3D Printing Spare Parts: Purpose & Limits

Lisa Ernst · 22.11.2025 · Technology · 9 min

The classic scenario: A small plastic clip breaks on the dishwasher, the machine no longer runs, the original spare part costs 35 CHF and has a three-week delivery time. Anyone who owns a 3D printer (or knows someone who can print) quickly thinks: "I'll quickly redraw the part and print it myself." In our workshop at 33d.ch, we hear such stories practically every week – and honestly, that's exactly how we started years ago.

The idea is compelling: digital spare part files instead of storage shelves, on-demand printing instead of an expensive logistics apparatus. At the same time, in practice, we also see parts that break in the wrong application, deform in a car in summer, or become legally tricky. In this article, we show where 3D printed spare parts make a lot of sense – and where we, as a professional 3D printing service, clearly advise against them.

Source: Own representation

Why 3D printed spare parts are so tempting

Manufacturers and service organizations have been experimenting with additively manufactured spare parts for several years. A study by the British market surveillance authority on 3D printed spare parts in household appliances shows that the parts can indeed function technically, but their safety strongly depends on material, printing parameters, and quality assurance. For manufacturers, this means: digital warehouses instead of shelf space, readily available parts, and less obsolescence.

It seems similarly attractive for private individuals: download STL, briefly check the settings in the slicer, filament might cost 2-3 CHF per part – done. However, in everyday life, we quickly realize that there's a big difference whether a part "just" holds a remote control on the wall or whether it has to withstand pressure, heat, or safety-relevant forces. That's why we internally make a very clear distinction between non-critical comfort parts and safety-relevant components.

Non-critical applications: our "green zone"

Anything that carries nothing and no one, and in case of failure is at most annoying but not harmful to anyone, lands in our green zone. Here, FDM 3D printing with PLA or PETG proves to be very reliable based on our experience – provided the print is well calibrated and the parts are not completely overloaded.

Source: 3ddruckmuenchen.com

We at 33d.ch print such small holders, clips, and inserts daily – this is precisely where 3D printing shows its strength as a flexible "small parts factory".

Holders, organizers, and "quality of life" parts

3D printed spare parts are ideal for holders and organizers. If a part breaks, it's annoying but not dangerous – and a reprint usually takes only one to two hours. Typical examples from our daily work:

• Holders for coffee capsules or filter bags that are not directly under the machine's steam lance.
• Wall holders for power strips, routers, or small power supplies that improve cable management.
• Inserts and dividers in drawers, toolboxes, or small parts magazines.

At 33d.ch, for example, a layer height of 0.2 mm, three to four perimeters, and 20-30% infill have proven effective for such parts. Infill, in simple terms, is the "inner life" of a part: the higher the percentage, the more massive the component becomes – and the more filament and print time it requires. These values are based on experience; depending on the printer, nozzle, and filament, slightly different combinations may work better.

Buttons and control elements without significant load

Rotary knobs on radios, volume controls, extensions for small sliders or buttons: such parts are generally non-critical as long as they do not transmit high forces and are not directly on hot components. Many decorative buttons on coffee machines or kitchen appliances are just thin plastic caps on a robust metal or original mechanism – here, a printed replacement can visually save a machine without compromising its safety.

Covers, bezels, and plugs

Screw covers, bezels for unsightly drilled holes, or small blanking plugs in car interiors are typical "green zone" applications. They have an optical or dust-protective function and carry nothing: no person, no significant load, no critical electronics. We regularly use 3D printed parts here – and after years, we hardly see any problems, except for occasional yellowed PLA parts with a lot of UV light.

Safety-critical components: where we are very cautious

As soon as heat, pressure, electricity, or people are involved, it gets tricky. In these areas, material data, printing parameters, and testing are crucial – things that are only limitedly reproducible in a hobby workshop.

