Fire-Proof Cardboard 3D Printer Enclosure

Ok, I know what you’re thinking already.

Mr. Wyqid, excuse me, but making a 3D printer enclosure out of cardboard is dangerous! 3D printers get hot. I even heard from my cousin’s friend’s nephew’s Facebook buddy’s dog who read an article on Reddit that 3D printers can go up in flames. Plus, I print only in PLA and I don’t need (yes you do - at least with an open front, for better prints) an enclosure.

    Yeah, I heard all about 3D fire makers too. BTW, that whole flaming printer thing was primarily with a specific model of printer with bad quality control. But I said FIRE-PROOF cardboard.

Nothing Is Truly Fire-Proof

    Even rocks burn at high enough temperatures. But it’s time for another very easy chemistry lesson where I will show you how to make cardboard virtually fire proof using a simple DIY formula that actually works with any paper product. 

You may already own some fire-resistant paper

    Did you know that crepe paper is extremely flame resistant? I mean think about it… It’s Melissa’s 50th birthday and you have decorated the area just over the dinner table with a network of lovely colorful streamers that look like a drunk spider ate a unicorn. You have super-thin paper strung up all over the place where you are going to carry a birthday cake with essentially your own tribute to the Burning Man festival on top. 

    A recipe for disaster… but those colorful streamers don’t burn easy. If you have some, try it yourself. Sure you can hold a lighter up to it and it catches on fire, but only for a brief moment. As soon as you move the lighter it snuffs itself out fast. They make it very fire resistant for exactly this scenario. But how do they do it?

    You can buy a commercial product such as MasterFlame or easily make your own for a fraction of the cost with some simple ingredients. I get it that not everyone likes to dabble in chemistry. So if you rather just buy a proven product that works then you can buy it online at the link below.

#CommissionsEarned - As an Amazon Associate, I earn from qualifying purchases.

    Now if you have the ingredients for the formula already you can try it before you build it. You’ll find that even a blow torch won’t make the cardboard I use for my enclosure stay lit. Of course I tested this myself. 

    But why would you want to make an enclosure out of cardboard anyway? I can think of several reasons:

    • You are a cheapskate like me.

    • Maybe you genuinely like to recycle and help the planet. 

    • You need a custom size enclosure (this was my main reason)

    Since I mentioned recycling I need to go off on a tangent here for a moment, so bear with me…

Recycling Is Mostly Fake

    Consider this my own little public service announcement. Because you know… recycling is important and we got polar bears dying in Louisiana… or wherever.

    You are doing your part. You are sorting your trash and putting the stuff that says it can be recycled into the special bin that the recycling company picks up. Maybe you go the extra step and wash out the cans and bottles. Maybe you are a little more informed and actually removed the labels and cut the little rings off the top of bottles from the cap area. Good for you. 

    But actually the whole point of recycling is to help the environment right? Prevent stuff from contributing to the landfill or save the forests and what not. What if recycling incorrectly (which nearly everyone does) hurts the environment more than it helps?

    My brother worked at a recycling center, so I have been enlightened. Allow me to enlighten you. 

    • Cardboard makes up a hefty percentage of the landfill mass. Huh? All cardboard is totally recyclable. No it isn’t. Only clean, plain brown cardboard, printed with vegetable based dyes, is recycled. Glossy full color print on the box? Not recycled. Waxy coating? Not recycled. Any kind of micro-thin plastic protective lamination film or coating? Not recycled. Plastic shipping tape left of the box? Not recycled. Food residue on the cardboard? Not recycled. Reinforced paper tape made with fiber strings to make it stronger left on the box? Not recycled. But why? Why? WHY? Because paper products that are recycled get diced up into tiny bits. Chemicals are added to make a slurry. This is done in very large batches. Most of this ends up being made into things like those brown egg crates, fast food drink trays, and other obvious items that look similar. If just one greasy pizza box is accidentally shredded and added to 50,000 gallons of paper slurry then the entire batch has to be dumped. That sucks.

