Doctor Blade

Doctor Blade Description:

Metal Industrial has prioritized meeting customer needs for many years by continuously adding new features to their ink doctor blade. Our blades are used in gravure packaging, flexographic printing, UV flexo, offset varnishing, decorative materials printing, pressure-sensitive printing, screen printing, and coating applications.

Metal Industrial uses precision CNC production lines to produce high-quality ink doctor blades. Our strict production and inspection processes ensure our products stand out in the doctor blade industry.

By adhering to a quality-first standard and focusing on customer requirements, Metal Industrial allows clients to maintain consistent print quality in long print runs and minimize downtime.

Our ink doctor blades are suitable for gravure and flexographic printing. Issues such as color tone, streaks, filament, stripes, and chrome layer wear commonly arise due to the variety of printing machines and substrate materials. Metal Industrial offers a range of blades to address these varied needs. For gravure packaging printing, thicker inks often cause streaks and extra wear on blades and cylinders. Our blades adapt to these inks and are reusable, reducing downtime.

Flexographic Printing:

Metal Industrial’s ceramic blades are ideal for coating and laminating processes in flexographic printing. Modern flexo presses usually use anilox rollers and doctor blades for ink transfer. The print width of flexo presses ranges from 200mm to 4000mm. Single-blade systems work for smaller presses, while closed systems are better for medium to large presses. Printing speeds range from 50 to 450 meters per minute. The reverse blades typically have a 30°-40° angle. Due to the smooth surface of ceramic anilox rollers, blade pressure should be minimal. Factors affecting blade life include the shape and line count of the anilox cells and blade thickness.

Metal Industrial’s ceramic blades suit flexographic printing, with 0.20mm and sometimes 0.15mm thick blades. Closed systems do not require backup blades, so standard, beveled, and composite blades are all applicable.

Halftone Printing:

For halftone printing, such as label printing, blade thickness is usually 0.075mm. The general principle is that thinner blades perform better.

Product Features:

• Smooth, straight, and ready to use without sharpening
• Suitable for forward, reverse, and closed scraper systems
• Reduces downtime

Specifications:

• Width: 8-80mm
• Thickness: 0.15-0.5mm
• Blade edge height: 1.3-1.5mm
• Blade edge thickness: 0.075mm
• Hardness: 580HV
• Straightness tolerance: 0.1/3000mm
• Packaging: 100m, 200m, or custom

Installation Requirements: For gravure printing, the ideal contact angle for blade installation is 55-65°. A smaller angle can result in incomplete wiping and plate fog.

What do Doctor Blade Mean?

A doctor blade is a thin, flexible blade, typically made of metal or plastic, used in various industrial coating and printing processes to control the thickness of a liquid film applied to a surface. In printing, particularly flexography and gravure, the doctor blade plays a crucial role in removing excess ink from the surface of the printing cylinder (anilox roll or gravure cylinder), ensuring that only the ink held within the engraved cells is transferred to the substrate. The term “doctor blade” originates from its function of “wiping off” or controlling the amount of liquid.

Beyond printing, doctor blades are also used in other coating applications to meter or level the thickness of coatings applied to various substrates.

Uses and Applications of Doctor Blades

Doctor blades have diverse applications across several industries:

• Flexographic and Gravure Printing: This is one of the primary applications, where the doctor blade ensures a consistent and controlled amount of ink is transferred to the printing plate or substrate by removing excess ink from the anilox or gravure cylinder. This is crucial for print quality, color consistency, and preventing issues like flooding or smearing. They are used in various printing applications, including packaging, labels, newspapers, and flexible materials.
• Coating Processes: Doctor blades are used in various coating methods to apply thin films of liquids onto substrates. This includes:
  • Doctor Blade Coating: A method used to create thin films on large surfaces, controlling the thickness of the applied solution. Applications include manufacturing of electronics, solar cells, and specialized coatings.
  • Paper and Board Machines: Doctor blades are used to scrape off foreign material that accumulates on rolls, ensuring web quality and preventing damage to soft rolls. They also redirect the web to prevent wrapping around rolls.
  • Textile Coating: Applying coatings to fabrics for various properties like waterproofing or durability.
  • Adhesive Coating: Applying even layers of adhesive onto tapes and labels.
• Cleaning: In some industrial machinery, doctor blades are used to clean rollers and remove debris or excess material.

