The arms are not operated with cables. That's primitive. A huge, vast system of lasers (set up throughout the solar system and controlled from within the cranes) directs the arms. The arms contain a liquid substance (again, discovered in another solar system) - the substance is a bit like that "expanding foam" that carpenters use to fill the cracks around windows. So, when an arm needs to expand, this substance "grows" and allows the arms to expand out. As they need to contract, it does this as well. It shrinks. And everything is all calculated into the system, so the arms know when to expand/contract and exactly at what rate. And the substance never has to be replenished. It expands and contracts over and over and never depletes itself.
And the arms are able to go through the sun, without interrupting what happens in its core. We could also expand the arms around the sun (and/or planets) if we needed to (the expansion substance is "that good"). Imagine these big "flexy" arms and hands roaming around space however we see fit. I know you don't believe this, but the INTP's on this forum and in this thread have all been briefed on this (and in fact, many of them contributed to the technology). If you're having a hard time comprehending it, well, I'm very sorry to hear that, but it's not my problem.
Cables. Pffff. Are you still on this "cable" trip?
We're cable free baby. Do you see cables going from your computer to mine? No, but we're still communicating. This is the 21st century here. Join us.
Cables. Seriously? Yeah, we'll be plugging in to the outlet in your wall too.
Robots. Machines. Materials from a different solar system. The properties that you are accustomed to...don't really apply here. Allow yourself to think outside the box, cuz if you limit your thinking to technology that you see in your little home town, it won't make sense.