelf space heats up, brand owners are looking to create more compelling-looking products. That means prettier graphics, more vivid colors and unique packaging. Today’s narrow web printers, also facing intense competition, are turning to UV inks and specialty coating formulas to produce higher print quality, speed up turnaround times, increase throughput and reduce downtime. Unfortunately, using a steel doctor blade to meter these chemistries often result in the UV ink spitting onto your print job, causing a speckled appearance. Where steel falls short, the TruPoint Orange® next generation doctor blade may be the solution in these applications.

Eliminate UV Ink Spitting with TruPoint Orange

The surface energy and flexibility of a steel blade can impede a smooth transfer of ink to the plate. The dyne level of a steel blade is higher than that of TruPoint Orange, causing the ink to have a greater tendency to adhere to the blade. With Orange, the characteristics of the material give the blade a significantly lower dyne level than steel, decreasing the attraction between the doctor blade and ink and facilitating a more fluid movement of ink to the plate.

Also, UV ink has a normal viscosity of 5-7 times that of water and solvent-based inks, and its thixotropic properties (ability to thin out when agitated) make it transfer differently on press. This thicker consistency applies excessive pressure to a steel metering blade, often causing the ink to sling off, or “spit,” especially at high press speeds. The TruPoint Orange doctor blade prevents UV ink spitting. The blade’s tip provides enough stiffness to maintain a strong contact area with the anilox roll and prevent ink from sliding under the blade.

Specialty Inks and Coatings Are Abrasive

Specialty coatings and tactile finishes such as glitter, pearlescent, textures and soft touch, are being used to enhance the look of product packages, but the same challenging properties of UV inks also exist in these formulations. They have high viscosities and contain large particles, making it difficult to accurately control the volume being applied. These chemistries, and coarse anilox surfaces used to apply them, are extremely abrasive to steel doctor blades – printers consume blades faster which increases downtime and costs. TruPoint Orange next generation polymer blades are highly abrasion-resistant and chemically compatible with all ink and specialty coating formulas; they last longer and minimize press downtime for blade changes. Click Here to Read “5 Ways to Conquer UV Ink Spitting”

As the industry evolves to keep up with the demands of the market, printers are faced with new challenges. The ink and coating formulas being used to make products stand out on the retail shelf and improve pressroom efficiency are difficult to meter with steel doctor blades. Due to its material properties and tip design, TruPoint Orange can help by reducing downtime and costs associated with UV ink spitting and accelerated blade wear.

Request a Free TruPoint Doctor Blade Sample
Plastic Doctor Blades – Advanced Polymers Compete with Steel

While steel doctor blades used to be the only option to produce high-end graphics, a printer had to deal with the shorter blade life and pressroom injuries that came along with using the material. No more! Recent innovations in materials technology and tip engineering have at last resulted in polymer doctor blades that can compete with steel and also resolve a number of common problems in the pressroom.

Steel doctor blades are thin and rigid which allows them to achieve a fine contact area with the anilox roll. A fine contact area is required for the blade to achieve an effective wipe on high line screen rolls used in more demanding graphics applications. Traditional plastic doctor blades, on the other hand, have long been preferred for their longer life in less demanding graphics applications. Plastic blades had to be engineered thicker in order to provide enough rigidity to maintain good contact with the anilox roll and achieve a sufficient wipe. The thickness and larger contact area prevented these blades from being effective when used to meter mid to high line screen rolls. While they lasted significantly longer and were safer to handle than steel blades, they tended to leave more ink on the surface of the roll; this produced dot gain and poor image quality in the printed piece.

Steel Blade Disadvantages

Despite its reputation for being the superior metering material, steel has many disadvantages. The blades wear quickly and need to be replaced frequently. Operators are also exposed to cut hazards when removing the worn blades from the press, and the metal fragments can come loose and score anilox rolls. The environmental impact of using steel can also be significant. There are huge energy costs associated with the manufacture of steel blades as well as anilox resurfacing, and additional station clean-ups generate a lot of contaminated waste. Despite these drawbacks, steel was believed to be the only doctor blade option to execute a clean wipe on a high line screen anilox roll, leaving printers no choice.

New polymer doctor blade contact area is smaller than steel

New Polymer Doctor Blades

Today, specially formulated polymer doctor blades offer the best of both steel and plastic. Unlike traditional plastic doctor blades, the next generation material allows for a precisely engineered micro-tip which wears slowly and evenly throughout the life of the blade. The micro-tip edge allows the blade to achieve a fine contact area with the anilox roll and deliver effective metering on line screens up to 2000 lpi or 785 L/cm. The long and steady wear period of the next generation polymer doctor blade maximizes press uptime and allows for consistent ink film thickness for the duration of the print job.

Compared to steel, the polymer material does not develop a dangerous cutting edge after use, and the worn blades are safe to handle. Also, the material will not separate, splinter or crack and produces no metal fragments that can lodge between the doctor blade and the anilox roll. A reduction in anilox scoring means better image quality, less downtime, less waste and lower roll replacement costs.

Polymer doctor blades have come a long way in recent years. A combination of advanced materials and a micro-tip edge has produced revolutionary new doctor blade option for printers: a blade that can compete with steel in the most demanding graphics applications while retaining the safety and blade life benefits of traditional plastic.

Request a Free TruPoint Doctor Blade Sample
UHMW Users Upgrade to DuraPoint for Longer Blade Life

Flexo Concepts’ exclusive TruPoint DuraPoint™ blade is a next-generation UHMW doctor blade with a proprietary high-density formulation for superior blade life and enhanced graphics. Used in applications that require extended blade life, DuraPoint has been shown to last 25-30% longer than traditional UHMW products and is a direct replacement as both a metering and a containment blade.

