Reverse engineering: a model from an existing part
Reverse engineering is a process where you work out the shape and dimensions of a finished object and create a new model from them. In 3D printing it is how copies and replacement parts are made.
No model? No problem, pick a ready one
These sites have thousands of free models. Download an STL or 3MF and upload it here. If you sell it or use it for business, check the model licence. How to pick a model and licence
Contents
What it looks like in practice
Reverse engineering means going from a finished product back to the design. For a plastic replacement part you have two routes. The first is a 3D scan, which is quick, but the mesh needs cleaning up. The second is measuring by hand with calipers and drawing the model in CAD software, for example Fusion or FreeCAD. The second route takes more work, but the result is clean and easy to change. For simple parts it almost always pays off.
What to watch for with a replacement part
- Tolerances. Add the small allowance printing needs to the key dimensions, see tolerances.
- Load. The original part may have been made of a different material, and a print in PLA or PETG behaves differently. PETG copes better with heat.
- Direction of strength. Orient the part according to the load, see model orientation.
- Shrinkage and clearances. Holes come out slightly smaller and shafts slightly larger, so allow a small clearance after printing.
Legality and your order
Copying a part for your own use or repairing your own item is normally fine. But if the item is protected by a design right, patent or trademark, making copies for sale may infringe someone else's rights. We do not check rights, and the responsibility is yours.
You upload the model as an STL, STEP or 3MF up to 50 MB, and you see the price per part and the date straight away. For replacement parts, start with a prototype to check that the part fits. We will also make a replacement part from a model you have drawn or measured, but we do not measure or scan samples. If you have a drawing with dimensions or a logo, write to us and we will agree whether we can design the model.
Step by step
- Measure the part with calipers and write down the dimensions, including wall thicknesses and hole diameters.
- Draw the model in CAD software or edit a scan.
- Add clearance for joints, see snap-fit and threads.
- Print the first part and try it in the original place.
- Correct the dimensions and order the final quantity.
Common questions
Is reverse engineering legal?
In principle yes, for your own use and for compatibility, but copies of protected parts for sale may infringe rights. In doubtful cases, consult a lawyer.
How accurately can a part be copied?
With hand measuring and a good CAD model, to tenths of a millimetre. FDM printing has its own deviations, so allow for clearance.
Will you make a model from my sample?
We do not measure or scan samples. If you have a drawing with dimensions or a logo, write to jakub.novak@boostello.com and we will agree whether we can design the model.
Related terms
3D scanning
3D scanning is capturing the shape of a real object as a digital 3D model. After clean-up, that model can be printed as a copy or used as a base for your own design.
CAD
CAD is computer-aided design, that is software for creating precise 2D and 3D models. A model from CAD is exported to STL or 3MF and sent to print.
Spare part
A spare part is a component that replaces a worn or broken part of a device. 3D printing suits this when nobody sells the part any more or it is disproportionately expensive.
Tolerances
Tolerances in 3D printing set how far a printed dimension may differ from the model and how much clearance to leave between parts that are meant to fit together.
Prototype
A prototype is the first sample piece of a product, used to check shape, size and function before the whole run is made. 3D printing is fast for this because it needs no tooling.
Photogrammetry
Photogrammetry is a way of calculating a 3D model of an object from many photos taken from different sides. A phone is enough for taking them.
SourcesSources checked 1 November 2026, 2
- Reverse engineering, Wikipedia, checked 2026-11-01
- 3D scanning, Wikipedia, checked 2026-11-01
We will print it for you
Upload a model and see the price per piece, the total with shipping and the date at once. We print in Košice, Slovakia, from PLA and PETG.
No model? No problem, pick a ready one
These sites have thousands of free models. Download an STL or 3MF and upload it here. If you sell it or use it for business, check the model licence. How to pick a model and licence