Motion System Design
Splitting hairs

Splitting hairs

BACKGROUND: InvenioSix from Invenios Inc., Santa Barbara, Calif., is a six degree-of-freedom robot designed to assemble consumer electronic products with submicron precision and repeatability.

DESIGN CHALLENGE: The robot’s toughest job is aligning active and passive components, a procedure that requires nanoscale precision. Compounding the problem are large heat fluctuations — the attachment process involves laser welding, laserassisted soldering, or thermally (UV) cured adhesives — which cause large time-varying forces that must be overcome with high static and dynamic stiffness.

Traditional solutions, such as stacked goniometer-based tools, achieve individual axis precision but, because of their serial link construction, lack multi-axis perpendicularity, stiffness, and thermal stability. Stewart platforms, on the other hand, can achieve high stiffness, but the geometry associated with multi-link actuation of extensible legs complicates straight-line motion and accurate angular motion.

DESIGN GOALS: In addition to meeting reliability, stiffness, and precision demands, the positioning system had to be built at a reasonable cost.

ENABLING TECHNOLOGY: Miniature ballscrews from Steinmeyer Inc., Bedford, Mass., provided the necessary dynamics to meet the design challenge.

DESIGN IN ACTION: The InvenioSix Automation Platform provides large angular and linear displacement with zero backlash using high stiffness, precision ground miniature ballscrews, and rotary flexures in a small footprint platform. The ballscrews make it possible to achieve 35-nm incremental step motion and 70-nm bidirectional repeatability while using a single-loop, high-bandwidth control system. Riding on miniature ballscrews, the positioning stages achieve unprecedented closed-loop stiffness and nanometer scale precision at an affordable cost.

In recent process validations, the mean insertion loss of an active transceiver component was reduced from 2.5 to 0.5 dB through the use of this six-axis automation platform — improving product yield from 60 to 97%.

For more information: Steinmeyer Inc.
(800) 297-6403

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