USS Dry Box Magnetic Spool Rewinder

20261101 Update:

• Prusa Spool update

  • Use a smaller magnet

20261029 Update:

• PolyMaker Refill Spool update

  • Use a smaller magnet

  • Add a bit more tolerance on the pins through the spool

20260828 Update:

• Split the rewinder into its own file.

• Reworked the rewinder to use 3 magnets to make it much stronger.

• Use a curved rearside on the rewinder base to make it much easier to slide along the edge of the lid.

• Reworked the clips and clamps for better printability.

• Reworked the clamps for less space usage on the filament side of the clamps.

• Ensure the magnet in the clip is aligned to the magnets in the rewinder.

• Added 'Polymaker Refill Spool Magnet Clip And Clamp'.

• Updated all 3mf files.

The USS Dry Box magnetic spool rewinder puts a clip on a spool, and clamps it tight. In the clip there is a strong magnet and once the spool sits inside of the dry box, a rewinder can be used to rewind the spool inside without opening the dry box, thus preserving the low humidity inside.

In the clip, the magnet is placed such that it sits just below the 'inside' ring on the lid of the box, so use the rewinder there. The reason for this is that the 'outside' ring has the door to the desiccant compartment which would get in the way while rewinding.

Note that strong magnets are needed: the usual 'attractive force' of a magnet is not the measure that should be looked at. Instead, the 'lateral force' is the important measure since the rewinder drags the magnet laterally. A magnet with a lateral force of at least 1.3 kg is needed.

When assembling, make sure that the magnet in the clip and the middle magnet in the rewinder attract eachother, and keep the orientations consistent over all dry boxes - this is easy to ensure by using the rewinder.

The clearance inside the dry box is also something to keep in mind:

• The new Prusament spools (the ones with flat surfaces) seem to have a maximum clearance of about 10 mm, so a magnet of at most 8 mm thickness can be used.

• The old Prusament spools (the ones with 'indented' surfaces) seem to have a maximum clearance of about 10 mm, so a magnet of at most 8 mm thickness can be used.

• The Polymaker Refill spools (https://app.air.inc/a/b288cf5d7/b/51414646-084c-49e3-a864-af22a21ebf07) seem to have a maximum clearance of about 6-8 mm, so a magnet of at most 4 mm thickness can be used.

The following magnets can be recommended:

• New Prusament spools / Rewinder: https://www.supermagnete.nl/eng/block-magnets-neodymium/block-magnet-15mm-15mm-8mm_Q-15-15-08-N

• Old Prusament spools / Polymaker Refill spools: https://www.supermagnete.nl/eng/block-magnets-neodymium/block-magnet-12mm-10mm-4mm_SALE-139

Historically I've mainly been using the 15x15x8 magnets but there seems to be a bit of a variance w.r.t. the clearances depending on the specific dry box and specific spool, so I've changed to using the 12x10x4 magnets everywhere within the spools to ensure that the filament path experiences no extra friction, and the 15x15x8 magnets in the rewinder.

For the rewinder it is recommended to choose a magnet that is as strong as feasible.

It is important that the magnets are top-bottom magnetised and not in their lateral direction.

The FreeCAD files are provided for easy adaptation of the models.

The FreeCAD files have a VarSet under the 'master' group which holds many parameters that can be tuned (but really should not). The main parameters that can be adjusted are the 'magnet*' parameters in case a different magnet is used.

Finally, if a multi material printer can be used then make sure to set up the print such that the final support interface prints in a different material than the main models since that will save a lot of print cleanup time and effort.