What is the purpose of a Bowed Roll?
- The Bowed Roll is an efficient method of Eliminating wrinkles, gaining width(stretch), and separating slits.
How does it work?
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The Bowed roll is similar to an idler roll except that it has a rubber type covering and the face length is in the configuration of a bow, instead of being straight. The inside of the roll is full of bearings to support the rubber convering, and allow the roll to be bent and still rotate. When the web passes over a straight idler roll the web direction changes vertically because of the amount of “wrap”. When the web passes over an offset idler roll, the web direction will change vertically because of the “wrap” and also horizontally because of the roll being offset. The bowed roll can be considered a double offset roll, and the web will try to follow the offset of the roll, since the offset esentially goes both horizontal directions at the same time the web follows both ways, with the result that the web tries to stretch in width removing wrinkles, or spreads slits in a slitter application. The amount of spread or stretch depends on the amount of wrap and the amount of bow. There are many calculations available in the design of the Bowed Roll, however these should be used only as a guide and a starting point, since such variables as web material, tension, web width etc can cause changes to the result. When the product varies on a “daily” basic it might be wise to consider a Adjustable Bowed Roll. A fixed bow can be used successfully when the same product is used continuously, and rarely needs to be changed.
What is the difference between a Fixed and an Adjustable Bowed Roll?
- The fixed Bowed Roll is just that, the bow is fixed at the time of manufacture and can only be rotated on its axis to control the amount of spread. The usual amount of bow is 1% of the face span.
- The adjustable Bowed Roll is made in such a way as to allow the amount of bow to change within a fixed amount i.e. 1/2% to 3% of the face and any amount in between. This allows much more flexibility in controlling the amount of stretch.
What type of rubber covering should be used?
- Rubber here is a “generic” name. In most cases the covering of bowed rolls is a synthetic compound, depending on the conditions that the roll has to work in. The standard covering is a Nitrile compound. Sometimes a Hypalon is used when the conditions warrant. Other types and hardness are used if required, and this is the reason we need to know what the operating conditions are. If the covering needs to be cleaned, make sure the cleaning material will be compatable with the covering. Some cleaners will destroy the covering very quickly. Contact the factory if not sure what to use. Call the toll free number in North America 1-888-421-1405 or email info@webancor.com
What diameter of roll should I use?
- The diameter of the roll is function of the roll face, web width, and the web tension. If the application is a replacement roll and the existing roll have given no problems, use that dimension. If a new application provide the information requested and our engineering dept. will advise the correct diameter.