Overview

A design for dispensing magnets one at a time. Looking for something to help when installing magnets into gridfinity parts, I came across the Magnet Insertion Tool by cjnaz, which I liked, but still needed a way to not have magnets act like a poltergeist was toying with me when I worked.

I do not know if or when I'll have the time to polish the design to a point that it would be easy for even beginners to print, but I'm posting what I have now in the hopes that it might prove useful for someone.

Also note, that the features are highly dependent on the size of the magnets being dispensed. The 6x2 magnets I got from Amazon are more like 6x1.62. Therefore, it isn't likely that a simple download and print of the STL files will produce a workable tool for others.

Versions

There are two versions:

• Version 1 is in a Fusion 360 file. It's the one that I did most of the design work in, so it has some inconsistent naming, parameters in the order I came up with them, and is a bit messy. It's the one with the large diagonal slice off the back to reduce the filament usage.
• Version 2 is an OnShape design where I decided to clean up the parameters (called variables in OnShape). It adds a cylindrical tool storage location including another magnet in the base to help secure it. It also slaps a 1x2 gridfinity module base to the bottom since I figure tools used to build gridfinity should have to work with gridfinity. It should be available via: https://cad.onshape.com/documents/fd32027a985bc33ea891cfb3/w/59eb6ed20ca7a7cd30f4ef31/e/0b0b6ec237fc732ffa5528c4

Operation

The idea is simple. The slider has a hole in it that will fit a single magnet. When the slider is pushed all the way in, that hole aligns with the feed tube holding the magnet supply and the feed magnet in the base. The stack of supply magnets will then be pulled down so that the bottom most magnet is surrounded by the slider. When the slider is pulled all the way out, the hole aligns with the "front" magnet. Using a 5 mm magnet in the front, there will be a 0.5 mm ring a plastic holding the dispensed magnet 1 mm away from the front magnet. If you don't use a front magnet, the magnetic field generated by the magnets in the feed tube will cause the magnet being moved by the slider to jump up and stick to the side wall. The front magnet is close enough to keep the magnet in the slider stable, but separated enough that when you touch the pick up tool to the magnet in the slider, the pick up tool will always overpower the front magnet.

Printing

Printer Settings

I printed these in translucent red and blue PETG filament. I used my default Ultimaker S7 settings:

• 0.15 mm layer height
• 0.4 mm nozzle diameter
• 15% infill
• Printing position
  • Pick up tool: horizontal
  • Top part: inverted
  • Bottom part: normal
  • Slider: normal
• Support
  • Pick up tool: Yes
  • Version 1:
    • Top: I used support on the front of the top portion (where the pick up tool goes to get the magnet). The diagonal slice off the back is just to save filament and should not be steep enough to require support.
    • Slider: No
    • Bottom: No
  • Version 2:
    • Top: I used support on the front and the tool storage feature.
    • Slider: No
    • Bottom: Optional for gridfinity magnet holes

I printed the pick up tool laying horizontally so that the tip wouldn't shear if any lateral forces were applied. 

Assembly

Place magnets

There are two or three magnet holes in the top of the bottom part. Both versions have a "feed" magnet toward the middle and a "front" magnet that holds the dispensed magnet in place for the pick up tool. The second version also has a magnet towards the rear that helps secure the pick up tool in its storage position.

The feed and storage magnets should be glued in so that they are flush with the top surface of the bottom part. The front magnet should actually be recessed (configurable, but defaults to a 1.0 mm recess) so that it can hold the magnet in place but won't prevent the pick up tool from capturing it.

Finally glue a magnet or two to the end of the pick up tool. See the section below for north/south convention.

Glue assembly together

The "design intent" was that the cubes align the parts, but that glue would only be placed on the horizontal surfaces between the cubes. I didn't want to risk having CA glue on the cube walls seize up before I was able to get the parts firmly mated.

Be careful that no glue gets squeezed into the slider channel. It works best when assembled with the top inverted as the slider can be placed in the channel, then the bottom part glued and set.

Design Notes

Design Goal

I wanted something that would allow me to pick up an individual magnet without having to fight so hard to separate it from the others that I was no longer sure which side was north or south.

I also wanted an obvious red/blue north/south distinction that would make it nearly fool proof to get magnets installed consistently.

North/South convention

My approach was to take a piece of thread and four 6x2 magnets. (I happened to have two magnets that each got too close to another while having CA glue on them.) Then I placed them together while the end of the thread was between them so they would securely hold the thread and I could avoid having to try to tie any knots. Then I dangled the magnets from the thread. Once they settled down, one face consistently pointed north while the other pointed south. The face that pointed north got smeared with a red permanent marker, the other face got blue.

My convention is that if I place a magnet with the red tool, it will end up with the red face exposed and the blue face will be glued down. At that point I just have to remember to use the Blue tool for Baseplates. The red tool is for the modules.

Parameterization details

Everything is set in the parameter/variable table - probably too many things - like close to 60 parameters.

My intent was that the magnet dimension parameters would be set to the size as measured by calipers. There are associated slack dimensions that allow for padding to account for material thermal contraction and printer idiosyncrasies.