replacing front y pulleys

This is a good post to read through
http://www.soliforum.com/topic/2361/all … onversion/
In the end though I think there are better ways to do those front idlers.  I like V-groove bearings with fish line myself.

My SD 3 started to make weird noises when making fast long Y and X movements . I determined it was my X and Y pulleys chattering . So I took them apart to grease them and re installed them .Then I noticed they wobbled a lot on the 5mm bolts which also showed signs of wear, black had worn off on one side. I using my drill press drilled the ends out about 2. 5 mm deep and inserted
(2)  5 x 8 x 2.5 mm ball bearings re assembled pulleys and no more noise no more vibration and oh so smooth . I have ordered some bearings for the rear shaft to replace the bushings next . I will post results when I get them in. I have also installed Lawsy's carriages with bearings, next is his extruder mod.       

              thanks to all members for their great works and postings     Bill D.

PS rear bearings went in nicely  and made it so smooooth

You probably have to drill out both ends and use two bearings per pulley.
Recommend using a drill press, you'll never get a round/straight hole otherwise.

Slimstar's method is actually much easier, but I went the other way and printed a new idler block with bearing seats for those same 8x5x2.5mm bearings. My pulley is fixed to a shaft with a set screw, and the shaft rotates in the bearings.

Attached, note that these are only intended for the SD3: they don't implement the tensioning thing necessary for the SD4
No guarantees, it's been a while, but I recall the things print bottom-up ok with no support, and have been pretty sturdy in my printer (not quite the production hours on it to mean much though!).

You'll need to clean up the bearing holes and the hole for the y shaft with an 8mm drill bit to ensure everything fits ok. Gentle with the bearing ones, don't want it to dig in to the step too much. 8mm bearings press into those recesses.

To search for 8x5x2.5mm bearings on eBay, lots of listings under code numbers "MR85-ZZ" (for shielded type) and "MR85-2RS" (rubbber-sealed type) - either are fine here. vxb.com (if you're in the USA) is good value for money most of the time too. The size is a standard size used in RC cars and motors, so they are cheap and in plentiful supply.

thanks I'll give em a go

To the best of my knowledge (perhaps someone could confirm by attempting it), I think you could fit ball bearings into the pulley (slimstar's method) for the SD4 quite happily: keeping the existing shoulder bolt and tensioner but eliminating the friction surface between the bolt and the pulley bore: this is not as good as a bearing, it wears out badly over time, leading to noise and jams.

Bearings allow for a bit more belt tension without increasing load on the motor, which can together improve speed and reduce backlash, so it is still a design improvement in my opinion.

My method, as I've already noted, is not going to work for the closed-belt SD4, as my blocks don't include any way to tension the belt.

I have a reel on my desk, if only time could be bought on eBay wound up on a reel like that.

If you really want to eliminate the backlash on "Y" drive,
and like to spend some money you should do such mod:
1) Let the Y motor drives the rear 6 mm rod(shaft) directly,
Y motor>>coupling>>bearing or bushing and its support-left side
>>left pulley>>right pulley>> bearing support-right side.
2）Use GT2 belts and pulleys to replace the XML belts.
3) Keep a right belt tension, for a closed belt, just adjust
The distance of center to center, for an opened belt, like
SD2, 3, etc., after you adjusted the belt, do not forget
to lock that adjusting screw by a nut, because the belt
Couldn't be turned, but the adjusting screw will be turned
Without a nut, then the belt tension will be changed .
A timing belt drive needs a very rigid frame to avoid
The backlash, but SD frame is made by the sheet metal
More easy to bend, but we couldn't change it.
For the low speed and low loading, use a ball bearing
Or a brass bushing, there is no a big difference.
And atruly a ball bearing has more noise.