Home > Coatings > Knife Over Roll Coating Process: How Does It Work?

The knife over roll coating process may seem complicated, but with the right manufacturing partner, you don’t have to worry about it. Conversion Technologies International has the info you need. Check it out!

What is the knife over roll coating process?

The knife over roll coating process fits under a larger coating “umbrella”. We call it roll to roll coating, but knife over roll coating has distinct qualities—especially the precision blade. The precision blade sets this process apart, because we use it to apply a coating layer over a substrate. The knife stays in a gap above a backing roll, and as the roll moves, it scrapes excess coating off the substrate. This creates a flat, uniform surface. We’re able to control the thickness of the coating through the gap between the blade and the substrate. That’s one reason why we use knife over roll coating. It’s easily customizable, and it’s perfect for high-viscosity coatings.

The knife—which we sometimes refer to as a doctor blade—is so precise, we can position it over the substrate within 2 microns. When we’re working with high-weight coatings, we’re able to scrape it down to ideal smoothness. Additionally, the knife comes in different designs and shapes. You can procure blades with radius edges with thicker coatings, and square edges for thinner coatings.

This system allows us to ensure uniformity, which is extremely important in mass production. We often use the roll coating process for large scale orders. Anytime a large scale order suffers from inconsistent production, you’re wasting time, money, and resources. Enter: the knife coating method! An additional benefit is the fact that the process can ensure a smooth coating even if the substrate itself has an uneven surface.

Don’t forget: the knife coating process is also more affordable than other methods. As you scale up your business, cost efficiency will only become more important. The best thing you can do is save money wherever possible. 

What are the three types of coating?

There are three main types of coating. You’ll select an option based on how they fit your specific project—because there isn’t one type of coating that fits every need.

The most prominent types of coating include:

  • Industrial Coatings. Third party manufacturers like CTI often cover industrial coatings. They’re some of the most commonly used coatings, with $8.7 billion worth of coatings sold in 2021 alone. Industrial coatings are multifunctional, addressing issues including functionality, appearance, and longevity. They’re durable, yet they also ensure a professional, appealing look, if not quite to the extent as purely decorative coatings. While coatings have evolved over time to become more durable, we’ve always relied on industrial coatings to ensure a functional and aesthetically pleasing product.
  • Architectural Coatings. If any coating outdoes the industrial coating in terms of prevalence, it’s architectural coating. We use architectural coatings to beautify and stabilize interior and exterior surfaces in residential, commercial, industrial, and institutional buildings. That’s not all—they also cover factories! Of course, the “catch” with architectural coatings is that they might not apply as much to your manufacturing needs. A lot of them are DIY, utilized by homeowners in the form of primers, varnishes, stains, decorative paints, lacquers, and clears.
  • Special Purpose Coatings. These coatings fall into the more unique, less easily categorized space. The only unifying factor is in how they’re applied—typically “on the field”. This means we don’t apply them as often in factory settings. Several major fields rely on special purpose coatings, including the automotive industry and even the federal government. For that matter, traffic marking paint—yes, the paint you see on the highway—is a special purpose coating. The point of special purpose coating is less uniform, which allows for broadness.

Which industries rely on knife over roll coating most often?

  • Packaging
  • Paper
  • Adhesives
  • Labeling
  • Automotive
  • Medical and Pharmaceutical
  • Construction
  • Textiles and Fabrics

Frequently Asked Questions

Still have questions? We get it. Let’s cover some of the most common ones below.

What are the main features we should expect from knife over roll coating?

The knife over roll coating process features these key identifying features:

  • A precision blade
  • A supporting roll
  • A visible gap between the blade and the roll
  • Optional additions like heated backing rolls and additional blades 

What are the top benefits of knife over roll coating?

The benefits of knife over roll coating include:

  • High precision
  • Versatility
  • Affordability
  • Ease of use
  • Durability
  • Adjustability

Ultimately, knife over roll coating offers more uniform results, which is a huge factor as you consider scalability and efficiency.

Should I outsource manufacturing?

It really depends on your needs and plans. Many business owners outsource processes like knife over roll coating, but it’s not required. The great thing about working with an experienced company like CTI is that you can consult with us before making a decision. We’ll answer your questions and address any concerns you may have. It’s our job!

What should I do next?

Start the conversation! Give CTI a call at 419-924-5566 or contact us here. We’re here for you!