Magnetic Self-Centering Panel Door Opener by randysteck

Last crawled date: 3 years ago

This is a mechanism that allows two abutting panel doors to be opened without the need for a knob on the door. It allows adjustment for flush fitting the doors and returns with good force to center using some very strong magnets.
I ran into a very unique problem in rebuilding a mantle for my daughter. Above the mantle was an alcove that she really did not want to see anymore since it was just an unattractive hole. We framed it out and decided to put two panel doors flush with the surrounding structure. They are mounted using some soft-close hinges built for an inset mount. We did not want to spoil the look by requiring a knob on the doors, and a magnetic closure (push to open and push again to close) did not work well with the soft-close hinges.
We decided that the "right" way to do this was for one door to be pushed in resulting in the other door popping out enough for finger grooves on the side of the panel to be used to open the door. It's kind of a unique requirement and I could not find hardware so designed this opener.
Instead of using springs (how gauche!) I decided to use magnets to both center the latch and to provide the centering force when one of the doors is pushed in. It turns out that the force at both the open and closed positions are maximum, something that is not possible with a spring closure, and I did not want the extra friction of spring-loaded ball mechanism.
This worked out very nicely.
The opener uses three magnets in the base, which is mounted about 5/8" behind the panel doors. A single magnet in the hinge arm is set to attract the center base magnet and repel the side magnets, thus giving the centering force. The arms are offset from center by 1.25" and allow flush adjustment of the panels using screws and an embedded nylox nut to avoid slipping. The end caps are just there to avoid damage to the panel surface.
The screws and nuts are all #6-32 and 1.5" long. The magnets are 1/4" diameter 1/4" long rings from K&J Magnetics (R424).
The center column acts as a stop for the panel door when pushed back resulting in the other door being pushed forward 1/2" for a total difference of 1", giving enough room to open the other door completely. The maximum deflection angle of the hinge arm is 23 degrees, which puts the center hinge magnet at the maximum repelling position from the side base magnet.
I know, lots of detail for such a simple thing, but it was fun to do.
I printed in semi-transparent PETG on a Prusa I3 MK2 and used 3 shells and 20% infill just to make sure it would be strong enough for the next dozen earthquakes.