Injection Molding IPhone Cases From Trash

We imagine you’ve heard this already, but waste plastic is a problem for the environment. We wrap nearly everything we buy, eat, or drink in plastic packaging, and yet very little of it ends up getting recycled. Worse, it doesn’t take a huge industrial process to melt down a lot of this plastic and reuse it, you can do it at home if you were so inclined. So why aren’t there more localized projects to turn all this plastic trash into usable items?

That the question that [Precious Plastic] asks, and by providing a centralized resource for individuals and communities looking to get into the plastic recycling game, they hope to put a dent in the worldwide plastic crisis. One of their latest projects is showing how plastic trash can be turned into functional iPhone cases with small-scale injection molding.

Pushing plastic into the mold

The video after the break goes into intricate detail about the process involved in creating the 3D CAD files necessary to make the injection molds. Even if you don’t plan on recycling milk jugs at home, the information and tips covered in the video are extremely helpful if you’ve ever contemplated having something injection molded. The video even demonstrates a neat feature in SolidWorks that lets you simulate how molten plastic will move through your mold to help check for problem areas.

Once you’ve designed your mold on the computer, you need to turn it into a physical object. If you’ve got a CNC capable of milling aluminum then you’re all set, but if not, you’ll need to outsource it. [Precious Plastic] found somebody to mill the molds through 3DHubs, though they mention in the video that asking around at local machine shops isn’t a bad idea either.

With the mold completed, all that’s left is to bolt the two sides together and inject the liquid plastic. Here [Precious Plastic] shows off a rather interesting approach where they attach the mold to a contraption that allows them to inject plastic with human power. Probably not something you’d want to do if you’re trying to make thousands of these cases, but it does show that you don’t necessarily need a high tech production facility to make good-looking injection molded parts.

This project reminds us of the tiles made of HDPE plastic with nothing more exotic than what you’d find in the average kitchen. Projects like these really drive home the idea that with the right hardware individuals can turn trash into usable products.

[via 3DHubs]

27 thoughts on “Injection Molding IPhone Cases From Trash

    1. Arguably small scale aluminum recycling has similar drawbacks to plastic recycling w/o virgin material added. Cans/thin sheet are notoriously bad since they have all that surface area to oxidize without some process controls most backyard foundries ignore. It’s just that aluminum impurities are insoluble in the melt making it easier to retain material properties if you’re willing to accept comparatively high waste losses.

      1. Also the Aluminium oxides are the same as the raw material used to make it in the first place. If you just chuck all your scrap Aluminium into the smelter it goes through the process much faster using less energy. The purity doesn’t matter that much.

      2. That’s why for a backyard aluminum foundry melting cans you need something to crush many cans together into blocks. That way the metal inside the block will heat and melt with minimal air to oxidize it. Adding to the problem is any leftovers of the contents, especially if still wet. Cleaning and drying lots of pop or beer cans takes lots of time and effort.

        None of the above is a big problem for commercial foundries because they use electric arc furnaces with inert gas and synthetic cryolite flux to keep the aluminum from oxidizing.

    2. The plastic waste have to be sorted, PE, PET, etc. so the right temperature can be used and you don’t mix chlorated plastics in there like Nylon. Undyed PE, like used in plastic Jerry cans and the likes, is quite pure. Black plastics have usually already been recycled once. So the trick is to find the right mix of undyed higrade and lower grade plastic to grt satifactory properties. The problem with plastics, even if they are not heated to more than their recomended temperature for casting, is that some of the polymers breaks up, and the material gets a little more brittle. If a correct amount of virgin material is used and time and temperature is observed, satisfactory results can be achieved.

        1. Nope. The UK and the rest of the EU has the same color/usage regulations as us. Red for leaded gas, green for unleaded, etc.

          BTW: That one is for water, not ‘fuel’. Hint: Milestone-Camping :P

      1. We regularly buy H2O2 for the pool and several other stuff in blue ones (we had also acetone and HCl in blue ones). I have uncolored for water, one also contained H2O2 before. I also have black and orange ones for gasoline. So there seems no color code.

    3. Main reason is, the labor and other expenses going to make an iphone case from scrap are greater than the value of the product.

      The greater cost to produce the item then translates into greater energy and resource use as translated through the economy, which means by recycling the object you actually consume more than you save.

      That’s because, you need to make money to cover the time and upkeep of yourself and the tools. You make that money through the economy. Since the economy is services-based (>80%) it means your efforts are largely not producing new value but consuming it, because the way you make money is by helping other people consume resources.

