Hello ,
Please explain someone, how to calculate the amount of balancing weight which I have to move from the head ends to the middle, of a roller dia400, l=6000 mm, 850 kg,1200 rpm, and when I have to do it. Are there any formulas or I have to use vectorial calculation?
Thanks a lot!
Iulian
Original Post
I'm not following what you are asking very well but assume English is not your native language. From your description it sounds like a roll from a paper machine such as a felt roll.

If that is indeed the case you first need to establish whether the roll is a ridgid or flexible rotor.

If ridgid the roll can normally be balanced using 2 plane balancing at the respective heads. If you don't have access to a calibrated balancing machine it can be done with portable vibration equipment on a soft balance stand. Ref run, trial run 1, trial run 2, add correction weights, run again and trim as required.


If it is a flexible roll then a 3 plane balance is required. (which I have not done but am working on it) Difficulty there is taking the measurement at the centre of the roll. A triangulated non contact laser will do or some way which doesn't damage the roll surface. I have not done this but have seen internal documentation from a company who build paper machines including rolls. The trial weight run at the centre involves strapping a weight on outside of roll (safety!!). Complete the 3 plane balance and now comes the interesting part. Once you know the balance weight it is split in 2 and a length of barstock is made to match 1/2 weight and attached at the quarter point from each end, INSIDE the roll. And that's the hard part. The way they do that is make the weight. Predrill and thread holes, threaded rod in one end, drill holes through shell, poke weight with rod in roll. A wire loop is dangled through one of the holes in shell, balance weight pokes through loop, loop pulled tight and the weight then lined up and bolted in. The other bolts follow. rod unscrews and is withdrawn. Protruding bolts made flush with shell. Repeat for other end.

You provided not much information so please let me know I didn't waste my time. Your referring to moving weight from heads to middle doesn't make sense as far as my experience goes. rgds

Did you try to Google? I just came up with this in under 10 seconds.
http://canmecrolls.com/pdf/ROLL_BALANCING.pdf
quote:
If it is a flexible roll then a 3 plane balance is required. (which I have not done but am working on it) Difficulty there is taking the measurement at the centre of the roll. A triangulated non contact laser will do or some way which doesn't damage the roll surface.


Technically, you can get the measurements at two or more speeds, a coastdown will do for the measurements (at the bearings).
Thanks Vibe and William. Your info were really useful . Is indeed about a flexible rotor, but I can not use a non contact laser for the middle. After measurements at 800- 1200 m/min, using a portable microlog SKF,I did a 2 plane balancing. For the weights bigger than ~ 1000 grams, split it in half and at each side, attached 1/2 along a quarter shell from each end, not more then 75-100 g for one weight. Threaded holes and weights. For safety, welded outside. Grind locally and polished. Almost like your solution Vibe - Rater, thank you very much. In my first post the question was ,,From what weight I have to split it, and in what proportion?" Thanks again.

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