An unexpected discovery led to this product: We could not find a cable-connector box small enough on the market that would be suitable for our intended outdoor use. But that's exactly what we needed for a project. We needed it quickly. It had to be really tiny. We needed about 20 of them. We also needed different variants to cover different cable sizes.
So, rather than continuing our desperate search for suppliers, we switched on our brains, fired up our CAD software and heated up our 3D printers to produce it ourselves in less than one week, from idea to final production.
Meet tiny connector box v1.0
The requirements are straightforward: up to four cables of different diameters must be joined together inside a box. The most critical aspect is, of course, the watertightness.
Fortunately there is a de facto standardised product called a 'cable gland' that is produced in large quantities and available at low prices. It is usually IP68 compliant and comes in different standardised sizes to fit cables of various diameters. 'IP' is the measure for 'Ingress Protection'. The '68' indicates the levels 'Dust-tight' (6) and 'suitable for continuous immersion in water in 1m ore more depth' (8). It seemed logical to us to use these prefabricated, easily available parts to manage the cables coming in and out.
The remaining challenge was to design a case that - based on the required cable diameter - takes up the minimum required space to house the glands and cables connected to an inner lustre terminal.
For our purposes, we needed five different cable gland sizes, which are defined by their diameter. To create a case of the minimum size for all possible combinations of sizes for our four connector box outlets, we will therefor need 24 different cases. 4 outlets x 6 sizes (5 gland sizes + the 'no cable outlet' option).
This use case is ideal for implementation in a parametric CAD system. With this type of software, you can define relations and constraints within a design and make them configurable. For example, if you change the desired outlet diameter, the entire construction will update according to this constraint. We chose the excellent FreeCAD software to produce the file.
FreeCAD is a free and open-source software project that we actively support as a sponsor. As we intended to release the source files to the public anyway, it was the obvious choice among the parametric CAD systems at our disposal.
We defined the parameter matrix for the 6 sizes for each of the outlets and connected them to the 3D-drawing.
The FreeCAD interface then allows you to chose the configurations for each outlet based on a handy select dropdown and updates the geometry of both parts accordingly.
The selected configuration of the connector case can now easily be exported from within FreeCAD to be 3D printed.
The remaining components to complete the product are easy to obtain:
- The terminal block for internal wiring
- One O-ring to create a watertight connection between the two case elements
- Two screws and bolts to secure everything together tightly
Releasing the source CAD files
We have released the CAD file to the public so that anyone can edit and adapt the design to their needs, producing the necessary geometry to feed into their 3D printer. This means that not only can everyone produce their own tiny cable connector box, they can also customise the design.
Find the source files and instructions here
Of course, if you manage to make it even smaller while still ensuring it works, we would be happy if you shared the resulting files as well. :-)