Rotary Delta

Version Support: This arm solution is supported in both Smoothieware v1 ✅ and v2 ✅ Limited Support: This is an experimental arm solution with limited documentation and testing. It is currently unsupported as no active developers have a rotary delta to test on. Use at your own risk.

Rotary delta is a new and relatively uncommon arm solution for robotic systems.

Unlike traditional linear delta robots, rotary deltas use rotating joints instead of sliding carriages.

What is a Rotary Delta?

A rotary delta robot uses three rotating arms with joints instead of the linear slides used in traditional delta robots.

This design offers some potential advantages:

  • More compact: No need for tall vertical rails
  • Different workspace: Can reach different areas compared to linear deltas
  • Interesting kinematics: Unique motion characteristics

However, rotary deltas come with significant challenges:

  • Complex calibration: Extremely difficult to calibrate accurately
  • Homing difficulties: Finding the home position is challenging
  • Limited tooling: Few resources and tools available
  • Unproven in practice: Very few working examples exist

Current Implementation Status

The rotary delta implementation in Smoothieware is experimental and incomplete. It probably does not fully work and will need coding work to fit your specific needs.

If you really want to use it, we do not have comprehensive documentation at the moment.

However, the source code may be helpful if you can read C++ code:

Configuration

To use the rotary delta arm solution, you would set in your config file:

arm_solution                             rotary_delta

[motion control]
arm_solution = rotary_delta

However, be aware that additional configuration parameters will be needed, and these are not well documented.

You will likely need to examine the source code to understand what parameters are required.

Challenges You Will Face

If you attempt to build and use a rotary delta with Smoothieboard, be prepared for:

  1. Mechanical complexity: Building the robot itself is challenging
  2. Calibration nightmare: Getting accurate calibration is extremely difficult
  3. Homing problems: Establishing a reliable home position is tough
  4. Code debugging: You will likely need to modify the source code
  5. Limited community support: Very few people have experience with this

Comparison with Other Arm Solutions

Feature Rotary Delta Linear Delta Cartesian
Setup complexity Very high High Low
Calibration difficulty Extremely hard Hard Easy
Build volume shape Hemispherical Cylindrical Rectangular
Speed potential High Very high Medium
Moving mass Very low Low High
Mechanical precision Extreme High Medium
Homing difficulty Very hard Medium Easy
Community support Minimal Good Excellent
Status Experimental Proven Standard

Alternative Arm Solutions

If you’re looking for a delta-style robot, consider these better-supported options:

Linear deltas are well-documented, well-tested, and have excellent community support.

Source Code

For developers interested in the implementation or considering modifications:

The source code contains the kinematic equations and may be helpful if you’re implementing or debugging a rotary delta system.

Contributing

If you have a rotary delta robot and want to help improve the Smoothieware implementation:

  1. Join the developer community on IRC (#smoothiedev on Freenode)
  2. Document your findings and challenges
  3. Submit improvements to the code via GitHub pull requests
  4. Help create better documentation based on your experience

Your contributions would be valuable for this experimental feature!

This is a wiki! If you'd like to improve this page, you can edit it on GitHub.