Good morning everyone, is it normal for the X and Y screws to have no bearings at the ends? In 40 years of mechanical work, I’ve never seen anything like this.
5 Pro bearing.zip (2.8 MB)
I have the S5 Pro, 4x4. If your referring to the lead screws on the axis’s then yes, the 2 Y’s and X have no “typical” bearing on the end opposite the stepper motor. It’s a retainer only since there is really no significant load on it. No problems with mine so far.
2 Likes
I think what you are referring to is called a “fixed-free” configuration. One end of the screw is securely mounted and fully constrained but the other end is essentially unconstrained.
If that’s what you are referring to, there are some benefits to this configuration and in this application, few downsides. It’s a pretty reasonable trade-off in my opinion.
Free end generally means you can’t drive the shaft nearly as quickly or you have to use larger diameter shafts to prevent whipping.
I’m no mechanical engineer but when I was looking into all this to build my own compact machine, I realized just how industrial these kinds of components are. There’s no way I could drive them past the rated values for whip or buckling without the machine completely destroying itself in the process 
So the free floating end saves on cost, saves on complexity, and is still far from the weakest link in the system. Whereas implementing the more complex end fixing would require upgrading more of the machine to fully realize any of the benefits.
These have been great machines to study in my hobby machine design adventures. Well designed with very clear trade-offs made for cost/benefit. All of the right corners cut and few decisions I would personally disagree with 
Cheers to the design folks 
Here’s a link to a decent description of different end configurations:
3 Likes
Thanks for the explanation, I was aware of it anyway. The people who designed the machine evidently adopted a hybrid “solution” between FIXED-FLOATING and FIXED-FREE, as you can see from the video… The problem, given the length of the screw, can arise when the milling machine transmits vibrations to the Z-axis, which will inevitably also affect the X-axis screw, generating reverberation at times (it happened to me), precisely because the end of the screw is completely free. The most effective and economical solution, in my opinion, would have been FIXED-FLOATING, simply using a rolling bearing of the same diameter as the screw.
1 Like