Common Materials for Doctor Blades

The selection of material for doctor blades is critical and depends on the specific application, the material being processed (ink, coating solution), the substrate, and the speed of operation. Common materials include:

• Metal Blades:
  • Carbon Steel: Economical and offers good initial sharpness. Different grades like bright and blue carbon steel are available.
  • Stainless Steel: Offers better corrosion resistance, especially with water-based inks.
  • Tool Steel: Provides enhanced wear resistance for longer blade life, particularly with abrasive inks or coatings.
  • Bronze: Used in some applications.
  • Coated Steel: Steel blades can be coated with materials like ceramics or carbide to increase wear resistance and reduce friction.
• Plastic Blades: Offer good durability and can last longer than steel in some applications. They are often self-lubricating and resistant to mechanical wear and abrasive chemistries like high titanium white inks and special effects coatings. Examples include:
  • Polyethylene: Good for soft rolls and when lubricated.
  • Polyester:
  • UHMW (Ultra-High Molecular Weight Polyethylene):
• Fiberglass and Carbon Fiber Composites: These materials offer improved wear resistance over metal blades, reduce roll scoring, and provide excellent cleaning performance. Carbon fiber blades offer the longest wear life and high flex resistance.
• Abrasive Blades: Used for specific applications like maintaining porosity of rolls or periodic removal of build-up. These can be made with fiberglass and epoxy resin or reinforced with carbon fiber.

Common Doctor Blade Shapes

Doctor blades come in various edge profiles and thicknesses to optimize performance for different applications:

• Straight Edge (Square Edge): A 90-degree edge, often used as a backer blade.
• Beveled Edge: An angled edge (e.g., Standard with a nominal 15° angle, Superhoned® with a 4.5° angle, Superhoned® Plus with a 2.2° angle) that provides a sharp contact point and controlled wiping action. The long bevel of Superhoned® edges helps control tip deflection and contact angle.
• Rounded Edge: Offers a strong, rigid, and polished working edge, suitable for lower screen anilox rolls or abrasive inks.
• Double Cut (Parallel Edge): Features two parallel cutting edges.
• Stepped Edge (Lamella Tip): A specialized profile that can improve wiping efficiency and reduce spitting in flexographic printing.

The thickness of the doctor blade also varies depending on the application and the required flexibility and stiffness. Common thicknesses for metal blades range from 0.004″ to 0.020″ or more.

Working Principle of Doctor Blades

The doctor blade operates by applying controlled pressure against the surface of a rotating cylinder (anilox or gravure) or a substrate being coated.

In printing:

1. Ink is transferred to the engraved cells of the anilox or gravure cylinder as it rotates through the ink fountain or chamber.
2. As the cylinder continues to rotate, excess ink remains on the non-engraved surface (land areas).
3. The doctor blade, held at a specific angle against the cylinder, wipes away this excess surface ink.
4. Only the ink held within the cells is then transferred to the printing plate (flexography) or directly to the substrate (gravure).

In coating:

1. A liquid coating is applied to the substrate.
2. The doctor blade is then drawn across the coated surface at a controlled angle and pressure.
3. The blade removes excess coating, leaving behind a film of a specific and uniform thickness determined by the gap between the blade and the substrate, as well as the blade angle and pressure.

The effectiveness of a doctor blade depends on factors such as the blade material, edge profile, thickness, the angle at which it is held against the cylinder or substrate, the applied pressure, the surface condition of the cylinder or substrate, and the properties of the ink or coating being used. Proper selection, setup, and maintenance of the doctor blade are crucial for achieving optimal results in printing and coating processes.

Welcome to inquire!

If you don’t find the shear blade you are looking for, we can also customize it, see our “Custom Blades” to learn how!

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Why Choose Metal?

1. One-stop hassle-free import service

Easy to enjoy the convenience of importing, from transportation to customs clearance, we handle the whole process, you just need to pay VAT and wait for the goods to arrive at the company.

2. Competitive Pricing

We have seen its blades used in countless applications and is ready to handle whatever project you throw our way -delivering accuracy, durability, and unmatched competitive pricing.

3. ODM & OEM Available

Whether you provide drawings, sketches or samples, we are able to draw and manufacture for you. We also have the ability to assist in modifying existing designs and specifications to improve almost any industrial tooling application. Please contact our dedicated sales team to discuss your specific requirements.

4. Quality Control

A series of testing and inspections are performed to control quality, including first article inspection, Incoming material inspection, and materials certified, In-process quality inspection, Final quality inspection.

5. Flexible procurement, unlimited cooperation

Whether you are an importer, distributor, wholesaler or end-user, we welcome you to join us with minimum MOQ, no hassle for inquiry and more freedom for purchasing.

6. Overseas monitor, production progress real-time report

Become your exclusive monitor, regular transmission of every important node in the production line, no matter how far away, the progress of the product as far as possible to grasp!

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