Open source robot arm to extrude organics

Research resident Andreea Bunica is using her time at Green Lab to develop an open source hobby robot arm to extrude organics.

Having conducted her first months research and protoyping she has successfully produced her first iteration of a robot arm using an existing open-source arm (Dobot desk arm) redesigning the frame and firmware code to do the following:

  • Incorporate a syringe organics extruder
  • Provide stability and accuracy through low cost fabricated PLA parts and lasercut pieces
  • Incorporate an Android app-controlled robot functionality

By Andreea Bunica, Research resident


Additive designing
Fig. 001 concept render version 01

To start the build process Andreea modeled an accurate version of the Dobot desktop robot arm and created template lasercut files.

The original Dobot arm is fabricated out of cut steel sheets, for mobility freedom- aiming to create a low cost, but effective version, the parts for the first design of the organics printing robot arm have been fabricated through a combination of lasercutting and 3D printing. One of the main aims throughout the ongoing design process is to fabricate the majority of the robot arm components (including couplings, bearings etc.) through 3D printing.

Here is an example of what the first tape-bound casing version looks like:

Tape bound first version
Fig. 002 first tape-bound casing version

Still in it’s draft form the robot arm is currently composed of lasercut plywood parts for the main and minor arm, and 3D printed components for the base case, as well as 3D printed stepper couplings and base fixing elements to ensure smoothness of rotation.

Working through a trial and error fabrication ethos each iteration and prototype enables testing and informs constant re-design in order to work towards creating a refined, cohesive and functional end design.


first draft of the base casing
Fig 003. First draft of the base casing

The construction of the base is divided into three main sections:
1. Fixed base
2. Rotating base
3. Base casing

Base construction
Fig 004. Base construction

You can find the .obj files for each part here

1. Fixed base
For the first draft design, the base is the weight point to give the arm stability and to create a solid motion pivot point for the rotating element.

Files/ Components:

  • Base cylinder (screw-in base for fixing the rotating element)
  • Cylinder neck (glue-on the base cylinder to provide enough height between the fixed and moving elements in order to avoid friction)

Fixed Base
Fig 005. Fixed base

2. Rotating Base

The rotating bases attaches to the fixed base through a screw-in fixture attached to the stepper motor coupling. For the first draft, the case fixing legs are glued-on.


  • Screw-in stepper fixing
  • Gasket ring
  • Base plate
  • Coupling
  • Casing fixing leg
  • Stepper plate
  • Stepper motor 1

Rotating base
Fig 006. Rotating base
Rotating base
Fig 007. Rotating base
Rotating base
Fig 008. Rotating base
Rotating base
Fig 009. Rotating base
Rotating base
Fig 010. Rotating base

3. Base Casing

The draft casing (supporting the stepper motors) slots-in to the base plate and is secured with fixing legs.

Files/ Components

  • Base Casing
  • Casing Fixing Legs

Base casing
Fig 011. Base casing

ASSEMBLY (so far)

Assembly so far
Fig 012. Assembly so far

To follow Andreea’s project as it develops you can head to her website

Syringe Hack for 3D Printer

This is my successful attempt (the first attempt failed) at hacking an Ultimaker Original to accommodate a syringe. It’s home is Green Lab, where it happily prints mush for growing mushrooms.

I followed Thingiverse instructions from: Ultimaker Syringe Extrusion System at

Step 1 – I printed everything below:

  1. Bowden Feeder Repair Kit:

  1. Generic Head Mount:

  1. Syringe Attachments:

I printed them all at 80% infill. Make sure your printer is set up accurately, because the files have a tight tolerance and no time for your errors. I was impatient and drilled away my many errors.

Step 2 – clean up the prints for the syringe and head mount:

I started by putting together the syringe and printing the head mount. In the online photo for the head mount, it is both white and red. For some time I thought this was 2 files, it is not.

The head mount part is completed by 2 cable ties which then attach the part to the printer head. I left this to one side until I had made everything else. Here are my printed files for the head mount and various other syringe parts, you can see the head mount in white next to the 2 white syringe rings (upper and lower):


I generally cleaned up the files and checked everything fit, I filed away many hours.

The holes on the syringe rings are bigger on one side. The bigger holes should fit your bowden tube. If not (mine didn’t) drill the holes on the prints wider so it does. The holes on the opposite side are smaller to fit the dyneema thread and they don’t need drilling wider. Top Tip: Don’t stab your hand while doing this.


Step 3 – put together the syringe attachments:

The ring with the rectangle in is the upper ring and this goes on top of the plunger. The rectangular hole should fit nicely over the pull ring (the bigger holes should be facing up). Twist it 90 degrees to secure in place. The syringe has a lip, and the lower ring needs to be pushed all the way up to that, position it so that the lip doesn’t cover over the holes on the print. This one needs the smaller holes facing up.

