Repair-Part Files: Verifying the Exact Part Reference Before You Print

Read the Marking on the Original Part Before Searching

Start with the broken part itself. According to the Prusa knowledge base, the names of printable parts always begin with a letter followed by a number, and that identification appears on parts large enough to carry it. On smaller parts where text does not fit, the manufacturer uses dots or squares: a single dot for the first version, with the number of dots matching the version number. Squares indicate custom plastics and follow the same counting logic.

Record the marking exactly and compare it with the file and the manual for the machine in question. If the marking is unreadable, the Prusa documentation reviewed does not prescribe a universal substitute: identify the model and part in the relevant documentation before choosing a file.

This convention is documented for Prusa printable parts. It does not describe other manufacturers’ markings. For another machine, check its model and documentation without carrying over Prusa’s letters or numbering system.

Farm Letters and Home Letters Are Two Separate Series

Prusa's documentation separates two families of markings. The letters A, B, C, D, E, along with dots and triangles, identify parts printed in the Prusa farm and shipped with printers or sold in the e-shop. The letters R, S, T and squares identify parts available on the Prusa Research profile on Printables, on the Prusa3D site or on GitHub, meaning the ones you can print yourself.

Prusa says the numbers may differ between a farm-printed part and the same part printed at home. A B2 marking therefore does not, by itself, tell you to choose a file numbered 2. Do not infer compatibility from a letter either; check the model and part in the relevant Prusa resources.

The useful check is to identify the part by its function and location, then pick the file published for your exact model. The Prusa Research collection on Printables sorts parts by installation area, which makes that identification easier without leaning on the number alone.

Complete Kit or Upgrade Kit: Different Part Lists

On the Prusa3D site, printable parts are split into two groups. Complete kits contain the full set of plastic parts for an entire printer. Upgrades contain only the parts needed to move to the new printer version. STL files are provided for all plastic parts, and pre-sliced G-codes are offered for all upgrades, according to the knowledge base.

When choosing from this documentation, check the starting machine and target version named by the kit or manual. Prusa distinguishes a complete set from an upgrade, but that description alone does not identify the right part for a partly modified machine without knowing which changes are already installed.

For a repair part, compare the reference with the machine’s manual and its actual upgrade state. The free STL files guide covers a broader topic; it does not replace this model-specific check.

Confirm the Supported Generation and Revision

Prusa’s MK3.5 upgrade guide is intended for MK3S and MK3S+; it says MK3 is not supported and directs MK3.5S builds to a different manual. Follow the document for the relevant model and version rather than extrapolating its parts list to other machines.

In this guide, Prusa asks users to print all required parts before disassembling for the upgrade. For a similar job, this can inform preparation: first check the parts list and steps in the exact manual. The passage does not prescribe a universal repair procedure.

Some cases are conditional. According to the same guide, the Enclosure-compatible xLCD supports only concern users installing the upgrade inside the Prusa Enclosure, and the extra PSU cover only concerns users replacing a silver power supply with the black one. A part listed in a manual is not necessarily one everyone must print. A specific manual also does not prove compatibility for a different machine or revision.

File Format and Documented Print Settings

For Prusa parts, the knowledge base says STL files for every printable part are published on Printables together with printing instructions. If you generate your own G-code, the documentation recommends PETG, the 0.2 mm QUALITY layer height preset and 15% GRID infill. The MK3.5 upgrade guide repeats those values for PrusaSlicer, with no supports. The general article also gives a separate instruction for the fan shroud, which directs air from the print fan to the part and should be printed in ASA or ABS with otherwise identical settings.

Use the page and manual matching the exact reference. The general settings above do not describe every Prusa generation. For another machine, find its own parts list and associated instructions. If a setting is missing, resolve that information before choosing a material, profile, or modification; a part with the same name may belong to a different assembly.

Prusa says it does not provide original project files, but makes STEP files available alongside STLs for modifying its parts. The source says project files are found only in the GitHub branch where they were first released. For parts designed with OpenSCAD, it says only the SCAD file exists, with no STEP; the page notes that this also includes metal parts. Check the repository and branch for the specific model. The STL vs 3MF guide explains formats, not whether a file exists for every part.

Post-Print Inspection and Limits of Use

In its MK3.5 upgrade guide, Prusa asks users to inspect printed parts before assembly: holes for screws or nylon filament should be clean, smooth-rod holes clear, nut pockets free of debris, and the part checked for straightness. These checks belong to that manual and its parts; follow the manual for your model.

For this guide, Prusa notes that tolerance may remain between a printed part and a nut and describes a pull-in method using a fully threaded screw. It advises against glue if it could reach the thread. These are instructions from this upgrade manual, not a universal assembly method.

This page organizes documented checks for Prusa parts; it does not qualify a printed part for a critical role. The reviewed documentation does not provide general strength or safety validation for other uses. For work where failure could have consequences, use instructions and parts approved for the relevant model.

Sources and limits

• Prusa — Printable parts and markings
• Prusa — Introduction to MK3S/S+ to MK3.5 upgrade

We organize manufacturer and community documentation; we have not measured these products ourselves. The manual for your exact model takes precedence over general guidance.