156B Week 3

Progress Since Week 2

Hardware

• McMaster Carr extrusions came in

• Reused FarmBot cable brackets to attach uprights to horizontal supports

  • Heights of supports are not permanent - can adjust vertically as needed

• Attached pulley system with swivel hook atop the uprights

• 3D printed sample spool and drilled holes into it for motor hub mount

CAD

• Made CAD model of our system

• For future CAD work - full assembly in CAD

Hardware - Goals for next week

• Connect motors

• Set up cable system

• 3D print more spools

  • Buy common spools

  • Keep in mind limiting diameter

Materials to Buy

• Braided polyester cables

• Spools

• Additional Swivel hooks to attach cables to UTM

• Swivel Pulleys

• Soldering Wire

Materials to Purchase through Sponsor/FarmBot

• Four more motors (for under-swung cable system)

• Five more motor covers

• 1 more set (left and right) of corner brackets

• 4 more z axis brackets

• More 40 and 60 Nutbars

• More 5-10 screws

• More M3-16 motor screws

Current Concerns (decreasing priority)

1. Can we accurately position the UTM with the cable driven system?

2. How well can we integrate our positioning logic with that of FarmBot’s system?

3. Will the mass of the UTM be sufficient enough to keep tension when spooling/unspooling? If not, can we attach our cable in a way that ensures the cable does not unravel or lose tension.

4. How can we incorporate extension springs or other mechanisms to counteract any swaying of the UTM?

Feedback from Meeting with Instructor

• Look into Marshall’s Industrial Hardware for any supplies

• Research ductility of aluminum sheets for modifiable components

  • Only oxidizes on the surface

  • Corrosion resistant

  • Softer and more ductile

• If we need to cut into hard metal, use slow RPM and cutting fluid

• User Manual

  • Must go through many iterations in order to achieve desirable level of understanding

  • Use all pictures - like lego and IKEA

    • Label all the figures and parts

    • Be specific with the titles and labeling of components

Feedback from Meeting with Sponsor

• If completion of the code does not seem feasible within the constraints of the course, look into already existing codes

  • Art project - cable driven system probably has that level of accuracy

    • Reach out to them to ask about their methodology and implementation

• Sourcing parts in San Diego

  • If there’s something available in Orange County, Nick can get it and ship it to us

• If there is a point at which we can benefit a lot from getting extra FarmBot pieces but don’t know if we’ll use them in final design

  • Feel free to buy them even if we don’t end up using them in the long run

Upcoming Goals

Weeks 4-5

• Fix swivel hook to pulley attachment

• Mount all motors, spools and pulleys

• Test positioning accuracy with only 3 stepper motors and current code

  • Use tape to create a grid that helps to visually assess positioning accuracy

• Work to convert FarmBot code from interpreting Cartesian coordinates to barycentric coordinates

Weeks 6-8

• Motorize the fourth motor/cable and adapt code to incorporate all four motors in positioning

• Assemble UTM and cables to plate

• Motorize end effectors for functionality

• Electronic Cable management

Budget Remaining: $2298.80