The red part you can see is a part to cuddle the syringe. 2 cable ties are needed to attach this to the syringe. I can tell you from personal experience these must be longer than 142mm (200mm long ones worked great).


Step 4 – put together the winder attachments:

The final 3 printed pieces needed are: the winder coupling – shown printing in white, the winder spool I printed in red earlier (you can see it in the photo below with the ball bearing attached), and the feeder repair kit.


You can see that I have put the bearing onto the spool already, I did that excitedly and then couldn’t take it off again to take a separate photo. I decided to ignore screwing it together and instead skip ahead to check whether it would fit in the winder coupling part. It didn’t. I hammered it in. It snapped. You can’t tell if I take the photo at the right angle.


Sub-step 4.1 – re-print and do better:

Having finally admitting to myself it needed doing again, this time I didn’t ignore the rectangle in the side of the spool. Turns out that is for a nut so you can screw in a bolt in the middle of the bearing. I had to file it out a fair bit. You can see the incredibly long (20mm) screw that I decided to fit in it. It was too long, duh. While trying to screw it in all the way, I ended up stabbing myself with the screwdriver. Points if you notice the bloody bandage in the rest of the photos. A 15mm M3 screw is just sensible.


I tied fishing wire to the spool, up through the nozzle on the coupling, and through the bowden tube. At this point I worked out that you shouldn’t try to make it cheaper by using fishing wire instead of dyneema thread. The fishing wire put tension on the plastic parts and the white thing cracked again.

I bought dyneema thread and 3D printed it again, this time in red to match my anger.


Step 5 – thread the thread (not wire) and join syringe to the winder:

I used about 1m of dyneema thread. Again, I started with the winder, looping it through the holes and tying it in a tight knot. Then through the hole on the coupling and the bowden tube. The next photo shows the other end of the tube feeding into one side of the upper ring on the syringe plunger. From here, just the string keeps going and threads through the same side on the lower ring and out the bottom hole. You’ll need another small piece of bowden tube here, one that just loops from one side of the lower ring to the other comfortably. You then go back up through the lower ring on the other side of the syringe and out the top as shown. You’ll need to tie it very tightly here otherwise it will escape your clutches.


Step 6 – attach parts to printer:

The feeder repair part clamps on top of the feeder. I didn’t screw it in place, fingers crossed that doesn’t fly off. Then the winder coupling sits on top, with the spool fitting very nicely onto the original bolt as shown. Then you can attach the syringe to the head mount, and finally cable tie that piece to the printer head. Have a drink, your stabbed hand deserves it. I had Kombucha which was home brewed in the lab!


Step 7 – Edit GCode

I set up a simple shape and put it through Cura. As it started up and tried going ‘home’ before beginning the print, the printer smashed into the side immediately and repeatedly all while making the most awful noise.

I apologised to the printer and opened the GCode in a text editor – this is the first time I’ve ever edited any GCode. I deleted the line(s) that looked to be most like the ‘home’ starting point with the intention that it would start from wherever I set it manually to instead i.e. wherever I moved the head to with my hand. I deleted these two lines, relatively near the start of the code, about 10 lines down or so:

G28 X0 Y0 ;move X/Y to min endstops

G28 Z0 ;move Z to min endstops

And, magically, that worked. It started from where I positioned it instead of returning to home and smashing into the sides. I set it to work with some wall paper paste I mixed up and it lasted a surprisingly long amount of time compared to what I expected. Or perhaps I’m a pessimist.

Next steps – work out how to set up a new base plate for the new and improved “Mush Printer” and identify a better way of cleaning the darned thing of said mush.

Digital Fabrication Machines

Trotec Speedy 100 – 60W Laser
  • Pricing and design guidelines
  • Notes for maintenance

    CONVEX UP in laser when installing
    Cleaning daily or when used
    Top mirror needs weekly cleaning
    Focus tool – use manual only
    Set up admin access to materials settings and the machine
    CO2 extinguisher in the room


    Order materials from

Roland CAMM Vinyl Cutter

Ultimaker 3D Printer

Ultimaker 3D Food Printer

Roland Modela desktop CNC

Piranha CNC

Growing & Lighting

We have a range of growing equipment for use at the lab. You can hire out grow trays, movable racking and lighting for periods of time to minimise your costs to get growing. We also have a lighting engineer that can help to build custom lighting for specific projects such as our greenhouse.

T5 Strip lights (x10)


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1m Grow trays (x10)

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3 Moveable racks (stainless steel)

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Palmar Greenhouse

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Assorted IBC's



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Aquapioneers aquaponic kit

Aquapioneers aquaponic kit