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90-degree turns on zipper enclosure

Postby Sriv_tsa » January 26th, 2017, 10:02 pm


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Wondering whether it is possible for zipper enclosures to work on sharp corners. My target design is a leather bag with sharp 90 degree corners. Was just wondering if it is possible to use a zip for the opening.

Do I need to add a small radius to the corner to make this work, or is such an opening possible with a zipper enclosure?

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Re: 90-degree turns on zipper enclosure

Postby Dan Lewis » January 27th, 2017, 7:46 am

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[quote="Sriv_tsa"]Wondering whether it is possible for zipper enclosures to work on sharp corners. My target design is a leather bag with sharp 90 degree corners. Was just wondering if it is possible to use a zip for the opening.

Do I need to add a small radius to the corner to make this work, or is such an opening possible with a zipper enclosure?



Have you every actually looked at zipper?

Re: 90-degree turns on zipper enclosure

Postby Cyberdemon » January 27th, 2017, 8:47 am

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Or I suppose more importantly, looked at leather.

Leather is soft and flexible - it can be laminated to substrates for form but you are not going to get a perfect cube out of an animal skin, the material in the corners would need to be folded (like wrapping a present), trying to stretch it would simply tear the material.

Re: 90-degree turns on zipper enclosure

Postby yo » January 27th, 2017, 9:37 am

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I think we can be more helpful guys.

Yes, you will need rather large radii for the zipper to run smoothly. You will also need to panel break the leather. Remember, leather is a sheet good. It can be molded but only very minimally, so it only likes to wrap corners in 2 dimensions and has a thickness of a couple of mm's depending on the grade, so it doesn't like tight turns. If the substraight it is mounted to is not radiussed it will also start to wear through.

A little reference, this might be a similar project. A headline cafe my team and I designed for the Definitive Technology Symphony 2 headphones. I recommend purchasing a few things that are similar to what you want to do. Cut them apart and study how they are made. They will also be good references for the factory you use.
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Re: 90-degree turns on zipper enclosure

Postby cwatkinson » January 27th, 2017, 9:43 am

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you could do a 90 degree turn but the trade off would be that you would need to have 2 zippers to create the corner - you would also most likely have a small hole where the two meet.

Re: 90-degree turns on zipper enclosure

Postby Brian_Donlin » January 28th, 2017, 2:37 pm


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You're going to need some sort of radius, yes. There are a few reasons:
- Zippers don't form rigid angles. The forces within the zipper teeth resist bending beyond a certain radius. Grab a pair of jeans and try bending the zipper. See how it works against you? If you try to sew a zipper around a 90-degree corner, the zipper will sort of stretch like this.
- Even if you sew a zipper around a really tight corner with a small radius, the zipper won't open and close smoothly. The slider will get caught at the corners, making for a poor user experience.
- You can sew leather as a box shape if each side is a separate panel. But remember, the seams need to go somewhere, which might ruin the rigid shape you're looking for.

So either you'll need to change the design to accommodate the zipper, or change the type of closure. I strongly recommend going to the mall one day and looking at leather bags to get some ideas. Purses, briefcases, whatever.

What's the purpose of this bag?

Re: 90-degree turns on zipper enclosure

Postby ralphzoontjens » January 31st, 2017, 3:19 am

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If you bend it too tight you will get compression and buckling effects, the best approach is to source the thinnest and most flexible zipper and my hunch is that you could reach a radius below, say, 5 mm.
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