Free 3D model

Enigma Cipher Machine

A rotor cipher machine you print. Push the key and the three rotors step like the ones in a real Enigma, double step included. Then follow your letter through the rings: in through the three rotors, round the reflector in the middle and back out to the outer ring, which gives the cipher letter. The rotors carry the wiring of rotors I, II and III of the Enigma I and the reflector is reflector B, so a message you encrypt on it decrypts on any Enigma I simulator set to the same start letters (rings at A, no plugboard), and the other way round. No electronics: the wiring is printed on the rings.

  • 13printed parts
  • 21 × 20 × 2 cmassembled (L × W × H)
  • ≈ 0.3 kgfilament in total
  • 196 mmacross, for the base and the outer ring: a 200 × 200 mm bed
Download all files ZIP · 1.3 MB

Free for personal use under CC BY-NC 4.0: print it, remix it and share it with credit to Shapekit. Please don't sell the files or the prints.

Take it apart in 3D · Parts · How to build it

In 3D

Turn it, take it apart

Every part as you print it. Pick colours to see what your filament will look like.

The 3D model (5.2 MB) loads when you get here.

Preview colours

Base, outer ring and reflector
Their letters
Rotor III (outer)
Rotor II
Rotor I (inner)
Rotor letters
Key and pointer

Drag to rotate · scroll or pinch to zoom

In the download

13 parts, ready to print

Every STL is already placed the right way up. Download them all at once, or one by one.

Base

The body: a pocket for the key lever under the rotors, the post the lever turns on and three printed springs that click the rotors from letter to letter. Four holes underneath for the outer ring's screws.

Size
196 × 196 × 8 mm
Print
Flat side down. No supports.
Filament
≈ 125 g
STL 0.3 MB: Base

Key lever

Push the key to the right and the lever turns all three pawls by one letter. Pawl 1 always steps rotor III. Pawls 2 and 3 can only reach the next rotor through a notch in the rotor outside it, which is how the carry and the double step work.

Size
121 × 51 × 13 mm
Print
Flat, as in the file. PETG keeps the sprung pawls springy longest; PLA works.
Filament
≈ 9 g
STL 0.2 MB: Key lever

Rotor III

The fast rotor, on the outside. 26 ratchet teeth underneath, and a notch that lets rotor II step when this one moves on from V.

Size
168 × 168 × 5 mm
Print
Face up. Load it together with its letters as one object for a second colour.
Filament
≈ 35 g
STL 0.5 MB: Rotor III

Rotor III letters

The alphabet on its outer track and the wiring of rotor III on its inner track.

Size
161 × 161 × 1 mm
Print
With the rotor, as a second part, or swap filament at 5.0 mm.
Filament
≈ 0 g
STL 0.6 MB: Rotor III letters

Rotor II

The middle rotor. Its notch at E lets rotor I step and makes rotor II itself step twice in a row, as in the real machine.

Size
134 × 134 × 5 mm
Print
Face up, with its letters.
Filament
≈ 27 g
STL 0.5 MB: Rotor II

Rotor II letters

The alphabet and the wiring of rotor II.

Size
127 × 127 × 1 mm
Print
With the rotor, or swap filament at 5.0 mm.
Filament
≈ 0 g
STL 0.6 MB: Rotor II letters

Rotor I

The slow rotor, next to the reflector. It has no notch: nothing comes after it.

Size
100 × 100 × 5 mm
Print
Face up, with its letters.
Filament
≈ 18 g
STL 0.5 MB: Rotor I

Rotor I letters

The alphabet and the wiring of rotor I.

Size
93 × 93 × 1 mm
Print
With the rotor, or swap filament at 5.0 mm.
Filament
≈ 0 g
STL 0.6 MB: Rotor I letters

Outer ring

The fixed ring with the letters you type and read. Four M3 × 8 hold it from under the base, and its lip keeps the rotors down.

Size
194 × 194 × 5 mm
Print
Face up, with its letters.
Filament
≈ 34 g
STL 0.2 MB: Outer ring

Outer ring letters

A to Z and the index at the top, where you read the start letters.

Size
187 × 182 × 1 mm
Print
With the ring, or swap filament at 5.0 mm.
Filament
≈ 0 g
STL 0.3 MB: Outer ring letters

Reflector

Reflector B, in the middle. Its hex sits on the post so it can't turn, and its lip holds rotor I down.

Size
69 × 69 × 6 mm
Print
Face up, with its numbers.
Filament
≈ 14 g
STL 0.1 MB: Reflector

Reflector numbers

The numbers 1 to 13, each twice: the two spokes with the same number are wired together.

Size
64 × 62 × 1 mm
Print
With the reflector, or swap filament at 5.0 mm.
Filament
≈ 0 g
STL 0.8 MB: Reflector numbers

Pointer

Turns over the dial on the centre screw, with a window along one spoke to keep your place.

Size
106 × 16 × 3 mm
Print
Upside down, as in the file.
Filament
≈ 2 g
STL 26 KB: Pointer
Also needed

Parts you buy

  • One M3 × 12 screw and a washer: it holds the pointer and the reflector on the post.
  • Four M3 × 8 screws for the outer ring, from under the base. They cut their own thread in the plastic.
  • A pencil and paper for the letters you get.
Print settings

Slicer settings

0.2 mmlayer height
3walls
15%infill
5.0 mmfilament change for the letters, unless you print them as a second part

For a 0.4 mm nozzle. Filament amounts are estimates for these settings.

Assembly

How to build it

Print the parts

Nothing needs supports. For letters in a second colour, load each rotor, the outer ring and the reflector together with its letters file as one object, or pause at 5.0 mm and swap filament. Clean any elephant's foot off the undersides of the rotors: they slide on the base.

Lever

Lay the lever in its pocket in the base, the hub over the post and the key sticking out at the front. It should swing freely between its two stops.

Rotors

Drop in rotor I, the smallest, then rotor II, then rotor III. Each one's lip lies over the edge of the one inside it. Turn each by hand: it should click from letter to letter.

Outer ring and reflector

Put the outer ring on with A at the top (the screw holes only line up one way) and screw it on from below with four M3 × 8. Set the reflector on the post, the pointer on top, and screw both down with the M3 × 12 and a washer, just tight enough that the pointer stays where you leave it.

Set the key

Turn the rotors so the three letters under the index at the top spell your key, from the inside out: rotor I, II, III. The animation starts at A D U.

Press the key

Before every letter, push the key to the right until it stops and let it back. Rotor III moves on one letter, and now and then the others move too, just as when you press a key on the real machine.

Follow the letter in

Find your letter on the outer ring. Go in along its spoke to the outer track of rotor III, read the letter there and find the same letter on the inner track of rotor III. From that spoke go on in to rotor II and do the same, then rotor I.

Reflector and back out

In the reflector, go to the other spoke with the same number. Then go back out: read the letter on a rotor's inner track and find it on its outer track, which is in alphabetical order, rotor by rotor. The letter on the outer ring is your cipher letter.

Decrypt

Set the same key and type the cipher text the same way: you get the message back. Any Enigma I simulator set to rotors I-II-III, reflector B, rings A-A-A and no plugboard gives the same letters.

Small parts and screws: keep them away from small children.

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Open the makers