"Marblevator, Grippers" is the latest in my Marblevator series of marble runs. Featuring a "hardware handshake" of sorts, the mechanism utilizes a nested rhombus to pick up a marble from the end of the track, pass the marble to a second nested rhombus, then place the marble at the start of the track for the journey back the the end.

The rhombi utilize magnetic joinery and as such great care must be used to keep all the magnets in the proper orientation and to make certain each magnet is flush with the surface.

As usual, I probably forgot a file or two or who knows what else, so if you have any questions, please do not hesitate to ask as I do make plenty of mistakes.

Designed using Autodesk Fusion 360, sliced using Ultimaker Cura 4.12.1 Engineering profile, and 3D printed in PLA and TPU on Ultimaker S5s and an Ultimaker 3e.

Supplies

Soldering Iron and Solder.

Step 1:

I acquired the following parts:

One "uxcell 16mm DC 6V 60RPM Speed Torque Gear Box Electric Motor for Robot".
One four cell AA battery box with switch.
Four AA batteries.
Thirty four 6mm diameter by 2.6mm thick neodymium magnets.
Two 14mm plastic marbles.

I 3D printed the following parts in PLA at .15mm layer height, 20% infill and no supports, unless noted otherwise:

Two "Arm.stl".
Two "Axle (8.4mm).stl".
Two "Axle, Gear, Yoke (1.5m 32t).stl".
One "Base.stl".
Nine "Bolt (M8 by 8).stl".
One "Gear, Motor (1.5m 8t).stl ".
One "Gear, Yoke, Left.stl".
One "Gear, Yoke, Right.stl".
One "Gripper, Left.stl" (TPU).
One "Gripper, Right.stl" (TPU).
Two "Link 1.stl".
Two "Link 1A.stl".
Two "Link 2.stl".
One "Link 2A, Left.stl".
Two "Link 2A.stl".
Two "Link 3.stl".
Two "Link 3A.stl"..
One "Mount, Motor.stl".
One "Yoke, Left.stl".
One "Yoke, Right.stl".
One "Stand.stl".
Two "Tower, Magnet.stl".
One "Track.stl".

This is an ultra high precision 3D print and assembly model using at times very small precision 3D printed parts in very tight spaces. Prior to assembly, test fit and trim, file, sand, polish, etc. all parts as necessary for smooth movement of moving surfaces, and tight fit for non moving surfaces. Depending on you printer, your printer settings and the colors you chose, more or less trimming, filing, sanding and/or polishing may be required. Carefully file all edges that contacted the build plate to make absolutely certain that all build plate "ooze" is removed and that all edges are smooth. I used small jewelers files and plenty of patience to perform this step. And polish all moving parts!

The model also uses threaded assembly thus an M8 by 1.25 tap and die will assist with thread cleaning if necessary.

Step 2: Base Assembly.

To assemble the base, I performed the following steps:

Slid "Yoke, Right.stl" over the pin on "Gear, Yoke, Right.stl", slid the assembly into "Base.stl", then secured it in place using "Axle, Gear, Yoke (1.5m 32t).stl"
Slid "Yoke, Left.stl" over the pin on "Gear, Yoke, Left.stl" and slid the assembly into "Base.stl".
Aligned the yoke gear pins to their closest position.
Secured the left gear yoke to the base assembly using the remaining "Axle, Gear, Yoke (1.5m 32t).stl".
Pressed one neodymium magnet into each "Arm.stl" with matching polarity.
With the yoke pins aligned at their closest position, secured both arm assemblies to the base assembly using two "Axle (8.4mm).stl" such that the arms were slightly below horizontal and pointing away from each other.
Pressed one neodymium magnet into each "Tower, Magnet.stl" matching the polarity with the arm magnets.
Attached the two magnet tower assemblies to the base assembly.
At this point I made certain the mechanism operated with ease.
Pressed the gear motor into "Mount, Motor.stl" then soldered the battery box wires to the gear motor.
Secured the motor mount assembly to the base assembly using two "Bolt (M8 by 8).stl".
Pressed "Gear, Motor (1.5m 8t).stl" onto the gear motor shaft.

Step 3: Rhombi Assembly.

For rhombi assembly, I performed the following steps:

Pressed two neodymium magnets into the "Link 1.stl" open magnet pocket matching the polarity of the magnet tower magnet and making certain the magnets were flush with the link1a surfaces.
Pressed one neodymium magnet into each of the two remaining link 1 magnet pockets matching the polarity of the previously installed magnets and flush with the surface.
Attached link 1 to the base assembly.
Pressed one neodymium magnet into "Link 1A.stl" matching the polarity of the link 1 dual magnet pocket and flush to the surface.
Pressed one neodymium magnet into each of the two remaining link 1a magnet pockets matching the polarity of the first link1a magnet and flush with the surface.
Attached link 1a to link 1.
Pressed one neodymium magnet into both magnet pockets of "Link 2.stl" and "Link 2A.stl" matching the polarity of the magnets in link1 and link 2 and flush with the surface.
Pressed "Gripper, Right.stl" on the end of the link 2a assembly noting the orientation.
Attached link 2 to link 1, link 2a to link 1a and link 2 to link 2a.
Pressed two neodymium magnets into the "Link 3a.stl" open magnet pocket matching the polarity of the arm magnet and flush to the surface.
Pressed one neodymium magnet into the remaining link 3a magnet pocket matching the polarity of the previously installed magnets and flush with the surface.
Attached link 3a to link 1a and to the arm.
Pressed one neodymium magnet into each magnet pocket in "Link 3.stl" matching the polarity of the previously installed center magnet in link 1 and flush with the surface.
Attached link 3 to link 1 and link 3a.
Repeated the previous steps for the left rhombus using "Link 2A, Left.stl" instead of "Link 2A.stl" and noting the left rhombus is a mirror image of the right rhombus.
Pressed "Gripper, Left.stl" onto the end of the left link2a assembly noting the orientation.

Step 4: Final Assembly.

For final assembly, I performed the following steps:

Attached "Stand.stl" to the base assembly using four "Bolt (M8 by 8).stl".
Attached "Track.stl" to the base assembly using three "Bolt (M8 by 8).stl"
With the battery box switch off, inserted the AA batteries into the battery box.

With assembly complete, I turned on the battery box switch, added the marbles and off it went!

And that is how I 3D printed and assembled "Marblevator, Grippers".

I hope you enjoyed it!