Doctor blade? Roll cleaning blade? Scraper? The term is used differently depending on the industry but the product’s purpose is the same–to clean or remove contaminants from a cylindrical surface. It’s not always easy to figure out which doctor or roll cleaning blade is best for a given application, so I sat down with Kadant Solutions’ Mike Six, Regional Applications Manager – Doctoring, to better understand roll cleaning blades and how to choose the correct one. Mike has worked for Kadant Solutions in various roles for over 12 years and currently supports the sales and service groups as a doctoring and roll cleaning expert.
V: What is a doctor or roll cleaning blade?
M: A doctor blade, roll cleaning blade, or scraper is any material in stick form that is run against a roll and is used to keep the roll clean. It can be just about anything like composite, metal, or plastic.
V: How does a doctor or roll cleaning blade work?
M: For a doctor blade to work it needs to be loaded against a roll with a proper doctor blade holder. The blade also needs to be set at the proper angle and with the proper pressure for the application. More specifically, the doctor blade scrapes the roll clean as it rotates and directs debris away from the process.
V: Why is a doctor or roll cleaning blade important?
M: If used properly it will save the customer money by increasing efficiency and decreasing maintence. If used wrong, it will have the opposite effect and potentially cause damage to the roll.
V: Where can a doctor or roll cleaning blade be used?
M: On any turning roll, roller, or cylinder. The most common applications are found in paper, steel, nonwovens, food processing, and synthetic fibers. But we have found that doctor blades are used in a variety of industries and applications; basically any process that requires clean rolls.
V: What type of doctor or roll cleaning blade should be used for high speeds? Low speeds?
M: Speed is not typically the primary consideration when deciding which type of blade to use. However, in general, for high-speed usage, a blade with higher carbon fiber content that has high wear resistance is considered desirable. For low-speed applications, a poly, cotton phenolic, or fiberglass blade may be used because the operating conditions are not as demanding. Typically, the roll characteristics and cleaning requirements are more important in determining the type of blade to use.
V: What type of doctor or roll cleaning blade should be used for high temp applications?
M: Temperature, like speed, is not typically the primary deciding factor when choosing a blade. However, one of the biggest considerations when choosing a blade is knowing the characteristics of the operating environment, including contaminants to be removed, roll temperature, line speed, and specific cleaning requirements.
V: What type of blade should be used when the application calls for gentle scraping?
M: The aggressiveness of the doctor or roll cleaning blade material depends on two things. First, the roll material. Second, the corresponding softness of the roll material. For example, consider a polyethylene roll cover. Poly roll covers can be hard or soft, so if only considering that factor it might seem safe to run a fiberglass blade on a hard poly cover. However, experience has taught us that only poly blades run cool enough on poly covers to be 100% safe for use, even if the cover is hard. Understanding WHY gentle is required is the key factor to selecting a gentle blade as gentle for one type of roll surface could be aggressive on a different roll surface.
V: What should you look for when choosing a doctor or roll cleaning blade?
M: Having an understanding of the roll surface, material, hardness, cleaning requirements, speed, and temperature are all important when selecting the most appropriate blade. Determining what the user is trying to achieve and how a clean roll would benefit the process are also important elements.
Most importantly, utilizing doctoring experts who have extensive knowledge and application expertise in both doctoring and roll cleaning can make a big difference in selecting a cost-effective blade for any given application.
Click here to download a free technical bulletin on doctor blades and roll cleaning solutions.