Plastic pill boxes made from grocery bags and yogurt containers

Milt Able

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My wife needed some boxes for her pills. I made an apparatus to compress melted HDPE grocery bags to make a pretty dense plastic. I also melted some Polypropylene yogurt containers which made harder plastic that was easier to single point thread. The HDPE worked well, but the threads get a little fuzzy where the thread starts. The PP is great to machine, but in my picture you will see some flaws on top where my parting tool deflected and tore the top and I didn't have enough excess material to machine away the flaws.

I made a form out of aluminum stock that I produced in my washing machine foundry. I then machined the od to be a friction fit with a steel pipe and pressed it into the bottom of the pipe.

I compress many bags in the steel pipe with the form in bottom in my 12 ton shop press while cold. I heat the grocery bags to 330 degrees in the steel pipe in my wall oven. When they are heated, they puff up. So I made a device to compress them while they are in the oven by turning the top nut. This device also is used to pull the plastic out of the form when it is cooled and after the mass is pressed out of the steel pipe by turning the lower nut. The yogurt containers were placed on a cookie sheet and also melted at 330 degrees. I used a wide blade to quickly scoop up the melted containers and put them in the steel pipe with the form in the bottom and pressed the material in the shop press.

Using 7tpi on my lathe, I cut a 1/7 lead with a double start thread resulting in 14tpi in order to have a coarse thread with half the thread depth.

Below are the pictures of the various parts. I think it is interesting to learn that those flimsy grocery bags can make a very usable and machinable plastic.

pb1.jpg pb3.jpg
pb5.jpg pb7.jpg
pb8.jpg
 

Superburban

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Very interesting. The other day, I saw a post that showed using milk jugs, they softened them to make a solid piece, but did not do any more then that. I was wondering how machinable the stuff would be. One person used a blender to chop up the pieces before heating. Then they did the cookie sheet deal (using a Teflon liner so things do not stick), and folded the mass several times, to make a brick.
 

Norseman C.B.

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One of my classmates at college made an injection molder for the cnc class to write mold programs, milk jugs and caps
were the used for it, nice little unit...........
 

Milt Able

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Very interesting. The other day, I saw a post that showed using milk jugs, they softened them to make a solid piece, but did not do any more then that. I was wondering how machinable the stuff would be. One person used a blender to chop up the pieces before heating. Then they did the cookie sheet deal (using a Teflon liner so things do not stick), and folded the mass several times, to make a brick.
I have tried the blender idea. It worked pretty well with PP peanut butter lids, but containers like yogurt or sour cream tend to break into long strands (probably due to the polymer chains). I also made two different types of plastics shredders that did the job, but it finally dawned on me to just put the whole container into the oven. I first tried putting them on parchment paper, but then realized it wasn't needed because the melted goo scoops up rather nicely and packs well into the steel tube. I do then put the tube back into the oven to make sure everything is good and melted before quickly putting it into the shop press. It also helps to give the press a few pumps every couple of minutes at first because there will be shrinkage.
 
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eugene13

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This site never fails to blow my mind, trash to treasure.
 

homebrewed

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If you put a nozzle on the exit side of your press, you've got the start of your own 3D printer :grin big:. Just a few more steps.....
 

ericc

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How do you press the plastic out of the pipe with the lower nut? It seems like the plug is captured at the bottom of the fixture. Cranking on that nut would tend to spread the frame of the structure. The top nut could be used to extracted the threaded rod, but it may become detached from the plastic plug. Maybe the bottom can be removed somehow?
 

Milt Able

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How do you press the plastic out of the pipe with the lower nut? It seems like the plug is captured at the bottom of the fixture. Cranking on that nut would tend to spread the frame of the structure. The top nut could be used to extracted the threaded rod, but it may become detached from the plastic plug. Maybe the bottom can be removed somehow?
Sorry, I wasn't very clear about that. The top nut is used for compressing the plastic while in the oven. The pipe is removed from the assembly after it is cooled. The form and plastic mass is pressed out of the pipe in the shop press. The form is then screwed back into the assembly (with the plastic mass still attached) and the long rod is screwed into the top. This is possible because some of the rod was down inside the hot plastic by design and formed excellent threads. The bottom nut is then used to liberate the plastic from the form by pulling the plastic up while the form remains screwed to the bottom of the assembly.
 

Ulma Doctor

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Excellent use of recycleable materials!!!
Great design!
 

Milt Able

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Very interesting. The other day, I saw a post that showed using milk jugs, they softened them to make a solid piece, but did not do any more then that. I was wondering how machinable the stuff would be. One person used a blender to chop up the pieces before heating. Then they did the cookie sheet deal (using a Teflon liner so things do not stick), and folded the mass several times, to make a brick.
I have had good success melting ABS in a waffle iron to make a solid sheet about an inch thick. I did use parchment paper on top and bottom to keep things from sticking.
 
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