Upcycled Plastic to Laser Cut Boxes (to Store More Plastic!)

This how-to, will explain how to turn garbage plastic into sheets you can use for precision laser cutting! It's a compilation of our experiments figuring out ways to make strong, interlocking structures starting from raw materials, and has many tips along each step! Get your makerspace a sandwich press and start reusing waste!

This in-depth video I made for this will explain everything with lots of detail, or you can read through this whole article!

Laser cutting (and other types of CNC manufacturing) are fantastic ways to make precision shapes and tools, but they generally rely on using new pure material. Also any kind of subtractive manufacturing, in general, necessarily results in waste scrap bits! Wouldn't it be great if you could use garbage to make sheets of material that you can remelt and re-use over and over?!?

Also when you are upcycling plastic, you tend to need lots of boxes all the time to sort the types and colors! Gosh wouldn't it also be cool if you could make the boxes out the garbage too?!?!

Well you can!

Basic Recipe

Make Upcycled Plastic Sheets
1. Source plastic of many colors (we used old PLA from 3D printer companies)
2. clean and sort by color
3. chop up into smaller bits
4. melt between baking sheets (350F for 15 mins for PLA)
5. let cool between something heavy and flat
Create Laser Cutting Designs
Cut the Plastic Sheets (Many Passes!)
Assemble and Weld
Re-use all the scraps

Laser cutters are much more tuned to specific materials (like acrylic plastic and certain woods) so they aren't quite optimized to cut the more recyclable plastics like HDPE, LDPE, PP, or PLA (can be difficult to cut!), but this article will give you tips we have found from all our experiments!

About

Our little jungle lab (www.dinalab.net) has been experimenting with new upcycled prototyping materials. We are based in the rainforest in Panama and it's a bit of a haul to get new materials from the city. Plus being surrounded by incredible nature makes you feel worse and worse about the garbage you are creating! So we have been launching our own initiative to recycle the waste in our little town. An added bonus is that we try to make scientific tools that stand up to abuse in the field. So we can turn the fact that many of these garbage materials don't decompose into a positive feature to protect our gear!

Usually these pieces of wood or acrylic just get tossed out and add to the landfill, but we have been trying to use up every last bit!

This can be as simple as making small designs (like keychains and earrings) to cut up the scraps into as tiny bits as possible! You can turn garbage into a pride flag! Or we can even harvest those blue disposable masks being littered everywhere because of Covid-19 and turn them into useful tools like Ear Savers!

Other's cool projects!

Note none of this we just magically "came up with on our own" (nobody comes up with anything "on their own!"). Instead this all comes from experimenting with ideas documented before, especially by folks at PreciousPlastic project and this is a great instructable also about laser cutting PLA!

https://www.instructables.com/Plastic-Smoothie-DIY...

Every time you try something out that you learn, you can learn more new things about it! and if you share it back with the world, new interesting things keep spreading!

Supplies

Source of plastic (people got plenty of garbage in this world, just ask!)
Temperature Controlled Griddle (We used a panini press)
non-stick baking sheets (look up "teflon oven liner")
Laser cutter or CNC Mill
vector designs you want to cut (many included in this document!)
Boxes to store raw materials (bit of a chicken and egg problem here)

Step 1: Source the Plastic

Lots of folks have garbage they want to get rid of! Just ask around!

We have had great luck by just messaging the 3D printing companies in Panama (Lozury Tech and Mecamaker) who had hundreds of pounds of 3D misprints or bad filament sitting in boxes not knowing what to do with them. We told them we would gladly take the garbage off their hands and turn it into something cool!

You can also hunt around places people dump garbage (like dumps or beaches) and help clean up the environment yourself.

I also went into an abandoned recycling center here in Panama that people have just been dumping garbage in anyway, and jackpot! lots of #2 HDPE (milk bottles)

Step 2: Clean the Plastic

The plastic we got from 3D printer companies was great because it was already clean, but if you are getting other plastic from the garbage, you probably want to give it a bit of a clean first!

Why clean it?

get rid of foreign particles that won't melt to your plastic
get rid of any oils or grease that will stop your plastic from sticking to itself
Make sure there are no BAD THINGS (more in next step)

Step 3: WATCH OUT FOR BAD THINGS

There are three main things you need to be careful of when sorting garbage plastic: METAL, BAD PLASTIC, BAD SUBSTANCES

Metal Bits

Even if the people you are getting your plastic from swear that it is sorted, always double check that there aren't secret metal bits stuck inside. Sometimes people make 3D prints with nuts, or other times people clean up a messy workspace and mistake a piece of wire for a piece of filament (both examples shown in the pictures). The metal is bad because A) it will hurt the teeth of your plastic grinding robot friend) and B) if it gets mixed into your plastics, and you try to laser cut it, the laser won't do anything and you will have parts all stuck together.

BAD PLASTICS

if you are sourcing 3D printing plastic, make sure it is sorted by type of plastic. PLA is pretty common and works great for this! ABS used to be more common, but is really gross and fume-y, plus it can be dangerous if you try to laser cut it. AVOID ABS! Plastic #6 (polystyrene) is also a creeper plastic that will sometimes show up trying to act like it is a nicer thermoplastic. If you melt it is also releases terrible fumes! Avoid #6!

