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FarmBot Genesis V4

A project log for FarmBot - Open-Source CNC Farming

FarmBot is an open-source CNC farming machine and software package built for small scale, hyper local, DIY food production.

Rory AronsonRory Aronson 08/19/2014 at 01:120 Comments

Genesis V4 exhibits the following changes from Genesis V3

Tracks

V4 tracks feature simplified connecting plates that are about half the size of V3 plates and use half the number of screws for each connection. This simplifiction reduces the number of components and assembly time significantly. Additionally the plates are flat on the top and flush with the track extrusions, creating a cleaner aesthetic for tracks mounted to short posts as seen in the renderings. Also different from V3 is that the mounting holes for attaching to the post are 20mm apart rather than 40mm, allowing the plates to attach to 20x40mm extrusions.

Also new in V4 tracks is the use of a cable carrier/drag chain for cable management along the tracks. This is less visually and spatially impactful than the wire and trolley system introduced in V3 hardware. Though it will be more expensive, it is more suited to smaller FarmBots such as Geneses. A series of light duty bent metal brackets are in place along the tracks to support the cable carrier.

There is the possibility of moving the cable carrier to alongside the tracks as seen with the gantry's cable carrier. This would allow the elimination of the custom bent brackets in favor of using more affordable screws and teenuts for support. For this to work, the track connecting plates would need to be lower profile, allowing the top half of the track extrusions to accommodate screws and the cable carrier. This would not work in situations where the track supporting posts extended upwards as in the case of using fence posts or the studs of a greenhouse.

Lastly, the tool holder has been modified to accommodate the new tool design.

Gantry

There are five changes to the V4 gantry from V3:

  1. The main beam is now attached to the front of the corner brackets rather than behind them. This change was so simple and minor but it greatly improves the design. This allows the user to slide on and off the cross-slide without detaching the main beam from the corner brackets. This is hugely important from an ease of assembly and maintenance perspective. The change also allows the gantry width to be adjusted more easily because the extrusion can be longer than necessary and hang off the edges. Lastly, this change allows the cross-slide to more fully move within the farm-able area, rather than being stopped prematurely by the corner brackets. Looking forward, the new design allows for an extended gantry to be implemented that is two extrusions wide or more.
  2. The addition of a 3D printable housing for the gantry drive motor. It's fairly simple but should get the job done. There may be concerns with a 3D printed part being completely watertight, in which case a vaporized acetone process may be able to help, or an injection molded part may be used.
  3. A cable carrier/drag chain is used for cable management instead of the wire and trolley system of V3. This is more aesthetically pleasing and prevents hanging wires and tubes from interfering with the plants.
  4. The angled slots on the gantry/track plates have been reverted to plain holes and will use the eccentric spacers from OpenBuilds. The eccentric spacers were originally removed from the design because they were found to be so small that they would dig into the plates and wear them out. However, the OpenBuilds team has changed the design of them to be significantly larger, preventing this type of damage. They are still expensive at $2 per spacer, but they seem to provide a better experience for the user. Which design is better has yet to be determined but we figured we would try out the new spacers in this version.
  5. The power supply has been removed from the gantry and placed at the end of the tracks in order to conserve space and weight on the gantry column.

Cross-Slide

There are three changes to the V4 cross-slide from V3:

  1. The motor is slightly re-positioned to support the 3D printed housing
  2. The cross-slide plate is narrower to accomodate a 20x20mm Z-axis instead of the 20x40mm one in V3.
  3. Extra holes have been added for a 3D printable bracket to support the cable carrier.

Z-Axis

Issues and Proposed Solutions

Universal Tool Mount

The V4 Universal Tool Mount has been completely redesigned to be actuator-less, simpler, smaller, 3D printable, and more affordable to produce. The primary mechanism for holding the tool in the mount is a pair of strong ring magnets, one on the tool and one on the mount, each held in with 5mm screws. Both the tool and the mount are tapered to allow easy coupling an de-coupling of the components.

In addition to the magnet holding screws, there are three additional pairs of screws in the tool and the mount that make physical contact when the tool and mount are coupled. These three screws, along with the magnet holding screws allow for power and data to be passed from the mount to the tools, with the magnet holding screw being ground. The three screws have springs between the heads and the mount, enforcing them to make consistent electrical contact. In addition, the three screws act as keys to prevent the tool from rotating undesirably in the mount.

FarmBot will use the Z-axis's leadscrew to have enough mechanical advantage to pull the mount off the tool when the tool is in the tool bay.

Issues and Proposed Solutions

Electronics

The power supply has been moved from the gantry to the tracks to save space and weight on the gantry.

Manufacturing Files

All of the plates can be CNC routed, laser cut, or waterjet cut and the motor housings, Universal Tool Mount, and Tool "Blanks" can be 3D printed. .STL and .DXF files for manufacturing can be downloaded here.

3D CAD Files

FarmBot Genesis V4 was designed natively in SolidWorks 2014. Using SolidWorks 2014 or a newer version will provide the most seamless experience if you are interested in viewing or modifying the 3D part files. For those without access to SolidWorks, we have converted the files to other commonly used file formats.

Files can be downloaded here.

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