Overall: Absolutely love the simplicity of this design. For the price it is an excellent system. Of course, don't expect to match a $10,000 system though. There are a couple of short comings to the design. First and probably the weakest point is the anti-backlash springs. They are way too weak. When you purchase this system also purchase TWO of the cheap anti backlash T8-4 (2mm pitch with 2 starts) nut assemblies. Use the springs from those sets instead of the ones included in this kit. Secondly, the design relies on the stepper motor's bearings--this is bad. You can partially fix this by purchasing 8mm locking rings. You only need two but they appear to come in sets of 10. Mount them snugly against the bearing on the far side of the T8 screws so as to apply pressure back into the motor. This isn't the best of solutions but it does help.Modification: Consider purchasing 500mm long 10mm chrome steel rods and a 500mm T8-4 (2mm pitch with 2 starts) and a couple of pieces of the 20mm x 20mm linear rail each cut to about 520mm. Longer won't hurt and a little shorter just means you won't be able to extend the axis quite as much (2cm less). With these parts you can end up with a system with a working field of about 12"(305mm) x 16"(406mm). I've done this mod using 600mm parts and it still works well. If doing this mod one MUST be aware that overloading the chrome steel rods will bend them! Slow down your vertical (plunge) feed rate so as to minimize the forces on those rods.
Joe Rich 
