Magnets can help attach and align parts, as long as they’re installed in the correct orientation.
A frequent issue is incorrectly orienting magnets during installation. Of course, this is easy to do because the two poles of a round magnet look exactly the same!
Designs that make poles distinguishable via shape or markings can help prevent these issues. Alternately, we could also eliminate the need to distinguish poles by using steel components.
Below, we’ll provide three methods for different situations.
Option 1: Replace One of the Magnets with a Carbon Steel Screw
Magnets attract not only each other but also other steel components. For light-duty applications (e.g., lightweight lids), replace one magnet with a carbon steel screw. This can reduce the costs of a project and also make it impossible for users to reverse the polarity of the magnets during assembly
Stainless steel screws, like those made of 304 or 316 stainless steel, aren’t attracted to magnets, so be sure to double-check the material when purchasing screws! Maker’s Supply offers various sizes of carbon steel screws, which work well with magnets.
Take the controller of CyberBrick for instance. Its cover relies on magnetism to attach to the main body. Replacing one side with steel carbon screws is a good approach. Place the magnet in the thin cover, and put the screw on the main body side where there’s ample space.
Figure 1: Lid of CyberBrick General Controller, using a fixed screw to avoid polarity issues.
Option 2: Use Disc Countersunk Hole Magnets to Distinguish Magnetic Poles
If the two poles of a magnet have different shapes, it becomes easier to distinguish them. The disc countersunk hole magnet is an example of this.
In the version offered by Maker’s Supply, the larger recessed face is the N-pole, and the smaller flat face is the S-pole. Users can accurately distinguish the poles through these shapes. Furthermore, adding a slight protrusion to the mounting surface can create a foolproof design, effectively preventing installation errors.
Figure 2 : The polarity of the disc countersunk hole magnets from Maker’s Supply
In the D20 Dice Box magnetic[Membership Ver.] designed by Preischl 3D, the sum of the numbers on opposite faces of a D20 dice should be 21. The magnet installation holes, with their alternating magnetic poles, help ensure the lid only closes properly when oriented correctly.
When installing the magnets, place the chamfered side down into the holes with pillars, and the flat side down into the holes without pillars.The bottom of the pillar has a protrusion, so incorrect magnet installation will cause unevenness, alerting users to check the direction.
Figure 3: Determine the installation direction via pillars and chamfers
Option 3: Mark the Magnet Surface
Marking the poles of magnets is also a viable method to consider.
Intersect your users to check which faces of their magnets attract each other before installation and mark the poles with pencils, markers, or stickers. These marks can help to avoid mistakes in magnet pole installation.
Figure 4: Use a marker to indicate the magnet pole before installation
- We are grateful to @MaKim for helpful feedback on earlier drafts of this guide.
Tips From Users: Use Magnet Insertion Tools
Some talented creators have made a number of magnet installation tools, such as Magnet insertion Fast-Tool by Jorge Rui, Embedded Magnet Dispenser Tool for 3D Prints by Brian Dean and Magnet Insertion Tool v2 by EmGi.
You can use the colors of these tools to distinguish the magnetic poles, preventing installation errors. Additionally, these tools make it easier to grip magnets and provide guidance during installation.
Summary:
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Option 1: Replace One of the Magnets with a Carbon Steel Screw
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Pros: Eliminates magnet polarity errors entirely; lower project cost.
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Cons: Slightly reduced magnetic force;
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Option 2: Use Disc Countersunk Hole Magnets to Distinguish Magnetic Poles
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Pros: Unique structure enables anti-mistake design.
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Cons: Slightly higher project costs.
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Option 3: Mark the Magnet Surface
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Pros: Suitable for existing designs and installation processes.
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Cons: More steps needed; attention still required for marker orientation during installation.
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Use Magnet Insertion Tools
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Pros: Fits existing designs; easier installation.
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Cons: Need to print multiple tool sets; different sizes required for different dimensions.
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Previous chapter(s) about magnets in 3D printing
Upcoming chapters about magnets in 3D printing
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Using Magnets in 3D Printing 3: Installation Issues & How to Avoid Them
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Using Magnets in 3D Printing 4: Ensuring Even Installation
