Captive Ring Lift
The captive ring lift was an experiment to create an adjustable stage for a new smartphone microscope.
Design requirements:
-Stage must stay flat and not wobble under load, when static or moving
-Incremental, smooth, one-handed height-adjustment
-No glue or support material
-Reversible disassembly, replaceable parts.
-Opening (window) for backlight
I chose to go with the screw mechanism as it is a very common and recognizable operation that doesn’t require explanation. Similarly, the use of pegs in assemblies is something with which most are familiar (even if it is octagonal pegs and teardrop-shaped holes). I have found they require less tuning and are more forgiving regarding tolerances between printers.
There are files for three pegs of different diameters. I find the 4.0mm pegs work well for me in PETG when printed without brim. My Ender 3 PLA prints required a brim and 3.9mm pegs worked well after trimming the excess plastic. You may have to print a few of each size to see which works for you.
The window in the center measures 45.75mm x 55.4mm (~1 13/16”x 2 3/16”), and is friction fit into the assembly.
To make a complete captive ring lift you need to print:
1 x Base
1 x Ring
2 x Stage
4 x Peg
The parts should be ready to use right off the print bed. If there is resistance when turning the ring on the base then check to make sure the threads are clear of debris and stringy plastic.
Assembly:
Insert the pegs into the four holes of one of the stage pieces.
Carefully maneuver the ring past the guides into the slot below.
Line up and push together the other half of the stage, trapping the ring in place. The ring should spin freely in the stage assembly.
Slowly screw the ring onto the base while being careful to line the guides of the stage with their corresponding channels.