Pick Head

The pick and place head sits on the end effector of the robot, and is used to pick up components from feeders, trays and cut tape, orient them, and place them down on the board. The pick head may also contain several sensors used by the robot. Two approaches are being developed at this stage, a single and a 4 way head.

Concept 1 - single rotating nozzle head

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A single rotating head consists of a shaft onto which the nozzle is connected. This shaft is rotated by a motor in order to orient the part on the nozzle.
Vacuum or air supply is accomplished via two air tight bushings. Rotation of the nozzle is not restricted by a flexible hose.
The motor shall be directly coupled to the shaft, and a shaft encoder. .
There is currently no nozzle spring force implemented in the design. We will test load cell sensors in the mounting bracket of the head in order to sense component pick up and placement. We will also be able to adjust placement force from 100 gram to 500 gram.

Pro
simple
low mass

Con
placement speed

Actuators

#UseDescription
1rotate nozzle low inertia dc servo motor (eg maxon A-max)

Sensors

#UseDescription
1measure angle of nozzle US Digital EC35 10k cpr quadrature encoder

Concept 2 - 4 position rotary head


The current concept is to use a 4 position rotary head, with 4 individually rotatable nozzles. This allows the robot to pick up 4 components, then traverse to the board and place them, decreasing the average traversal time per component.

quadhead1.jpg

quadhead2.jpg

quadhead3.jpg

quadhead4.jpg

Pro
much faster placement of small components

Con
Complexity
Cost
More motors, encoders
Higher moving mass, so cost impacts in robot actuators

Actuators

#UseDescription
1rotate nozzle wheel Servo
2rotate nozzle Servo / dc motor
3second nozzle rotation Servo / dc motor, optional, used to pre-rotate nozzle before reaching camera for parts 90deg away from target orientation

Sensors

#UseDescription
1Camera facing nozzle for orientation sensing of picked parts


Further references

http://www.cnczone.com/forums/rc_robotics_autonomous_robots/141835-open_source_p_p_revolver.html Original post on CNCZone discussing multiple nozzle heads

http://www.cnczone.com/forums/rc_robotics_autonomous_robots/145909-wikiplacer_project.html Discussion of newer 4 post head