      In order to reclaim the value of the plastic, it’s often not even useful to collect it, because the collection costs resources. That’s a good way to gauge whether the recycling is worth it: if they pay you money, the material must be worth more than the money. If they demand you to sort/collect/return the items for nothing, it’s probably not worth recycling and should be burned with regular trash.

      1. Value to who?

        ‘Normal’ people. Yeh, sure. It would be almost impossible.

        Pitch them at hipsters and eco-nuts who only care about appearances and not facts. That’s doable.

    4. There are many problems with plastic recycling. I wanted to make 3D filament from recycling and that is when the problems hit you in the face.
      1)Our current system for identifying the type of plastic is totally inadequate. #5 plastic is a wide variety of plastics
      2)Unlike Consumer food grade Aluminum, most plastics are blends. The same additives that give plastics some very beneficial properties also cause problems when you try to recycle them.
      3)The plastic degrades when you heat it. The additives cause problems when you heat them and as a result you don’t always end up with what you start out with.
      4)Outgassing from the heated plastic is a real crap shoot. What chemicals are you subjecting yourself to when you heat these up?

      1. Also, lets not forget the duality of sustainable vs durable. On the one hand you have biodegradable plastics, which wont last hundreds of years if left in the environment, but these are also much more prone to falling appart during heating. And on the other hand you have the plastics that you can recycle, but which will last forever in the scrapheap.


      1. Also, I have seen projects that weave them together to fashion stuff like rugs, baskets, rope, etc.

        Those bags don’t seem very UV stable (tend to go brittle and crumble when left out in the sun), but maybe useful indoors or if kept in a dark area.

    1. , , ,

      etc etc etc.
      the jist of most of the articles I’ve seen posted around here is that what you’ll end up with is some pretty inferior stock. if you where concerned about upcycling the materials you’d be doing so at a loss because you’d have to mix in higher quality stock and properly mix it in with the mulch so it blended adequately. with all the inks pigments and general discrepancies between any two shopping bag though you’ll end up with densities that wouldn’t be very good for much of anything- well aside from a plastic mallet made of milk jugs but that’s already covered.

  1. “We imagine you’ve heard this already, but waste plastic is a problem for the environment.”


    I’m a little suspicious of this idea that home fabrication can be a positive way to help the environment though.

    First, let me say, this does not in any way mean I am against the idea. I love the concept of encouraging individuals to make more stuff themselves. I very much think that encouraging making over consumerism will give us a much more creative, knowledgeable and self sufficient population that ultimately will do greater things and make a better world.

    But… before I can be convinced that home plastic recycling can be a useful tool for helping the environment I would need to have a couple of questions answered. First, how does the energy efficiency of some guy in his garage recycling plastic compare to that of a high volume factory? I suspect it’s pretty poor. Second, how about emissions? Factories (in the developed world) are regulated, regularly inspected and usually employ high tech scrubbing technologies on their emissions. The garage maker who blows air through a box of aquarium charcoal is probably ahead of the curve when it comes to non-professionals.

    So again, I am all for encouraging people to do this. I just don’t think selling the idea as ‘saving the environment’ is necessarily honest or correct.

    1. “Factories (in the developed world) are regulated, regularly inspected and usually employ high tech scrubbing technologies on their emissions.”

      How many factories are in the developed world and have these high standards. I live in China and work in the area of plastics recycling and I can tell you right now that many factories are not meeting standards and there is no “formal” recycling system in place. Since the plastic import ban (which btw makes localised solutions even more important) this is beginning to change in more economically thriving areas of the country e.g. Shanghai, Shenzhen etc. but there is a lot of work to do. Note: Very good and highly developed factories do exist in China and if navigated correctly it is a wonderful place to produce.

      On another note, the above comments in this section prove exactly what is wrong with the sustainability community, people spend so much time talking about what’s better or worse that no one actually does anything. Emissions in X vs. emissions in Y. Frankly, no one cares about emissions and the big companies and starts ups that use these materials don’t wait around calculating if one options emits 0.00001 CO2e than another. They start, the fail, they redo, they prototype and the achieve success. That’s why I love precious plastics, they have launched a community and I guarantee the product in 10 years will be so much more advanced than the current MVP. If he had sat around having conversations like the above he would probably still be calculating the lifecycle analysis and debating the difference between boat vs. truck logistics costs to the environment….. but I guess a lot of people are paid to chat and not to do.

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