On my particular printer design, it definitely appears the company switched from flex couplings to solid couplings on purpose to improve the printer, and to prevent well-meaning users from adjusting the previous flex couplings. Whether or not this is a good design overall, is left for the reader to decide. It's certainly simple and cheap to use the motor itself as one of the leadscrew thrust bearings, but in the future I might add a micro-adjustable bearing block in place of the motor, and then couple the motor to the leadscrew with a flex coupling. That would be more typical of the way it's done on CNC machines, where the stepper bearings are isolated from any machine loads.
Original post: I bought a Artillery X1, supposedly the latest V4 version. It's my first printer, but I have experience with CNC machines. Although the pictures and YouTube videos all show the Z axis steppers connected to the leadscrews with flexible (spiral type) couplings, the printer I got has solid couplings.
I thought flex couplings were important to prevent binding, so I was going to buy some flex couplings. But as I look at the printer, it appears the leadscrews actually are supported by the stepper motor itself at the bottom...there are no thrust bearings, so the weight of the printhead is supported by the stepper motor directly through the coupling. Since the spiral flex couplings can compress slightly, is the use of solid couplings deliberate in order to make a more precise machine? If I install flex couplings, will it make my printer worse by introducing "spring" into the system? Is this a typical design, or do other printers have thrust bearings or "hang" the leadscrews from the top?
There are a lot of reviews and videos about this printer where people noticed the leadscrews were internally touching the end of the motor shaft inside the coupling, and people thought that was wrong, so they spaced them back apart. Now, I wonder if the shafts touching was a deliberate design decision, and maybe the company even switched to solid couplers to prevent people from adjusting the couplers back. Please help me solve this mystery of the solid motor couplings.
EDIT: I found a related application where the axial rigidity of the stepper couplings matter. In the following YouTube video the author deliberately jams together the lead screw and stepper shaft in order to eliminate spring from the flex coupling. This tends to solidify my theory that this printer uses solid couplings deliberately, and other printers with similar Z axes could potentially benefit as well. The X1 uses floating support bearings for the X stage to prevent binding, which probably helps.
Also, in this YouTube video the author describes how he deliberately decided to use rigid couplings on this printer to improve his Z axis and references other sources which come to the same conclusion.