Bad Substances

Sometimes folks want to be really helpful and give you all kinds of garbage that might be the correct type of plastic, but the plastic had been exposed to substances that might be bad to melt or cut and you can't clean it that well. For instance, i don't take motor oil bottles or 3D printing resin bottles even though they are both #2 because I cannot clean them well enough to get the nasty resins off of them.

Step 4: Sort the Plastic

By Type

It's important to sort your plastic by type because some of the plastics melt at different temperatures and can also have a hard time sticking to each other. So get some bins, label the bins, and sort them by type of plastic.

By color

This is a purely optional step, but it is VERY REWARDING! You can then easily make all kinds of wonderful rainbow creations!

Get even MORE BINS (or make them using this how-to!) and sort by color!

It may seem overwhelming at first, but give yourself some slack and just get 7 buckets ( ROY G BIV) and start sorting stuff like that!

Sorting by color also has the added benefit that you will also likely be sorting by similar sources of plastic. this can help troubleshoot things if one type of plastic is melting weird or takes longer. For example when making rainbow sheets of plastic, I was using only PLA, but I noticed the purple I had and the orange I had would take longer to melt than the other colors. So even amongst plastics that are theoretically the same, there can be variation!

Step 5: Shred the Plastic

Option A: By hand
Get yourself a really big pair of shears, or if you are using a more brittle plastic like PLA, you can get a hammer and smash it up!

Option B: Blender (Plastic Smoothie) if it is getting annoying doing this manual shredding, you can use this plastic smoothie technique in this video. Basically you can use a normal blender, add some water or rubbing alcohol (evaporates quicker!), and blend up your plastic. (the liquid helps it blend and keeps the plastic from melting into a glob destroying your blender!).

Option C: Industrial Shredder

The most fun and easy option for plastic shredding is of course going big! Here at Dinalab we have been running our own in house-recycling program and have "Terri la trituradora" a nice robot that loves chewing up plastic! You can build one off open-source designs on http://preciousplastic.com/ * or you can buy an industrial one like we did online. The term you want to look for is "plastic granulator" and you can find a shredder for about $1600-$2400 USD free shipping in the USA (getting it to panama was more difficult).

*if you are building a shredder off precious plastic designs, I would highly reccomend spring for the extra $$$ to build the V2 with double grinding teeth. I have had many people complain about the V1 grinder and they suggested just cut your plastic by hand and save up for an industrial shredder or the Precious Plastic v2.

Step 6: Melt the Plastic

I recommend using a cheap appliance and melting your plastic outdoors or in an area with lots of ventilation. When properly melting #2 #4 and #5 plastics don't really make any fumes or smells, PLA makes a kind of sweet smell, but mostly you want to avoid breathing in this stuff if you can. We have used an open face electric skillet before, and it worked fine, it just takes longer. The sandwich press works a lot quicker and more uniformly. It is also much better if you don't have a good shredder for small bits of plastic.

Pour plastic on the sheet

It helps to have a small cup, and pour it on your baking sheet. Keep a wide margin so your plastic doesn't overflow and spill everywhere.

Put on top sheet and Close the Sandwich Press

I usually put some weights on top to get a good hot smush

Cook the Plastic

We have been experimenting with the plastic to see what gets the best results. If you cook the plastic too hot it burns a bit and gets brittle and crumbly. Also if you cook it too hot, or it takes too long to cool, it can get all bubbly and crumbly too. I think you want to melt it at the lowest temperature that it all becomes nicely liquid, and then cool it very quickly for best results. So far it seems like for our Panini press and the PLA 350F for 15 minutes does a pretty great job! Here's our list for other plastics PLA 350F for 20 minutes #5 (PP) 400F for 8 minutes #2 (HDPE) 425F for 30 minutes #4 (LDPE) 425F for 15 minutes

Step 7: Play Around With Color and Texture

Color

We have had a lot of luck laying down stripes or other simple geometric shapes to make cool swirls. If your plastic had been ground into very small pieces, it can be super cool to mix 2-3 colors up every evenly and then pour it onto the skillet. You will get really neat effects.

You can also take something like a fork, and once your plastic has melted, drag it through your plastic puddle to make marbling textures like Ebru or Suminagashi paints.

Texture

Note: your plastic will take on the surface texture of whatever it melts on.
Our teflon sheets have a fabric feel that leaves a nice matte- finish on the plastic. If you want a glossy surface, you could melt it onto Kapton sheets, or you can prop your panini press open so the upper plate is just above the surface of the plastic. Then the plastic will melt without touching anything and emerge very glassy.

Step 8: Cool Under Pressure

After you take the plastic off the heat source, you need to cool it between heavy flat things.

Most of the plastics you might melt can shrink a bit when they cool, so unless you want them to get warpy, you need to keep it squished between things that will hold it flat.