Material & Temperature

Most home printers work with FDM materials such as PLA, PETG, or ABS. PLA, the standard material for many beginners, softens from around 60-65 °C and loses significant stiffness. In a parked car, such temperatures can be quickly reached or exceeded inside; measurement series from weather services and studies show interior temperatures significantly above 50 °C to about 70 °C depending on the weather, while dashboards get even hotter. A PLA phone holder on the windshield will then often last exactly one summer – we at 33d.ch have had this as a "melted" customer example on our table several times.

More temperature-resistant materials like PETG, ASA, or special high-temperature polymers are much better suited for warm environments. However, they do not automatically make a part "safe": without tested material data, defined printing processes, and load tests, a hobby print cannot replace an approved vehicle part or a component of a coffee machine.

Recommended Video: Comparison of 3D printing materials in tensile and flexural tests – useful for getting a feel for the differences between PLA, PETG, and ABS.

Mechanical Load & Layer Direction

FDM parts are anisotropic, meaning they hold up worse in the layer direction than within a layer. In everyday life, this means parts often break along the layer lines. A furniture connector that has to withstand tension or bending perpendicular to the layer direction usually withstands significantly more than an identical part that is stressed exactly in the layer direction.

We therefore consciously test critical components to failure first before recommending them to a customer – and in the orientation in which they will be installed later. Especially with clips, snap connectors, and thin arms, we prefer to plan for a little more wall thickness and choose a layer orientation that does not directly lead to a risk of falling or crashing in case of breakage.

Hygiene & Food Contact

Even cleanly printed FDM parts have fine grooves and micropores where food residues and bacteria can settle. The Food Packaging Forum points out that such surfaces are difficult to clean hygienically without a suitable seal, and that additives from filaments can migrate into food. Therefore, classic hobby 3D printing is only very limitedly suitable for long-term contact with beverages, milk pathways in coffee machines, or hot food.

A pragmatic approach from our workshop: cookie cutters, pastry cutters, or serving aids that are only in brief contact with food and are then thoroughly cleaned can be made with some caution. We consistently advise against drinking cups, permanent pet food or water bowls, and components in the hot, hard-to-access interior of a machine for private use – here we recommend certified original or third-party parts.

Recommended Video: Food-safe 3D printing? Limits and possibilities – a good introduction to the topic of food contact.

Three typical practical scenarios from our workshop

To make it more tangible, here are three situations we often see at 33d.ch – with our experience-based conclusion.

1. Coffee machines: accessories yes, water pathways no

Coffee machines are a classic for 3D printed spare parts. Countless buttons, levers, and holders can be found online as STL files. However, technical studies on 3D printed spare parts in household appliances also show how sensitively safety-relevant components react to material and process fluctuations.

• Green zone: Holders for tampers, cleaning brushes, or blind filters; bezels that only cover a hole; decorative buttons that operate a robust original mechanism.
• Yellow zone: Parts that only get warm briefly or are exposed to splashed water but do not need to withstand pressure – e.g., covers in the splash water area. In case of doubt, we test several prototypes here.
• Red zone: Anything in the high-pressure path (espresso boiler, milk pumps, valves), permanently carries water or steam, or is difficult to clean. In our opinion, these parts should only be used as tested original parts or demonstrably certified industrial components.

Recommended Video: Repairing a coffee machine with a 3D printed small part – a good example of a non-critical spare part.

2. Furniture & Household: much is possible, but not everything

Furniture parts are grateful candidates for 3D printing because they are usually operated at room temperature and the consequences of a defect are manageable – with exceptions.

• Typically non-critical: Plugs for holes, clips for back panels, sliding elements for light furniture, holders for LED strips or cable channels.
• With caution: Drawer connectors that bear the weight of dishes or tools; holders that children might hold onto. Here we deliberately dimension generously and test in the assembled state.
• No-go: Load-bearing connections for bunk beds, chairs, or ladders. As soon as a breakage can lead to a fall, we do not print such parts for real use, but at most for functional prototypes.

