Part 1 introduced the project, part 2 covered the mechanics and part 3 the electronics. Part 4 covers the software side and part 5 is about troubleshooting.

1. Troubleshooting

1. Pivot servo position varies/is not repeatable/slow
  • loosen the screws holding the servo and move it back slightly so the gears are still meshing but there is no sideways pressure on the servo shaft.
  • make sure the pivot servo is not near the limit of it’s range at any point. When near the limit it will attempt continuous rotation and will lose it’s position.
  • check the hub retainer is not touching the lower bearing.
  • move the gear housing away from the servo and make sure it rotates freely.
2. Disc snags on sides of in tray when being raised
  • rotate the in tray outwards slightly and update the in tray position in config.xml. This will move the center of the in tray slightly further from the center of the pivot.
  • make sure y axis is vertical (see item 6).
3. Disc snags on sides of out tray when being dropped
  • rotate the out tray outwards slightly and update the out tray position in config.xml. This will move the center of the out tray slightly further from the center of the pivot.
  • make sure y axis is vertical (see item 6).
4. Disc falls off grabber
  • make sure both sides of the grabber are vertical.
  • raise the toolhead microswitch so that more of the grabber is lowered into the hole in the center of the disc.
  • make sure that the y axis is exactly horizontal.
5. Two discs are picked up
  • make sure that the y axis is exactly horizontal.
  • check that the Y axis is vertical (see item 6).
  • make sure that both sides of the grabber are vertical.
6. Y axis is not vertical
  • make sure the hub retainer is close to, but not touching, the lower bearing.
  • loosen the nuts holding the gear housing to the threaded rod and re-tighten while pressing down on the rear of the gear housing.
  • check the y axis is securely attached to the threaded rod.
7. Disc falls off grabber when being picked up from drive tray
  • adjust the two M8 nuts on the threaded rod at the hub to shorten/lengthen the arm from the pivot to y axis. Make sure the grabber is exactly over the center of the disc.
  • tweak the drive tray position in config.xml

2. Ideas for Improvements

  • Increase DVD capacity for faster PCs.
  • Redesign main gear housing to use less plastic.
  • Sugru veneers for grippers.
  • Eliminate Raspberry Pi.
    – merge BotServer into JacktheRipperBot.exe
    – PC communicates directly with Pololu Maestro
  • PC farm for faster ripping
    – use Raspberry Pi to create image of discs which are then put into a queue. A farm of PCs work on encoding the queue.
  • Cable management on top of support ring to keep wires away from gears.
  • Stack two or three DVD drives vertically so the robot can load and unload into all of them.
  • Add support for ripping “profiles” to JacktheRipperBot.exe, allowing different Handbrake settings to be used for specific discs in the in tray.