SoliForum - 3D Printing Community — replacing front y pulleys

Re: replacing front y pulleys

2014-11-21T05:03:34Z

The force to keep the tension of belt is very small,
so you added the ball bearings at front pulleys
Is a not big deal, didn't help to reduce the backlash
on Y belt.
the main loading is not from the fraction force between a pulley and a bolt (
shoulder screw), it is the fraction force between nozzle
and melt filament when printing.
This is why Makerbot and XYZ didn't use the linear bearings,
on thier X and Y drives, just use the simple brass bushings,
A good linear bearing is very expensive, and just save
a little bit of power, may be we can ignore it.
To use GT2 belts and pulleys, and make the frame
more rigid that I think is the right mod direction.

Re: replacing front y pulleys

2014-11-20T04:58:12Z

AOYOU3D wrote:

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.

AYOU, I like your
Technical poetry so here
Respond in haiku:

The loading is from
Belt tension, which is needed
To reduce backlash

The bushing friction
Rises much more with loading
Than the ball bearing

Shielded ball bearings
Don't get full of dust and wear
As fast as bushings

The noise from bearings
Compared to stepper motors
Is negligible

I consider these
Significant differences
Worth using bearings

Re: replacing front y pulleys

2014-11-20T03:52:40Z

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.

Re: replacing front y pulleys

2014-11-19T04:44:52Z

I certainly can appreciate that!

Re: replacing front y pulleys

2014-11-19T04:39:56Z

wardjr wrote:

Some day I'm going to convince you to try the fish line

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

Re: replacing front y pulleys

2014-11-19T03:22:52Z

grob wrote:

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.

Some day I'm going to convince you to try the fish line

Re: replacing front y pulleys

2014-11-19T03:18:22Z

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.

Re: replacing front y pulleys

2014-11-18T06:36:10Z

These ball bearings(two per a pulley) maybe Ok for SD 2,3 or some SD4(opened belt),
But then this front pulley is fixed, couldn't adjusted in left-right direction, this pulley
Is driven part, it should be adjustable, in the newest SD4 with a closed belt, the front
Pulley is able to move on a shoulder screw (likes a ball bearing) in left-right direction, and two adjusting screws with locked nuts are used to keep the belt tension, It is right design.

Re: replacing front y pulleys

2014-11-18T03:40:48Z

thanks I'll give em a go

Re: replacing front y pulleys

2014-11-18T03:40:26Z

Yep, those are the ones I just replaced they work well.

Re: replacing front y pulleys

2014-11-18T03:37:28Z

satman49 wrote:

thanks to all for the suggestions, I'll have work on it. grob mind sharing that STL?

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.

Re: replacing front y pulleys

2014-11-18T00:58:03Z

thanks to all for the suggestions, I'll have work on it. grob mind sharing that STL?

Re: replacing front y pulleys

2014-11-18T00:53:38Z

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.

Re: replacing front y pulleys

2014-11-17T22:51:29Z

slimstar2 , which side did you drill out collar side or the other?

Re: replacing front y pulleys

2014-11-17T21:50:20Z

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