Odd circle test results (Page 18 of 24)

I bought hardened steel shafts. I didn't do any of this without the guidance of other forum members. The rods are 8mm all the way. No real detectable deviation. mcMaster has high quality everything. Nothing on mcmaster is bad. If it is they will fix it because it shouldn't be. It's expensive for a good reason.

If anything is bad on my end, it's the bearings. If you didn't know LM8UUs have a high failure rate (seriously like 25%) you are a fortunate person! The thread for the lawsy carriage says buy 12 when you need 8 for a good reason. Some just suck. I didn't get my bearings from MC though because $18 each is ridiculous. I'd rather buy cheap crap and throw away half than spend that much. I paid a buck each for mine from RRD.

I think my bearings suck.  Damn chinese knockoffs from ebay.  12 for $10.  I've not replaced the original SD rods so I'm still on stock rods but I've measured them up and down.  The rods which I've been demonstrating are actually 7.92 to 7.98mm in diameter (stock x-axis rods).  These bearings do not slide on their own.  As soon as I take the force of my finger off them, they stop; even when vertical with nothing on them but their own weight.

If these bearings don't work out, I'm going to have to invest in some higher quality bearings.  I'll be looking at Misumi USA as well.  I think Privan is talking about part number LMU8.

has anyone noticed these bearings also have seals on ends (least mine do) to wipe grease/dirt off rods? these are snug to rods and will cause slight drag on dry rods enough to maybe not let them glide by gravity from 20% tilt.

but also should not keep from moving with slight touch or flick. grabbing and pulling is too snug for stepper motors, belts, pulleys etc.

also dont force them on ends of rods. smooth ends with emery cloth to remove burrs etc so bearings dont get damaged.

Excellent! I will likely pick some up because I am obsessed with doing anything within my power to improve my printer's drive system. Thanks pirvan.

Goodness those are some bad bearings where did you get them? Your stock bearings don't slide that poorly do they?

In an effort to save on shipping costs, I am looking at the Misumi 8mm Shafts as well. Apparently their shaft pricings are the same price as McMaster Carr's.  I'm looking at shaft model PSFJ8 @ 358mm and 334mm for the y/x axis shafts.

Ordering 10 bearings and the 4 shafts comes to $103.  Damn....

Should I focus only on the bearings?

So I got my flanged bearings today meant to replace the bushings on the sides and the pillow block (Solidoodle 4).
However, I can't get the bearings to pop off with all of my force. For those who have done this mod: how did you get the bushings out? Maybe there's a drop of glue used to keep them in place, I don't know...

Maybe not a linear bearing quality problem,
Check tolerance of shaft and bearing from misusi,
Maybe your shaft diameter too big.
Use the ball bearings or flange bearings instead of
SD stock bushings, doesn't make a sense, because
The SD frame is made by 1 mm thk. Sheet metal,
It is not rigid as a solid metal bars, and all holes
are not aligned up well, so use GT2 belt and pulleys,
It is a better way to reduce the backlash on Y drive.
Of cause if you Like to make a big mod, to move
Y motor to outside of the frame, and drives 6mm
Rear rod (shaft) directly, it is a best way to reduce
The backlash on y direction.

Those look good. Let me know what you did to replace them because I'll be doing this soon. The lawsy carriage would remove a lot more mechanical play (particularly on the right carriage piece) and should yield further improvement. My circles look about like yours now so the carriage upgrade should get you close enough that you won't have issues with tolerance.

Make sure there's no wobble anywhere in your hotend as well.

Friction anywhere is a problem and if you want the perfection you seek linear bearings are a requirement. The stock carriage has plenty of friction. You've just never felt the smooth movement of linear bearings so you don't know what you're looking for.

Keep in mind there are plenty of other potential mechanical culprits, the wiring clonkig into the bed and the filament feed both put lots of stress on the drive system. You're looking for perfection so you have to address all these variables. If you don't you'll never get what you want. So it's up to you. There is no smoking gun.

If you have the bearings why have you not put on the new carriages? They make a huge difference and all of the information on how to do it is here. If you are having a warping problem try that slurry stuff everybody likes. Haven't tried it myself.

what about the carriage having rods loose in it letting it flex?