    • Almost no plastic (easily less than 20%) is recycled for multiple reasons. Well all know about that recycle triangle logo of arrows with a number inside that is supposed to help recycle centers sort the plastics by type, right? Maybe that’s what it is supposed to be there for, but actually it just helps the sorting folks know what to toss out. Recycling has to be fast and efficient otherwise it becomes much more expensive to buy a recycled item rather than a new item (usually it is already a little more expensive). In order to keep costs down, recycling centers primarily only keep #1 and #2 plastics…IF…and I mean IF… the label is removed (the label is probably different type of plastic, and you can’t mix types)… and IF the little cap seal ring is not on the bottle (also probably a different type of plastic)… and IF there is no residue in or on the bottle. They don’t have time to remove labels, cut cap rings off, and wash bottles. What are #1 and #2 plastics? PET (not PETG filament) which is usually clear like water and soda bottles, LDPE and HDPE which is semi-transparent like milk jugs. Just about every other plastic with a rating of 3 and above is not recycled, not cost effective to recycle, or just simply incapable of being recycled.

    • Some people think they are helping the recycling companies by pre-shredding paper and/or plastic, as well as adding their filament scraps to the bin. They are! They are helping recycle center employees not waste time because they send shredded plastic and paper straight to the dump. Why? Because they don’t know what type of plastics or paper types are in the mix. They can’t risk an entire batch of viable material by tossing in someone’s mystery-eco-salad blend.

    • Most glass bottles and metal food and soda cans actually do get recycled (the labels are destroyed at the temperatures used to reform glass and metal).

    • A lot of energy and toxic chemicals are used for most all of these processes no matter how you slice it.

    So to summarize: First, a fleet of diesel powered trucks picks up thousands upon thousands of recycle bins for any given community. A bunch of people sort through it all in a huge factory and throw about 80-90% and what they receive into dumpsters. Then another fleet of diesel trucks haul it all to the same place your normal trash goes: the county dump. I’m not against recycling or the environment. But unfortunately, we will probably never get even half the population to do it properly to avoid these issues. 

    If this was the Super Bowl, the scoreboard would read something like…

Recycling: 14
Pollution caused by recycling: 17

    But it’s only the end of the second quarter. Maybe we can get it right after the half-time show.

    What was I talking about? Oh yeah, the best way to recycle is to UP-CYCLE. Up-cycling is repurposing something without all the industrial processing or chemicals. 

Let’s focus on what we came here for

    Back to building this supposedly fire-resistant enclosure out of cardboard.

    It’s not entirely cardboard technically, just the main structure. It’s also wrapped in aluminum foil with aluminum foil tape for the edges. You could alternatively go for a more decorative look and buy those aluminum self-stick tiles made for kitchen backsplashes, but they are somewhat expensive. 

    I actually bought an enclosure and then ditched it when I got more printers. This was mainly due to the fact that I wanted my printers on a big steel commercial metal shelf. The shelves are very heavy, stable, and strong. You know the kind… those 6 foot tall, 4 foot wide, 2 foot deep heavy duty metal shelves they have in kitchens and warehouses for supplies that hold hundreds of pounds? I have 11 of them. Why? Because apparently my entire extended family thinks I’m a free storage facility.

    So after I got more printers, I wanted an enclosure that could custom fit to the space between two shelves. The top, sides, and back are enclosed. The front is open. My printers sit on flame proof wood leveling pads I made from MDF (Oh yeah, the formula works on wood too. Paper and cardboard are wood products). I made the platforms because those metal shelves are not perfectly level. They get smacked around, hammered when you need to adjust the height of shelves, etc.. Each platform has a 3D printed foot attached to a bolt in each corner. They work the same way your printer bed leveling knobs work, except this is so I know the printer itself is level. Here is a photo of one of my printer shelves with an enclosure built for two printers:

    For the main structure, if you want to make it like mine, you will need:

    • Two-ply cardboard. You want sturdy thick cardboard, like the kind that flat screen TV’s and appliances come in. If you look at the edge of it you will see that it is actually two pieces of cardboard sandwiched together with wood glue. This serves two purposes: it prevents warping and it provides great insulation.

