Pulling belt pulleys?

[kharrisma]

I'm sure someone here's run into tihis.   I'm changing the belt sheaves on my X & Y axes from OEM generic no-name to genuine Gates (along with the belts.)  Of course, the Gates sheaves are thicker than the generics (generics = 8mm, Gates = 10mm), so they won't fit into the belt tensioner yokes.  Solved that one by milling the adjuster yoke openings a bit wider, with a bit of extra to accommodate spacer shims so the sheave won't be rubbing against the yoke.  The steppers are a very different story.  Typical Creality; the damned things are either press-fitted onto the shafts, or they're heated and pressed, then allowed to cool for a *really* tight fit.  Checked the sheave using a loupe; absolutely no detectable sign of a set-screw or a through-pin.

Snagged one of these cheap little pullers; general opinion is thtey're not adequate, but I figured that heating up the sheave with a small torch would be enough that it would be able to do the job.  

         

Nope.  Even really hot, the thin strap that slips under the sheave bends, and no sign of the sheave moving in the slightest.  I'd really rather not stick something under the sheave and pru up against the motor endplate; if it's on there *that* tight, there's a chance of pulling the shaft right out of the motor armature.   I know, steppers are cheap, but at thie point it's the principal of the thing; I'm not going to let it beat me!   

Anybody come up with a reliable way to yank these stubborn sheaves without resorting to an expensive specialty tool?

[SuperBoppy]

If you have access to a hand grinder like a Dremel, you can carefully cut through the pulley parallel to the shaft and get the pulley off that way. If you don’t have access to that tool, a fine toothed hacksaw blade can do the job. Just wrap some tape around it to make a handle.

[sleepster217]

2 hours ago, SuperBoppy said:

If you have access to a hand grinder like a Dremel, you can carefully cut through the pulley parallel to the shaft and get the pulley off that way. If you don’t have access to that tool, a fine toothed hacksaw blade can do the job. Just wrap some tape around it to make a handle.

Becareful using a dremel on pulleys as the aluminium can block the stones and overheat the stone and cause the stone to fly apart and let's say u don't want to be on the receiving end 

 

That said I have used a grinder to cut aluminium and cleared the stone by cutting a bit of mild steel from time to time but with a dremel the stones are so small not sure how well that would work

[kharrisma]

Relative to this issue (still haven't managed to yank that 'welded-on' sheave, going to try using drill press as an arbor press later); is there any solid reason I can't just substitute the 42-34 stepper used in X & Y with a 42-40 stepper instead?  I have a couple of those onhand with the right shaft length.  I'm pretty sure I'd have to reset the "run_current" in the "[tmc2209 stepper_y]" section of printer.cfg to account for the larger current draw of the 42-40's over and above the 42-34's on the stepper drivers.  Does anyone know of any overriding reason Creality chose to use 40-34 steppers on the X/Y/Z axes?  I'm provisionally going with lower cost, given that the Ender 3 was an entry-level machine.  Don't see where the extra capacity would hurt things... and I wouldn't have to fuss over getting that $*$@!! belt sheave off to re-use the original Y stepper!

[Penatr8tor]

Why not right?

 

[SuperBoppy]

19 hours ago, sleepster217 said:

Becareful using a dremel on pulleys as the aluminium can block the stones and overheat the stone and cause the stone to fly apart and let's say u don't want to be on the receiving end 

That said I have used a grinder to cut aluminium and cleared the stone by cutting a bit of mild steel from time to time but with a dremel the stones are so small not sure how well that would work

 

True. Cutting wheels made to cut steel may not cut aluminum so well. They have fiberglass reinforced wheels which would work best. A little water on the cutting area would help, as well as not forcing the cutting wheel, but letting it do the job. Dremel also makes a deluxe wheel that is supposed to perform better and last longer: https://www.dremel.com/us/en/p/ez506hp-2615e506ha

Honestly, a hacksaw blade may be the best option to cut through the aluminum, as well as the safest. It wouldn't take any time at all to hack through a small pulley like that.

 

[kharrisma]

FINALLY got the bugger off!!  Drill-press wasn't working either, even with a good amount of heat.  Got fed up and put it in a vise with a couple pieces of flat tool steel beneath the sheave and gave it one good whack with a hammer... and it MOVED!  Tapped it a few more times and it came off.  Guess the secret is to break the grip by 'starting' movement with a hammer and punch, then use a press or puller to complete the job.

Yeah, most cutting wheels clog up quickly when cuttiing any non-ferrous metals.  A saw is better, but like the cutoff wheels, they tend to be grabby if you aren't holding them dead-steady, and if you get too aggressive with feed they'll grab and kick out.  Definitely a hairy proposition... plus you can't really cut through the whole thing anyway because the cutting wheel is eventually going to make contact with the circular 'boss' surrounding the output shaft on the motor endplate, so that hacksaw blade would have to come into play at some point.  Thanks for the ideas

[sleepster217]

Glad you got it off ok