Pipetting bot - GOSH ColDev Round 1 - Updates

Dear community,

From now on we’ll be using this thread to post project updates.

As kindly reminded by @biomakers_lab in their post, this is part of our responsibilities towards the GOSH 2022 Collaborative Development Program.

Link to the project presentation: Pipetting bot - GOSH ColDev Round 1 - Presentation

Activities summary

So far so good :slight_smile:.

Photo album! :framed_picture:

I’ll be posting pictures to a photo album in case you’d like to check out the latest photographic updates.

Parts purchased and printed :3

Future updates

Future updates will be shared as a reply on this same thread, hopefully on the following subjects:

  1. Decision on collaboration.
  2. Build videos and full documentation for the final prototype.

Plan deviations

  1. Budget change: a budget redistribution was requested on the collaboration items was approved, merging the budgets into one collaboration for the hardware tasks. The software tasks will be absorbed by yours truly.
  2. We are apparently behind schedule, since work on projects was to happen between the 1st of April and the 5th of July, according to the program’s timetable. The estimated delay is around 1 or 2 months, and is mainly due to administration tasks and shopping taking longer than expected.
  3. There are no Raspberry Pi 4 boards available in the local market, due to global supply problems. I am using a spare board for now, but if this continues we may be forced to rethink at least a part of the electronics/control system.
  4. The future of GitBuilding is uncertain. Even so, we remain committed to use it to document our entire project, and I want to thank him enormously for his guidance, and for the incredible work he has done. Thank you @julianstirling :slight_smile: .


Progress would have been impossible without the help of the GOSH community (mostly behind the scenes), and many friends helping out at each step; from suggesting collaborators to finding the right fiscal sponsor!

Stay tuned for the next update (?) :stuck_out_tongue:


Project updates! 2022-07-15

Prototype build

  • XYZ axis parts are printed and in assembly :3
  • We’ll ditch the tip ejector servo, in favor of a fixed “tip ejection post”, with a tip discard tray underneath.
  • We are considering a custom tool-changer, instead of Jubilee’s (read on…).

Original prototype (left) and new version in progress (right).


Renan, Solomon, and Pipe have agreed to collaborate with the project, and a meeting should happen soon.

  • Felipe (Pipe) is in charge of general design, usability, and enclosures.
  • @Renan has started modelling toolchanger alternatives.
  • @Solioboni will also work on modelling (details TBD).

Next meeting is scheduled for next week, probably on Thursday.

I also wrote to @Glyxon to arrange a meeting. Him, @adrianMolecule and I discussed our projects and experiences, and will setup a group in JOGL to set collaboration goals for the short or mid-term :slight_smile:


Renan has started working on a toolchanger design, using highly available low-cost parts.

Our Z-axis does not lend itself to accommodating the Jubilee toolchanger, not naturally at least. So we may need to change the design drastically.

Though Jubilee toolchanger is really awesome, we are not sure if it will stand the vertical forces needed to place a tip, if it would handle larger tools correctly, and there is no simple way to fit the toolhead to our Z-axis.

We will make out final decision on this point next week with Pipe’s and Solomon’s input.

General design

Assembly models had to be updated to include most of the parts.

This allowed Pipe to start working on a nice enclosure, and tidying everything up (cables, electronics, power, etc.).

A first render of a enclosure idea is shown below:

Next objectives (in spanish) are:

  1. Limpiar el diseño de las partes para que sean lindas y revisar que no tengan problemas.
  2. Pensar e implementar un diseño de toolchanger con Renan y Solomon.
  3. Pensar en formas de mejorar la usabilidad y que sea seguro de usar.
  4. Organizar la electrónica y el toolchanger.
  5. Armar la carcasa.


Yours truly has been using the first prototype to test improvements in the driving software:

  • Speed has been doubled by:
    • Implementing more reliable GRBL-Pipette synchronization routines (relying on the G4 dwell command; rationale here).
    • Doubling acceleration on all axis.
  • Consider using Klipper as a firmware and low-level control software.
    • This would allow us to modularize controller hardware, instead of enforcing our custom software solution tied to the Arduino CNC shield.


Many-a-videos have been recorded, the assembly documentation will be written from them.

Some changes were made to the models, and have been reflected in the original documentation (the repo’s READMEs).

Duties and Schedule

Slow we are indeed! Fortunately the GOSH board has granted an extension, and we’ll continue working for about a month (at most, ideally). Our substantial and financial final reports are due in September.

Next update

Probably on August 15th. Hopefully we’ll have a working robot by then.


Project updates! 2022-08-06

Changes in the team

For personal reasons, @Renan will step aside from the first phase of the project. We wish him the best of luck focusing on his studies during the semester. :mechanical_arm: :heart_decoration:

After some discussion with Felipe and @Solioboni, we decided to keep going. They are able to finish the project with the time that is left; around 4 weeks.

They will take over the design of the toolchanger, and the first fabricable models are due next friday, just in time for the project update planned for the 15th of August.

Preview of next update

Structural frame complete

Frame complete.

Development of a new baseplate development is next.

Toolchanger drafts are on!

New toolchanger models (drafts): models/modelos_XYZS/freecad_toolchanger · master · pipettin-bot / Pipettin Grbl · GitLab

Draft toolchanger models.

Printed draft parts for the cheapest toolchanger ever.

As described in the relevant gitlab page, the toolhead is attached reversibly to tools using small strong magnets. The toolhead will dock with the tool using a pair of linear rods, which will have a “fillet” on the ends to ease the docking process.


DIY fillet made with a Dremel grind disc and sanding paper.

The three relevant parts: parking post (left), tool (middle), and toolhead (right).

This is not as precise as the kinematic coupling of Jubilee’s toolchanger, but not incompatible either. We shall add it later on if required.

The tool will dock to the parking post using the same two rods, and bind to it reversibly with a hysteretic “push latch” mechanism (similar to the ones in ball pens), which makes this design a purely mechanical solution to toolchanging (no electronics, no sensors, no programming :3).


Example commercial “push latch” thingy, used for drawers and similar stuff.

That’s all folks!