I was thinking exactly the same about the mjkzz ultra. The wider and longer base of those 4 ball carriages with the spindel right in the center should give a much more stable setup, than all those single carriage solutions.ray_parkhurst wrote: ↑Mon Oct 26, 2020 1:35 pmI have not used either the mjkzz ultra nor the stonemaster systems, but I can make some general comments regarding their construction that might be helpful.
The mjkzz ultra system is built around an industrial rail system. The system is not specified, but the picture shows something that looks like a THK/Misumi/NSK/HiWin type of linear guide rail. This type of rail is a significant improvement over mjkzz's own SR90P system, which uses just a single linear carriage rail having far less stability and precision than the linear guide type. The stonemaster system (based on their website photos) is similar to the mjkzz SR90P, with a single linear carriage, so pricing-wise and precision-wise the stonemaster should be compared to the SR90P, with the expectation that neither is as capable mechanically to the Ultra system.
Another option is to build your own system using surplus rails. Indeed that is the path I took, with THK linear guides, and can certainly shoot at 50x with no issues.
I'm not sure whether a threaded spindle is fine for sub-µm steps, may be ballspindle would work better. But up to now there seem to be no complaints.
I also think a THK k2602B (B=2 carriages) and other parts of MKJZZ could also do the job at smaller invest.. In such a setup both carriages could be coupled (to distribute load and to minimise play), or the front be fixed carrying the lens and the back one to carry the camera for shifting of focal plane. This could be very versatile and stable at the same time. The large 2mm pitch of the KR26 could be overcome by an appropriate stepper and control.