Possible cheap feedstock: grocery bags May 18, 2008 01:55AM Registered: 14 years ago Posts: 174
Check out this instructable on how to mold with grocery bags:
[www.instructables.com]

The author recommends using an oven to melt the bags rather than a flame, which produces potentially toxic by products.

If we could make a plastic bag "harvester" and a plastic bag "digester" for reprap, we could reduce the cost of reprapped goods. However, parts produced through this method aren't exactly pretty.
 Re: Possible cheap feedstock: grocery bags May 18, 2008 09:54AM Registered: 15 years ago Posts: 32
There's a whole collection of posts about just such plastic and plastic bag re-use over in the thread "Reusing the plastic" here:
[forums.reprap.org]

I think those bags could be cut into strips and fed directly into the extruder with the right feeder mechanism.
 Re: Possible cheap feedstock: grocery bags May 18, 2008 11:04AM Registered: 15 years ago Posts: 447
I've melted grocery bags in the oven, using a baking dish. Takes quite a few bags to make a decent amount of plastic.
 Anonymous User Re: Possible cheap feedstock: grocery bags May 18, 2008 11:54AM
degroof Wrote:
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> I've melted grocery bags in the oven, using a
> baking dish. Takes quite a few bags to make a
> decent amount of plastic.

I buy bags for my store in boxes of 1000, which weighs about ten pounds. About 6 bags to the ounce, or 5 bags to the gram. (not accounting for breakdown and evaporation) How many bags would it take to make all the plastic parts for a RepRap?
 Re: Possible cheap feedstock: grocery bags May 18, 2008 12:42PM Registered: 15 years ago Posts: 370
The rough number that has been thrown around is about 1kg of parts - so about 450 bags (I think the correct number is 3.6 grams/bag, not 5 bags to the gram, based on your earlier number). Possible if you can buy them wholesale like you did, but probably too many to be an effective way of recycling used bags (my family probably only generates 4-5 plastic bags a week). How much do 1000 bags cost?
 Re: Possible cheap feedstock: grocery bags May 18, 2008 12:59PM Registered: 15 years ago Posts: 447
That's about right 1-2 kg for printed parts. I think I worked out that a year's worth of grocery shopping would net me enough to build one set of parts.
 Re: Possible cheap feedstock: grocery bags May 18, 2008 01:41PM Admin Registered: 15 years ago Posts: 13,651
... you should better go the way salvaging old printers, scanners or other devices with ABS-housings.

Then you have some hundred grams of ABS per device, brake/cut or grind it down and melt the plastic and then extrude it through a 2,6mm-nozzle to form 3mm-filament-threads ...

Viktor
 Anonymous User Re: Possible cheap feedstock: grocery bags May 18, 2008 05:50PM
It's about 15 bucks for 1000 bags. You're almost certainly better off buying bulk plastic from an industrial supplier.
 Re: Possible cheap feedstock: grocery bags May 18, 2008 08:42PM Registered: 14 years ago Posts: 174
I'm not talking about buying plastic bags, I'm talking about using the ones that litter the streets and fields.

BTW, they are trying to ban plastic bags where I live because they supposedly clog up the storm drains.
 Anonymous User Re: Possible cheap feedstock: grocery bags May 19, 2008 09:55AM
I know people who have complained how they accumulate bags, so I bet I could get a lot just asking around.
 Anonymous User Re: Possible cheap feedstock: grocery bags May 19, 2008 08:48PM
If you have a local recycling center, you might be able to get some quantity.
 Re: Possible cheap feedstock: grocery bags May 20, 2008 12:52PM Registered: 15 years ago Posts: 447
There's another instructable here [www.instructables.com] that shows how to make yarn/rope out of plastic bags. I wonder if that could be used as feedstock.
 Anonymous User Re: Possible cheap feedstock: grocery bags May 20, 2008 05:11PM
What you really need is something that can draw in the bags and force them through the print head.

I recall a version of the Cabbage Patch Kids doll that could "eat" plastic french fries using a mechanism not disdimilar to what might be needed. The doll was discontinued after a little girl got one of her braids caught in the doll's mouth.

I picture a Cabbage Patch Kid's head incorporated into the RepStrap design.
 Re: Possible cheap feedstock: grocery bags May 25, 2008 10:11AM Registered: 14 years ago Posts: 46
its far cheaper(calculate the cost of time and effort) to just buy plastic in granule form i think
 Re: Possible cheap feedstock: grocery bags May 25, 2008 10:27AM Admin Registered: 15 years ago Posts: 1,915
r2kordmaa Wrote:
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> its far cheaper(calculate the cost of time and
> effort) to just buy plastic in granule form i
> think

Guys, buying the filament isn't that damned expensive.
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