Upgrade from UHMW to DuraPoint

DuraPoint’s construction makes it ideal for printers who produce moderate graphics but want the added benefit of longer blade life. The properties of the material allow it to maintain more consistent metering throughout the life of the blade for increased graphics requirements. By upgrading To DuraPoint, corrugated printers can increase press uptime while maintaining all the benefits provided by traditional UHMW.

DuraPoint is available in the same widths and thicknesses as Flexo Concepts’ UHMW blade and offers a drop-in replacement for standard UHMW. The blade fits in existing blade clamp configurations, requiring no shims or modifications to the holder.

Flexo Concepts is the leading global supplier of UHMW products. DuraPoint and Green are the company’s premier products for corrugated applications that demand longer blade life and enhanced graphics.
Steel Doctor Blades Cause Anilox Roll Scoring and Injuries
Steel doctor blades are often the cause of anilox roll scoring and severe personal injuries. Switching to nonmetallic blades can not only ensure print quality and minimize waste, but also prolong the life of anilox rolls and reduce the risk of lost-time accidents.

Anilox Roll Scoring from Steel Doctor Blades

Score line on an anilox roll

Steel doctor blades are the cause of many anilox roll scoring incidents. Improper blade installation and excessive blade pressure can cause small fragments of the metal blade to break away, become lodged against the roll and destroy rows of anilox cells as the roll turns. The damaged area or “score line” appears as a thin band which runs around the circumference of the roll. The corresponding area of print will either show a dark or light streak depending on the depth and severity of the score line. Either way, the roll has to be resurfaced or replaced at a significant cost to the printer.

To reduce anilox roll scoring from steel doctor blades:
- Ensure the roll’s engraving is smooth when received from the anilox supplier
- Filter inks using current magnet technology
- Maintain a good anilox cleaning regimen
- Ensure proper chamber alignment and blade installation
- Change blades and end seals frequently
Injuries from Steel Doctor Blades

Steel doctor blades can also be blamed for a large number of pressroom injuries. As steel blades wear, their edges become honed through contact with the anilox roll. This leaves razor-sharp tips that pose a significant cut hazard. Press operators always need to be cautious when handling steel blades but especially careful when removing the worn blades from the press for this reason. There are substantial costs associated with accidents that occur on the job in addition to the emotional impact of a workplace injury. The cost of lost-time accidents from a steel doctor blade ranges from an increase in insurance rates and workman’s compensation claims to medical bills, labor replacement expenses and press downtime.

When it comes to the pressroom, safety is everyone’s concern. To reduce the risk of injury and eliminate the risk of anilox roll scoring, consider switching to non-metallic blades instead.
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
Doctor Blade Installation: Correct Angle and Pressure are Needed for Consistent Performance

The anilox roll and doctor blades are designed to work together to deliver a precise amount of ink to the plate. It is important to take time during a doctor blade installation in order to ensure print quality.

A doctor blade that’s installed correctly will have uniform, balanced contact with the anilox roll and remove ink consistently across its surface. Blade positioning, orientation, angle and pressure will aﬀect the delivery of a precise amount of ink to the plate, and proper installation will give the printer control over consistent, repeatable print quality.

3 Keys To Doctor Blade Installation Success
1. Handling
It’s essential to handle the doctor blade with care to prevent damage. Additionally, make sure to clean the surface of the doctor blade holder before inserting the blade.

2. Orientation
It is essential that the metering and containment blades be positioned correctly when they are installed. Depending on the rotation of the anilox roll, the metering blade could be positioned on the top or the bottom of the chamber. Keep in mind that the metering blade is always the last blade to contact the roll before the ink transfers to the plate. The containment blade is installed in the opposite location. If the two blades are installed in reverse, the metering blade will not achieve the appropriate point of contact with the roll and remove the correct amount of ink before transfer. It is important to remember that the MicroTip or bevel should point away from the roll or towards the chamber to prevent streaking.

The angle at which the blade comes into contact with the anilox roll is also crucial to proper doctor blade installation and optimum blade performance. Ideally, the contact angle should be 30° tangent to the anilox roll circumference. In reverse angle and chamber blade applications, the doctor blade angle should be between 28° and 32°. If the blade angle drops below 28°, a larger part of the blade’s edge will come into contact with the roll. When this happens, the contact area is too big to meter eﬀectively and the blade may allow ink to pass underneath or “hydroplane” at high speeds. If the angle exceeds 32°, it will result in faster wear on the blade.

3. Pressure
When a doctor blade chamber is properly aligned, light pressure between the anilox roll and doctor blade is all that’s needed to produce a clean wiping action. In fact, applying the lightest possible pressure necessary to maintain sealing and metering will produce the best results. Excess pressure can cause a deterioration in print quality, wasted ink and substrate, and accelerated.

blade and anilox wear. A good way to tell if you’re using the correct amount of doctor blade pressure is to look at the roll once it’s inked. Before increasing pressure, the anilox roll will appear glossy. This is a sign that too much ink is remaining on the surface. Pressure should be increased gradually until a satin ﬁnish appears on the surface of the roll. A satin ﬁnish is a good indication that the correct amount of pressure has been achieved and the doctor blade is eﬀectively shearing the excess ink from the roll. If pressure is increased beyond this point, the doctor blade edge will bend and hydroplane. The roll will again begin to look glossy because it is ﬂooded with too much ink.

The doctor blade plays a key role in the performance of the anilox roll and the printer’s control over print quality. Take the time to double-check blade positioning, orientation, pressure and angle during doctor blade installation to guarantee that the anilox roll delivers the precise volume of ink for which it was designed.

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