Overview:

The Leak Test Cell uses four pressure-decay leak testers to verify the seal on an electronic toothbrush handle.  The test is performed without a chamber, using a hypodermic needle to pierce a thin elastomeric section of the housing.

Process Description:

To make rate, up to four pallets are processed at once. The four pallets enter the cell in line, coming to rest approximately in line with the four pneumatic needle heads. When all four pallets are in the proper position, a secondary position device under each pallet pushes the pallets back up the conveyor, positioning them accurately in the clamping fixtures, and ensure that each pallet is free from its neighbors so that the clamping process is not impeded.

With the pallets clamped, the hypodermic needle is inserted into the handle button and the decay is performed. Failed units are electronically tagged and removed from the conveyor at a downstream reject station.

Technical Challenge:

Piercing the product to perform a pressure decay leak test works well with water-sealed applications, provided that the piercing remains constant. During release testing of the product, it was determined that the sharpness of the needles greatly affected the size of the pierced hole, and the overall waterproofing of the product.  As the needle dulled, the pierced holes became unacceptably large, creating a notable route for water incursion.

To eliminate this problem, a DOE test was performed to determine the acceptable process window for needle sharpness.  This window was then used to create a software change limit for the cell.  During operation, the system would regulary halt and signal the roving operator to change needles, keeping the pierced hole size always within limits.