There are many design changes from Genesis V1 to V2 that make this version a huge improvement:
- Design and implementation of custom brackets and plates for greater strength and a more optimized design. These could be produced at home with a drill and a printout, a CNC router, waterjetting, or laser cutter
- Endstop integration to let the microcontroller know when FarmBot is at the end of itself
- Changed from looped belts to belt and pinion style movement for both the X and Y directions, allowing for simpler installation, less belt usage, and keeping all electronic components moving together with the gantry (no motors attached to the tracks)
- Features synchronized belt movement along the tracks via a shaft and a single motor to drive both sides of the gantry
- Began Universal Tool Mount integration with a door locker solenoid rather than all tools attached to the bot at once
- Angled slots for wheel adjustments rather than expensive eccentric spacers
- Z-axis leadscrew is positioned closer to the gantry for less induced torque on the cross-slide and wheels
- Minimization of number of parts and simplification of them providing easier and faster assembly, accessible screw locations, and greater affordability
There were two major issues with V1 tracks:
- Buckling and shifting at the track joints
- Incompatibility with orienting gantry wheels on the top and bottom of the track
V2 tracks solve both of these issues by changing the orientation of the track pieces and the mounting bracket design. The brackets are larger and placed at the end of each track section so that one rigid bracket connects two extrusions. This keeps them from buckling or shifting, minimizes the number of brackets needed, allows for wheels to roll on the top and the bottom of the tracks, and allows for connection to a support post or another extrusion.
The Gantry has seen significant change in V2. The most notable is the switch from a looped belt drive system that ran the full length of each track to a belt and pinion style system. Feeding the belt through the extrusions in V1 was hard for 1.5m length tracks and nearly impossible for 3m length tracks. The belt and pinion system uses half of the belt length and greatly simplifies installations and tightening of the belt. It also eliminates the need for pulleys and mounting plates at the end of the tracks.
In addition, the belt and pinion system allows the drive motor to be positioned on the gantry, allowing it to move with the other electronics, thereby simplifying wiring as all electronics move together. Also, a single drive motor in combination with a driveshaft allows for synchronized movement between both sides of the gantry along each track.
The other major improvement is the use of custom brackets which greatly simplifies the construction while making the Gantry more rigid. In V2, 1 base bracket and 4 wheels at the track/gantry interface replaces the 1 extrusion, 3 brackets, and 8 wheels for this same interface in V1. The base plates also provide locations for the endstops to be mounted.
The Genesis V2 cross-slide saw a lot of improvement and change from V1. This version is constructed from three custom 3mm plates that have only the necessary holes to accommodate the needed hardware. The cross-slide moves along the gantry with a belt and pinion style drive system which saves on belt length, and is easier to install and tighten the belt. Endstops for the cross-slide and the z-axis are mounted onto the plates and are actuated by small plates that can be easily repositioned along the gantry for a different ending position. The leadscrew block for the z-axis is also mounted to one of the plates, which is hugely important because that block did not even exist in V1 hardware. The expensive eccentric spacers are replaced with angled slots for wheel adjustment and tightening. And the number of wheels for each axis of movement is reduced from four in V1 to three. Lastly, the Tee shaped plates are identical, making installation and manufacturing easier.
The Z-axis of Genesis V2 is not any different from V1 other than the fact that we actually assembled the leadscrew into a real prototype rather than just designing it in the computer. The leadscrew is an 8mm diameter ACME screw thread that connects to the cross-slide via a delrin block. The system is smooth and reliable and all components are available from OpenBuilds.
Not shown in the renderings on this page but in the photo to the left is the delrin block being originally located far from the main gantry beam, attached onto the Tee shaped plate. This configuration created a large moment force on the cross-slide, attempting to torque it off of the main gantry beam. This torque can be seen in the photo to the left as the Z-axis becoming significantly angled. This configuration was modified so that the block is on the plate closer to the main gantry beam in order to reduce the induced moment force acting on the cross-slide by reducing the length of the moment arm the weight of the leadscrew was acting on.
Universal Tool Mount System
The Universal Tool Mount system was introduced in V2 hardware as a way to allow FarmBot to switch tools in an automated way so that it does not have to carry all of the tools at once. In addition, whichever tool is being used, generally has to be the "lowest" in Z-height so that it can reach the soil or plant. With all tools being mounted to the Z-Axis at the same time as in V1 hardware, all tools were competing to be the lowest. The Universal Tool Mount solves this issue.
The Universal Tool Mount system consists of five components:
- A 3D printed tool mount
- A 3D printed (or modified PVC pipe) tool "blank" that can be filled with electronics, motors, or anything else that defines the tool
- A solenoid operated "door locker" that locks a tool into place when inserted into the tool mount
- Four sets of spring loaded 5mm screws that allow power and data to be passed between the tool mount and the tool
- A "tool bay" that is a 3mm plate for unused tools to be stored on
Using the FarmBot Web App, the user will define which tools are in which bays. FarmBot can then move to that position to pick up a tool, and load the necessary software "driver" to be properly use that tool. This system allows others to create new tools and drivers for any type of operation they can dream up, as long as it fits into the Tool Mount and incorporates the same four power and data screw configuration.
Issues with V2 and Proposed SolutionsCable Management
Issue: There is no way to manage cables and water tubing.
Proposed Solution: Integrate cable carriers or another solution.Universal Tool Mount
Issue: A few of the features are not optimized for 3D printing
Proposed Solution: Avoid cliff hangers with tapers and chamfers
Issue: Very little clearance between the screws that pass power and data
Proposed Solution: Decrease screw size from 5mm to 3mm screws
Issue: Tight fit of solenoid dead bolt in the tool mount hole, creating unnecessary tolerance requirements and friction
Proposed Solution: Increase size of hole in the tool mount
Issue: Tools are not inline with the leadscrew, creating a greater moment force on the Z-axis and Cross-Slide
Proposed Solution: Flip the orientation of the Universal Tool Mount so that the solenoid locker and tool are switched
Issue: Tool mount and tool are very tall
Proposed Solution: Optimize the tool and mount to be shorterTrack Belts
Issue: The track belts have an interference with the screws and tee nuts of the gantry corner brackets
Proposed Solution: Reconfigure the gantry to accomodateEndstops
Issue: The small plates/brackets used to actuate the endstops are not necessary
Proposed Solution: Replace these components with just a screw and a tee nut to reduce number of custom components. Reconfigure the endstops if neededCross-Slide
Issue: The tee shaped brackets are not necessary and add complexity to the assembly of the cross slide
Proposed Solution: Remove them and mount the endstops on the main cross-slide plateNumber of Screws
Issue: There is an unnecessary number of screws holding the tracks together and the gantry together. This is more costly and increases assembly time significantly
Proposed Solution: Reduce the number of screws
3D CAD Files
FarmBot Genesis V2 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.