In practice, it has been shown: When customers come to us with a broken chair connector, we almost always recommend a metal solution or an original spare part – even if the part could be geometrically printed well.

3. Car interior: order yes, safety no

Source: formlabs.com

Additive manufacturing is being extensively tested in the automotive sector – but for safety-critical components, there are high hurdles and approval requirements.

There are many exciting application areas in car interiors: phone holders, organizers in the center tunnel, adapters for mounts. At the same time, cars combine high temperatures, UV light, and safety-relevant systems such as airbags and seatbelts.

• OK: Organizer inserts, holders that can simply fall off if necessary, small bezels in the center console without safety functions.
• Tricky: Clips in the ventilation that get hot in summer, parts in close proximity to airbag covers or seatbelt guides. The failure scenario is crucial here.
• Absolute No-Gos: Parts related to airbags, seatbelt mounts, seat rails, or brake pedal mechanisms, as well as components that absorb energy in a crash or influence restraint systems. Legal and product liability analyses explicitly warn against replacing safety-critical vehicle parts without approval.

Our daily work at 33d.ch: We gladly print an individual phone holder or an insert for the storage compartment – anything that could affect crash safety is consistently left out.

Law & Liability: when you become a manufacturer

Besides the technical side, there is a legal one. The German Federal Institute for Occupational Safety and Health (BAuA) clearly reminds in its guidelines on 3D printing that individuals or workshops that sell 3D printed products or systematically provide them to third parties are legally treated as manufacturers and must fulfill the obligations of the Product Safety Act.

Legal analyses of 3D printed spare parts also emphasize that in case of damage caused by faulty parts, not only the printing service provider but also, depending on the constellation, the suppliers of CAD files or filaments can be held liable. In the EU, product liability rules are also constantly being expanded, so that in the future, digital manufacturing files and software may also be considered products.

For us at 33d.ch, this specifically means: we document materials and settings for functional parts, refuse print orders for obviously safety-critical applications, and communicate clearly when a part is only intended for testing or prototype construction.

• You order or sell printed parts regularly via platforms or your own website.
• You offer 3D printing as a service (e.g., "I'll print your spare part for a fee").
• You provide CAD files for safety-critical spare parts with a clear intended use.
• You install printed parts in devices that other people use without informing them about the risks.

Our decision check before every spare part

Source: hdcmfg.com

For highly loaded, safety-critical parts, manufacturers often rely on metal 3D printing with strict quality assurance – far from the typical hobby setup.

Before we print a spare part at 33d.ch, we mentally go through a quick checklist. Many customers later adopt this logic themselves:

• Does the part affect safety or health? Can a breakage lead to a fall, accident, fire, or electric shock? If so, we clearly lean towards original or tested spare parts.
• Is there heat, pressure, electricity, or food contact involved? Parts near heaters, boilers, pressure lines, or mains voltage, as well as components with permanent food contact, are classic red zone items.
• How bad would spontaneous failure be? A broken capsule holder is annoying but harmless. A broken handrail, seat bracket, or belt guide is not.
• Is there a tested spare part at a reasonable cost? If an official spare part costs 20 CHF, the legal and technical gray area of your own print is usually not worth it.
• Can we test safely? Hooks or holders can often be tested near the floor or with weights. For safety-relevant car parts or pressure components, a realistic, safe test in everyday life is hardly feasible.

Recommended Video: Engineer analysis of functional 3D printed parts – helpful for getting a feel for safety factors and failure modes.

In summary

• 3D printed spare parts are ideal for holders, organizers, buttons, and bezels where a defect is annoying but does not endanger anyone.
• As soon as heat, pressure, electricity, food contact, or personal safety are involved, classic FDM home printing quickly reaches its limits.
• Legally, "just printing something quickly" very quickly becomes a manufacturer role with clear obligations – especially if you offer parts for money or regularly for others.
• An honest safety and liability check before printing saves trouble, avoids damage, and ensures that 3D printing can shine where it is truly strong.