Stop! 12 Objects You Shouldn’t 3D Print

3D printing is an exciting technology that empowers makers, hobbyists, and professionals to turn their ideas into reality. However, just because you can print something doesn’t always mean you should.

Whether you're a beginner or already deep into STL files, it’s important to recognize the potential risks—from safety hazards to legal issues. Some objects simply don’t belong on the build plate. Let’s explore 12 things you should never 3D print —and understand why.

1. Firearms and Weapons Police inspector Geoff Desanges with a 3D-printed firearm seized in Bayswater. Credit： Nic Ellis Creating functional firearms or weapon components with a 3D printer is both highly dangerous and, in many regions, illegal. Even non-functional replicas can lead to serious legal consequences, particularly in public or high-security settings. Laws vary by country and jurisdiction, but in most places, manufacturing weapons without proper licensing is strictly prohibited.

So, are 3D printed guns dangerous? Absolutely. Even if intended as a prototype or for personal interest, these weapons are often untraceable, unregulated, and illegal. More importantly, they are structurally unreliable—common materials like PLA or ABS are not designed to withstand explosive force. Attempting to print a firearm could result in catastrophic failure, severe injury, or significant legal trouble.

2. Food Containers Without the Right Filament

Printing your own food containers or utensils might seem convenient, but doing so with the wrong filament can be harmful to your health. Most standard 3D printing filaments, like PLA, ABS, or PETG, are not inherently food-safe.

Even filaments labeled as “food-grade” can become unsafe if printed on a non-food-safe nozzle or contaminated printer bed. Moreover, the layered structure of 3D prints creates tiny crevices that are nearly impossible to fully sanitize—ideal environments for bacteria to grow.

If you do want to print food-related items, you must use certified food-safe filament, stainless steel nozzles, and apply a food-grade epoxy coating to seal the print. Even then, it’s generally safer to avoid printing anything that will come into direct or prolonged contact with food or beverages.

3. Critical Car Parts

3D printing replacement parts for your car might sound like a money-saving hack, but it’s a dangerous gamble—especially for critical components.

Materials like PLA or ABS can’t handle the mechanical stress, vibration, and temperature extremes experienced in an engine bay or suspension system. Even stronger filaments like carbon-fiber infused nylon aren't guaranteed to meet safety requirements. A minor failure in a structural or engine-related part—like a brake pedal bracket or belt tensioner—could lead to catastrophic consequences.

For critical components that affect performance or safety, it’s best to stick with OEM or certified aftermarket parts. The short-term convenience of a printed part is not worth the potential cost of mechanical failure or an accident.

4. Medical Devices (Without Certification)

3D printing has revolutionized the medical field by enabling custom prosthetics, surgical guides, and anatomical models. However, printing medical devices at home or without certification presents serious health risks. Medical devices—everything from splints to surgical tools—must meet stringent regulatory standards to ensure they are safe, biocompatible, and effective.

Consumer-grade printers and materials rarely meet these standards. A printed brace, for example, may not offer proper support, potentially worsening an injury. Worse still, internal-use devices like inhaler components or catheters must be sterile, toxin-free, and structurally flawless—something that typical hobbyist printing setups can’t achieve.

Even with the right intentions, producing unverified medical items without proper guidance could expose you to legal liabilities or ethical consequences. If you want to help medically, consider working with certified programs that validate and distribute 3D-printed medical tools.

5. High-Voltage Electrical Components

Printing high-voltage electrical components is particularly hazardous because incorrect materials might lack the necessary insulation and can lead to electrical malfunction or fires, increasing the risk of accidents and injuries.

Most common printing filaments—like PLA and ABS—are not rated for high voltage and offer poor insulation properties. In fact, they can become conductive when exposed to moisture or heat, leading to short circuits or even fires.

If you're building or repairing electronics, stick with certified, industrial-grade insulating components and cases. When it comes to high voltage, don’t rely on home-printed plastic—it’s just not worth the risk.

6. Counterfeit Products

Printing branded logos, characters, or merchandise might feel like harmless fun, but it can easily cross the line into copyright infringement. Just because an STL file is available online doesn’t mean it’s legal to download, print, or share. Distributing or selling 3D models based on copyrighted designs—without permission—can lead to serious legal consequences.

