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Possible cheap feedstock: grocery bags

Posted by Gene Hacker 
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Gene Hacker
Possible cheap feedstock: grocery bags
May 18, 2008 01:55AM
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.
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TheGuy
Re: Possible cheap feedstock: grocery bags
May 18, 2008 09:54AM
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.
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degroof
Re: Possible cheap feedstock: grocery bags
May 18, 2008 11:04AM
I've melted grocery bags in the oven, using a baking dish. Takes quite a few bags to make a decent amount of plastic.
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Anonymous User
Re: Possible cheap feedstock: grocery bags
May 18, 2008 11:54AM
degroof Wrote:
-------------------------------------------------------
> 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?
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Kyle Corbitt
Re: Possible cheap feedstock: grocery bags
May 18, 2008 12:42PM
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?
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degroof
Re: Possible cheap feedstock: grocery bags
May 18, 2008 12:59PM
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.
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VDX
Re: Possible cheap feedstock: grocery bags
May 18, 2008 01:41PM
... 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
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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.
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Gene Hacker
Re: Possible cheap feedstock: grocery bags
May 18, 2008 08:42PM
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.
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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.
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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.
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degroof
Re: Possible cheap feedstock: grocery bags
May 20, 2008 12:52PM
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.
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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.
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r2kordmaa
Re: Possible cheap feedstock: grocery bags
May 25, 2008 10:11AM
its far cheaper(calculate the cost of time and effort) to just buy plastic in granule form i think
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Forrest Higgs
Re: Possible cheap feedstock: grocery bags
May 25, 2008 10:27AM
r2kordmaa Wrote:
-------------------------------------------------------
> 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. smiling bouncing smiley
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