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2025

A gripper tool for OLA & Jubilee - Part 2

This is a follow-up post to A gripper tool for OLA & Jubilee - Part 1.

Background and requirements are listed there.

homing

Tracker: https://gitlab.com/groups/open-la/-/epics/20

Homing Implementation

The wripper sits on a freely-rotating wrist, which makes wiring sensors on the tool-side complicated.

To get around this, the homing sequence proceeds in two ordered steps:

  1. Home the wrist axis.
  2. Align the gripping axis to the second endstop.
  3. Home the gripper.

gripper-cad.png

The most reasonable endstop options, given what i had around, were either optical or magnetic. I went with magnets because they are far more forgiving than opto-endstops in terms of alignment.

I used electromechanical Reed switches, soldered to Makerbot-style endstop boards, each one fixed to the "stator" part of the gripper.

Control

This time I just stuck the control board onto the tool, and routed only 24V and USB to it.

I really didn't want to do any more cable management. Reducing the cable count to just 3 is a real achievement.

Behind this is a firmware capable of syncronizing motion between multiple control boards. At the time of writing, I used my klipper for CNC fork.

With it I get all of the klipper goodies, and two important bits:

  • Kinematics for an additional axis set; A for gripping and B for turning in this case.
  • Homing through generalized probing (i.e. G38 commands) and basic macros.

Klipper is slowly working towards its own multi-axis features, so hopefully I won't have to maintain the fork for too long.

If you know about other firmware projects that might replace Klipper, please let me know. There is now Prunt, but it's not what I am looking for.

Proof of concept

Here is a video of it homing clumsily on a pair of stepper motors: https://www.youtube.com/watch?v=3veRTsW12Zw

Up next

Get involved. Introduce yourself and browse to the OLA tools forum.

Get in touch, join the chat! https://discord.gg/GmCeXTHpM4

A roadmap:

  • Replacing the servos with NEMA8 motors.
  • Print a Jubilee-style tool mount.
  • Add endstops, probably optical, probably coupled to each other (or with just one).
  • Review or redesign the mechanics to fox the jankiness in the motion.
  • Figure out kinematics for rotation & gripping.
  • Have a little fin with it.
  • Integrate to the OLA lab automation stack as a new tool: https://gitlab.com/open-la

There will be a "Part 3", no ETAs though. :)

A gripper tool for OLA & Jubilee - Part 1

After a couple years, this project has finally received my attention.

alt text

Tracker: https://gitlab.com/groups/open-la/-/epics/20

Background

I want a gripper tool for this lab robot: https://docs.openlabautomata.xyz/

Notable previous works include:

Some requirements

  1. Gripping action: for tiny (e.g. seeds) and medium-sized stuff (well-plates and petri dishes). Nothing too heavy.
  2. Wrist action: with unbound spinning angle.
  3. Affordable, ubiquitous components.
  4. Mostly 3D-printed parts.
  5. Upgradable.
  6. Open-source hardware.
  7. Synchronizable motion.

Nice to haves:

  • Eccentric grip.

Implementation

  • Hollow-shaft concept: a pair of concentric shafts transmit force to different parts of the actuator.
    • The broader shaft (8 mm) rotates the wrist.
    • The narrow shaft (5 mm) passes through it, and actuates the gripper claws.
    • Because of this arrangement, the wrist is coupled to the grip action. Both motors will need to turn in sync for the claws to rotate and hold a certain grip.

alt text alt text alt text alt text

Proof of concept

Here is a video of it running clumsily on a pair of servos: https://www.youtube.com/watch?v=_W5kAROLW5M

Up next

Get involved. Introduce yourself and browse to the OLA tools forum.

Get in touch, join the chat! https://discord.gg/GmCeXTHpM4

A roadmap:

  • Replacing the servos with NEMA8 motors.
  • Print a Jubilee-style tool mount.
  • Add endstops, probably optical, probably coupled to each other (or with just one).
  • Figure out kinematics for rotation & gripping.
  • Have a little fin with it.
  • Integrate to the OLA lab automation stack as a new tool: https://gitlab.com/open-la

Check out "Part 2" of this project.

  • in Blog
  • 4 min read

Traveling Prusa

So I decided to bring my Prusa MK3S+ with me to Bariloche by plane.

Preparations

Naturally it required partial disassembly to fit in the case. So I took it apart:

  1. Carefully cut the zip ties that secure the cables coming from the PSU, Z-axis motors, and LCD panel.
  2. Disconnect the heated bed cables, and remove the entire Y-axis (rods and all).
  3. Disconnect the LCD cables from the mainboard, and unscrew the entire LCD panel.
  4. Detach the entire X axis (extruder included):
  5. Remove the top-side stops of the Z axis
  6. Carefully moving it upwards by turning both leadscrews until the nuts disengage.
  7. Unmount the Z-axis motors, including their 3D-printed holders.
  8. Unscrew the "long" aluminium extrusions from the middle (i.e. not the screws on the front).
  9. Don't lose any part, nut or screw. Some of the tiny square nuts will fall out without you knowing.
  10. Carefully move the parts to your suitcase, tucking them in with abundant clothing (or bubble wrap and such things).

Here is the end result:

alt text

Putting it Back Together

Some notes:

  • Try not to swap the Y-axis rods with the Z-rods. You'll feel crazy thinking that the Z-axis rods "grew" on the plane.
  • There is not much else to this really. Use the official Prusa assembly guides when in doubt.

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