Overview:

This assembles brush heads for electronic toothbrushes. Each brush head is comprised of four pieces - body housing, brush, resonator and seal. None of the components were designed for automated assembly, requiring the use of custom feeding systems and machine vision for part acquisition.

Process Description:

The assembly process begins with installation of the body housing in an active nest on the rotary indexing dial. The body plastic is fed to the system from supply tubes using a horizontal tube feeder. The singulated housings are then located precisely using a fixed machine-vision sensor. Once located, the housing is picked and placed into the assembly nest by a SCARA robot. The active nest pneumatically clamps the body plastic after it is loaded.

Once the body is loaded, a seal is acquired from a flexible feeder.  The flexible feeder presents the seals on a flatbed conveyor for location using a fixed machine vision sensor.  The seals which are not located are dumped into a bin, and recirculated onto the conveyor bed over time.  The feeder provides a very open feeding process, which is not easily jammed, and is not impaired by parts sticking together (both behaviors being prominent with the elastomeric seals).

The acquired seal is then held before another fixed-mount machine vision sensor.  The sensor determines the orientation of a rectangular hole in the seal.  The seal is then placed onto a servo-controlled mandrel. As the mandrel shoves the seal into position in the throat of the housing, it rotates to correctly align the rectangular hole with the correct assembly datum.

After insertion of the seal, the resonator is inserted into the housing. The resonator is fed from a matrix tray, and loaded into the assembly press using a SCARA robot. The assembly press, a ball-screw servo device, inserts the resonator with 500 pounds of force in approximately 250 milliseconds.  

Finally, the brush piece is installed with a fourth SCARA robot.  The brush is fed from another horizontal tube feeder, and is picked and placed inot a smaller ball-screw servo press.  The brush is then press fit into place when the assembly indexes into position.