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Topic: Ridges on rollers

Christopher Duvall
Jedi Master Film Handler

Posts: 500
From: Denver, CO
Registered: Dec 1999

posted 02-17-2002 05:56 AM

I screened the print of Super Troopers Thursday night and all went well as planned. When I came in for the evening shift, the projectionist on duty quickly came to me and told me that that print got scratched during the second show of the day by one of the rollers below the analog sound head. Upon investigation, I discovered that the roller had a raised ridge down the center that was not there before. It was not any sort of build up, just plastic from the roller.

Now for the question, what would cause the roller to produce the ridge down the center? I would like to prevent this from happening in the future.
BTW Brad, Film Guard once again came to the rescue. Covered those black scratches right up. Thank you and the Film Gods.

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Dave Macaulay
Film God

Posts: 2321
From: Toronto, Canada
Registered: Apr 2001

posted 02-17-2002 09:19 AM

I need a picture to understand this.
Roller plastic does not suddenly decide to reshape itself.
Some - many - rollers have a center ridge slightly smaller than the edges where the film touches. This prevents some problems with film buckling if the turning angle is too obtuse or the tension is too high. The film should never touch this ridge in normal operation.
This ridge will scratch the film if it does touch because the ridge's surface speed is slower than the film speed.

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Stan Gunn
Expert Film Handler

Posts: 176
From: Clematis, in the hills near Melbourne Australia
Registered: Aug 2000

posted 02-17-2002 11:07 PM

Maybe the film edge ran on the centre ridge and edge of roller,
I have seen this happen on some rollers.

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John Pytlak
Film God

Posts: 9987
From: Rochester, NY 14650-1922
Registered: Jan 2000

posted 02-18-2002 02:08 PM

AFAIK, some less expensive plastic rollers may be injection molded, and the ridge is a "seam" where the mold was separated, or where two sections were joined or welded together. Normally, any ridges, rough spots or "flashing" should be removed and polished.

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Research Labs, Building 69, Room 7525A
Rochester, New York, 14650-1922 USA
Tel: 585-477-5325 Cell: 716-781-4036 Fax: 585-722-7243
E-Mail: john.pytlak@kodak.com
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