Potential Pitfalls

Magnets are attracted to the steel nozzle and heater block
- Make the magnet pocket retain the magnet, this can be done by adding retaining nubs into an oversized pocket to grip the magnet.
Crashing the nozzle into a magnet will damage the nozzle, causing jams in the future
- Ensure the pocket is deep enough that the magnet is below the top layer after insertion
- If a crash occurs, ALWAYS replace the nozzle. Using a crashed nozzle is a sure way to get a jam.
Magnets are damaged when heated above their maximum operating temperature.
- See K&J Magnetics' article.
- Most heat comes from the bed. Move the magnet at least 5mm away from the bed and place it near a side wall of the part instead.
- Choose a magnet with a maximum operating temperature greater than 100°C/212°F.
  - For neodymium magnets, use grades ending with an 'H', such as N35AH (220°C/428°F) or N42SH (150°C/302°F)

Modelling

Magnets will damage the nozzle if it crashes into it, ensure the pocket is deep enough that the magnet is below the top layer after insertion
Place the top of the magnet pocket a whole number of layers up, for default profiles this is a multiple of 0.2mm
Oversize the pocket by 0.25mm, then add nubs to the edges of the pocket to grip the magnet (Example photo is for 1/4" (6.35mm) wide magnet)
- Nubs smaller than 0.5mm in their longest dimension are not recommended

After plating and slicing, drag the layer bar on the right edge of the preview window down to the top of the magnet pocket, right click on the '+' icon and select 'Add custom G-code'.
In the custom gcode textbox type 'PAUSE'
Re-slice the job
In the slice preview, make sure the retaining nubs actually turn up in the finished part. Nubs smaller than 0.5mm in their longest dimension are not recommended:
Export and upload as usual

Run the job as usual, when the machine pauses press in the magnet
ENSURE THE MAGNET IS FULLY SEATED BELOW THE TOP LAYER USING A STRAIGHTEDGE
OR NOZZLE DAMAGE WILL OCCUR.
Resume the print