Also if the things you are cooling it with are too insulative, it will take long for the thing to cool, and it will end up all bubbly and fragile (see image).

I use some old ceramic tiles and some weights to help give them a final squeeze. For most plastics a good rule of thumb is to let them cool for as long as you heated them up (so 20 minutes for PLA)

Step 9: Create Your Box Design

Making boxes is a classic of laser cutting prototyping! In fact there are some great resources available that can generate the box designs for you in a ton of different ways! Instructables has a great page that lists a bunch of different box designs!

But my favorite, and the one we used for all the boxes here, is Festi Boxes https://www.festi.info/boxes.py/

I used it to create designs for open finger boxes, hinged boxes, and stackable boxes for storing more shredded plastic!

You can even save all your parameters as a custom URL to return to. So for example, you can create the same boxes I did with these direct links:

HingeBox

Stacking Box

You can also design your box entirely from the ground up in programs like OpenScad or Fusion 360! For instance I am collaborating on a friend's project who is designing an open-source incubator for scientific tools, and we wanted to make the entire device (minus the electronics) entirely upcycled. The reason being that you don't need to destroy more nature to study nature, and if you need to change this scientific instrument, you can just melt it down and cut it into new shapes!

Here's a link to our evolving design on that (and expect a full how-to article once we finish that too!) https://a360.co/2U2pNNR

DESIGN CONSIDERATIONS FOR WORKING WITH MELTED GARBAGE

Unlike fancy sheets of new plastic you might buy, your plastic might be a bit funky. For instance your upcycled plastic will likely have

Uneven thickness
Large irregular kerf (the width of the space the laser cuts into the plastic)

This is okay! We can design around it!

Laser cut with MANY MANY PASSES at higher speeds
- Most laser cutters are good at cutting acrylic sheets and some types of wood. PLA is a bit trickier to cut, and HDPE and PP are much trickier!
- These other plastics tend to absorb a lot of the laser's heat and the edges melt a lot more. So it's better to make quick cuts that don't leave melty globs everywhere.
- PLA - 10 passes
- PP - 15 passes
- HDPE and LDPE - 25 passes
Create Loose Tolerances
- The PLA cuts surprisingly cleanly but the PP and especially the HDPE and LDPE get pretty melty around the edges of the cuts
- In many of the box generators you can adjust the tolerances for how closely the parts fit together. Make these decently loose. We used a "play" of about 0.3mm and it worked great!
Use larger, thicker finger joints
- Each feature (like a finger joint's curve) is a potential point of something getting screwed up when cutting. You can minimize these errors by making your fingers larger and just having 1-2 finger connections on each side of your box.

Step 10: Cut the Plastic

Load your sheets into your machine, measure the focus distance (or if it is a bit uneven, take an average), and start cutting!

After it has been cut, your plastic may have retained some heat. It can be good to leave it for a minute or so to let it cool down so it doesn't warp when you pick it up!

Step 11: Check the Fit

Get all the parts of your box together and check that they fit. Sometimes you might have a bit that ended up too thick and won't fit, or there is a part that got melted weird. None should be too much of a problem, just grind it down a bit until they fit!

Step 12: Weld the Plastic

Now that you have all the parts of your box and they go together, we just need to permanently attach them. There's a couple ways you could do this.

Adhesives

Glue

Super glue works great on acrylic and pretty fine on PLA. It doesn't work as great on HDPE though

Hot Glue

This will make an alright connection on most of these plastics, but probably not the strongest. Set your glue gun to super hot so the glue sticks really well

Welding

3D print pen

If you are using PLA, this is by far the quickest and easiest way to do any of this! Just set your pen on super hot (so the plastic comes out nice and gooey and really sticks to the PLA), and stitch all the parts together!

Janky Homemade 3D print pen

Let's say your 7 year old 3D print pen broke halfway through making this how-to article, and you wanted to figure out a way to still melt the plastic together good. You could just shove some filament into the back of a hot glue gun! It kinda works, some of the plastic comes spitting out of the back though and creates a bit of a mess. You can 3D print tubes, like this great design from Bruckard on Thingiverse https://www.thingiverse.com/thing:2294351, where you print a hollow tube and load it with PLA, and then loading those into Hot glue guns. It works a lot better! Make sure you have a glue gun that gets really hot though or else it takes a REALLY LONG TIME

Soldering Iron

This is the quickest but stinkiest. Wear a good mask and be in a ventilated area if you want to do this. Basically you just heat up a soldering iron and smooth out the edges to connect all the side of the box.

Step 13: Hinge Box

The hinge box (https://www.festi.info/boxes.py/IntegratedHingeBox?language=en ) is just a tiny bit trickier than the other types of boxes to assemble because it has moving parts. You need to assemble it in a certain order to make sure the hinge is trapped correctly.

Weld the front 3 sides of the LID of the box together
Take the back of the lid and connect it to the two circles (make sure they are the correct orientation!)
Weld the front and the back to the bottom of the box
Take one side of the box and attach it and then slide the back hinge with the circles into it
Weld the final side of the bottom of the box to trap the moving hinge
Connect the lid to the hinge