Since its launch, the Hybrid Hexapod® from ALIO Industries (an Allied Motion Company) has revolutionized the approach to 6D motion, and redefined the role of motion control in applications that need flatness and straightness of motion plus stiffness such as for machining and bonding applications.
Bill Hennessey, President of ALIO Industries says, “In the world of 6 degrees of freedom (6DOF) nanotechnology applications, the Hybrid Hexapod® technology allows for the provision of documented proof of performance over all 6DOF of a body in motion at the nanometer-level of precision. As such it is unique, and this is the first time that this has been possible. We now see leading blue-chip OEMs working on nanometer applications in the optical, semiconductor, manufacturing, metrology, laser processing and micro-machining sectors, and achieving successes previously unattainable.”
All hexapod motion systems operate within three-dimensional space, and have errors in all six degrees of freedom. However, hexapod motion systems have typically only been characterized by performance data of a single degree of freedom. This practice leaves error sources unaccounted for in several degrees of freedom, especially in the areas of flatness and straightness, which are critical precision needs at the nanometer level. So saying a legacy hexapod will exhibit loss of precision in the tens of microns per axis when measuring flatness and straightness of travel. The Hybrid Hexapod® overcomes these issues entirely.
Hennessey continues, “Because hexapods have six independently controlled links joined together moving a common platform, the motion error of the platform will be a function of the errors of ALL links and joints. Hexapods are known to have optimum accuracy and repeatability when performing Z-axis moves, because all links perform the same motion at the same relative link angle. However, when any other X, Y, pitch, yaw or roll motion is commanded, accuracy and geometric path performance of the hexapod degrades substantially because all links are performing different motions. In the case of legacy hexapods built with non-precision joints and motion controllers that are not capable of forward and inverse kinematics equations, the source of error is even more pronounced.”
The Hybrid Hexapod® was developed by ALIO to address the critical weaknesses of conventional legacy hexapod designs, as well as the weaknesses of stacked serial stages, and to achieve nanometer-level accuracy, repeatability, and high-integrity flatness and straightness during motion. It utilizes a tripod parallel kinematics structure to deliver Z plane and tip/tilt motion, integrated with a monolithic serial kinematic structure for XY motion. A rotary stage integrated into the top of the tripod (or underneath it depending on application needs) provides 360-degree continuous yaw rotation. In this hybrid design, individual axes can be customized to provide travel ranges from millimeters to over one meter, while maintaining nanometer-levels of precision.
Hennessey concludes, “Let’s look at the manufacturer of 4K lenses. Typical 4K lenses demand extremely high-tech material technologies, precision assembly practices, and very sophisticated manufacturing processes and techniques. Tolerances are pretty much zero in all directions. The manufacturing processes used to create the lenses can often lead to inaccuracies, which is why they need constant active alignment. The sensor and lens are lined up while multiple targets are projected along the lens, to the sensor and then the image is taken. Modulation transfer function (MTF) is always constantly monitored by the active alignment device to keep each MTF value within pre-determined limits. When the limits are satisfied, an adhesive is partly cured using ultraviolet light, and then a total thermal cure will be completed later. This ensures extreme accuracy when aligning the lens and sensor planes. The Hybrid Hexapod is proving to be perfect for this application, as its absolute repeatability and precision produces accurate results again and again.”
“Engineers working at the cutting edge of what is possible must be stimulated to ask more as they see that this technology achieves things others cannot, has the potential to promote innovation, and can optimise efficiency and cost-effectiveness in manufacture. The Hybrid Hexapod® is orders of magnitude more precise than traditional hexapods, being 100 x stiffer, 30 x faster, and with 10x the usable work envelope of industry standard options.”
