Doctor or Roll Cleaning Blades, Materials and Coatings, and Specifications and Designs
Doctoring? Roll cleaning? Scraping? Flaking? Continuous belt cleaning? These are terms for a similar process used differently depending on the industry, but the product’s purpose is the same–to clean or remove contaminants from roll surface.
What Is a Doctor or Roll Cleaning Blade?
A doctor blade, roll cleaning blade, scraper blade, knife, or flaker blade is any material in stick form that is run against a roll and is used to keep the roll clean. Doctor blade or roll cleaning materials can be just about anything such as fiber-reinforced composite, metal, or plastic.
In even simpler terms, a doctor or roll cleaning blade is a scraper which removes something off a spinning roll. Think of it similar to an ice scraper which removes snow and ice from a windshield, or a razor blade removing a sticker.
In processing industries, the doctor blade might remove paper pulp, water, or contaminants from a paper machine roll. The flaker blade could remove potato flakes or corn flakes from a food processing plant. Or a scraper blade might remove asphalt in roofing shingle manufacturing. Kadant roll cleaning blades are also used in the production of fiberglass mat, lithium-ion batteries, metals and steel processing, carbon fiber, synthetic fibers, tissue, wetlaid nonwovens, and many other process industries - any rotating roll that needs to be cleaned is an application for doctor blades.
Blade Materials and Coatings
Doctor and roll cleaning blades can be made from metals such as carbon steel, stainless steel, or bronze, plastics such as polyethylene or engineered polymers, or composites such as fiberglass or carbon fibers in a resin system. Some of the blades also have coatings to extend blade life or condition the roll’s surface. Additives such as abrasives or nanoparticles may be included which make the blade last longer. Different blade materials are selected depending on the application and roll surface to be cleaned.
Blade Specifications and Designs
Doctor and roll cleaning blades are typically between 0.035” (0.089 cm) and 0.250” (0.635 cm) thick and the widths are usually 2-3” (5.08-7.62 cm). The blade length is determined by the roll length to be doctored or cleaned. In some applications the length may be 40” (101.6 cm) or 50” (127 cm) but in larger mills such as paper and tissue, the blade length could be up to 400” (1,016 cm) long. The tip of the doctor or roll cleaning blade which contacts the roll surface usually has a bevel to improve cleaning and get under the roll surface. The back edge of the blade often includes punches, machined grooves, or some type of hardware like rivets, buttons, or clips to ensure the blade fits well in the blade holder and can do its job of cleaning the roll.
