Fabricatable axes
These fabricatable axes are built up from individual modules and come together to form a complete machines. We are in the middle of the development of a new generation of axes. We have identified four main axis types for different machine needs and fabrication equipment:
- Rigid axis – for fast fabrication of rigid machines like CNC mills
- Flex axis – for fast fabrication of non contact machines light duty machines like 3D printers, pen plotters and laser cutters
- Bootstrap axis – for making large machines without access to a large format CNC mill
- Proper axis – for making machines suitable for industrial use
Status: In use on Metal Humphrey, Wood Humphrey and Hurtig, pending design revision and parametric generator
CNC milled parts with self locating features form the axis and axis plate. 3D printed concentric bushings on bearing screws enables tuning. Direct drive rack and pinion with naughty [CNC friendly rack and pinion]. The rack is modular and CNC milled from high performance plastics like Polycarbonate or POM. The pinion is CNC milled from 12.7mm POM/Delrin or similar.
Pros
- Fast to fabrictae
- Can be made with a wide variety of sheet materials: Plywood, MDF, POM, HPL, Aluminium etc.
- Modular rack, can be replaced/upgraded
- High degreee of DIY
- Medium to high positional accuracy
- Medium ridity
- No exotic hardware
Cons
- Requires large format CNC milling machine
- More vulnerable to dust build-up than v-wheels and linear rails
- Many tuning points
- Tuning requires patience
The roller axis is a linear guide system that uses 12 ball bearings mounted on eccentrically adjustable spacers. This design is made from aluminium plate.
For a self adjusting roller axis made from plastic see Rake Reeds work here
The test results were very promising.
7 Videos of tests (on youtube)
The next step is to make a dust protection system. For this I am developing standardized 3D-printed parts. 14 of 36 of the rollers will have the same dust cover and the same viper holder will be used 4 times per axis. The remaining dust covers are work-in-progress.
Video of a test of the viper block (youtube)
More info and a full working set of vipers and dust covers for Humprey v2
The roller axis and dust cover system has successfully been installed on Humphrey v2!
Just the vipers and dust covers
Status: Early test prints, not yet tested on a machine
A linear and rotary axis that needs no tuning. Even the bearings are 3D printed, resulting in a very accessible BOM. The herring bone type gear helps stabilize against sideways loads. The pressure from the flexures compensates for the backlash in the 3D printed bearings.
Pros
- No tuning needed
- Can be made with only a 3D printer
- Only M3 screws and stepper motor needed
- High positional accuracy
- Suitable gateway drug to machine building
Cons
- Low rigidity. Will wobble under load, acceleration and deceleration
- Flex pressure might need to be tuned in with the Freead parametric generator files
- Stl files for direct 3D printing
- Parametric freecad files for generating custom axis lengths and rotation ratios
Dependencies for parametric generator: Freecad open source CAD program with Fastener and Gear workbenches installed (the workbenches can be installed from the "Add-on manager" inside of Freecad). Once you have a file open in freecad, double click on the "Spreadsheet" object to edit inputs (axis width, height, tolerance etc.). It can be nice to dock the 3D window and the spreadsheet window side by side.
- Test the herring flex axis on a complete machine
- Refine/redo parametric generators
- Develop solution for making longer axes with 3D printed modular rack pieces and lasercut/milled flat parts
- Test herring rack on V-slot / C-Beam extrusion (potential hybrid between flex axis and ready made alu extrusion from Openbuilds / Oooznest, see images bellow)
Printing many modular rack pieces will take time, but require little manual labor. Damaged rack pieces can be replaced easily
Note how the V-shaped profiles on the 3D printed rack part parts helps align position the rack pieces at the right height and in a parallel line
The rack pieces could screw into nut pieces with M3 screws
- Herringbone involute gear and rack with the FCGear Freecad workbench by looooo
- Threads for fastener with the Fasteners Freecad workbench by shaise and ulrich1a
- Dual arm flexures from from the the great work of Jake Read at CBA
Status: One axis made, not yet tested
Pros
- Axis and axis plate can be made with traditional woodworking equipment or be ready made hardware like a shelf
Cons
- Requires skillful positioning of bearing holders and rack
- Requires a manual wood working skills
- Bearing holders takes a long time to print
Status: Concept phase, early ideas
Store bought linear rails in combination with gearbox driven rack and pinion. Mounted to a sturdy beam like a rectangular section steel tube or aluminum extrusion. The steel tube can be potentially leveled with slow curing epoxy.
Potential pros
- High rigidity
- High positional accuracy
- Low maintenance
Potential cons
- Higher cost
- Less DIY
- Requires manual metal working and epoxy casting skills.
2020 Linear rail
2017 Chamfer rail Chamfer rail rotating axis
2016
V-bird
2015 Column