Doctor Blades
Originally founded as Lodding Engineering, Kadant has been a market leader in doctor blades for over 60 years. During that time, our blades have earned a reputation for superior precision, efficiency and reliability. Currently operating in thousands of installations worldwide, our doctoring technology continues to prove its excellence in applications ranging from the routine to the highly specialized. When you work with Kadant, you don't just get a choice of quality blades, you also benefit from 24-hour customer support. Our network of field service engineers is strategically located to respond quickly to the needs of mills. We'll help you identify problems, show you ways to increase efficiency, and recommend the right blade for specific applications. The result—a more productive, cost-effective mill and a higher quality sheet.
At Kadant Web Systems, doctor blade evaluation and development is strictly customer-focused. Our R&D engineers keep in close contact with field staff and paper mills to compare laboratory testing with actual field experience. Their skills are used in all phases of research and development, from testing existing and prototype blades to developing new blade materials. Evaluation and design is accomplished in the R&D laboratory with the use of the following resources:
Solving Special Doctor Blade Problems
Added Flexibility - If more blade flexibility is desired for applications such as press rolls, breaker stacks or calenders, one of our patented unidirectional composite blades may be the solution. The carbon fibers in these specialty blades are oriented such that the blade has over five times the stiffness in the machine direction compared to the cross-machine direction. This stiffness ratio allows for conformability across the face of the roll surface, as well as adequate transfer of load and superior sheet shedding.
Heat Relief - If a metal doctor blade tends to bow from end to end as a result of thermal changes, a composite blade may be a more effective solution. Composite blades generally do not experience the high temperature changes that metal blades often do. Testing has shown that composite blades have a lower rate of thermal expansion than metal blades, and thus eliminate the problems of bowing and warping due to heat. This provides more uniform load to the blade tip without the need for special punching of the blade.
Ceramic Roll Doctoring - With the use of ceramic rolls, specialty doctor blades are used. Among these are composite blades, some with abrasive particles, that can adequately clean the roll surface while retaining the surface release that allows the ceramic roll to shed the sheet. Some of these new blades contain carbon to provide long life and extra lubrication where showering may not be possible.
High Temperature Applications - In the past, the use of composite doctor blades was limited to low temperature applications. Standard phenolics and epoxies were used in most of these older composite blades. With advanced materials, however, composite doctor blades can be used in applications up to 500° F, and this limit is increasing as polymer technology advances and becomes readily available to the composite laminators.
Maintaining High-Speed Precision - Metal doctor blades in the last dryer, calender, or reel position—where machine speeds are over 1500 fpm (457 meters per minute)—can often chatter or vibrate. With composite materials, vibrations are minimized resulting in more successful doctoring. As machine speeds continue to increase, there is a growing need for more composite blades on the paper machine. With the use of these specially designed blades, wear on the roll and dryer surfaces is dramatically reduced.