What is the most important thing to remember when using bowed rolls?
Maintain the proper geometry!
Bowed rolls can be a very effective and aggressive web spreading device. However, to get the most from your bowed rolls it is extremely important to maintain proper geometry. Here are some rules of thumb when applying bowed rolls:
- Almost all of the spreading takes place in the entry span to the roll. The longer your lead-in distance (unsupported web distance leading into the bowed roll) the more spreading you will get. The lead-in distance should be roughly double the lead out distance (unsupported web distance leading out of the bowed roll).
- Keep your lead out distance to a minimum. The smaller this distance, the less chance you will have of wrinkles returning to your web.
- Keep wrap angles to a minimum. Often times when I am in the field and see bowed rolls that are not operating properly or they are causing more trouble than they helping, it is because wrap angles are too great. My opinion is (and I have had many people argue with me about this) that wrap angles around bowed rolls should NEVER exceed 30 degrees.
- One last word about bowed rolls; when applied properly they will effectively remove wrinkles. But the question is, what are you doing to your web by utilizing a bowed roll! The potential problems with bowed rolls are not that they do not take wrinkles out, they do. The problem is that the web tension profile as the web travels over the bowed roll is not even. Due to the raised center of the bowed roll, you will deliver added tension to your web in its center. How will that affect your material! Will your material be distorted by your bowed roll! That is the question to ask when using bowed rolls to remove wrinkles.
- Join us and discuss this tech tip or anything converting at our LinkedIn Group page. This groups function is to develop into a beneficial discussion of all things converting, thus benefiting the industry as a whole - click here for our LinkedIn Group page
Engineering Manager at Converter Accessory Corporation
8 年Jason, CAC (the company with which I am affiliated), manufactures a 3.5" OD, fixed bow, bowed roller with a maximum speed rating of 1,500 feet per minute with a non-reinforced (standard) rubber sleeve. The rubber sleeve can be reinforced within the rubber (similar to steel belting in a car tire) to allow for faster running speeds. We would need to understand more about your application to advise the maximum allowable running speed with reinforced rubber sleeve. Beyond that, generally speaking, larger diameter bowed rollers can handle faster linear speeds.
Manufacturing Excellence Manager at Essity - Hygiene and Forest Products Company
8 年I agree with the geometry, but what about speed? Who has an opinion/experience on the proper rotational speed of a bowed roll? I look forward to hearing your opinions....
Account Manager chez Egzatek Inc
8 年Excellent article !
RETIRED
8 年Good article! Of the geometry items stated, angle is most important. Too much & the friction between roll surface & web will be too great to allow the web to flatten. Also, holding the angle with infeed & outfeed guide rolls. Not allowing the angle to change with process, however slight.
Agreed Dave. Too often people tend to apply too much wrap around bowed roller.