Pneumatic System / Vacuum
The following vaccum system was realized. To avoid influencing the vacuum level while picking and placing in the two nozzles, they were separated and two pumps used. To switch the vacuum, directly actuated valves are used.
Protective Circuit for VAC pump
Next to the mandatory diode, caps were wired to the vacuum pump from Robotdigg.
Tests of different rotary joints
- Vacuum pump: 24V Vacuum Pump from Robotdigg
- Vacuum pump EMC: 1x100nF from + to Case, 1x100nF from - to Case, 1x100nF from + to - (had issues before, recommended
- Vacuum reservoir: 1l Laken Alu Bottle with 3d printed screwed cap
- Nozzle: Juki 506
- Nozzle Adapter: Tool changer from Peter Betz
- Vacuum Sensor: NXP MPXV6115VC6U
- Stepper Motor: Nema 8 hollow shaft nipple end
- Motor Driver: A4988 on CNCshield with GRBL
- Motor Current: 0.65A (already slightly overpowered, motors getting really hot)
| Images / Files | Description | vac. nozzle open [kPa] | vac. nozzle closed [kPa] | vacuum sufficient? | loosing steps? | Evaluation |
|---|---|---|---|---|---|---|
| reference: vaccum tube only. value for “nozzle open” is tube just open ended, value for “nozzle closed” is with a finger on the end | -3.2 | -49 | - reference only - | |||
| reference: vacuum tube directly mounted to nipple end of nema8 hollow shaft stepper motor | -10.9 | -36 | - reference only - | |||
  
| 3d printed adapter with o-ring ID: 7,8mm pressed against motors rear end (left side in photo) | -7.3 | -13.5 | no | no | vacuum so low that parts got lost sometimes |
| n/a | 3d printed hose with r-ring ID 4,5mm on nipple end of motor | n/a | n/a | ? | ? | not tested, because DIY store had no sealings with ID4.5mm available |
 | rotary joint from robotdigg connected via flexible tubing to hollow shaft (right side in photo) | -12 | -35 | yes | sometimes, especially after long still standing machine | torque load of these adapters applied to the nema motor seem to be very near at their limit |
 | rotary joint from local supplier, manufacturer Sang A | -12 | -35 | yes | yes | too expensive compared to robotdigg adapters and not less torque as was expected |
 | 3d printed rotary joint with 2 rubber sealed bearings | -10 | -20 to -27 (actual value depends on how tight the printed adapters fit the bearing) | yes(?) | no | vacuum OK, quite leaky, nearly no additional torque |
  | 3d printed adapter with o-ring 5mmx2mm pressed slightly against motor rear shaft, same principle as with original OpenPnP part but adapted to my machine | -9.5 | -25 to -30 | yes | no | realized that, little grease reduces friction significantly |