Internal Gear and Pinion Display

Update Nov. 21, 2024: Added "internal gear wheel cushion" to replace rubber band. Put this in the internal gear wheel's groove. It should be printed in rubber-like material. I used TPU 85A. Depending on how you slice it, you might need to cut and file off the flash to smooth the seams.

This internal gear driven with pinion is part of my collection of mechanical displays.

See the files for assembly instructions.

The internal gear has a groove around the outer diameter which accommodates three 695ZZ bearings that hold the gear in place. I put a 3 mm x 160 mm (total length) rubber band in the groove to make the action smoother and quieter. The groove requires supports. I use minimal tree supports, but for the smoothest operation (especially for PETG) careful sanding of the groove inner surface is needed to completely remove the support material.

The gear, spacers and knob are intended to be lightly press-fit onto the shafts. You may need to adjust your print settings to achieve this. The gear has pilot holes designed to be tapped to accommodate a 3 mm grub screw, but I don’t uses the screw in this display as the light press fit is sufficient.

The stand has cutouts on the corners to help prevent warping. Glue stick and organic supports are recommended for this part. There is also a hole for attaching a 10 mm bolt and nut(s) as needed to ensure the display doesn’t tip forward.

The bearing holder needs supports. Organic supports are recommended for flat horizontal surfaces. I recommend NOT using supports for the screw holes. The smaller diameter holes are intended to be M3 tapped. 

The back plate should be printed with a higher number of top layers if using white PLA to prevent the internal fill pattern from showing thru. I used 8 top layers and 20% cubic infill.

Other key parameters:
 

• 0.20 mm layer height (0.30 mm recommended for stand to reduce printing time.)
• 3 perimeters
• Cubic infill at 20%
• Supports for bearing holder
• Filament: PLA or PETG

Non-3D printed parts:

• 5 mm x 60 mm aluminum rod 
• 695 bearing (5)
• M3 x 25 screw (2)
• M5 x 25 screw (3)
• M5 washer (3)
• M5 spring washer (3)
• M5 nut (3)
• 3 mm x 8 mm tapping screw (6)
• 3 mm x 160 mm (total length) rubber band