Current systems try to keep the cables on a six-axis robot static while everything operating around them is dynamic. Instead, consider a six-axis robot as three separate sections: the sixth to third axis; the third to second axis; and the second to first axis.
IPR Robotics offers a wide range of servo-driven 7th axis linear rails for industrial robots. These rails come in ten different sizes and are constructed from modular high strength extruded aluminum sections to handle payloads of 100 kg to 1600 kg or from steel to handle 2000 kg payloads. This variety of rail sizes allows each application to be sized correctly, controlling the space required and the price point. The drive train design of these rails utilizes helical gear-racks and is proven over 10 years to be repeatable and reliable, even in tough foundry applications.