Motion System Design
Tab inserters use couplings for smooth operation

Tab inserters use couplings for smooth operation

Couplings provide high-speed tab inserters with smooth servo drive operation and zero backlash.

UMG Technologies Inc. in Danvers, Mass., makes highspeed tab inserters used in the assembly of printed circuit boards for automotive and consumer interconnect devices. The company’s PLT-901 dual-head inline tab inserter is considered the industry standard in interconnect assembly machine technology, performance, and reliability. The X-Y and rotary stage moves at speeds up to 20 ips with throughput rates to 18,000 insertions per hour.

To achieve this high output level, the interconnect material for the tabs must feed through the system with high accuracy and smooth motion. Tabs must align accurately at the cut and excise station where the system’s insert head transfers the interconnect into the printed circuit board, while the lower anvils support the press-fit insertion. Because of the high feed rate, there is no room for motion disparity when the anvil and insertion head meet. Otherwise, the tabs misalign and the system shuts down.

To keep things running smoothly, the automated inserters use ServoClass couplings from Zero-Max Inc., Plymouth, Minn., to connect the 200-W servomotors to the ball screws. The couplings damp any backlash or harmonic tendencies that might occur in the system’s rapid step and repeat cycles as it precisely inserts connecting tabs into circuit boards. With a torsional stiffness of 309 lb-in./deg and axial stiffness of 160 lb/in., the coupling also provides inertia and torsional stiffness. This torsional rigidity is required in servo connections to eliminate any harmonic vibration tendencies and backlash that can affect servo controls’ positional and dynamic accuracy.

The SC035 coupling UMG Technologies uses has a 50-lbin. operating torque at a maximum 10,000 rev/min. The coupling’s misalignment capacity is 0.009 in. parallel, 1° angular, and 6 0.02 in. axial. It has a moment of inertia of 0.0899 lb-in.2, which allows it to accelerate from 0 to 3,000 rpm every half second — and do so continuously. The only downtime needed is when an insertion run for a specific tab size is complete and a new one is started, or when the interconnect inventory reel is empty. The design provides misalignment capacity, as well as flexibility, to reduce reaction loads and extend operating life.

For more information, visit Zero-Max Inc. or call (800) 533-1731.

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