3D Printed On/Off Magnetic Base

This tutorial will show you how to build a compact, switchable magnetic base compatible with a variety of printed tools. My design includes a phone stand, a camera stand, a vice, various translation stages, or a modular lab holder system.

It can be used to place a phone or camera on any magnetic surface, a sample on a microscope plate or a device on an optical breadboard.

There are two versions using 10x or 20x magnets. I tested the force generated and the 10x version was able to lift 3.6 kg, while the 20x version can lift more than 5 kg (I ran out of weight to test it to the limit). While compact (65 mm wide, 17 and 20mm thick for the 10x and 20x magnets versions), those base provide enough stability to fix a phone, a camera or a dial indicator reliably.

If you end up on this tutorial because you are just curious about switchable magnets or if you want an idea of how it works before building it, you can go directly to step 8, where I give some background explanations.

This magnetic base uses only 3D printed parts and commonly available hardware components. The 3D files are available on thingiverse. For tinkerers, STEP and Solidworks files are also available for easy modifications. I used PLA+ for its ease of use and good toughness, but the base main body can be printed in PLA, PETG, ABS or pretty much any materials. The design also uses TPU pads to increase the friction with its supports, which you can do without but I highly recommend using it.

Apart from 3D printed parts, this build also requires:

1. 10x or 20x 12 mm diameter 3 mm thick cylindrical magnets
2. 60x 12 mm diameter 1 mm thick washers (stainless steel washers do not work), take nickel plated or plain steel washers). The central hole should be as small as possible, M3 or M2.
3. 4x 12 to 14 mm M3 bolts
4. 3x M3 nuts
5. 4x to 13x M3 melt inserts 4.2 mm OD and 4 mm thick

The last step of this tutorial includes a series of possible links to purchase those parts. I have no tie to those links and cannot endorse the quality those products. They are just provided for reference.

Required tools:

1. Allen key / screwdriver
2. Soldering iron (for melt insert installation)
3. File (recommended, for washers with sharp edges)
4. Vice/hammer (facultative, for M3 nuts insertion)
5. Oil (facultative, for easy lever movement)

Depending on your preferences, you can find the 3D files on thingiverse, Printable or Makerworld. If you use BambuStudio, you can find a 3mf file with the right printing parameters. Otherwise, download the STL file corresponding to the version you want to build (10x or 20x magnet) and the "TPU_pads" file.

All STLs are pre-oriented, so you can conserve the parts orientations. I recommend using 0.2mm layer hight, 4 walls and 25% infill for the rigid parts and 6 walls and 60% infill for the TPU pads. The parts should be printed with supports for the screw sockets and the magnet holes.

You may want to print the lever in a different color from the casing. Having the washer retainer in a clear (a little transparent) color makes the assembly slightly easier.

After gathering all the parts, start by inserting the 3x M3 nuts in the bottom casing part. You may need to use a vice or a hammer depending on the printing tolerances of your 3D printer.

Then, use a soldering iron to add the melt inserts on the top casing part. There are 13 insert holes in total but you don't need to fill them all depending on what tool you intend to use.

Take the magnet retainer and insert magnets from the bottom. To distinguish between top and bottom, the bottom corresponds to the face touching the bed during printing. On the top side, the lever forms a protrusion.

Insert magnets on half of the holes on the retainer, leaving one of every two positions empty. For the 10x base version, each hole contains one 3-mm thick magnet. For the 20x version, each hole contains two magnets. All the magnets should have the same orientation, presenting either their north or south side.

Then, turn the retainer around, and add one washer in each hole. Those washers will help you keep the magnets in place during the following steps.

Turn the magnet retainer down again, and add the remaining magnets. Make sure the magnet orientation alternates every time.

Then, finish adding the washers on the other side (3 washers per hole). Make sure the washers do not protrude from the holes and use a file to remove the sharp edges if needed. Low cost washers are typically produced by punching. This process imprints a typical geometry with a round top and sharp edges on the bottom. Those sharp edges can be an issue as we want to pile up the washers in a compact manner.

