Decided to go with the linear shafts recommended to me by Heath Harper from Laser Weld Design.
However, I am still on the fence with the linear bearings. Regular ball linear bearing have slop and wear out, so I’d like something better. I’ve seen the Ultimaker using brass bushings, which are cheap, but how well do they do in comparison to ball bearings, I don’t know. I have also found polymer bearings from igus. The are more expensive, but seem to have a lot of advantages.
Is there anyone that has compared these or has used igus linear bearings?
How much printing are you planning on doing that bearing wear could possibly become an issue? Also if you are going to print that much you should probably figure that the bearings are also a consumable item and plan on replacing them when they wear out. If you are going to be printing commercially build component replacements and maintenance costs into your pricing.
@Joe_Morrison I’m not really trying to minimize wear. All bearings are going to need to be replaced at some point, so the cost is negligible. What I am really trying to eliminate is slop and ball bearings ruining me shafts. The igus bearings are ten times the cost as cheap ball bearings, but don’t need lubrication and the replacement inserts are cheap. Brass bushings are cheap too, but I have never used them. I guess I’m trying to find justification for buying something other then ball bearings. They are noisy too.
I was using the ball linear bearing and you are right they are loud, need greased, and have some play, but very low resistance. I have just recently switched to printed ABS bushings with silicon spray on the linear rails, and I have to say that they don’t move as freely. There is a bit of initial resistance at first(the bushing is compressed around the rail by the mount), but they are quiet, have nominal play, don’t need to grease, and I can print replacement stock, so no shipping cost either lol. Don’t know how long they last yet.
Check out this comparison
@Jeremiah_Coley I’ve considered printed bearings before, but I really don’t want to be forced to tear down my printer to replace bearings every few months. Igus bearings are essentially the same thing, but they are more durable and self lubricating.
Not a fan of the brass bushings. Too much drag and resistance for me but they do work. There might be a middle ground here for you using the cheap ball bearings and silicon lubricant spray. I have found that combination to be very quiet and smooth with very low resistance. I also rotate the bearings so I have two tracks riding on the upper portion of the rod. Seems to distribute the load more evenly. As I mentioned on another thread another factor is the carriage plates the bearings are Mounted on. You want those as flat as possible. Helps the bearings align parallel to the rods.
@Jeff_Parish Price isn’t that bad, replacement inserts are only about $1.50 US. So it’s only the initial cost that is much higher (about 5x cheap Chinese bearings). The plain ones are meant to be pressure fit to obtain their true inner diameter, something I don’t want to tease out by prototyping and are not much cheaper then the RJUM. I can get ones without the o-rings, but they are so the bearings will self-align, which is important when two or more bearings are fixed together.
@Kura_kuea True, however it looked like anything 8mm or smaller was press fit. That is the size I would be interested in trying out. If you go this direction let us know how they work out. I would like to see how easy they are to swap out.
@Jeff_Parish The ones with compression housings are direct replacements, I believe. Otherwise, for the plain ones, you have to undersize it just the right amount to squeeze the inner-diameter to 8mm. I designed a new x-carriage, so I can use anything I want really. But the ones I linked seem to be the best option for me, since I have to put two bearings in series in the front and back bearing mounts. I’ll also print some cylinders to find the perfect fit around the o-rings, before I print the whole carriage.
The problem is the very cheap LMxUU style bearings are usually pretty bad and they’re often sold to go with bad rods that aren’t properly hardened and sometimes not even ground well if at all. I’ve since switched to linear ball rail, which is a rectangular rail with rectangular cars. The hobby tends to know more as MGN type, though I use other types more. It allows for better framing anyway.
I tried to use Simplicity plastic lm12uu bearings which are competitors to igus plastic bearings without success.
Even if I had compensated bearing in my dual rail setup (in x, y and z) i would always get binding to occur.
Using Chinese linear shafts of unknown precision, I places the fault on them because I made all possible efforts to align things to the best of my abilities and tools.
So I went back to Chinese lm12uu to fit my sc12uu blocks, and ordered twice the amount of bearings I needed to weed out the bad ones.
Printer has been running for years now without significant bearing damaging the linear rails.
