In this article we will illustrate the mechanism of Chinese padlock, and how to make a Chinese lock via 3D printing.

We have always wanted to make some traditional items through digital manufacturing tool, here traditional item means classical products in Chinese traditional culture. Through this kind of making we can experience engineering thinking and STEAM learning process, pay tribute to the spirit of the old time craftsmen.

This time we made a padlock, although made by 3D printing, it is still capable to lock a box. All of our makings can be used as a real product.

Step 1: Tools and Materials

3D design software
(like 123D, Solidworks)

3D printer and material

3D slicer software (like Crua)

Chinese lock 3D source code (can be downloaded)

Step 2: Introduction

Ancient Chinese padlocks can be classified into two categories: the splitting spring locks and the letter-combination locks. A splitting spring padlock has to use a key for opening, and it has the types of broad locks and pattern locks. And, a letter-combination padlock has no keys for opening. The lock we will make is a most common splitting-spring padlock, the broad lock.

Step 3: Design

We must know the structure of Chinese lock before design and make one functional one. Broad locks are kinds of horizontal positioned spring locks, mostly made of bronze.

A splitting spring padlock consists of a lock-body, a sliding bolt, and a key.

A paper named 'The Secret and Beauty of Ancient Chinese Padlocks' explains how the padlock work:

The lock-body provides a keyhole for the key to insert and the supporting guide for the sliding bolt to move. The sliding bolt has a shackle for hanging the lock and a stem for bonding one end of the splitting springs. The key is designed corresponding to the configuration of the splitting springs, and the location and shape of the keyhole. When it is locked, the sliding bolt is trapped by the opening springs against the inner wall of the lock-body. For opening, the key is inserted and its head squeezes the opening springs so that the sliding bolt can be separated from the lock body.

Now we know the mechanism, so we can use 3D design software like 123D to design an ancient Chinese padlock.

Key is the most interesting part in ancient Chinese padlock, there are many weird shapes of keyhole, looks like Chinese character 一,十,士, even 喜. Our key’s shape is like Chinese character 凹, just upside down, although it is a variation to a simple design which based on character 一, we must use specific methods to put the key into the keyhole.