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winding a paper core - making a centre on which to wind it

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AdeV:

--- Quote from: BillTodd on November 06, 2018, 07:22:50 AM ---I've just finished a spiral winder , on a somewhat different scale to the one in your picture , I had to deal with +/-1um tolerances and one dimension spec'd at 3.2um .
--- End quote ---

 :bugeye:

What on earth are you winding - DNA???

BillTodd:

--- Quote from: JerryNotts on November 06, 2018, 10:35:01 AM ---i''m sorry Bill I am not sure which parts you mean, or which winder.

Jerry

--- End quote ---

i was just amused by the similarity of the machine to wind paper and what I made to wind tungsten tape

BillTodd:
Are you winding a few or looking to go in production?

Taking a close look at a bog roll core , I see it is made of a couple (maybe more)  of layers of card offset to cover the join. My guess it that they are spiral wound to enable continuous production i.e. the tube spirals off the end of a mandrel in a long length and is cut to length my a second operation (just like spiral ducting etc.)




should have search youtube first ;-)



Bill

JerryNotts:
Sorry I didn't reply to your last post Bill.

I'm hoping to make about 50 individual cores initially.

At one time I was closely involved with companies using these things, but although I often wondered how they were made I never had an opportunity to watch the process. Now I have spoken to some who worked on these specific machines.

As you say the winding is a continuous process, the some of the power of the drive to the belt is consumed  in the effort required to push the freshly wound spiral along the mandrel. That's one of the reasons to keep the mandrel as smooth and slippery as possible. Formulation of the glue is also important: it must set-up quickly. The cores are cut to length as they come to the end of the mandrel; Usually using rotary knives working against each other on opposing sides and moving horizontally with the wound spiral as the cut is made. If you do a search on the manufacturers, often Indian or Chinese, you will see they make a big thing of their ability to hold core length to size.

' kraft paper' is usually used for cones (German: kraft = strength,strong) (sorry if I am teaching my grandmother) and the winding angle  25 -30degrees imparts crush resistance. Crush and bending resistance is important especially when there is a roll of paper wound on to it which might weigh around 20 tonnes.

I am currently trying to draw out  a model of a spiral care winder and have only just begun to think about all this so take whatever I say with a large bag of salt.

Jerry

JerryNotts:
After a lot of cogitation and even more guesswork I've made a start on the drawings.

I have started on the most important part of the winder, the winding uinit itself. The components are shewn in the second picture and the proposed assembly iin the first. The relationship of the mandrel to the winding belt (not figured out how to draw this twisted thing in Inventor yet) is in any case and the first picture represents the view along the centre line of the two drive rollers and the end of the mandrel

This drawing is based on a mandrel diameter of 10mm for ease of doing the sums.

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