    • A roll of heavy duty aluminum foil that is NOT the non-stick kind. The generic stuff. Both kinds of aluminum foil (regular and non-stick) have a shiny side and a dull side. With the more expensive non-stick coated stuff, the dull side is what you cook your food on. With the generic stuff your food would probably stick to either side.

    • A roll of aluminum foil duct tape. This is the tape that HVAC (air conditioning) installers and repair people use to connect your vents in your house to the actual air conditioner via your attic or floor. It’s pretty strong stuff. It’s been holding your AC ductwork to your vents for years. You could actually cover the entire cardboard with just this aluminum foil tape (which would look nicer), but that might be a bit expensive.

    • A box cutter tool.

Cardboard Is Free

    Post on NextDoor, Facebook Marketplace, Craigslist (anyone still use Craigslist anymore?) and people will give you a ton of it.

 Tip: Tell people you intend to recycle it and they will be more eager to contact you. It’s not a lie, you are going to recycle it. 

 Even better: If you really want them to make your phone ring non-stop, tell them you are building a giant cardboard castle for your grandkids. Awww… I have some! Me too! Call me. You still need cardboard? How’s the castle coming along? 

    Shamefully I admit to using that last one. Holy cow the number of messages I got! I use a lot of cardboard to make compost for my garden. I needed a truckload of cardboard. While I did not make a giant cardboard castle for my grandkids (no g-kids yet), I did truly recycle every bit of it. Everyone thought the idea was adorable and wanted to donate to the cause. I even posted a pic I found online of what I supposedly wanted to build that looked pretty cool actually. I considered building it, but the evil Wife’s Eye in Mordor is ever so watchful. She see’s all, she knows all, and she has the one ring.


    You can get your aluminum foil, aluminum foil duct tape, and box cutter tool from your local hardware/grocery store, or you can support this site and buy some online using the links below. 

Planning your Enclosure Design

    Let’s start with some planning. As you can see from the photo of my shelf with two printers, The walls are exactly the full height of the space, the depth is actually a little deeper because the shelf is a couple inches from the wall so I can run cables behind it, and bottom of the next shelf above the printers is the top of my entire enclosure. Even if you only print with PLA, having this ‘open front’ style enclosure prevents drafts of air that warp your prints and maintains a warm stable zone. Heat rises, so there is no need to build a bottom. Also, the bottom has a shelf liner that prevents any upward air flow and the printers sit on little platforms. 

    It is best to build this as separate panels. Don’t try to make it all out of one giant piece of cardboard. This is ideal especially if you have defects like creases in the cardboard. Try to cut your panels only out of the best sections of the box that are perfectly flat. 

Measure Twice, Cut Once

    Get out a piece of paper and sketch your overall design. You can draw a box right? Write down how deep the box is, how tall the box is, and how wide the box is. For my enclosure, the back wall is approximately 48 inches long and 24 inches tall. I made this from two panels of cardboard that I cut 24 inches by 24 inches. 

Getting It Square

    Naturally you want it to be neat and square, but you don’t want to start at the edge of the box because the fold may not be a perfectly straight line or crushed/damaged. The best piece will be cut out of the center of the box probably. What I do is use something I know has a perfect 90 degree corner like a large picture frame (or a sheet of foam board from the dollar store) and a marker to draw one corner. Now I know I have a perfectly square corner. From there I use a yardstick or something with a long straight edge and extend the line to the size I need for my panel. You can then use the large picture frame for the other 90 degree right angle. You get the picture… pun intended. Since it is two-ply cardboard, you probably want to cut it with several light slices on each line. This is easier to do if you use something like a metal yardstick or a piece of angle iron. Something long, flat, straight, and metal. 

