At the end of this module, you will be able to:
- Identify the two main functions of tissue machine roll doctors
- Identify the components of a doctor
- Identify the purpose of the doctor components
- Distinguish between mechanically-adjusted and self-conforming blade holders
- Identify where roll doctors are typically installed on tissue machines
- State why doctors and doctor blades should be regularly inspected
The following key questions are answered in this module:
Why are flexible, self-conforming doctor blade holders used on some rolls?
Flexible, self-conforming blade holders utilize two fluid-filled or air-filled tubes to load the blade against a roll surface. They maintain a uniform pressure on the blade across the machine and automatically compensate for changes to the roll surface, including roll deflection.
Why should you avoid increasing the load on a used doctor blade?
This can cause the blade tip to lift up, which greatly increases the risk of the sheet wrapping the roll.
Why is it important to change doctor blades on a regular basis?
This is important because as blades wear, blade angles change, which makes them less efficient.
Where are air doctors used?
Air doctors are used on grooved rolls or belts. The air doctor prevents damage to the surface.
Why do doctor blades oscillate?
Moving the blade back and forth in the cross machine direction helps the blade remove contaminants from the roll and also helps to maintain the sharp edge.
Below is a transcript of the video sample provided for this module:
On tissue machines, doctors are typically installed on the breast roll, forming roll, and various wire rolls in the forming section, on the suction pressure roll and felt rolls, or on rolls in the through air drying section, on the Yankee, and on the reel drum. In the forming and press sections, doctors are often accompanied by roll showers to provide lubrication and help clean the roll surfaces. Deflectors and saveall trays are often installed to help direct the white water and any contaminants removed from the rolls away from the sheet and fabrics.
Use the additional resources and links below to learn more about this topic: