****** - Verified Buyer
4.5
I previously reviewed a twotrees BMG style extruder which turned out great, so I figured I'd give their linear rails a try for an Ender 3 conversion. Both rails arrived with the typical cheap rail grease, and needed to be cleaned. No surprise there. Some cleaning and application of super lube and the first ended up fantastic. I mounted it on Y. The rail I intended for X was rough even after cleaning. I tried everything. I even sanded down the rail after watching some videos on how to further enhance the rails. checked the bearings again. noticed a few missing, and replaced them with higher grade bearings. It somehow got even worse. The carriages barely moved now. I headed to the listing again to find in the reviews that the bearings are a non-standard size. They looked identical to the standard 3/32". Now the bearings are mixed and I have no idea which are which and are stuck with a useless rail. Not so great. If it had been decent from the get-go I wouldn't have had any issues.I bought one of these around a year ago for my Voron 2.4 to do the single MGN12H X-Axis mod. It's a quality rail, nice and smooth once cleaned and lubed up properly. It's worked great since then. Nice and smooth, no catchy spots and no grit once broken in.Recently however, I noticed a significant wobble in the toolhead, up and down. Over the ~2000 hours of printing I've done with this rail it's developed significant play between the rail and the carriage. It's not a big issue, and print quality doesn't seem to be affected by it, but it is strange. It was properly lubed and maintained along with the other linear rails in the printer and this is the only one that developed such play. It did not have this much play when it was new, in fact I don't recall it having any.YMMV, like I said it doesn't seem to have impacted print quality in a negative way, though if you were doing some sort of speed race pushing accels and speeds super high you might notice it more.As shipped the rails needed some cleaning and lubing but overall they work terrific. The ones I got use a specific bearing size that is a niche part. Overall would purchase again.Quality control seems a little variable here.I purchased two sets a year or so ago and have had zero problems. They were well packaged and incredibly smooth running after properly cleaning and lubing.Came time to upgrade something to linear and I bought another shorter rail block kit, and it's really gritty in feel. I ultrasonically cleaned it with an appropriate 25 percent alcohol solution, and lubed with some fresh synthetic oil, and it seems there's just not enough ball bearings in there. There's large gaps, and while I don't recall, or want to disassemble my other two rails to check. I feel the others weren't gappy like that, and definitely didn't intermittently grind to a halt, only to kind of shake it out in the same spot a moment later.It suggests it isn't the rails. More the mechanics of the balls moving in the carriage. Could be that this would work it's way free, and the cleaning helped some.. But it doesn't feel like the first two did.Requesting a replacement. But also some upgrade ceramic balls in the mean time to see if it's the balls themselves. Will update.*update*The replacement was noticeably smoother.I tried replacing the bearings anyway with 3/32" 2.381mm ceramic bearings, and while they fit (just), the carriage was considerably too tight now to allow movement. I measured both replacement bearings and the current ones, and found the twotrees bearings to be 2.36mm, and the ceramics, 2.38 as promised.Mixing the two left the carriage with a wobbling feel to it. In short, they aren't a standard size, and are not replaceable, which is odd as I've read of people swapping the bearings out in these.I've asked twotrees what's up with it, and will report back if I hear.If the bearings aren't replaceable due to using non standard bearing sizes, it leaves these as being a one time use non repairable bearing, and as such, the price isn't that great after all.They got back to me, nicely asking how many bearings I needed but not answering why they used a non standard bearing size.Fuzzy as to whether you'd be able to repair these down the road. Had I known, I would have used a brand that used a standard size.I asked again, and they replied that they are 2mm bearings. They simply are not.They measure 2.36 on my calipers. Because of the differences, neither a 2.38mm bearing and especially a 2mm will not fit. A 2mm likely wouldn't even hold inside of the metal rails without falling through.One rail cleaned up great and ran smooth as butter. The other, not so much. Turns out there was a ball missing in that carriage (24 balls on one side, 23 on the other) which may or may not be the root cause yet. Going to upgrade balls on both carriages as once theyre installed in the machine I dont want to have to tear it back apart later. Measurements show my MGN9C carriages are using 2.0mm balls instead of the "standard" 1/16" expected for a MGN9 rail. Of course they may turn out to be 5/64" which would majorly suck since the diff in size between those and 2.0mm are a scant 0.016mm so I have to hope my vernier calipers aren't lying to me on the size.These rails are a good for the price, a bit noisy but smooth and precise movements out of the box. I cleaned and oiled them without disassembly and work fine on my 3d printer without loss of quality.Simplemente son de buena calidad tanto que compre los 5 de diferentes tamaños para mí Ender 3 v2 y corren muy bien en los siguientes días actualizaré para dar más detalles.
