The beginning of the end of resonance. Genuine HIWIN linear rails arrived…
Plan isn’t 100% ready but will start with Y axis (or X in the normal world, the one the extruder rides left to right on) as this the one with the worst resonance.
Sweet! Let the good times roll 
The MGN15 rails were too big to replace the skinny linear rods without interfering with the belt drive. Will resume in two weeks with MGN9 
…
Impressed by the price point these Chinese vendors are now selling seemingly genuine Hiwin products. $23 for 200m rail and a MGN9C bearing block. Its possible its factory rejects, but they’re miles apart from the Chinese made clones and still somewhat affordable.
The wider the better for sure, reduction in “Yaw” play is key here. I’m also going to install a wider rail and bearing block once I get through publishing the first round of Cetus mods. Unfortunate the MGN15’s won’t fit without modding other components!..damn, they would have been sooooo sweet to have running on your printer!
Are you sure we can’t get those on your printer??
Oh it would be possible, just easier to wait for the MGN9 rails and use the existing holes than to drill new holes. Then again I wouldn’t be surprised if it turns out the existing holes aren’t perfectly aligned anyways 
A supported MGN9 rail will be a lot more rigid than a unsupported round 6mm linear rod, only reason I tried the 15 rails first was I got a descent rate when ordering “a few” for a cnc project.
But but …the rails must be perfectly aligned otherwise they will bind because of the yaw tolerance. The 6mm rod and linear-bearings are far-more forgiving comparatively.
I do have a 0.01mm dial indicator for the alignment; will see how it turns out. Wouldn’t be surprised if I end up making a mounting plate for both rails, time will tell.
Yup, that’ll get you where they need to be. Hope all goes well for you @bjorn , if you need another set-of-eyes, poke me…but not too sharp-a-stick 
I did get new MGN9 rails last week, but now I see the mounting screws for the motor will get in the way, and quite randomly I was invited to beta test a new controller board that I’m fitting to the CNC router so that eats up most of the time.
But some day I’ll be back with a plan! (Having the router fixed may well be the way forward anyways:)
I was wondering how you were doing with your mods, can’t wait to see you get this working and the results of your efforts!
cheers!
Hey buddy i think you can help me. I am thinking to purchase Linear rail for my cnc work. I need some direction, I read an article from which i think Erayco 3 Piece DIN Rail and Reliabot 400 mm MGN15 Linear Rail Guide are good.
But i think i will better understanding from customer experience.
Is your HIWIN linear rails works well? Looks like you are also woodworker like me.
I want one in budget range.
you’d want HGR (or better) and not MGN rails for cnc. (MGN works for printers because there is no cutting forces, lust the weight of the axes)