Y axis belt/pully plates popping when build plate moves

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Y axis belt/pully plates popping when build plate moves

Postby Panopticon » Mon Aug 26, 2013 12:19 am

I'm having a strange mechanical issue where either the two small plates or the pulleys that hold the belts will pull up and pop back down quickly as the bed moves up and down the Y-axis. This creates small anomalies in my prints as it affects the movement of the build platform. Has anyone encountered and resolved this issue? I tried tightening the belt by moving the plates back and re-tightening the screw but the problem still occurs. I've also noticed I can't get the plate tight at the front of the printer, no matter how much i tighten there is a little play in the plate with the pulley on top of it. It's audible as well - it will make 5 pops if I move the build plate up or down the Y-axis (pop,pop,pop,pop,pop).

Any thoughts?
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Re: Y axis belt/pully plates popping when build plate moves

Postby rickmellor » Mon Aug 26, 2013 2:30 am

Not sure if related but I did have an issue where the bolt that tightens down the pulley bracket was too long and would bottom out in the channel. This would smash the nut plate up to the top but the bolt head would not seat against the pulley bracket so it would have a bit of play. To fix it I pulled the bracket off and drilled a hole in the channel where the bolt scored the extrusion (when the belt was tight). This allowed the bolt to go down as far as it needed into the extrusion so that the pulley plate would seat fully. I could have also ground down the bolt for the same result (really the better solution), but I didn't have a bench grinder handy at the time.
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Re: Y axis belt/pully plates popping when build plate moves

Postby Panopticon » Mon Aug 26, 2013 6:31 pm

Hi Rick, thanks for the heads up,you were right about the bolt being too long, I just switched mine out with a shorter one and the plate is nice and tight now but it still pops!

Here's the problem! I took a look at the pulley attached to the back end of the Y axis motor and low and behold there's a small crack running vertically up the teeth. Good thing I have a few extra pulleys. Seems like and easy fix now!

8-)
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Re: Y axis belt/pully plates popping when build plate moves

Postby dave3d » Wed Aug 28, 2013 6:19 pm

I have had similar issues with my build. The kit I have was supplied by Automation Technology Inc.

I found the Y pulley was cracked (from new). Barely discernible, but the drive belt showed it up.

Another issue was the bolts holding down the pulley bracket. I found they were also a tad too long. Instead of shortening the bolt, I fitted a thin stainless steel washer under the head. It now bolts down firm. I Also used a thin washer under the Y axis idler pulley to get a better belt run, so it cleared everything.

Does anybody from Automation Technology read this forum?
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Re: Y axis belt/pully plates popping when build plate moves

Postby rickmellor » Wed Aug 28, 2013 6:36 pm

FWIW, my kit was from ATI as well.
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Re: Y axis belt/pully plates popping when build plate moves

Postby Panopticon » Fri Aug 30, 2013 5:19 am

I see. Part of my setup came from RepRapDiscount.

I wish the pulleys were made entirely of metal!
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Re: Y axis belt/pully plates popping when build plate moves

Postby dave3d » Fri Aug 30, 2013 8:16 am

I replaced the Y axis idler with an all metal pulley. Nice job I got it on Ebay UK.
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Re: Y axis belt/pully plates popping when build plate moves

Postby cvoinescu » Fri Aug 30, 2013 12:58 pm

I've seen the pulleys from RepRapDiscount and I was not impressed (one cracked, new, out of six). "Proper" plastic pulleys are made of glass-filled polycarbonate, which is nearly indestructible. RRD pulleys are not glass-filled, and they don't look like polycarbonate to my untrained eye (probably polystyrene or ABS at best). The rest of their stuff seems quite good, but the pulleys are too cheap. On the other hand, I probably pay twenty times as much, in bulk, for mine...
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