This is a special joint I was playing with to use three 4mmx8mm cylinder nm52 magnets instead of just one on each arm for a Delta printer. This seems like it will work, but I have not tried it on a Delta printer. The idea is that 3 magnets connecting a steel ball will be a much stronger connection than just 1 magnet. The only problem I can see with this is the joint is thicker & may interfere with another part on the carriage or the effector. I included an openscad file where you can play with the different variables to change the part to suit your needs. If you go above a 4mm diameter, the joint will be thicker & may cause more interference problems. I also made this part so you could add an M4 Steel Setscrew or short M4 steel bolt to hold the magnet in place. Be sure NOT to use Stainless for these bolts as magnets will not stick to most stainless steel. This was designed to use 10mm steel balls. I did not have any steel ball bearings on hand, but used the pan head of a bolt to see how well it stuck. I used a carbon fiber arrow from Walmart as the shaft size. I also added a 10mm printable sphere with a hole to put a steel setscrew or bolt for testing. Another advantage of this idea is you maybe able to use less strong N35 magnets instead of nm52. When inserting the 3 magnets, you might want to orient them all to have the magnetic poles going the same way. I do not know much about magnets, but this is probably not a problem unless you are attaching these 3 magnets to another magnet
Here are the magnets I am using. (I had the wrong link initially here)
The weight of 36 of these magnets is .84oz on my scale.
Another way you might be able to use this idea is to hold the ball bearings on the effector & carriage with these magnets embedded in the plastic behind them. You would probably need a little layer of plastic between them to keep either from falling out. Insert the magnets from the bottom & the steel balls from the top. The magnets & the steel ball would both be pulling each other towards the center.
Am not sure that I will use a magnetic connection on my delta printer, but thought I would upload this file in case someone else wants to test this idea further. You will probably have to adjust the variables a little for a tight fit on the magnets & shaft.