Patent heralds new take on hexapod technology

Jon Lawson

Alio Industries has just received a US patent on its next generation Hybrid Hexapod. 

Hexapods have a long history in motion control applications, but in recent years traditional 6 Degree of Freedom (6-DOF) positioning devices have been found wanting when confronted with the industry demand for higher accuracy, improved repeatability, and better geometric performance. 

Simply speaking, hexapods are devices where six links or actuators (that extend and retract) join a stationary bottom plate with a top plate that performs coordinated motion in 6-DOF. A sample, fixture, sensor, or any device can be mounted on the top plate and can be manipulated to be in any location and orientation in the available range of travel.

In complex applications where high precision, 6-DOF motion is required, a hexapod is the go-to solution due to its compact size and the fact that it is more reliable than serial stacked stages with their inherent stack-up of errors, alignment difficulties, and cable management issues. 

With the exponential demand across industry for sub-micron levels of miniaturisation and the requirements for process applications motion systems that move from micro to nano levels of precision, traditional hexapods cannot achieve the desired results. 

This is due to performance limitations inherent in traditional hexapod designs that require the accurate coordination of the movement of all six axes to accomplish a motion profile, even if the requirement is only for a simple single-axis motion. In addition, despite the fact that the general perception is that hexapods exhibit good stiffness compared to serial stacked multi-axis systems, this is really only in the vertical Z axis, with weaknesses in the XY plane.

Alio’s Hybrid Hexapod takes a different approach to traditional 6-DOF positioning devices. Rather than 6 independent legs (and 12 connection joints) Alio’s approach combines a precision XY monolithic stage, tripod, and continuous rotation Z axis to provide superior overall performance.  

The combination of serial and parallel kinematics at the heart of it’s 6-D Nano Precision stages renders traditional hexapod kinematics obsolete, with orders-of-magnitude improvements in precision, path performance, speed, stiffness and a larger work envelope with virtually unlimited XY travel, and fully programmable tool centre point locations. 

It has less than 100nm 3-Dimensional 6 axis Point Precision repeatability, making it a useful technology for applications in the laser processing, optical inspection, photonics, semiconductor, metrology, and medical device sectors,



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