Robertson was pushed all the way by Tom Ford before grinding out a 4-3 win but Ding had things easier as he romped to a 4-0 success over Kurt Maflin.
Robertson looked on course for a whitewash too in the opening semi-final after going 3-0 in front with a break of 80 in the third frame being the highlight of the opening exchanges.
Ford fought back though – a 60 was the cornerstone of the fourth frame and then runs of 51 and 66 saw him took the fifth.
He made it 3-3 in the next but Robertson took the final frame 72-29 to secure his final place.
Ding meanwhile has been knocking in the centuries all week, including a 147 on Saturday, but he did not need to be at his best to beat Norway Maflin.
Breaks of 53 in the first and 73 in the second were the best he could manage but it was still enough against Maflin who only scored 52 points in the entire match.
The final takes place on Sunday evening.