I would appreciate some advice on the best way to improve both the precision and accuracy of the Z Axis. I have installed my Z Axis stabilizers and the Z smooth rods are now rock solid. This has improved the print quality but I am still seeing a repeating wave pattern on the Z axis. Under high magnification I can see that the cause is a very slight variation in the thickness of the Z layers in a repeating pattern (about 1.5mm apart). (I'm not able to post a picture as I can't get the right level of magnification on my Nikon ATM) My Robo still has the stock imperial rods. And it has a wobble of around 1-2mm on the left side coupler which obviously causes the Z threaded rod to wobble. One or both of these issues is probably causing the Z axis thickness variation. So I am looking for how best to upgrade the Z Axis. Seems like the best option is to replace the stock rods with fine (1 mm) thread 8mm metric rods and flash the Ramps with the correct number of steps per mm. Obviously I also need to reduce the wobble (probably by replacing the couplers) Is there a better option?