The defending champion surged ahead 3-1 before his opponent reduced the deficit to 3-2.
However, the Australian held his nerve to clinch the contest by winning the following three frames.
"To get to another final is an amazing feeling but I still have a lot of work to do," Robertson told BBC Sport. "I will do what I have been doing all week and come back refreshed tomorrow.
"I have been pouncing on mistakes this week with big breaks and I can put that into my opponent's mind. You have to punish people.
"I have made a lot of centuries in my career, but my potting gets me out of trouble - I am trying hard not to do that now. I am nowhere near the finished article but I am getting there."