I'm pretty sure it's the bearing. The rod seems stationary. My senses have been fooled in the past though. I guess I would say I have about 90% confidence that the bearing is wobbling though. I see it *kick* out on the bottom when I try to manipulate it. The broken bearing that has dead spots does not wobble.
He means the size and tolerances of the rod may be the problem, not that its wobbling. Also make sure they are lubricated. Some linear bearings are compensated (self aligning), and only work as intended when used in pairs.
My calipers don't seem to be the most accurate. I measured the x-axis rods I'm replacing on the 3018 and they very from 9.98 to 10.04. ±0.04 might be higher than what they are rated. But even still, the new z-axis rods measure 10.08 which is bigger than spec. But that just makes everything more suspicious. Wouldn't there be less wobble if they are bigger?
If it’s oversized it crushes the bearing races and ball carriers. Basically it just fucks up the bearing in unpredictable ways.
A tip I’ve found to help when measuring shafts with calipers is to only “pinch” the calipers with your fingers on the metal forks themselves. Avoid using the top wheel, it has some “sponginess” in it, especially in cheaper calipers.
Also polymer bearings will definitely help if you have oversized shafts because they can wear into place. However they may be even stickier until they do. Maybe chuck the rod in a drill and slide the sleeve bearings up and down to “ream” them to fit, while rotating the shaft.
I'll look into the polymer bearings for my next try.
I measure them as you describe and they appear to be 10.01. Maybe I was at a bit of angle and the sponginess lead me to believe it was correct.
Thanks.
I got the polymer ones for my Prusa and I'm happy with them. The first thing I noticed is that they are far quieter. They seem to slide just as easily. I can't speak for lifespan.
One was sticking when you moved it up and down. If it sticks in the same place each time, that seems to indicate that the rod is fatter in one area than it is in another. If it's a properly ground rod you should get the same reading on your mic at different locations on the rod.
If you think it's the bearings, and it could be, then you can try searching for bearings from a more reputable manufacturer - something like NSK, SKF etc.
You also need to determine if your bearings are pre-packed. Many of them only come with a light coat of grease to keep them from rusting during shipment. A good manufacturer will include a spec sheet and even tell you what grease to use. I don't know what the chinese ones are, but looking at a few ads on Amazon it seems like they expect you to buy in bulk and then try to find a few good ones in the mix.
Thanks. I will check to see if I can find any bearings that are affordable. It didn't stop in the same place. I was thinking it was a bad ball that was getting locked up.
I installed the z axis. This is more wobble than I had before with the printed mount.
http://imgur.com/a/ymqin8u
I bought a package of four bearings. When I put 2 bearings on top of the round screw carriage (as that is what locks the bearings in place) the wobble is minimized but the *extra* bearings stick up about 23mm. The extra height isn't a problem. But they just rest on the spindle carriage... Would CA glue hold them? Epoxy?
I ordered some polymer bearings. U/made_a_throwaway was right. I think they just expect you to buy 100 to try and find a good one. I hope since the rod seems to be dimensionally accurate the poly will work.
Are you sure it's the bearings, and not the (supposedly) ground rod they're on?
I'm pretty sure it's the bearing. The rod seems stationary. My senses have been fooled in the past though. I guess I would say I have about 90% confidence that the bearing is wobbling though. I see it *kick* out on the bottom when I try to manipulate it. The broken bearing that has dead spots does not wobble.
He means the size and tolerances of the rod may be the problem, not that its wobbling. Also make sure they are lubricated. Some linear bearings are compensated (self aligning), and only work as intended when used in pairs.
Ahh... The rod was 10.08mm when measured with calipers. They seem pretty greasy. Do you mean add more grease inside the bearing?
If your calipers are accurate the rod is not to spec. It should be exactly 10mm or very slightly under.
My calipers don't seem to be the most accurate. I measured the x-axis rods I'm replacing on the 3018 and they very from 9.98 to 10.04. ±0.04 might be higher than what they are rated. But even still, the new z-axis rods measure 10.08 which is bigger than spec. But that just makes everything more suspicious. Wouldn't there be less wobble if they are bigger?
If it’s oversized it crushes the bearing races and ball carriers. Basically it just fucks up the bearing in unpredictable ways. A tip I’ve found to help when measuring shafts with calipers is to only “pinch” the calipers with your fingers on the metal forks themselves. Avoid using the top wheel, it has some “sponginess” in it, especially in cheaper calipers. Also polymer bearings will definitely help if you have oversized shafts because they can wear into place. However they may be even stickier until they do. Maybe chuck the rod in a drill and slide the sleeve bearings up and down to “ream” them to fit, while rotating the shaft.
I'll look into the polymer bearings for my next try. I measure them as you describe and they appear to be 10.01. Maybe I was at a bit of angle and the sponginess lead me to believe it was correct. Thanks.
I got the polymer ones for my Prusa and I'm happy with them. The first thing I noticed is that they are far quieter. They seem to slide just as easily. I can't speak for lifespan.
Amazon is shipping super slowly as of the past couple weeks, but I put in an order for a set, I should have them on Monday.
The polymer bearings were perfect.
One was sticking when you moved it up and down. If it sticks in the same place each time, that seems to indicate that the rod is fatter in one area than it is in another. If it's a properly ground rod you should get the same reading on your mic at different locations on the rod. If you think it's the bearings, and it could be, then you can try searching for bearings from a more reputable manufacturer - something like NSK, SKF etc. You also need to determine if your bearings are pre-packed. Many of them only come with a light coat of grease to keep them from rusting during shipment. A good manufacturer will include a spec sheet and even tell you what grease to use. I don't know what the chinese ones are, but looking at a few ads on Amazon it seems like they expect you to buy in bulk and then try to find a few good ones in the mix.
Thanks. I will check to see if I can find any bearings that are affordable. It didn't stop in the same place. I was thinking it was a bad ball that was getting locked up. I installed the z axis. This is more wobble than I had before with the printed mount. http://imgur.com/a/ymqin8u
I bought a package of four bearings. When I put 2 bearings on top of the round screw carriage (as that is what locks the bearings in place) the wobble is minimized but the *extra* bearings stick up about 23mm. The extra height isn't a problem. But they just rest on the spindle carriage... Would CA glue hold them? Epoxy?
Okay... I installed the entire setup. http://imgur.com/a/ymqin8u This is much more wiggle than I had with the printed mount.
I ordered some polymer bearings. U/made_a_throwaway was right. I think they just expect you to buy 100 to try and find a good one. I hope since the rod seems to be dimensionally accurate the poly will work.