3D Printed Spare Parts: Purpose & Limits

Lisa Ernst · 22.11.2025 · Technology · 9 min

The classic: 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 this part and print it myself." In our workshop at 33d.ch, we hear such stories almost every week – and frankly, we started exactly the same way years ago.

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

Quelle: Own Presentation

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 storage instead of shelf space, quickly available parts, and less obsolescence.

For private individuals, it seems similarly attractive: download STL, briefly check the settings in the slicer, filament might cost 2–3 CHF per part – done. However, in everyday life, we quickly notice that it makes a big difference whether a part "only" 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 clear distinction between uncritical comfort parts and safety-relevant components.

Uncritical applications: our "green zone"

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

Quelle: 3ddruckmuenchen.com

We at 33d.ch print such small holders, clips, and inserts daily – this is exactly where 3D printing plays to 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 re-print usually takes only one to two hours. Typical examples from our daily life:

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

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, simply put, is the "inner life" of a part: the higher the percentage, the more solid 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.

Knobs and control elements without significant load

Rotary knobs on radios, volume controls, extensions for small sliders or buttons: such parts are usually uncritical as long as they don't transmit high forces and are not directly on hot components. Many decorative knobs 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, panels, and plugs

Screw covers, panels for unsightly drill 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 heavy load, no sensitive electronics. We regularly use 3D-printed parts here – and after years, we see hardly 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 tests are crucial – things that are only limitedly reproducible in a hobby workshop.

Material & Temperature

Most home printers work with FDM materials like 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 in the interior can quickly be reached or exceeded; measurement series from weather services and studies show interior temperatures ranging from well over 50 °C to about 70 °C depending on the weather, while dashboards get even hotter. A PLA phone holder on the windshield often lasts for exactly one summer – we at 33d.ch have had this happen to us several times as a "melted" customer example on our table.

More temperature-resistant materials such as 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 bending tests – good for getting a feel for the differences between PLA, PETG, and ABS.

Mechanical load & layer orientation

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

We therefore deliberately test critical components to breaking point first before recommending them to a customer – and in the orientation in which they will later be installed. 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 accumulate. The Food Packaging Forum points out that such surfaces are difficult to clean hygienically without suitable sealing, and that additives from filaments can migrate into food. Therefore, classic hobby 3D printing is only very limitedly suitable for prolonged contact with beverages, milk paths in coffee machines, or hot food.

A pragmatic approach from our workshop: cookie cutters, custom molds, or aids that are only in brief contact with food and are then thoroughly cleaned can be made with some caution. We consistently refrain from using them for drinking cups, permanent pet food or water bowls, and components in the hot, hard-to-access interior of a machine – in this case, 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 things tangible, here are three situations we often see at 33d.ch – with our experienced conclusion.

1. Coffee machine: Accessories yes, water paths 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 sensitive safety-relevant components react to material and process fluctuations.

• Green Zone: Holders for tampers, cleaning brushes, or blind sieves; panels 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 splash water but don't have to hold any 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 carrying water or steam, or 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 small 3D printed part – good example of an uncritical 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 uncritical: Plugs for holes, clips for back panels, sliding elements for light furniture, brackets for LED strips, or cable channels.
• With caution: Drawer connectors that bear the weight of dishes or tools; holders that children could hold onto. Here, we consciously 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 metallic solution or an original spare part – even if the part could be easily printed purely geometrically.

3. Car interior: order yes, safety no

Quelle: formlabs.com

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

In the car interior, there are many exciting fields of application: phone holders, organizers in the center console, adapters for mounts. At the same time, cars combine high temperatures, UV light, and safety-critical systems such as airbags and seatbelts.

• Ok: Organizer inserts, holders that can simply fall off in case of doubt, small panels in the center console without a safety function.
• Tricky: Clips in the ventilation system that get hot in summer, parts in immediate proximity to airbag covers or seatbelt guides. Here, the failure scenario is crucial.
• Absolute No-Gos: Parts related to airbags, seatbelt anchorages, seat rails, or brake pedal mechanisms, as well as components that absorb energy in a crash or affect restraint systems. Legal and product liability analyses explicitly warn against replacing safety-critical vehicle parts without approval.

Our daily life at 33d.ch: We are happy to print custom phone holders or compartment inserts – 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 for 3D printing that individuals or workshops that sell or systematically provide 3D printed products 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, depending on the constellation, also the suppliers of CAD files or filaments can be held liable. Furthermore, product liability rules in the EU are continuously being expanded, so that in the future, digital manufacturing files and software may also be considered products.

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

• You regularly order or sell printed parts 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 used by others without informing them about the risks.

Our decision check before every spare part

Quelle: hdcmfg.com

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

Before we at 33d.ch print a spare part, we mentally run through a short 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 tend towards original or tested spare parts.
• Is there heat, pressure, electricity, or food contact? Parts near heaters, boilers, pressure lines, or mains voltage, as well as components with continuous food contact, are classic red zones.
• 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 printing your own is usually not worth it.
• Can we test safely? Hooks or holders can often be tested close to the ground or with weights. For safety-critical car parts or pressure components, a realistic, risk-free test in everyday life is hardly feasible.

Recommended video: Engineer's analysis of functional 3D printed parts – helpful for developing a feel for safety factors and failure modes.

In summary:

• 3D printed spare parts are ideal for holders, organizers, knobs, and covers where a defect is annoying but not dangerous.
• 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.

Fits well with this at 33d.ch

• Understanding 3D printing tolerances
• Storing and drying filament correctly
• Basic slicer settings for stable functional parts
• Material comparison: PLA, PETG, ASA in a practical check
• Checklist: From idea to a safe 3D printed spare part