It’s important to respect the intellectual property rights of creators, designers, and companies. Remember, there's a clear difference between making something “inspired by” and producing a direct, unauthorized copy. When in doubt, choose originality over imitation.

7. Pressure Vessels

3D printing a pressure vessel — such as an air tank, gas cylinder, or pressurized container — is not just ill-advised, it's downright dangerous. These vessels are designed to contain gases or liquids under high pressure, which requires incredibly strong and uniform materials, often tested to industry standards for tensile strength, wall thickness, and integrity.

Layer lines — a hallmark of FDM printing — create weak points where cracks can form under stress. A sudden rupture of a pressure vessel can result in explosive decompression, sending shrapnel flying and potentially causing severe injury or damage.

Even if you’re using a strong material like polycarbonate or carbon fiber-filled nylon, the risk of delamination or microscopic air gaps remains. No hobbyist printer can match the quality controls of professionally manufactu

So, while 3D printing might be fine for a prop scuba tank or airbrush holder, anything meant to hold actual pressure should be left to certified products made from metal or molded composites.

8. Structural Furniture (Step Stools, Load-Bearing Chairs)

While 3D-printed furniture parts like knobs, handles, or decorative trim are completely reasonable, attempting to print load-bearing furniture — like a step stool or weight-supporting chair — can be a recipe for disaster.

Over time, repeated stress (like sitting on a printed chair or stepping on a stool) can lead to fatigue failure — and that failure will happen without warning.

Use 3D printing for functional or aesthetic components — sure. But if you need something to support human weight, skip the filament and go for metal or professionally made materials.

9. Currency or Government IDs Counterfeit money confiscated by law enforcement. Credit： Johnson City Press It may seem obvious, but printing replicas of currency, coins, or official government documents like IDs, passports, or driver’s licenses is illegal in nearly every country. Even if you’re doing it as a novelty, for cosplay, or for educational use, you’re venturing into legally risky territory.

If you want to design something “inspired by” official designs for movies or games, that’s one thing — but avoid copying real-world IDs, licenses, or currency. It’s not worth the legal trouble, and it sends the wrong message about how 3D printing should be used.

10. Safety Gear (Like Bike Helmets, Knee Pads, etc.)

Printing your own safety equipment may sound innovative, but it's a serious safety risk. Items like bike helmets, knee pads, or wrist guards are designed to absorb impact and protect you in case of accidents. They must meet strict standards for material strength, deformation limits, and durability.

Most printing materials—especially PLA and ABS—are brittle under high-speed impact and may shatter or crack instead of absorbing force. Additionally, the layer lines in FDM-printed gear make weak points that can fail precisely when strength is most needed.

Furthermore, actual safety gear undergoes rigorous impact testing and certification (e.g., CPSC, ASTM, or CE ratings) before hitting the market. A helmet that looks strong might offer no real protection in a crash—and a failure could result in serious injury or worse. Your body isn’t a prototype — don’t trust your life or limbs to an untested, home-printed part.

11. Kids' Toys

Kids love toys, and 3D printing can be a fun way to create custom figurines or learning tools. However, printing toys for young children—especially babies and toddlers—comes with serious safety concerns.

Even seemingly harmless toys like puzzle pieces or mini animals can present risks if they aren’t printed with the correct infill, resolution, or finish. Second, printed toys can have sharp edges, weak joints, or small parts that break off—creating choking hazards.

If you want to 3D print toys, make sure they’re intended for older kids, use non-toxic, food-safe filament, and avoid small or breakable parts.

12. Explosives or Dangerous Devices Shown is a bomb that could be a threat to public safety Credit：machinedesign It goes without saying: printing anything that functions as or supports an explosive device is highly dangerous and illegal in most jurisdictions. This includes fireworks casings, homemade rocket parts, igniters, or any component that could be weaponized.

3D printing should be used to solve problems, create art, build tools, and empower innovation — not to manufacture danger. Use your creativity for good, and steer well clear of anything that can explode, ignite, or harm others.

Conclusion While 3D printing opens up a world of possibilities, responsible use is key. Always consider safety, legality, and material limitations before hitting "print." For everything else—be creative, be smart, and print on!

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