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Motion System Design

Operation donut: Dispensing technology pulls out all the stops

One highly controlled dispenser simplifies a UV-anaerobic sealant application.

When electrical component manufacturer FTZ Industries, Simpsonville, S.C., set out to create a new electrical splice, they had a vision in mind: To create an innovative splice that uses ultraviolet-anaerobic sealant technology together with a high-speed dispensing system that turns out finished connectors at a fast clip. The company turned to adhesives, sealants, and dispensing equipment manufacturer Hernon Manufacturing Inc., Sanford, Fla., to help develop their groundbreaking Cool Seal product and dispensing unit. After the Cool Seal won the Popular Mechanics “Editor's Choice Award” at the 2007 SEMA automotive show, product demand soared, as did production requirements for the manufacturing equipment.

How it works

The unique sealant is partially cured to secure it into the electrical connector, and is then cured anaerobically when the end user employs the connector to splice electrical wires. While developing the dispensing system, the goal was to build a machine that could accurately dispense a metered amount of sealant into the inside diameter of each end of an electrical connector, maintaining a “hole” profile throughout, while partially curing the sealant. Adding to the design challenge, equipment needs to work with three dissimilar electrical connectors at even higher production rates than before.

Traditionally, pneumatic dispense valves and pressure reservoirs are used for sealant dispensing, but these components are not accurate or efficient enough for high-speed production. Instead, Hernon engineers designed a high-speed dispense pump system called the Sureshot 3000 to handle the required speed of this sealant application.

Sureshot's pump system uses two Titanium Nitride-coated, valveless positive displacement dispense pumps to meter sealant into each end of an electrical connector; each Sureshot machine uses a digital drive to rotate a piston inside the pump. As the piston rotates, it pulls sealant through an inlet port and discharges it through an outlet port. One complete piston revolution is needed for each suction/discharge cycle. Flow rate and volume are precisely controlled by manually adjusting the pump's angular deflection with respect to a zero point on a scale, as well as speed of the digital drive, which receives inputs from a PLC.

Need for speed

To meet FTZ's production requirements, Hernon engineer Tom Bray designed a multiple conveyor system to continuously process connectors. The beginning of the operation involves coordination between the PLC, proximity-sensing inputs, and servomotors. In auto-cycle mode, the servo-driven primary conveyor acts as an indexing wheel. Connectors start on a rotating conveyor; as the conveyor rotates, it carries each connector to its next operation. A secondary conveyor controlled by a variable-speed gearmotor continuously runs at a predetermined speed; this conveyor catches connectors from the primary conveyor and delivers them to a UV tunnel and finally out to a receptacle for splice processing and packaging.

Preprogrammed, precise servo-driven slides bring the Sureshot's dispense heads to each connector as it is positioned in its index fixture, which contains V-shaped bearing guides to retain each connector as it rotates in the nest. Simultaneously, slide actuators move forward, conical tips enter connectors at a predetermined angle, and the Sureshot dispenses sealant in a threaded pattern, filling 75% of the connector ends and leaving a “donut hole” in the middle. The complete, turnkey Hernon equipment system uses five PLC-controlled servomotors, which are used to control dispense pumps, spindle rotation, left and right slide actuators, and conveyor indexing.

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