Magnetic personality


Following on from Kossel 3D Printer, I purchased some magnetic balls and ball joints on eBay, because they were extremely cheap (or cheaper than the other balls/joints that I had seen elsewhere), without really thinking about what I was going to use them for, or how I was going to mount them.

This is the tale of what happened.

The purchases

I first saw these rods being offered very cheaply, L200 Diagonal push Rods Arms + Steel Ball + Magnetic Joint For Kossel 3D Printer, AU $17.99 Approximately £10.49 + AU $0.59 (approx. £0.34)

Magnetic rod kit
Magnetic rod kit

However, after having purchased 5 meters of 6 mm x 4 mm carbon tubing, 5x Carbon Fibre Tubes 6mm x 4mm x 1000mm (T6-1000) : £26.75 free p&p, it seemed daft to purchase even more tubing, when all I really needed were the extra magnetic fixings. After looking into the price of just the balls, joints and grub screws, I found these:


Don’t get me wrong, the complete kit is definitely worth the money, as the rods come out at costing only £4 or so. However, if you already have the rods, and can cut them to whatever length you so desire (rather than just being lumbered with 200 mm rods), as I do, then just get the magnetic bits, as it makes more sense. At least to me it does.

Other options are, the much more expensive, Magnetic Ball Joints Carbon Fiber and Delrin (50um precision): Kossel, Delta, 3D, $75.00 (£58.24) + $25.00 (£19.41).


These rods are used on the Blue Eagle Labs’ Metal Delta, and are known as Haydn’s Carbon Fiber Arms from $75.00

Hayden's Magnetic Arms on Metal Delta
Hayden’s Magnetic Arms on Metal Delta

Just the threaded balls, however these are more expensive than the tapped balls. Also, none appear to be both 10 mm in diameter and M4 threaded…

12 mm Ball Screws
12 mm Ball Screws

Putting them to use

I found these printed parts (STL files) to use them with:

Aluminium Alternatives

Using tapped balls on the effector and vertical carriages – cylindrical magnet on rod ends

Instead of putting the balls on the rod ends, as with the printed solutions above, the balls are placed on the effector and vertical carriages. The ball joints, which are now on the rod ends, can take the form of the magnetic joints or cylindrical magnets in conjunction with a printed convex joint.

This method is actually emulating Haydn’s Carbon Fiber Arms, see above .


If you don’t like using printed parts for the effector, you could use the tapped M4 balls in conjunction with an M4 effector:

with some headless 20/25 mm M4 bolts, or long M4 grub screws. The screws could be locked into place in the balls using red loctite, or blue – if you think that you do not want them permanently screwed in.

Vertical carriages

If you don’t like printed vertical carriages, you could use the tapped M4 balls in in conjunction with the 4 mm threaded aluminium vertical carriages,  3pcs Aluminum Delta Kossel Mini Carriage Belt Slide M3 Tackle Effector Hammock, £12 (option of 3 or 4 mm rod threads). Again using 20/25 mm headless bolts, or grub screws, with red, or blue, loctite.

Or, if you are upgrading a 3 mm set of carriage,  you could find some M3 tapped, or threaded, 10 mm diameter balls and use them, with existing 3 mm threaded aluminium vertical carriages


These options, because the balls are thread on to the effector/vertical carriages, and not the rods themselves, would require different magnets, and rod ends, like those shown in Rostock Delta Magnetic Ball Ends with Effector Concept at @2:36. The magnet is a 3/8″ (9.525 mm) N52 cylindrical magnet, with a printed rod end, with a socket machined to match the 10 mm ball.

You could use the 12 mm magnetic sockets above, but the printed cylindrical casing would then be 14 – 16 mm in width and, as well as the additional weight, may be too wide and come into contact with the effector/vertical carriages.

Here are some STL files for magnetic rod ends

Using tapped balls on the effector and vertical carriages – magnetic joints on rod ends

Alternatively, you could just epoxy the 12 mm magnetic sockets directly on to the ends of the carbon rods – it might look ugly, but should work, and then the rod ends would be just 12 mm wide and the perfect size, with the socket already built in. However, to be precise:

  • Just be sure to center them correctly on the ends of the carbon rods.
  • The carbon rods ust be of an equal length  the ability to adjust for cutting errors is lost as there is no longer an M3 grub nut thread to use to adjust any imperfections caused by the cutting process
  • The epoxy can not alter the overall length

Useful reading


Other options


Rostock Delta Magnetic Ball Ends with Effector Concept

Rostock Max Delta Magnetic Ball Ends in Action

Second Print: Rostock Max Delta Magnetic Ball Ends with J-Head

Kossel Plus


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