Roller Coaster Gantries
Scratch / Landing page for the roller-bearings and 2d-sheet-stock axis system.
With RCT, we break axis into individual kinematic elements - and roll those elements into machine designs.
A reasonable system for beginners, and easy to manufacture (with another CNC mill). Particularely, this system begets the Madison Park Vocational Machine
Building Axis and Machines from 'Kinematic Elements'
Machines are made of degrees of freedom, and those degrees can be assembled from 'Kinematic Elements' i.e. here I have one Motor / Pulley Unit, as well as Lateral (into the gantry) and Cross (across the gantry) supports. I'm doing a mediocre job of explaining this, but here are some images:
To scratch a machine together, I pull elements into Rhino as .step files, and lay them out into axis - here's one linear degree of freedom:
Then I assemble those axis together, keeping track of where I'll be adding plates of material:
Then I go about filling in detail design, adding tabs etc to bring beams and chassis together.
Fabricating Axis
I then mill these axis on our shopbot, or any CNC mill you like - the N17 size elements can likely be laser-cut with acrylic or similar (delrin would be nice, but is expensive and a bit toxic to cut, so goes the lore).
I do CAM in Fusion with a .step I export (after flat-packing) from Rhino.
Assembling Axis
I typically assemble machines one axis at a time. That's not saying much, but here's an image to get a sense of how the hardware goes together:
The 'adjustable' elements use a captured nut to pre-load bearings against gantries. TODO is better documentation of this, but here's an image of the flexure in simulation to get a sense for what I mean:
CAD for You
RCT Elements NEMA17 Size
CAD For these elements is available in the repo cad/elements/rctElementsN17
This set assumes you're building with 1/4" HDPE or similar, Nema 17 Motors with GT2 Pulleys of 6mm width, and have access to a set of M3 Socket Head Hardware and 'MR115' or '5116' trade names or similar, 5x11x4mm. Lots of those.
RCT Elements for NEMA23 Size
CAD For these elements is available in the repo cad/elements/rctElementsN23
This set assumes you're building with 3/8" HDPE or similar, Nema 23 Motors with GT2 Pulleys of 9mm width, and have access to a set of M5 Socket Head Hardware and 'skate bearings' - 608ZZ or similar, 8x22x7mm. Lots of those.
Hardware Notes
! to add here
- hardware stackups, BOM, tuning note