To ensure the mechanism functions smoothly, you can add a little mechanical grease or oil on top of the magnets.

Then, place the washer retainer on top of the magnet retainer. Make sure that the washer retainer is oriented so that each "spike" is on the center of the magnet below (so that each washer spot is astride two different magnets). Then, start adding washers until each spot has a pile of 3.

Once again, make sure to file the washer edges if they prevent a compact piling.

Insert the whole assembly into the bottom casing, washer retainer down. It should sit flush with the shoulder part. Otherwise, you may need to remove the washers and reposition the washer retainer correctly.

Once it sits flush, you can try to action the lever and check that the bottom side becomes magnetic.

If it works as intended, add the top casing and secure it with 3 M3 screws.

Turn the base around, and add the final retaining screw and the TPU pads.

Congratulation! Your magnetic base is complete.

This magnetic base is designed with a variety of attachment points to allow you to fix any tools you may want to design/adapt. However, I also designed a collection of useful tools you may be interested in, including a universal phone holder, a camera base, a vice, a set of modular lab holders, and a variety of translation/rotation stages for precise positioning. This mount is also compatible with my articulated arm design, you may want to use a few of its ball join links for increased positioning freedom.

Magnetism is quite complex, but if you want a quick and intuitive (and probably slightly flawed!) explanation of how a switchable magnet works, read below:

Magnetism is often visualized using the magnetic field lines revealed when iron filings are placed around a magnet. Outside the magnet, these lines go from the north pole to the south pole.

These magnetic field lines extend into the space around the magnet, but their path can be strongly influenced by materials with high magnetic permeability, such as iron. The magnetic field preferentially passes through these materials rather than through air.

The force generated between a magnet and a piece of iron depends on the magnetic field at the interface between them. As a very rough visualization, you can think of it as being related to the "number of magnetic field lines" passing through the iron.

In switchable magnets, permanent magnets are used to generate the magnetic field, while iron parts are used to redirect the magnetic flux. By changing the position of these iron parts, the magnetic field can either be brought to the outside of the device or mostly confined inside it.

Iron can therefore be considered as a kind of "magnetic conductor". Once the magnetic field enters an iron part, it preferentially follows the shape of the metal, providing an easy path for the magnetic flux.

For example, if a flat iron piece is placed against one pole of a magnet, it provides a path for the magnetic flux to reach the other side of the iron piece. The magnetic field therefore extend outside the iron.

However, if both a north and a south pole are connected to the same iron piece, the iron provides an easy path for the magnetic flux to travel directly from one pole to the other. Most of the magnetic flux then remains inside the metal, and the magnetic field outside the part become very small.

This is the principle used in switchable magnets. Iron parts are mechanically moved between two configurations: in one configuration, they connect the permanent magnet to the working surface and guide the magnetic flux outside the device. The device is then "ON" and can stick to iron.

In the other configuration, the iron parts connect opposite poles together and provide a path for the magnetic flux to close inside the device. Much less magnetic flux reaches the outside surface, so the device is effectively "OFF" and no longer sticks strongly to iron.

The design in this tutorial arranges a circular array of magnets and an identical array of washers. When the washers and the magnets align, the magnetic flux is transmitted. When the magnets are rotated by 18 degrees (1/20th of a rotation), the washers bridge two opposite magnets and contain the magnetic flux.

I sourced my own components from Taobao, as it is the most practical and economical given my current location in Hong Kong. However, it can be challenging for non Chinese speakers (unless you have a beautiful and intelligent wife like mine!) and I tried to include other links. Please bear in mind this is not an endorsement and those links are only here as reference.

1. 12 mm diameter, 3mm thick magnets: Taobao, Aliexpress, Amazon
2. 12 mm diameter, 1mm thick washers: Taobao, Aliexpress, Amazon
3. 12 to 14 mm M3 bolts and nuts: Taobao, Aliexpress, Amazon
4. M3 melt inserts 4.2 mm OD and 4 mm thick: Taobao, Aliexpress, Amazon