Continue to Site

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

  • Congratulations SSS148 on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

rolling up plastic sheets

Status
Not open for further replies.

lowside

Mechanical
Aug 10, 2004
1
we are building a machine to roll up sheets of out product (we are currently getting it made rolled, but its expensive and wasteful when shipping)

basicly the product is about 1mm thick plastic with dimples on it in a uniform pattern. the dimples are about the size of a nickle and about 1/2" deep. this isnt important. what is important is the size. the sheets will be comming in various (known) widths from 5' to 14' and the length will be about 60 feet.

we need to quickly, and precisly be able to roll these into tighty packed rolls that are no larger than 11" across (the ones we have prerolled are less than 11" but they are very tight') so basicly the problem should be a simple one
this is the machine the boss built so far. (simplified but overall accurate enough)


the two rollers on the left are machined true and straight, they roll easy, and are each independantly adjustable up and down on each end by about a foot. they provide tension by pressing down on the material as it rolls through. they are aligned perfectly level with a laser currently.

the 3 middle bars do not roll, they are welded in place, their job is to provide extra tension via friction, and they do this well. they are not adjustable.

the roller on the right is powered by a motor, unimportant. it has a slot in it to feed the material too, so that it can rotate, and drag the material through all the other rollers, and wind itself up under heavy tension.

we can modify this 100% in any way add or change or subtract. but we dont have 60 feet of length to work with to build a long table.

we have tried using guides and other such things, they have not worked at all. the material is under such tension it just goes up and over the guides.

the problem:
the rolls do not wind up with flush ends, they wind up crooked. what i attribute this to, is that the tension is not on the loose end of the material, holding it straight, a degree or 2 at the feed rollers (the two big ones) will translate into a lot of movment over 60 feet. some how we need to be able to tension and align the material from the far end, or more hopefully, keep the machine compact and have it align itself as it rolls. we want to roll these sheets up in about 1-2 minutes a piece, and we will have thousands of them to do, so time savings are critical...

have you guys got any ideas? i was thinking that the material might be more easily aligned if it fed from the back of the machine underneath, and up to the feed rollers then through the machine as i have shown in the image, so it does a soft fold over on itself. if the loose end and the tensioned winding end are ligned up, the whole thing should stay aligned, no?

anyway what are your ideas anyone who is good at problem solving, this should be a simple thing.... but its proving not to be


oh yah, and when we eliminate the feed rollers from the equation and roll the material up it rolls up perfectly flush every time ( the dimples align themselves and it keeps straight) but the rolls end up being huge in width because they are loose.
 
Replies continue below

Recommended for you

Could you take the length of unrolled material from the left and loop it over the whole machine? Then you could align the free end with the tensioned end on the roller. This should help the alignment.

Is there anyway to make the 3 tensioning bars roll? If something is out of alingment, I don't think these help in getting things back into alingment. Also as they roll, they should still provide tensioning.

What material is this film? Can it be recycled? Perhaps the solution is to manufacture the roll a few inches wider, roll it, trim the roll square and recycle the scrap.

Ray Reynolds
"Computers in the future may weigh no more than 1.5 tons."
Popular Mechanics, forecasting the relentless march of science, 1949
Have you read faq731-376 to make the best use of Eng-Tips Forums?
 
I would suggest using a crowned roller near the wind up roll. To calculate taper/radius, percent wrap and size of the crowned roller that should work well for you I would go to a conveyor belting mfg. web site. There has been a lot of reasearch invested in belt tracking and the belt people are the easiest place to get it. Seigling and Hasibit are two of the big players. I know Seigling has some really good info in their Translon catalogs. A search for luggage or bulk belt conveyor should get you started.

A couple of basic rules of thumb:
The more wrap the more effect.
It is much easier to track feeding onto a roll.
Choose either side guide or crown not both. A crowned roll with side guides is a 3 crowned roll and the belt will track to the highest point it is running on.

Barry1961
 
As curently arranged, variations in friction are probably causing side-to-side variations in tension between the last fixed bar and the roll-up roller.

I agree that the three smallers bars should actually be rollers. Also, one should probably provide some "steering" ability.

Control the steering be either monitoring the tension on both sides, or measuring the actual length of material travelled on each side, and steer accordingly.

If you can count on both edges to be straight and parallel to each other, you could also control by position of the edges.

 
I highy recommend the Web Handling Research Center at Oklahoma State University, check out their website at
They offer a short-course twice per year on just the sort of issues that you are seeking help on. I attended it and recommend it.

In the event that you can't wait until the next web handling seminar, Mr. Bruce Feiertag does independent consulting on the subject and is extremely knowledgable, you can contact him through the OSU website.
 
do some research into the plastic film industry. They have a number of devices that will address your needs. Turret or surface winders along with tensioning and guiding equipment. Mount Hope has an extensive line of live adjustable crowned rollers. Fife is a big name in substrate guiding.
 
Status
Not open for further replies.

Part and Inventory Search

Sponsor