If the chain is the foundation for all distance traveled, that is a poor basis. The error in the chain will be accumulative. You would be better served with a rack gear on the table, and the servos driving a gear pinion to move the X and Y axis. Rack gears are made with a uniform pitch, and the rack is cut with precise distance tooth to tooth.
For example, if each link was 1/2", but to be more precise if might be .502 from pin to pin, +/- the manufacturing tolerance. If you pulled the chain tight and measured 10 links, your total distance would be 10 X .502=5.020 inches. The actual distance is .020 over 5", not very noticeable.
Now take 100 links of your same chain, and do the same test. 100 x .502 = 50.200 inches, or almost 1/4" over 50.000 inches. Very noticeable.
I hope this makes sense.
John