    Once we have all the panels we need we need to make the cardboard fire-resistant using the flame retardant formula. The best way to apply it is to use a spray bottle. You will need to saturate the cardboard pretty good and let it dry completely. Wet cardboard will curl and warp as it dries. To keep this from happening, you can place long wood boards along the edges or put a bigger piece of wood on top of it. A fan blowing on it speeds up the drying process.

    You probably have a spray bottle you can use, but if not you can always buy one online.

Flame-Retardant Formula for Wood and Paper

    At long last the formula. This stuff is super easy to make. You only need 4 things and you might have all four already.


    • 3 ounces of Boric Acid by weight (A very common white powder commonly sold as roach killer. Read the label, make sure what you are buying is Boric Acid. Don’t be alarmed by the name. Boric Acid powder roach killer is actually non-toxic. It’s not a poison that roaches ingest. It’s also not what you think of when you think of acid. It’s fairly harmless stuff, unless you are a roach.

    • 7 ounces of Borax by weight (A specific type of laundry detergent. Again, read the label.) 

    • 2 Quarts of Distilled Water  

    • Some latex or nitrile gloves. (The formula dries out my skin. I prefer to wear gloves.)

    Since the Boric Acid and Borax are powders, you should weigh them with a scale. It’s not super critical if you just use measuring cups, but powders sometimes get compacted as they settle during shipping and you could be using more than the recipe calls for. I always weigh powdered ingredients, as do professional Chef’s. That being said, it won’t change the effectiveness of the formula significantly if you using measuring cups. But if you don’t have a kitchen scale and want to buy one online, click the link below.

    If you don’t want to make this much flame-retardant spray, you can use 50% less of each ingredient and make half a batch. 


Step 1.

Heat the distilled water to a simmer. It does not have to be boiling, just nice and hot.

Step 2.

Slowly stir in the boric acid and borax and keep stirring until completely dissolved. (About 15 minutes)

Step 3.

Allow the solution to cool to room temperature and then pour it into your spray bottle.

Step 4.

Put on your gloves and spray your cardboard until it is very damp. If your cardboard has a printed waxy or laminated side, spray the solution on the opposite side that is just plain brown cardboard so it will soak in.

Step 5.

Place your long wood boards around the edges and something heavy and flat in the center, or use a piece of plywood bigger than the panel to hold it flat until it completely dries. This usually takes about a day or so. Using a fan that is blowing directly at it will speed up the drying. If it still looks or feels damp after a while, wait longer. 

    Below is a video by Lyn Perk showing how to make the solution and comparing it to the commercial product that does the same thing.

Assembling Your DIY 3D Printer Enclosure

    Once all your cardboard panels are dry, it’s time to put it all together. This is fairly straight forward. Cover the panels one strip of aluminum foil at a time. Cut a section of aluminum duct tape the same size as your strip of foil. Tape the edge of the aluminum foil to the top edge of your cardboard panel and wrap the tape over the top. Next, tape the bottom edge of the aluminum foil to the cardboard with another strip of aluminum tape. 

    I covered both the front and back of each panel with the foil-tape combo. It might be easier to get someone to help you hold the foil while you tape it to avoid wrinkles. I use an old gift card to smoothly apply the tape and foil, just like people who apply window tint do to avoid bubbles. You can also apply the tape to the foil first and then attach it to the cardboard. Do not use any regular packing tape. Only use aluminum duct tape. Wrinkles don’t make the panels any less effective, it’s just cosmetic. 

    Once all your panels are finished, attach the panels edges together using the aluminum duct tape. If you want a fully enclosed structure (not recommended for PLA or PETG), you can add some 3D printed hinges. You only need a fully enclosed structure for high temperature filaments or filaments that produce toxic fumes like ABS. If that is the case, you would want to add something like a computer fan and some dryer duct so you can vent it outside. 

    For PLA and PETG the main point of an enclosure is to prevent drafts and to keep the temperature around the printer fairly steady. For that you don’t need or want it to be sealed on every side. 


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